E-SOUVENIR-APPLE RUBY DAY-MEET

A SPECIAL SOUVENIR TO COMMEMORATE THE FIRST INDIAN EXPERIMENTAL COMMUNICATION SPACECRAFT APPLE REACHING LANDMARK OF 40 YEARS SINCE IT’S LAUNCH ON 19TH JUNE 1981 Released on 19th June 2021 H.BHOJRAJ R.ARUNACHALAM T.K.SUNDARAMURTHY M.V.KANNAN

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 which took a toll on many of our colleagues and my classmates. When the D Day of 40 years of APPLE launch (June 19, 2021) was nearing I mentioned to our G 4 friends (T.K.Sundaramurthy, R.Arunachalam and M.V.Kannan) whether we can have a virtual function with Dr R M Vasagam and other dignitaries who worked for APPLE Project. The valiant, untiring efforts of the team fructified into planning this virtual meet on D Day. We have the pleasure of A Quick Prelude to this web Meeting meeting the entire team (barring a few). My profound thanks to the team members: Mr T -H.Bhojraj K Sundramurthy, Mr M V Kannan and Mr It is a momentous occasion, when we are R.Arunachalam for their marvellous efforts in celebrating the 40 years land mark of India’s bringing all the veterans together on this First Experimental Communication Spacecraft virtual platform. APPLE, launched on 19th June 1981 from We are thankful to all invitees/key players French Guiana, this year is also a golden year who have kindly accepted our invitation to of Space Activities in India. talk and share their experiences during the project realisation/execution. It has been a great time working with such great stalwarts in Space Department for 40 We thank one and all for making the meet a years since 1972 and celebrating the 40th year grand success. of APPLE launch on 19th June 2021. H.Bhojraj In one of our chance meetings with Dr R M Vasagam and Mr Madhavan at the wedding T.K.Sundaramurthy reception of Ms Kapila, daughter of Mr.T.K R.Arunachalam Sundramurthy, I casually suggested that we, M.V.Kannan the contributors of APPLE must come together someday for dinner. They were very positive about the proposal but we had to forget about it due to the Pandemic, particularly during the horrible second wave

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 APPLE was an acronym Ariane Passenger Communication experiments like TDMA, SSMA, computer networking, telemedicine, Payload Experiment and it was based on a Teleconferencing, Tele-education, emergency free launch opportunity on the Ariane launch communication and disaster mitigation, hook- up for national events using mobile and vehicle under development by European transportable terminals. Space Agency (ESA) in the 1970s. The project, Though it carried only a single C-band transponder, APPLE yielded rich dividends in conceived in 1975, chosen by ESA from among technology development and operational experience in communication satellites, thus seventy-two competing proposals in 1976 and laying the foundation for the INSAT system. approved by Government It gave ISRO valuable hands on experience in designing and developing three-axis stabilized of India in May 1977 with geostationary communication satellites as well as in orbit raising manoeuvres, in orbit thirty months’ time deployment of appendages, station keeping, etc. schedule with limited APPLE laid the foundation for indigenous infrastructure in development of operational communication satellites which grew into a very large industrial sheds in constellation of satellites in INSAT and GSAT series which revolutionized the technological Peenya, Bangalore and Rs 21 crore outlays, and economic growth of the country. Newer applications like Tele-education, Tele- culminated in launch on 19 June 1981 from medicine, Village Resource Centre (VRC), Disaster Management System (DMS) etc., Kourou, French Guiana atop Ariane LO3. have enabled the space technology to reach the common man. APPLE was designed and built as a sandwich A team of over 2,500 young engineers, passenger carrying Meteosat on top and CAT scientists, technicians and administrative personnel ably assisted by Indian and (Capsule Ariane Technologique) module international institutions / industries accomplished the mission. The average age of below. the APPLE team was twenty-seven years. Apple had touched the citizens of India cutting It gave ISRO valuable hands on experience in across all age groups. designing and developing three-axis stabilized geostationary communication satellites as The Project was successfully realised by none well as in orbit raising manoeuvres, in orbit other Project Director Padma Shri R M deployment of appendages, station keeping, Vasagam and team across all centres of ISRO. etc. The APPLE spacecraft was utilised for more than twenty-seven months in orbit, exceeding its design life of two years and was used by ISRO and Telecommunication Research Centre of P&T for conducting advanced satellite

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 APPLE in Retrospect Padma Shri.Prof.R.M.Vasagam FIG.1 Evolution of APPLE S/C Proposal It is a momentous occasion when we are APPLE was designed and built as a sandwich celebrating fifty years of space activities in India. As one who was fortunate to join the passenger carrying Meteosat on top and CAT Indian space programme in its formative years and also had the opportunity to lead APPLE, (Capsule Ariane Technologique) module India’s first geostationary experimental communication Satellite Project during 1977- below. APPLE incorporated integral orbit 83, I would like to highlight the challenges and exciting moments of the project from concept transfer and orbit and attitude maintenance to completion. APPLE was an acronym Ariane Passenger Pay Load Experiment and it was propulsion systems, three axis attitude based on a free launch opportunity on the Ariane launch vehicle under development by control system with momentum wheel and European Space Agency (ESA) in the 1970s. APPLE made India to master the state-of–the- Sun and Earth sensors, driven deployable art technologies in satellites for space communication missions as well as solar panels and nickel-cadmium batteries, technologies for Earth observation and scientific satellite missions. The project, carbon fibre face skin antenna, honey comb conceived in 1975, chosen by ESA from among seventy-two competing proposals in 1976 and deck plates, multilayer thermal blankets and approved by Government of India in May 1977 with thirty months’ time schedule and optical solar reflectors for thermal control, C- Rs 21 crore outlays, culminated in launch on 19 June 1981 from Kourou, French Guiana band communication transponders and VHF atop Ariane LO3. The evolution of Apple spacecraft proposal is shown tracking, telemetry and command system. Judicious choice was made for using space- proven and indigenously developed systems compatible with the tight time schedule of thirty months. The C-band communication payload compatible with Satellite Telecommunication Experiments (STEP) infrastructure was planned to carry out advanced satellite communication experiments beyond SITE and STEP using ATS- 6 and Symphonie satellites. The concept to completion of APPLE is depicted in Fig. 2. The Special issue of Aeronautical Society of India journal August –November 1983 chronicles the APPLE by the project team members across all ISRO centres.

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 Figure-2 Figure-4 – Work Centres of APPLE Project and Structural tests including combined stack Development Plan tests, thermo-vac tests mission and software activities and control systems simulation were all done at hectic pace. In all, five-and-a-half models were built for structural, thermal, engineering, proto- flight, flight and flight spare purposes. Fig. 3 illustrates the APPLE in disassembled configuration. The work centres of APPLE project and development plan are shown in Fig. 4. Figures 5, 6, 7 and 8 show the Apple composite stack test at Toulose, thermal test at ISAC 4 m Thermo-vac chamber, solar simulation test on APPLE thermal model at the space simulation chamber at Toulose and the integrated Apple spacecraft at ISAC clean room respectively. APPLE on Ariane LO3 and take off from Kourou on June 19, 1981 are presented in Fig. 9 and Fig. 10. The global TTC network for APPLE mission and orbit raising operations are shown in Fig. 11 and Fig. 12. Figure-5: Mechanical Qualification Test of APPLE Figure-3 Overall Characteristics of APPLE Spacecraft

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 Figure-6: APPLE Test in 4 Meter Thermo-Vac Chamber Figure-9: Apple on ARIANE LO3 Figure-7: APPLE Thermal Model Undergoing Solar Simulation Test Figure-8: Integrated APPLE Flight Model Figure-10: ARIANE-L03 Take off

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 Facility at STEX, High Altitude Test (HAT) facility for solid apogee motor tests (with steam generation capacity equivalent to 200 MW thermal power station and based on nitric acid, diesel and water rocket) and setting up APPLE Mission Control Centre at Sriharikota were posing great challenges all the time. The development of tribology laboratory for momentum wheels and solar Figure-11: Global TTC Network for APPLE array drives, carbon fibre antenna and honey Mission comb deck plates, and Vacuum Ignition Testing Facility at VSSC were taken up with exemplary speed. The facilities at Space Application Centre for building the payload and antenna tests were equally difficult to come through. Thermo-vacuum chamber of 4 m diameter at ISAC was to be ready for thermal model testing and also for tests on proto-flight and flight models. We can look back with satisfaction that everything was accomplished in time with less than 5 per cent Figure-12: APPLE Mission Profile escalation, well within the contingency provisions. More than that, we met the APPLE development plan spanned over six demands of ESA. In case the flight model of years. Many ISRO work centres were involved APPLE was not ready in time, we were to in the project. There were moments of launch the flight-worthy structural model successes and setbacks in this project. The stored at Toulose, after composite stack test, project activities were taking place at all ISRO which would be returned to India only after Centres and also in all continents. Please note the launch. What a shame it would have been that this was at a time when only telephone if we had not delivered the flight model on and telex were available for domestic and the agreed date? We also had to set up an overseas communication and that too you independent safety office in ISRO. We did the had to book and wait for your call to come coupled loads analysis for the first time! through. Same was the story for mission Transporting of solid apogee motors on operations. You had to hire dedicated link aircraft and its storage in France, moving it to from OCS (Overseas Communication System). Kourou later, transporting Indian-made As ISRO did not have enough mainframe hydrazine to Kourou by ship, etc., were things computers, the computing time needed for accomplished against great odds. Air India had structural, thermal and mission analysis could been our carrier but at a critical moment we be met only through our engineers availing were facing difficulty of getting the chartered the night hours at IISc, IIT Madras and TIFR! aircraft to come to Toulose to carry the Our means of realising the hardware were spacecraft to Kourou owing to violation of centred around HAL, BEL, ITI and ECIL, setting Lome Convention of 1975. Kourou being a up the three-in-a-batch solid motor casting French overseas territory, we had to engage facility at SHAR, enhancing Vibration Test

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 Air France! But it turned out to be cheaper! way of blending the best of the East and During launch the Australian Post, Telephone West! and Telegraph workers went on strike severing our redundant overseas communication link from Kourou. For every one day delay in launch on our account, we would have to pay 100,000 Francs penalty! At Kourou we had the CNES staff strike jeopardising the launch schedule. But the French military personnel came to the rescue and manned the facility. The only problem was that we had to move around with passes and passwords even at the launch tower! Further we had to pray for success of the third Figure-13: Payload Test (time delay for the developmental launch as the second signal to up and return from the satellite) developmental flight ended up as a failure in boost phase itself (on recovering the APPLE was dedicated to the nation on 13 hardware from Atlantic ocean it was later August 1981 by then Prime Minister Indira found to be attributed to a piece of cloth in Gandhi. It was again a unique experiment and the engine assembly). APPLE had an anomaly. an experience to all when the APPLE One of the solar panel did not deploy and the development team members, assembled at mission team evolved the operations plan in the Vikram auditorium at Space Application real time and succeeded. While one panel Centre, were introduced to the Prime Minister power was sufficient for operations in by Satish Dhawan, then Chairman ISRO, geostationary orbit, problems arose in present at New Delhi Earth station, through thermal management. With one half of OSR two-way videoconferencing – one half of the (Optical Solar Reflector) blocked, we had screen showing the Delhi Earth station scene temperatures rising and finally we had to do and the other half showing Vikram pitch rotation to even out the Sun load for auditorium! APPLE development story was four months around the winter solstice. The telecast to all metros having TV stations and reacquisition of Earth was hampered by relayed through transportable terminals as scintillation problems. The successful well. But it was black-and-white TV as colour functioning of the transponder was tested television came to the country a few years using a live dance programme signal sent to later during the Asian games. The Prime and received from the satellite. Fig. 13 brings minister symbolically handed over the model out the time delay for the signal to up and of APPLE to the Minister for Communications return from the satellite. The time delay for and said that APPLE marked the ‘Dawn of nearly 80000 km (to and fro distance to India’s satellite communication era’. The satellite) is about 270 milliseconds. APPLE Prime Minister’s address to the nation on 15 transponder also transmitted Rabindranath August from the Red Fort was carried live to Tagore’s dance drama Chitrangada. While the country by APPLE. characterising the end-to-end performance of The APPLE spacecraft was utilised for more the APPLE communication link, it was our own than twenty-seven months in orbit and was used by ISRO and Telecommunication

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 Research Centre of P&T for conducting advanced satellite communication experiments like TDMA, SSMA, computer networking, telemedicine, teleconferencing, tele-education, emergency communication and disaster mitigation, hook-up for national events using mobile and transportable terminals. The Apple utilization programme is depicted in Fig. 14. The transportable terminal is shown in Fig. 15. The Apple utilization network is shown in Fig. 16. Figure-16: Apple Utilization Network Figure-14: APPLE Utilization Programme A moving experience happened when APPLE Figure-15: Transportable Terminal was harnessed to link Gandhinagar Secretariat and Amreli District Collector’s office when the entire road and communication network collapsed due to cyclone hitting Amreli district. With emergency communication terminals at both the places and ESCES acting as a hub to achieve the link margins, more than 50,000 messages (from the birth of a child to bereavement to postponement of betrothal) passed through APPLE for 10 days. The Chief Minister of Gujarat came to SAC for thanksgiving and he said, When we gave our land at Jodhpur Tekra for ESCES we never knew that it is going to be extremely useful in our times of distress. You are our friend in need.’ Similar was the experience during a volcanic eruption at Andaman Islands. Real- time interbank reconciliation performed with SBI Bombay and Calcutta branches using rooftop terminals, printing of The Hindu newspaper at Bangalore (using APPLE link and Chengalpattu Earth station acting as hub and jeep-mounted small terminals at Madras and Bangalore of The Hindu office) with much less error compared to microwave links were some of the experiments paving the way for dedicated operational systems. Another experiment of great interest was for tracking the location of wagons of Indian Railways, the major source of earning for them. APPLE was also used to conduct satellite communication

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 course, APPLE telling its own story to seven able to take it to a twenty-two-and-a half- campuses in India with audio-video downlink hour equatorial orbit from the initial elliptical and audio uplink for interaction in a transfer orbit for a period of ten hours and a sequential mode. The Robotics course of the half, inclined to the equator at 17 degrees. Institute of Electrical and Electronics We loaded the hydrazine tanks full availing Engineers was conducted for students at the final margins released by Ariane LO3 seven locations with resource persons at mission. Attaining the final Twenty-four-hour Ahmedabad, New Delhi and Detroit. orbit was made possible by series of burns of Operational systems soon followed. The four of the 1 N hydrazine thrusters for hours successful month-long telemedicine in continuous burn mode at appropriate times experiment between AIIMS, New Delhi, and in orbit. The orbit-raising strategies for INSAT Civil Hospital, Ahmedabad, extensive trials of and Chandrayaan-1 and planned Mars the emergency communication and also the missions go back to those days of doing things VIP terminals became operational services in out of necessity. Necessity is the mother of the INSAT period. I have to now bring out the invention. How true it has turned out to be! tense moments we went through. On orbit, APPLE operated for over twenty-seven APPLE had an anomaly. One of the solar months in orbit exceeding its design life of panels failed to deploy. The power from one two years. The last moment of APPLE panel was adequate for the on-orbit phase occurred on 19 September 1983. Sitting at but we met with a formidable thermal ISAC at Peenya in constant communication problem. One half of the optical solar with the operations team at Sriharikota, we reflector surface was blocked and it led to a witnessed the fall of thrust from hydrazine raise in the temperature of satellite thrusters. Slowly, the last few drops of subsystems like the Earth sensors, momentum hydrazine came out and the thrusters were no wheel bearings and batteries operating near more capable of producing rotation and their qualification limits during the period translation of the spacecraft. As a last-ditch around the winter solstice. A pitch rotation effort, attempts were made to access residual manoeuvre was designed to rotate the quantity of hydrazine trapped in two of the spacecraft like rotisserie manoeuvre for four tanks due to a shut latch valve. However, this hours every day in the night time and to did not bear fruit. With tears in our eyes, we reacquire Earth lock after four hours and had to send the last command to shut the continue normal operations for the rest of the spacecraft as part of the predetermined plan day. The mission operations team at of shutting down all subsystems and making Sriharikota had nightmarish experience to the beacon silent. This was the last of the regain Earth lock as the VHF TT&C link was more than 90,000 commands sent to the affected by ionospheric scintillation and spacecraft and faithfully executed but for one, succeeding after a number of attempts each which was traced to be due to a fault in the day. One has to remember at this juncture ground system! APPLE, though ‘handicapped’, that 1981 was ‘UN Year of the Handicapped!’ was the most forgiving satellite and it was our APPLE teams had many other interesting test bed for learning from L (learning) board experiences .The apogee motor of APPLE with to Experts! We had lost the Sun lock and the 314 kg propellant load was capable of Earth lock a number of times due to supporting 616 kg spacecraft weight; but anomalies in subsystems, and the operations owing to increase in spacecraft weight it was team used to keep the spacecraft in safe

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 mode and start recovery operations, the redundant systems were indigenously sometimes even taking the ISAC team by bus built. After one year in orbit, we switched to Sriharikota. On one such occasion we were over to indigenous systems and acquiring able to get the normal operations restored performance and qualification data paving the back to support the Indian Air Force fire way for self-reliance in critical subsystems like power demonstration event at Tilpat range momentum wheels, sensors and RCS. The just in time! Setting up and locating ISTRAC at technology of orbit raising and orbital Bangalore, came out of such APPLE operations perfected through APPLE and experiences. Many tense situations occurred thermal and power management became the during the development and testing of the core of operational satellite missions like APPLE spacecraft. The cage instability problem INSAT and IRS which followed. APPLE being in the momentum wheel was valiantly solved transported on a bullock cart has become a by the Inertial Systems Laboratory paving the symbol of our innovative approach and has way for indigenous momentum and reaction been characterised as collision of centuries by wheels, which became our mainstay for Newsweek, which said that between the tail future missions. Similarly, perfecting the of the ox and the sophisticated APPLE vacuum ignition of solid ABM (Apogee Boost spacecraft kept on a clean tent, centuries are Motor) also contributed to the success of SLV- coming together. APPLE was put on a bullock 3 project one year ahead of APPLE launch. The cart to provide a non-magnetic environment rupturing of plumb lines of RCS on the proto- and to conduct the antenna test in an open flight model was another incident. This was field to remedy the TT&C link problem caused owing to inadvertent cooling during thermo by impedance matching problem. The solution vac test causing demineralised water (used as was found in about five hours and at a cost of simulated fluid) to turn to ice leading to Rs 150 for hiring the cart! It would have expansion. The cause was traced to be the resulted in considerable expenditure and time erratic power from mains and the time delay delay to conduct this test in a facility outside in getting the backup on. It required India. We were close to the point of corrective action at the supplier’s facility in a transporting the satellite to Toulose for final fire fighting mode to be back in time to serve tests of the composite along with CAT and as flight standby. The last minute polarity Meteosat to be followed by launch from error detected in Lockheed Earth sensor flight Kourou. model (traced to be due to change of wiring team at manufacturing stage), collapse of High Bay Building roof of Cast And Cure Facility of SPROB due to hovering of severe cyclonic storm over SHAR for eight hours, collapse of VHF antenna mount due to wind conditions at SHAR, collapse of the 40 m tall water tank feeding High Altitude Facility at STEX, etc., were some of the incidents causing Figure-17: Apple on a Bullock Cart at Peenya, setbacks but fortunately no casualties! The Bangalore judicious mix of make-buy options paid the dividend. For the main system we chose The storage of APPLE ABM was in the French space-proven items from outside vendors and Munitions Facility. Our engineers went every day crossing the fortified barriers including

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 guard dogs to perform rotation of the motors administrative personnel ably assisted by by 120 degrees every day like wine bottle Indian and international institutions storage to prevent grain deboning. This was /industries accomplished the mission. The another unique experience. Hydrazine made average age of the APPLE team was twenty- at Thumba was transported by ship to French seven years and I was thirty-seven at the Guiana in specialised small containers beginning of the project. ‘We did not know certified for maritime transport of explosives. that we did not know’ made us to perform in It is worth noting that the Guiana Centre a daring manner against all odds! APPLE authorities tested and found our hydrazine to symbolised the romantic phase of our space be of superior quality compared to that programme. It touched the hearts of all demanded by US Air Force specifications. Indians. Dhawan was asked by his highly While we brought the flight stand by ABMs to concerned vegetable vendor “APPLE Kaisa India, the balance quantity of hydrazine was Hai” and he said that APPLE will not be neutralised in a special facility at Kourou at renamed as was done for earlier missions! At our cost as the charge of transportation was Anand Bhavan, Allahabad, while delivering the much higher. Same was the story of Nehru Memorial Lecture I was confronted by transporting our igniters for mating and the aunt of Indira Gandhi from amongst the testing with the Thiokol safe and arm device audience of a few thousand people on 14 in their facility with police escorting in New November 2001 as to why APPLE was running York and New Jersey States – of course at our hot when the north was facing cold wave and cost! Our ITLU (ISRO Technical Liaison Unit) also on consequential misery including loss of office at Washington had to do such life. I had to explain our thermal problem in coordination tasks at very short notice. winter solstice and the remedial pitch rotation Release of the flight worthy structural model operations! The state-level science was authorised only after successful launch of competitions held next day had so many APPLE. This was brought back along with the students demonstrating APPLE elements using proto-flight model, ABMs and integration and simple components. Thus apple had touched checkout equipment by Air France to Delhi in the citizens of India cutting across all age pallets and subsequently transported to groups. When Apple was inaugurated Prime Bangalore by road. The excellent performance Minister Indira Gandhi called it “Dawn of of ECIL made computers supporting the India`s communication satellite Era”. How mission operations in the initial orbit- raising true it became! Today we are in the forefront phase for forty-five days in non-stop mode, of space communication and Earth arranging tanker-loads of liquid nitrogen for observation systems for our needs. We have twenty-one days from Indian Oxygen, Madras, missions to go to Moon again and Mars as with special exemption from power cut during well. Our own navigation satellites and human President’s Rule there, authorisation to the space flight enablers are in the works. Project Director for granting air travel for one way and return by train for people accompanying the spacecraft items subject to submission to the DOS and Member (Finance), Space Commission, are some of the things unique to this project. A team of over 2,500 young engineers, scientists, technicians and

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES Padma Shri.Prof.R.M.Vasagam Figure-18: Prime Minister dedicates Apple to Apple was India’s first experimental the Nation geostationary communication satellite making use of the free launch opportunity offered by ESA and ISRO commemorated the silver the Ariane developmental flights. jubilee of Ariane LO3 and APPLE launch at Incorporating the emerging technologies of Paris on 16 June 2006. APPLE symbolises the integral orbit transfer and orbit and attitude fruitful cooperation between ESA and ISRO maintains propulsion system, driven paving the way for strong ties between the deployable solar panels, momentum bias two organisations in the years to follow. 3axis control system with sun and earth sensors ,Al alloy structure and honeycomb R.M.Vasagam, Project Director, APPLE deck plates thermal control systems with paints and optical solar reflectors, power (Courtesy: https://www.isro.gov.in/sites) system including battery, communication transponders in C Band, carbon fibre reflector. Apple became a forerunner for operational communication satellites for the country as well as remote sensing satellites to follow. It paved the way for designing, building, testing, launching ,operating in orbit and utilising the spacecraft for advanced satellite communication experiments for about 27 months .TDMA, SSMA, emergency communication,teleteaching,telemedicine,tel ecomputing,transportable and emergency communication terminals were part of the experiments conducted and carried forward for future operational missions. A whole host of technologies were developed like apogee boost solid ABM, low thrust

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 hydrazine propulsion system, solar panels collector’s compound after a devastating with honeycomb backup, carbon fibre cyclone carrying more than50000 messages of antennas, sun and static and scanning earth bereavement birth of a child and sensors, mission planning and operations, postponement of betrothal touching the heart structural analysis, static and dynamic testing, of Gujarat CM to come and thank SAC for control system analysis, design and testing, their timely support using Apple! telemetry and command systems. System Apple story was broadcast to 7 engineering reliability and quality assurance and safety college campuses for 21 days with aspects were to be part of the launch video/audio downlink and audio uplink for clearance requirements. interaction with resource persons and Apple project was approved in May 1977 with participants. 21.5 crore budget and 30 months to go for IEEE robotics course was taught through launch. it was a sandwich passenger with Apple in 7 campuses with resource persons planned 616 Kg launch which at launch from US, New Dehi and Ahmedabad. Printing touched 672 Kg with added hydrazine in the of The Hindu using satellite link turned out to fuel tanks. The Apogee boost motor put it in be better than microwave link and paved the 22.5 hour near equatorial orbit and the on way for their connecting Chennai with New orbit hydrazine propulsion system was used Delhi, Hyderabad and Bangalore and Other to raise the orbit to 24 hour period after firing cities for latest news to be included. the low thrust engines for 9000 se Anomalies occurred in orbit as one solar panel Interbank cheque clearance and reconciliation failed to deploy leading to thermal problems. using rooftop terminals by SBI between Work around plan of pitch rotation was Mombasa and Kolkata, digital connectivity devised and spacecraft operations continued experiments for remotely located paper mill up to 27 months. plants with corporate headquarters at Kolkata , wagon tracking experiments for railways are Apple was the most forgiving spacecraft other examples of use of satellite allowing operations team to restore the connectivity. orientation to sun and earth by the combined teams of development teams and operating The most rewarding experiments in persons sometimes at critical moments for telemedicine were performed between AIIMS important national events. and Civil hospital Ahmedabad paving the way for Telemedicine to emerge as a cost effective Using Apple transponder in video and lifesaving application in our country. conferencing mode dedicating Apple to the country by Then Prime minister of India with While these are touching society at large PM at New Delhi earth station and Apple Telecom Research Centre partnered in digital team at Ahmedabad was a unique moment communication experiments and TIFR as also the Red Fort speech of PM on partnered in Computer networking Independence Day1981 telecast live to metro experiments. cities is etched in the memory. The last moments of Apple came in Apple was used in restoring communication September1983.The hydrazine fuel was between Gandhinagar and Amraeli district exhausted and we saw the last drop coming

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 out through the thrusters at ISAC Peenya terminal in the early hours the main operation team at ISTRAC at Srihaikota.Mr.V.A Thomas and myself were there with Mr.Bhushan. A formal press release was made in the afternoon announcing the end of Apple Mission. There are many such moving moments in Apple programme and you must have been fortunate to be part of Apple Saga. Tense moments in subsystems developments and overcoming, still leaves the Apple memories sweet. The Apple team has left a legacy of winning the battles and mastering cutting edge spacecraft technologies to the successive generations of ISRO human resource. Some who were part of the teams are no more with us and let us pay our tributes to them at his moment. Thank you all. R.M.Vasagam

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 Aerospace, I got a call to meet the Chairman, REMINISCENCES/MESSAGES Prof. Dhawan. He said that he had concluded that Vasagam needed a deputy due to the overwhelming complexity and unprecedented Sri.P.Ramachandran, DPD tight schedule of APPLE and that he was “requesting” me to take the job. While he would not stand in the way of my going to USA he urged serious consideration of the “request”. Given the spontaneous respect that he commanded and especially after he said that Vasagam was in favour of the idea, I readily complied. APPLE down memory lane Thus began, arguably, the most intense, demanding, stressful and exciting phase of my My intensive involvement with satellite career. We were building almost everything technology really began in 1975 on being for the first time in ISRO –three axis stabilized made a member of the APPLE Proposal team. satellite, mono propellant RCS, deployable solar panels, light weight structures, thermal The team debates on the choice of dual spin management for GEO, momentum wheels, IR vs. three axis satellite configuration for the Earth sensors, carbon fibre antenna, C Band different weight classes on offer by Ariane, transponder, Orbit determination and Mission provided me with spacecraft systems management for a GEO spacecraft, real-time education on steroids. The mentorship by telemetry processing on ground using example that I got from Prof. Vasagam on indigenous minicomputers, to mention a few. system tradeoffs and from President Kalam on I had to get up to speed in a hurry. The ISAC Project management, greatly helped me in my library adjoining my office as well as the career. In fact, in the mid 70’s, the three of us insights, unstinting help and cooperation of and A.Chandran, would invariably have the project team, were of great help. dinner together and discuss space technology threadbare until late at night on Kalam’s That the spacecraft was delivered in time and doorstep. met its goals over the planned two year lifetime is now history. It was the direct result When the APPLE S/C Project was formed I was of the ISRO management and work culture not released from VSSC due to my work on that had all the ISRO centres pulling together PCM Telemetry for SLV-3.Later, I was selected as one team. Even outside agencies such as as Program Manager, Mission Operations, for HAL did their share on tasks and schedules the INSAT-1 Project. One day in late 1978, that they were unaccustomed to. Everyone even as I was packing up to go to USA to join from the Chairman and Centre Directors to the resident oversight team at Ford the engineer’s technicians, draughtsman, facilities, administration, accounts, purchase, transportation and canteen staff pitched in on an almost 24x7 basis. I remember taking Prof. Rao to task for not being in his office when I needed his support one Sunday. He

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 sheepishly explained that he had stopped this was a first. I had to disabuse them of that coming on Sundays at the insistence of notion with a picture of the Ariane LO3 stack. Mrs.Rao! Many thanks for remembering me on this Despite all the hard work and the occasion and my heartfelt thanks to all who comprehensive testing, an element of participated in this “one small step” to GEO. providence, or luck, is indispensable to My best wishes for health and happiness for success and we did have our fair share of you and your family and my homage to the lucky breaks. While doing interface reviews departed stalwarts. May ISRO continue to (an excellent suggestion from Madhavan) I keep up its grand tradition with many more found an automatic thermal cutoff relay achievements that are the envy of the world! existed to isolate the battery, ostensibly to P. Ramachandran, protect it if its environmental temperature Deputy Project Director, APPLE limit was exceeded. I got an override for it included. Since the North solar panel on Spacecraft Project,ISAC APPLE did not deploy and the battery was under it, the temperature limit was frequently exceeded. But for the override, we may have ended up protecting the battery but losing the mission! The North solar panel non-deployment was a mystery solved only nine years later, while testing the deployment of the INSAT-2 solar panels. When pyro fire was commanded, a current loop in the pyro fire circuit could sometimes fuse the PWB track and prevent it working again. The North panel was test deployed before launch by firing the pyro. This presumably fused the pyro fire circuit preventing panel deployment in orbit. Luckily we did not test deploy the South panel too at Kourou or the spacecraft might have been lost! As they say, “fortune favors the brave”. Forty six years later, here at Los Angeles, on the other side of the world, it seems like a previous lifetime. Sometimes, it also seems like yesterday, with history repeating itself. Until recently, I was a consultant at Boeing Satellite Systems (formerly Hughes Spacecraft),on a two satellite all-electric propulsion system design with one satellite acting as a launch adaptor and carrying the other. Just like APPLE! Boeing claimed that

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES R.Madhavan geosynchronous orbit from the intermediate APPLE spacecraft execution recollections orbit provided by the launcher. The project started functioning from industrial sheds in Peenya, near Bangalore, using the infrastructure created for Aryabhatta and Bhaskara scientific satellites under ISSP(INDIAN SCIENTIFIC SATELLITE PROJECT). ISAC(ISRO Satellite Centre) thus evolved from ISSP to meet the requirements of the project with the addition of infrastructure and expansion of functional divisions and facilities. A matrix organization was implemented with APPLE Spacecraft was the brainchild of Prof identified project personnel for the RM Vasagam, the Project Director, evolved to development of equipment and components give shape to the vision of Vikram Sarabhai for reporting to line management while exploiting space based services for simultaneously being responsible to the leapfrogging development of the country to project for the deliverables, in a dual role. All the Indian populace in particular covering centres and units within ISRO were rural and remote areas. The preliminary participating on various hardware/software proposal for implementing the project was and facilities for the project. This included the made in the context of the opportunity SLV3(Satellite Launch Vehicle) project afforded by Arianespace for the free launch of developing the ABM as a derivative of the passenger payloads onboard the 3rd fourth stage of SLV3. A model philosophy development flight, LO3, planned for 1980-81. encompassing a structural model(SM), a The proposal for a communication payload on Structure-Thermal model (STM), a Prototype a three-axis stabilized platform sandwiched model (PM) and a Flight Model (FM) with between launcher equipment platform below appropriate spares was adopted with a and METEOSAT,with a Meteorological payload schedule of milestones for the project on a spin stabilized platform on top was deliverables. Work packages and presented as a composite payload in 1976 to a responsibility matrix for the participating ESA(European Space Agency)/CNES(Center centres were evolved as part of the operating Nationale Es Spatiale) forum and got documents provided to ESA. The design accepted. The detailed project report with reviews and the flight readiness reviews were execution and financial aspects was approved to be conducted at the end of each phase of by the Indian Space Commission under the development with the participation of ESA stewardship of Prof Dhawan and the project representatives. Democratic leadership was inaugurated in March 1978 It was a truly reflected in the participative management ambitious endeavour to realize in a three year approach with Project Management Board time-frame, a three axis stabilised satellite (PMB) consisting of project personnel with with an integral solid Apogee Boost delegated authority to implement schedules Motor(ABM) to boost it into a and budgets, Configuration Control Board (CCB) for design and configuration management and Test Review Boards (TRB)for

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 test planning and review at spacecraft level verification were implemented on compatible and subsystem level to progress the schedule. Towards a nationwide development. The model and configuration infrastructure for sustained support of philosophies defined the implementation of spacecraft development, the participation of redundancies at subsystem level with primary private and public sector industries and component performing the normal phase educational institutions and national operations and the redundant subsystems laboratories were proactively sought during based on indigenous development to be various phases of spacecraft development, operated during special phases for testing out testing and reviews. Offices of ISRO Reliability operational capability. Administrative and ISRO Safety to oversee the respective machinery was fine tuned to meet the special areas encompassing all ISRO centres were procurement efforts for the large volume of created at ISRO Headquarters to certify materials and identified spacecraft equipment Spacecraft elements for safety and Reliability and components (where indigenous in line with ESA’s organizational expectations. subsystems were yet to be proven) through Concerted efforts on spacecraft and facilities the process of RFPs and Contracts. The development were progressed with a contracts involving legal and financial clauses participative and synergistic approach by to ensure timely deliveries with documented technical, management and administrative testing and approvals were to be pursued. personnel supporting the top management Where ever necessary, the participation and plans. Some snippets on the nostalgic approval from ISRO personnel at the reminiscences of events encountered during contractors’ facilities was to be the implementation of the project are accommodated on a mandatory basis. Specific presented as follows: At a critical time of to mention are the contracts for Momentum schedule crisis for the very first milestone of wheels, Solar Array Drive and Power transfer structural model realisation, ISRO chairman assembly (SADAPTA alias BAPTA), took up the matter with HAL Chairman for monopropellant reaction control thrusters, according top priority in HAL shop floors for star tracking sensors, TWTs, Power Amplifiers APPLE related fabrication to accelerate the and solar panels. . Special contracts for work and this ensured the structural model procurement of radiation hardened electronic availability in time for testing. Meteosat components with assurances of storage and structure failed during composite payload distribution meeting the foreign structural model vibration testing and could governmental laws were also pursued. not be refurbished in time by the agency, Simultaneously, ground facilities for providing a breather in the initial phase of the integration and checkout of spacecraft models project. Ariane LO2 launch failed extending such as large clean rooms, vibration testing, the LO3 launch schedule to 1981 and the and Thermo vacuum testing were planned extensive analysis and corrective action and implemented. Special facilities for implementation provided adequate subsystem and equipment level assembly and confidence in the expectation of a successful testing such as clean rooms for momentum LO3 launch. Flight momentum wheel wheels, functional and zero-g deployment component identified as defective was testing of solar panels, testing of three axis replaced by Teldix personnel at ISRO site. The stabilization control components as well as BAPTA (Bearing and Power Transfer High Altitude testing of ABM for performance Assembly) units had to be removed from the

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 Flight model spacecraft due to a moisture Nevertheless, a hitch in the solar panel ingression from an eventful Thermal vacuum deployment system resulted in the non- test of Flight model spacecraft and were sent deployment of one of the panels in the back to British Aerospace for refurbishment. geosynchronous orbit and reduced the The units were finally assembled on the onboard power availability as well as spacecraft at Kourou, the Launch centre, spacecraft Thermal control ability after during the final launch campaign. There were reaching the appointed location on the concerted efforts supported by the space geostationary orbit. There were contingency Applications Centre management to make the operations implemented on a daily basis to TWTA developed by the local team as the ensure thermal management with pitch primary system for c-band downlink but the rotations during winter solstice periods at the proposal was not accepted by the Spacecraft expense of reaction control system fuel Management Board in view of possible arcing resulting in reduced operational life of the in the high voltage system and such defect spacecraft, thus only realizing 2years of life was indeed witnessed in Spacecraft testing as against the original planned 7years. The well. Since the Flight ABM had reached spacecraft was dedicated to the nation by the Kourou much ahead of its scheduled then Prime Minister Indira Gandhi and she integration with the spacecraft, special was introduced to the APPLE team by procedure for ABM rotation on a fixture Chairman, ISRO with the two way TV link designed for the purpose was evolved and established between Delhi and Ahmedabad. launcher crew was trained on the procedure The spacecraft operations were finally called to be carried out while in storage. The Flight off on Sep 19, 1983 when the hydrazine model and other equipment transportation by reaction control system fuel was exhausted. an AN-12 cargo aircraft was an involved R.Madhavan,Project Manager,ISAC exercise during cargo loading at HAL airport and in the absence of containers, the loading ------ took 6hrs, but the cargo had to be unloaded at Toulouse airport in France due to Governmental restrictions. The cargo was reloaded on an Air France Cargo aircraft in containers and airlifted to Kourou for the launch campaign. The launch campaign needed 60-75 ISRO personnel to be deputed to kourou in phases to ensure smooth progress of the pre-launch activities. During the launch countdown, issues were noticed with the tracking radar at the down range station and the countdown was briefly held up, but cleared subsequently in consultation with launcher Quality assurance based on availability of redundant tracking data. Finally, the launch was successful, and the spacecraft was injected into the intermediate orbit and orbit raising maneuvers were successful.

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 of small satellite APPLE. We REMINISCENCES/MESSAGES decided to use magnetic control for on orbit Roll/Yaw control, but APPLE 40 Years; remembering the unsaid simulation studies showed that if we control Roll/Yaw with magnetic Dr.P.S.Goel control, we get nutation instability. If we control nutation using magnetic control, the we get Roll/Yaw instability. This led to a totally new approach by designing a nutation filter, inverting its polarity and adding to roll error and it worked. This resulted in a publication in Journal of Spacecraft and Rockets. Mr S Rajaram worked with me on 1. APPLE Enabled ISSP to become ISAC this concept. He later moved to Prof U R Rao had a single point goal of USA at RCA. Recently, few days making ISSP a centre of ISRO for back he mailed me stating that satellite activity soon after Aryabhata. RCA found nutation buildup in This did not happen when we initiated orbit when they used magnetic SEO (later resulting in Bhaskara 1 and control in one of their 2). However, when it became clear communication satellites. I am that we are going to get APPLE happy that Mr M.V.Kannan is able project, ISSP was converted from to reach Mr Rajaram even though project to ISRO Satellite Centre. APPLE he left ISAC before launch of is one of the most important APPLE. milestones in the journey of ISAC 3. Non-Availability of Gyros (Now URSC) Current generation of control 2. Dual Spinner v/s 3-Axis Stabilization engineers find designing a control We had a long debate weather logic or mission management so APPLE should be a dual spinner or convenient using gyroscopes and 3-Axis stabilized. Fast turnaround inertial reference systems that it is time was one of the arguments in unthinkable to have AOCS without favor of dual spinner, but, it would these. MEMS based IMU and not open the gate for INSAT-2. One powerful computer on a chip have limitation projected from reduced power to a few watts and propulsion team was non weight to a few hundred grams. availability of 1 Newton thruster. A We had no access or affordability 10 Newton thruster was too big for of gyros or microprocessor in on-orbit mode (Roll/Yaw control) APPLE. This made us to master the

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 technique of pseudo rate damping was confident that if we start in using Pulse Frequency Pulse reverse direction, we will succeed Modulation for all control logics. in Sun Acquisition. I requested Prof This has been later used Dhawan, Prof Rao and others to extensively for IRS and other come to black board and they gave satellites. go ahead. We tried as last attempt 4. Sun Acquisition with one solar of that day, or perhaps last panel not deployed attempt as everyone was losing This is a well reported event in the hope, but we had the Sun story of APPLE, but it is so Acquisition. Rest is the story of the fascinating that I cannot resist successful mission APPLE. once again recalling it on this 5. Great Memories occasion 40 years of APPLE. After Today, after 40 years, as we gather the Solid Apogee Motor firing it as oldies, I recollect many who are was the turn of solar array not with us today. Dr Prabhakar deployment prior to 3-axis Kudva was a big strength in design acquisition. One solar panel and simulation of AOCS. He went deployed but the other did not in back to USA as Professor. I hope spite of all efforts. The 4 pie sun he is doing well there. Dr sensor segments were behind the Murugesan embedded what all folded panes. We had to make use control logics I wanted in the of this unpredicted configuration Control Electronics. He left for for Sun Acquisition. Sun acquisition professorship in Australia. He is had to be done at 6 AM satellite doing very well there. Dr local time. We started with low Anantharam was responsible for spin rate of about 0.2 degree per propulsion and he left for his second, but the space craft walked heavenly journey a few years back. away. Second attempt was also A very lively person with deep not successful and we had to close understanding. that day due to time window. We And, of course, Prof UR Rao, a started cautiously next day even at great visionary, a great leader, smaller spin rate, but the extremely hard working, and a spacecraft walked away again. A great motivator. Let me end with shivering feeling came that we an event, how he motivated us. may be losing the spacecraft. Mr Two ESA AOCS experts were Babu Kalakrishnan, our colleague invited to review whether we from sensors came to me and said could design and develop AOCS for that spacecraft has gone with APPLE, Dr Markland, a British much larger spin rate. That national and Dr Renner, a German moment came as a flash and I national. We had two days of in- realized what was happening. I depth discussion. Dr Markland was

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 very aggressive, but gave no schedule was near impossible to realize. I was suggestion of any kind. Dr Renner leading the team developing Sensors for the was patient and dropped little satellite. With very little knowledge of suggestion here and there. They instruments operating in three-axis satellite, gave their impression to Prof Rao. we could develop the sensors and test Dr Markland said that we have no facilities and successfully operate them in competence and will not be able orbit for two years. In-orbit experience gained to deliver. Dr Renner said that was very valuable for all future missions of though there are some ISRO. weaknesses, but we will be able to deliver as we are fast learners. Best wishes to all the veterans of ISRO, from top to bottom, on 40th anniversary of APPLE. Once they left, Prof Rao called me Dr.T.K.Alex,Former Director,URSC(ISAC) and said that he does not agree K.V.Venkatachari with assessment of Dr Markland and he has full confidence that we will be able to deliver. His confidence made all the difference. I miss him today as real architect of APPLE. Dr.P.S.Goel,Former Director,ISAC REMINISCENCES/MESSAGES My association with APPLE Dr.T.K.Alex APPLE marked a milestone in the evolution of Indian Space Program. The launch of APPLE satellite 40 years back was a memorable event for India, which For APPLE mission I was responsible to placed India among nations having the organise capability to design, build and operate a satellite in Geo-stationary orbit. Technically it  Telemetry Tracking and Command was a great feat. It took great efforts and the (TTC) support in VHF frequency band team faced very many challenges. The time during the early orbit and on-orbit phases of the mission from the TTC stations at SHAR and Ahmedabad with necessary augmentation.  Establishment of a VHF transportable telemetry and command terminal at Fiji Island for transfer orbit phase support.

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981  Establishing a C-band terminal at satellites became my career. We were SHAR for on orbit support for the responsible for the design, development and mission fabrication of a computer based Ground  Coordinate with External agencies for Checkout system and also for testing the integrated spacecraft and its launch from TTC support for the mission during Kourou, French Guyana. The satellite went transfer orbit phase. through several tests in the clean room, in  Establishment of a Satellite Control the thermo vac , a compatibility test with Centre at SHAR interconnecting launcher module at Toulouse and finally full Computer and all supporting TTC tests at launch site and launch from Kourou. stations  Coordinate with DOT for the establishment of fully redundant Being the first Indian communication satellite landlines for data, voice and there were many new features/functions teleprinter links with all supporting which were required to be simulated and TTC stations and mission computer. tested. We got experience of working on a For the first time asynchronous data three axis stabilized satellite with transmission at 1.2 Kbits was planned communication transponders and an AKM for the mission. having solid fuel motor. Integrated satellite tests in 4M thermo vac chamber was also All the above tasks were executed and ISTRAC supported the mission till the end of life. carried out for the first time. We had Lessons learned from operation this mission problems in thermo vac which led to especially in the areas of hardware realisation, evolution of precise temperature control of proximity of the design team and the the subsystems in the thermovac for future operating team were useful in establishing the satellites. ISTRAC S band TTC network. Working with Ariane was also unique. I K.V.Venkatachari,Former Director,ISTRAC visited Kourou to see launch facilities. The REMINISCENCES/MESSAGES clean room and launch tower with vertical vehicle integration were quite informative. V.R.Pratap The test and launch operations were very smooth and and on schedule. The daily meetings with launcher team and co passenger team were very helpful. The life in Kourou was very exciting. There were people of Indian origin settled there who felt proud that India could also launch satellites. Our team's visit to Paramaribo, Surinam was memorable where we were welcomed by Indian origin families. The launch was witnessed by Prof. S. Dhawan, Prof. U R Rao, Dr. APJ Kalam and many others. Working on A glance on Apple tests and launch. Apple was a big step on my learning curve and exciting. APPLE was the first communication satellite of V.R.Pratap, ISAC my career, thereafter communication

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES etc. were decided to be procured. I was asked to carry out the link calculations and plot the A few remembrances of APPLE the first one meter diameter C-Band antenna radiation communication Satellite Project of ISRO Contour projections on the Earth, keeping nadir pointing to Nagpur. It was required to Dr.Surendra Pal be part of the proposal to be submitted to Ariane Space/ESA. With the help of I was associated with the APPLE Spacecraft Mr.R.S.Bhat , I plotted the contour (With Project since its inception, including the manual calculations) , which was later on proposal preparation which was submitted to refined by Mr. CR Srinivasan, for submitting to ESA in 1976. All discussions were taking place ITU and WPC. From the discussions, today I at Cauvery Bhavan, then Headquarters of recollect that ISRO management submitted ISRO, which were led by Prof.J. P. Singh. We the proposal, but were not hopeful, since the had almost two weeks deliberations which launch was on Ariane Launcher were mostly concerned to AOCS, whether it developmental flight and there could be many should be spinner or three axis stabilized more competitors. Today when I recollect the spacecraft? In that time frame spinners were incidences, reason best known to Prof. popular due to the technology available with J.P.Singh, not many senior persons of ISAC, then Hughes Space Systems, who SAC or VSSC were involved in proposal manufactured large spinners for INTELSAT. preparation. Even to Prof. U R Rao I used to go After lots of discussions it was decided to go and brief, though Prof. U R Rao did clear the for Three Axis Stabilized system, looking in to project before submitting to Prof.Dhawan. I the future, with two C-Band Transponders, could see Mr.Narayanan from SAC and Prof. two deployable solar panels and TT&C in VHF Vasagam from VSSC to be main consultant to (Since C-band TT&C ground infrastructure was Prof.J.P.Singh. It was first time I heard TWTA not ready with ISRO, while VHF systems being to be pronounced as,”Twita”, from used for Aryabhata were available and TT&C Mr.Narayanan. To my remembrance requirements were minimal).It was also Pof.Vasagam and Mr. Narayanan had been decided to use the 4th stage Solid motor of earlier, part of some studies conducted in US SLV-3 as apogee boost motor for raising the for communication satellites. orbit. Whole of propulsion system, wheels Once clearance came for the acceptance of the ISRO Proposal, APPLE Project was formed. It was slated to be an inter-centre Project for supply of systems which fell in the expertise domain of a particular ISRO Centre e.g Mainframe and integration and overall management at ISAC, AOCS, propulsion ,wheels, pyros, deployment mechanism and ABM from VSSC and SAC was assigned the task of developing C-band communication systems. I presume there was initially confusion as whether the project should be

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 executed at VSSC or ISAC. Prof.Vasagam as The satellite was integrated and tested inside Project Director and Mr. Ramchandran as the newly constructed 4 meter chamber at Deputy Project Director, both from VSSC Peenya. along with a large team of Engineers came Since others will be writing many things about from VSSC to form the Project Management APPLE spacecraft and their experiences, I will Core Team. It took some time to define and write a few incidences which in my opinion allocate various systems for development to were unique to APPLE and the team involved: various ISRO centres. At ISAC Prof. U.R.Rao followed the Aryabhata Satellite pattern, VHF TT&C Link and Antenna Impedance where largely tasks were assigned to groups Measurements: as per their expertise. ISAC had experience of building and launching Aryabhata Satellite, Since Aryabhata VHF TT&C antenna were but APPLE was a different ball game. APPLE tested ,along with solar panels in the open Project provided funds to various centres, field at Peenya(Presently where LEOS ,Peenya which really gave us an opportunity to buy Police Station and couple of buildings have few equipments and components. The come up),it was planned to do the same for progress of the project in the initial phase was APPLE ,but it was a fully integrated spacecraft slow and there were invisible lines between ,while for Ayrabhata we could take the only VSSC and ISAC teams, which with time got, upper shell with solar panels. After washed away. In late 1979 Prof.U.R.Rao took discussions with all concerned persons. APPLE review of the whole project and started was to be mounted on a non-metallic monitoring activities on day to day basis, to structure to avoid its effects. Prof. U.R.Rao meet the tough launch schedule. Luckily we liked the idea and asked Mr. Katari to get a did get some extra time due to the failure of wooden bull cart. Mounting the flight model the earlier Ariane Launch (I think it was 3rd on the cart, in a pressurised dry nitrogen Developmental Flight) polythene tent was executed by the APPLE was a true forerunner for ISRO’s high integration team led by Mr. V.A .Thomas.The and complex satellites and it was also the first spacecraft was towed to the field by a dozen time ISRO’s various work centre teams healthy persons. Needless to say that, a dry worked in a coherent manner, which later on run was conducted with a mechanical became the trend, protocol and strength of equivalent model. Ground reflections and ISRO for, all future satellite projects. I feel, effect of cart metallic part were minimized going for three axis stabilization configuration using large RF absorbers. Measurements were was a proper decision, though whole successfully carried out. For photograph propulsion system at that time was bought purposes Prof. U. R. Rao asked a bull to be from outside, but did pave way for indigenous put. He gave the photo to an European developments. APPLE project laid the magazine with a caption that Indian space foundation for the development of various technology is meant for the common man and critical spacecraft technologies, used in future rural India. IRS and INSAT Series of spacecrafts. For APPLE most of the electronics, logics and programme were developed within ISRO and provided the much needed psychological boost that we can do.

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 The magazine did publish but a caption: India the neck. Someone applies lemon and salt on has means of manufacturing satellites but no the advice of some locals and had a crying means of transporting it. moment. In Kourou lots of persons of Indian origin, particularly from Puducherry settled. They knew French and Tamil very well. They helped a lot ,to our team in buying daily things and conversing with locals. One couple Mr. Mrs. Couria( Not sure of spelling) were really helpful. For When told to Prof. U.R.Rao, he laughed it Non-Tamil speaking engineers we had to go away. through one of our Tamil speaking colleague. Mr.KSV Seshadari was always ready to help. SOME SMALL STORIES OF KOUROU STAY He also did bargaining for CASIO digital watches for team members to carry, which were delivered at the Cayenne airport. Evenings used to be pleasant, with lots of fun and pranks. A large team of engineers from various In Kourou couple of Pakistanis were also centres went to Kourou. Three persons were staying, who were working for French Foreign put in to an apartment with 3 independent Legion ,a special type of army ,open to bedrooms, common kitchen and bathroom. healthy foreigners ,willing to serve the French Each one of us took enough groceries and army on outscores of France. One day a eatables for some 45 days stay. At Kourou couple came to our side and talked to Prof. airport we were received by Dr.S.P.Kosta. He Vasagam in Urdu. Needless to add, that, they gave lots of instructions in his characteristic were directed to us. His name was Parvez and style, which were to be followed. knew Urdu, Punjabi and French. His Urdu was more of Punjabi than Urdu. His wife a sweet I shared the apartment with Mr. YK Jain and housewife, with a toddler son, was always Mrs.Nalanda Basu. Needless to add that we curious to know about India. She had a assisted Mrs. Nalanda Basu in the kitchen and concept that in India all Muslims were took up the task of cleaning, vegetables Pakistanis and Hindus in Pakistan were cutting etc, and our Indian food was never a Indians. It took us some time to make them problem. For going to work some persons understand that we don’t have Pakistanis in were, who had driving licences, were given India but we have Muslims and they are cars. In our team Y.K.Jain knew driving and did Indians, whose population is more than oblige with his services. The team besides the Pakistan. Parvez and his family called, we satellite, checking jobs, spent time at the three to their home many times for dinner. He nearby supermarket. was with French Legion. He used to get us cola and other grocery items including water In the evening the Indian team members, bottles at concessional rates. particularly from south, used to roam in the open space in between the row apartments in For vegetables and fruits once a week one baniyan and dhoti. They were bitten by some vegetable vendor (Of Indian origin from Bihar insects and there were painful bristles around

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 or Eastern UP), from Suriname used to come . equatorial forest having a CSG optical tracking He was very liberal with Indians and used to station. The abandoned prison buildings were weigh more than asked for and sale at a still enough indicator of the inhumane concessional rate. He will speak Hindi,French treatment meted to prisoners. The famous and Dutch. His name was Ganpati -GirijaNand. novel : PAPILLON and movie are based on this He will come to us and converse over a cup of place, apparently the true story. We were tea. His greatest wish was to dip in holy Ganga trying to locate the buildings and places (I silently wished that his wish should never be mentioned in the novel. We sat on the rocky granted since Holy Ganga was dirty and more beach where prisoners might be taking so in Banaras). He used to tell,” Bhaijee please bath We were trying to imagine as how the come to Suriname , stay in my small-house main character of the novel could manage to and be my guest” swim across the rough sea and reach the An Interesting Anecdote with a few land?. It was first time that I saw green METEOSAT Team Members coloured large iguanas on trees and beach, some of them were of a small crocodile size. It APPLE was a Co-passenger with ESA was a very pleasant trip in a small boat, which METEOSAT. Actually, APPLE was an adaptor sailed through the Kourou river and a few between METEOSAT and CAT module of kilometres in the Atlantic Ocean, of course Ariane Launcher. Once a CSG ( (Guiana Space each one of us took one tablet of AVOMIN, to Centre) person brought couple of METEOSAT avoid sea sickness, since the ocean was very Engineers to APPLE side. METEOSAT had rough. made the integration hall as a large anechoic VISIT TO SURINAME chamber and had almost EIGHT PDP -11 computers, network analyzers and hordes of On a long week end a bus was hired to visit multiple test equipment. The CSG person told Paramaribo. It was a very pleasant journey to the METEOSAT persons that see Indians crossing three rivers, using a large barge, have brought much smaller number of where bus was also loaded on it. The whole equipment and a few RF absorbers, including journey was through the thick equatorial rain one PDP-11 for GC operations. To this one of forest. At the entrance to the Suriname the METEOSAT person replied, “They can’t territory, we met our friend Ganpati afford”. I remember from our side the prompt Girijanand. He left his truck and came with us response was,” You need ideas and not large and helped in exchanging franks to Suriname number of equipment”. The METEOSAT Team currency. He again requested us to visit his member had an audacity to retort,” If you house, which we agreed. Paramaribo is the can’t afford then only can have ideas”, capital and largest settlement in Suriname VISIT TO DEVIL’s ISLAND (Erstwhile Dutch Guinea). It was a beautiful place. We visited one Hindu temple and a On one of the Sundays a visit for a few of us Church. We were treated at both places with was arranged to Devi’s island. It was a small lots of love and respect. One morning we penal colony of Cayenne , operated in the 19th were invited for breakfast to one Ex-MP’s and 20th century in the Salvation Island of house (He was of Indian origin). In the evening French Guanine. The other two islands are Mr. Ganapati Girijanand took us to his house. While travelling he said on the main road Royale and St.Joseph Isles. It is a group of there are two large buildings, one is the three isles in Atlantic Ocean with lush green

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 Presidential Palace, next is my small house. Former: Vice Chancellor DIAT Pune and On reaching to his house we realized that the Small house was a much larger building with Distinguished Scientist, Associate lots of garden, hordes of servants, cars and all Director, Senior Advisor SATNAV modern facilities. We came to know that at one time he was also an MP. In Suriname lots (ISRO),ISAC of business persons and officials were of Indian origin whose forefathers migrated from Bihar and Eastern UP as sugar cane labourers. They are still maintaining their culture and heritage. We were welcomed to his house for a big Indian dinner, spread over a large table, both vegetarian and non-vegetarian. Along with various types of colas, he opened large bottles of Black and Red Label whisky bottles. The evening was wonderful. I could never imagine the so called humble vegetables vendor to be such a big host. I don’t wish to leave anything to the imagination as how our colleagues behaved there. The abundant availability of fine liquor made most of the person to drink more than eating. Once the holy water went inside (Liquor), everyone who claimed to be not knowing or understanding HINDI started speaking in Hindi with the host, his family and friends. Around 10 PM, myself, Dr.PS.Goel and Mr.Leo-Lasardo, who were limited to Cola, only carried manually the totally HINDI speaking crowd to the guest house where we were staying. I feel liquor is the best way to make someone speak in ENGLISH, HINDI and PUNJABI. Needless to add that, we three profusely thanked the wonderful host. I attended several dinners and lunches but nothing compared to the one offered by Shri Ganpati Girijanand. Dr.S.PAL

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES There are very many interesting things we have done for APPLE. I will try and recall a Dr.P.S.Nair few of these which touched my heart. Of course, time and age have a big effect on APPLE was the first communication spacecraft memory. of ISRO for which I was nominated Project Engineer for Mechanical Systems. One thing I remember and cannot forget is an order conveyed to us from ISRO HQ that For me personally, I consider APPLE as my “within the next few days “we need to graduation in spacecraft structural prepare and send a mathematical dynamic engineering after an exciting schooling in model of APPLE satellite to Ariane/Apex. At satellite technology through Aryabhata, that time, we were yet to start design work Rohini and other pre-APPLE projects. My and gather all essential input data. We were “post-graduation” came later with INSAT 2 told that this requirement is based on an series (including 2E) of spacecraft. Learning already agreed schedule with Ariane and the never stopped as many more interesting and order is with the knowledge of Chairman exciting projects and development activities ISRO. came along when we suddenly found that we reached the age limit for government work. After a lot of internal arguments and With the company of a very warm group of expression of concerns, I do remember being colleagues, seniors and juniors, all blinded by called to Professor Rao’s chamber. He the very interesting and exciting activities that explained the urgency of requirement. I required total dedication, I feel life could not slowly tried to explain to him activities like have been any better. The life with APPLE for design and analyses that need to precede the me was especially full of challenges and preparation of the mathematical model even excitement. if the model is simple. I also told what we could do and how fast. After listening to me, Even today, when I sit down for design of a without much discussion, I saw him taking the Lunar Lander craft with an Orbit Transfer phone and explaining whatever I told him in a Stage assembled below for launch into GTO, much simpler and more convincing way (to on way to Moon, the experience of APPLE prof Dhawan). After their talk he told me yes that carried METEOSAT on top comes into my take the minimum time and do what is head with all associated experiences. required. I was most pleasantly surprised at the turn of events, and all were happy to get into the task of design and modelling very fast. Till then I was thinking Prof Rao,as a scientist, will not understand or appreciate such problems. But Prof. Rao by doing what he did showed that he is better than the best engineer. As I already mentioned APPLE was the most intense and practical learning experience I had. There are countless things that can be

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 listed but most of you will not be interested. Paris, I remember giving company to Weather it is our first effort on delivery of Mr.Narasimhan who wanted to taste Snails as mathematical dynamic models, coupled load insisted by his French teacher. analyses, formal definition of qualification and A major APPLE activity was the Vibration tests test philosophy and so on. I do remember the done at SOPEMEA along with METEOSAT, an very friendly professional interactions we had already proven spacecraft bus, which planned with John Elwood of ESTEC who gave us to make another flight in LO3. When we confidence that others in the field also think reached SOPEMEA, Toulouse, the teams from like us. I remember when I had an argument LO3 and facilities were very curious to see and with disagreement on some structural topic interact with an inexperienced team from and Elwood supported us, Vasagam telling India talking about spacecraft and getting both of us the basic shortcomings of all ready for a very critical vibration test complex structures people around the world. I could even for them. They were genuinely take it only as a compliment then. concerned about our design. In fact, some of In this context I must say that much more them in a lighter vein asked me weather we than technical, I had a great learning have come prepared for packing and carrying experience in effective technical coordination back broken pieces. We got ready and had a as a Project Engineer, in Apple. I have been full discussion on the testing procedures. They rebuked by Director for non-compliance of placed a red emergency test abort button in fabrication drawing delivery dates to HAL and front of me to abort the test just in case Apple several such other similar slippages. There are appeared in any danger. I was most anxious many who came forward and supported me in and test run was completed without any my coordination task. I must mention that the manual abort. My heart also vibrated with Project Directors office was indeed a very Apple. We looked at results and were happy special place for many of us. Of course, Shri. to be congratulated by all for a successful test. Vasagam was easily approachable and was a We also were informed that METEOSAT storehouse of ideas, suggestions and also model had suffered some structural damages questions without interfering in our normal in spite of input being well within expected work. What made the PD’s office most values. This test was like a milestone event effective and attractive for some of us was the and our words gained much more weightage presence of Shri Velayudhan. He helped after this. everyone approaching in very many ways There were many interesting incidents while much beyond the scope of his duty. we were getting ready with the qualification Some of us were staying in Toulouse for model for tests. I have sent a record number extended periods experimenting with many of faxes to Bangalore reporting progress and things including food. Vietnamese hotel food also requesting help. There were reports of was good but not possible often, and I started fastener failure in AKM support frame during cooking a special mixed vegetable curry in the tests at SHAR on a replica model of APPLE. common kitchen of the hostel where Rajendra Following this we decided to change bolts and Prasad was staying. This curry-I call it requested for materials and a mechanic Toulouse curry- became my favourite dish several times. After some time, we got the back in India also because my daughter message that Prof Rao is arriving with bolts started liking it much. On way to Toulouse, in and struts. Mr. Mason of APEX asks us why

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 Prof Rao is coming without sending a many new things even for SOPEMEA. There mechanic. We had no answers as a Mechanic were reports in the local press about vibration never came but we changed the AKM support testing on the very tall LO3 payload stack bolts to high quality bolts brought by Prof consisting of CAT, APPLE and METEOSAT. Rao. Of course, by then, we knew the likely A very similar procedure was followed for reason for bolt failure at SHAR-an un-notched flight model also. Everything went well this high input test levels apart from poor quality time. I had by then developed a sentimental bolts. You must remember that nominal un- attachment with APPLE. After vibration tests notched Sinusoidal input at base for APPLE on APPLE at SOPEMEA it was straight shipped was 6g. Without notching (to limit QSL as per to Kourou Launch facilities. As a structures CLA) at resonance no well-designed satellite person I had no physical activity at Launch Pad can survive such levels. and so I was not required to go to Kourou. Another less known incident related to ISROs APPLE went from Toulouse to Kourou, and I first 900mm diameter parabolic CFRP dish bid goodbye to APPLE at Toulouse and came antenna that arrived as a separate package back to Bangalore. from CMS/VSSC Trivandrum. When the You all know the on-orbit performance of package was opened, we found that the APPLE including the non-deployment of one Aluminium Alloy end fittings of the supporting of the solar panels. I was not personally legs were all de-bonded and lying loose. We involved in any post launch activities of APPLE were shocked. As if by foresight the package and hence have nothing to add on that. had also contained room temperature curing adhesives and a procedure for repair. We did Let me express special thanks to the what was required and saved the day. organisers of this special meet on APPLE and APPLE helped us upgrade many technologies also for inviting me to say a few words. Also, I for satellite building. We established formal must use this occasion to thank all my FE modelling and analyses procedures with colleagues, juniors and seniors, who made my APPLE. ASKA software was bought. A semi- Apple experience very exciting and monocoque thrust tube with a clamp band professionally rewarding. interface was used for the main structure. Dr.P.S.Nair,Project Engineer, During detailed design phase we wanted to reduce the mass of APPLE structure, but could Mechanical Systems,ISAC not, as it would invalidate the mathematical dynamic model we had already supplied to Ariane. With APPLE we started use of honeycomb sandwich construction with potted inserts for equipment deck. In qualification testing it was a very comprehensive exposure and adaptation of state of art tools and technologies. As explained the vibration tests in SOPEMEA on APPLE qualification model was done ahead of Flight model work. The whole test involved

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES out the assembly operations and as well the testing of the satellite for its performance Reminiscence after 40years! verifications. It is a multi-disciplinary activity, needing careful study and execution of V.A.Thomas needed activities, with careful attention in handling the spacecraft elements, ground During the APPLE Project days, I had a display elements and test systems, till the spacecraft in my cabin, and it read: “All the Last-Minute is launched. Ideas and Untested Space Systems are blessed with Hundred Percent Failures”! While ‘Aryabhata’ was a simple spinner ISRO learned the basics of complex satellite satellite, APPLE was a 3-axi stabilised satellite technology through the design, carrying 2 C-band transponders for making developments, assembly and testing, launch communication applications, from GEO and on-orbit operation of India’s first satellite stationary orbit. It had many new sensitive ‘ARYABHATA’, launched in 1975. If we take elements, like solar array drives, momentum this to be an Undergraduate course, APPLE wheels, gyros, scanning sensors; hazardous project was a Masters course to further and high-pressure systems to operate harness the technology for realising future monopropellant control rockets; a solid operational GEO Communication satellites for propellant-based apogee boost motor with the country. APPLE project was conceived in ignitor and initiators, and pyro devices in it. response to a free launch offer from European Many operations involving ordinances Space Agency (ESA) onboard the Ariane LO-3 systems, hazardous and high-pressure Test Flight, from Guyana Space Centre, systems, filling and draining of corrosive towards the end of 1978 (launched in June, propellants etc needed special clearances for 1981). the safety of people and facilities, during the ground operations. These were new to the AIT I was inducted to APPLE project team through team. During the course of the project, we an office order from Chairman ISRO, as could successfully develop safe procedures Project Engineer, Spacecraft Assembly, and skills to carry out these operations Integration and Tests (AIT). At that time, I did without any accidents/incidents. I am really not have any prior information on this project. happy that after 40 years of the APPLE launch, The AIT Team resolves the intra-system and I am here to share the memories to you. inter-system interfaces, responsible to carry Soon after entering the project, I realised that most of the sensitive and hazardous new elements are being used for the first time in ISRO projects and the developing teams are learning and attempting to develop these from scratch. They are also considering import options, if there is a time crunch. As a system integrator, I was needing the exact details of their sizes, mounting details, mass-properties, and the special care needed to accommodate

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 these elements in the satellite. Many were APPLE was a middle passenger in the LO-3 not knowing these and we had to enlighten stack, sitting on the top of CAT (Ariane them the need for additional provisions Technological Capsule), carrying on the top a needed to meet the safety norms and monitor highly sensitive, higher weight Meteorological their subsystem status while on ground and in Satellite (METEOSAT). One METOSAT satellite orbit. We had many steps of two-way was in operation in orbit and its prototype learnings and came up with, may not be the was being attempted for launch, as a second best, but liveable solutions. satellite for standby operations. Any changes APPLE was the first satellite involving so many in this satellite were difficult for teams from various ISRO Centres/units. Each implementation. were separate work centres, located at By early 1978, we came out with the assembly different cities and concentrating on their of the Mechanical model of APPLE with special skills for their assigned tasks, having simulated subsystems and it underwent their own standards and work practices, not strength and rigidity tests. Since the suitable matching to the satellite space hardware dynamic test facilities were available only at needs. ISRO had to set-up an independent SHAR Centre the tests were done there. new safety group to bring uniform safety During a lateral axis test one strut supporting guidelines and practices, including the the ABM dummy failed. This needed to be spacecraft needs. So a considerable amount replaced. of efforts went to integrate these teams to But the model for joint stack test was at the satellite system practices. Toulouse already, for the thermal model tests Even at Bangalore, we were transforming the of APPLE. So we had to take an HAL engineer organisational set-up from ISRO Satellite with us to Toulouse and refit the modified System Project (ISSP) to a multi project ISRO struts there, to strengthen the ABM support. Satellite Centre (ISAC) by adding additional French law does restrict the weekend and manpower, office space, laboratories, High- extended hours of work. We have to do these bay areas and clean rooms etc. In fact, we without making official declarations. We did were still working from temporary industrial the reworks and used the model for LO-3 Joint sheds converted to electronic labs. Existing Stack Qualification tests and it got qualified. facilities could not handle a satellite of APPLE This model was the ‘stake satellite’ for LO-3 class, as some of you may remember. The Flight, in case we were delayed for the new generation ISRO engineers now working delivery of Flight model of APPLE for the with modern amenities, may feel sorry for the flight! ISRO teams who worked earlier with the In 1979 we were ready with flight model of limited facilities, in the ‘Stone Age’ of ISRO! APPLE after the assembly, integration and We had to establish a clean room, with a part acceptance tests at ISAC. The satellite with a of it as High-bay with over-head crane for host of test equipment and accessories was handling the assembly operations and the rest transported by a Guppy aircraft (UK Company) with a low bay for electronic sub-system to Toulouse and did the acceptance test for assembly. A High-bay mechanical testing area, the stack, both electrical and mechanical with mobile clean-air modules, was used for tests. such operations.

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 At this time, there was a failure in the LO-2 panels did not deploy fully, making it lame test flight for Ariane and ESA postponed the bird. Our Mission and Control teams made LO-3 launch, initially up to April of 1981. We efforts and innovatively used APPLE in orbit were asked to transport APPLE flight unit to for 9 months plus for various applications, Kourou and keep it under safe storage at CSG until it ran out of fuel! Maybe it gave better clean room. We had to generate a safe experience for survival! storage plan for APPLE then. There were some When I came back from Kourou, after needs to nitrogen purging for SADA units reshipping our equipment, looked at my inside the satellite. We also needed to check display in my room. I wonder now, is it a last the batteries kept in safe outside freezer. word! May be or may not be, but one should We got a Special Air France cargo flight to learn from a Failure! This resulted in ISAC transport the APPLE satellite from Toulouse to (URSC) forming the Spacecraft Mechanisms Cayenne in French Guyana, with the help of Group! French Aviation Minister. As per French laws, V.A.Thomas,Project Engineer,AIT,ISAC one cannot use any foreign aircraft to transport a cargo within the French territory! No one knew this law until 3 days prior to transport! Me and two more of my colleagues went to Kourou and verified the storage arrangements and returned to India. In March 1981, ESA announced a schedule for LO-3 launch campaign and the flight LO-3. APPLE team went to Kourou in batches in April and we had a few extra tests added due to the storage. We were totally 45 persons, distributed over the period for the campaign. Apple tests and final preparations went as per plan and flight readiness review, launch rehearsals etc. also went well, as planned. Prof UR Rao and Mr. Vasagam came a week ahead of launch for final reviews and Prof Dhawan arrived two days prior to launch. All operations went ok and as planned. The countdown and launch were perfect APPLE reached safe in orbit. Only disappointment for me was that I could see the launch only on TV monitors, as I was in the Launch Block House for Apple final operations and certifying our readiness for launch. We had one partially disabling failure in APPLE to start with initial orbital life. One of the solar

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES Then the pressure came from European Space Agency that our Spacecraft had to carry on N.Vedachalam top a 1000Kg Meteosat spacecraft. We worked together and arrived at a central MEMOIR ON APPLE cylindrical load bearing structural configuration to accommodate all the sub It was a sleepless night while staying at the systems inside and outside. ESA demanded a ISRO H.Q guest house in the Cauvery Bhavan penalty clause, if ISRO not ready for launch for our beloved leader “APPLE Project schedule of Ariane-3. We once again Director” and me while we were struggling to circumvented by assuring ESA that in the arrive at the overall configuration of the event of delay, they can launch the Structural APPLE Spacecraft. The following day Model of APPLE Space craft as it was qualified appointment with Chairman ISRO at IISc the for flight load. choice of the spacecraft configuration had to be selected among the proposals of ISAC, SAC, Perhaps the APPLE Project was started and VSSC. Shri PP Kale of SAC our neighbour from the concept stage onwards through was also awake! ISAC proposal was 350 Kg sleepless nights; it became a project culture Satellite for a GTO flight. Our proposal was by the entire project team APPLE to invited first by Chairman ISRO after he noticed successfully accomplish the project on time our red eyes!! aboard Ariane -3 flight on June 19, 1981 with the leadership of our Project Director Padma A 600 Kg Geostationary Spacecraft with Shree Prof RM VASAGAM. SLV-3 fourth stage as the Apogee Boost Motor, 3 Axis Body Stabilized by Momentum N.VEDACHALAM. Wheel, Reaction Control Thrusters, Driven Project Manager, MWA & SADA.VSSC deployable Solar Array, and one C Band Transponder as pay load. Shri. PP Kale also spent sleepless night and arrived at a similar configuration! In a matter of few minutes discussion ISRO Chairman decided on our proposal and gave approval for further progress.

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES India’s first Satellite Launch Vehicle SLV-3. The 672 kg Satellite with an on orbit life of 2 L.Satyamurthy years,served as the test bed for the Ruby day of APPLE Satellite Indian telecommunications space Nostalgia down the Memory Lane infrastructure arena. The satellite was used in several communication experiments 19th April 2021 marks the Ruby day- including relay of TV and Radio Networking completion of 40 years after the launch of which was one of the cherished dreams of APPLE (Ariane Passenger Payload experiment) Dr.VikramSarabai and which has lead to the Satellite, the India’s first indigenous present day Direct to Home (DTH) TV and experimental Communication Satellite. The Radio broadcast. Satellite was launched on Ariane Rocket, a launch vehicle of the European Space agency For many us who just had a short experience (ESA), from the Guyana Space Centre at of Satellite technology through Aryabhata and Kourou in French Guyana, South America. Bhaskara Satellite projects, it was indeed a While the satellite Aryabhata became the great challenge to face the technology harbinger for the Indian Satellite program, demands for the development of aGeo Apple Communication Satellite and Bhaskara Stationary communication Satellite to be Remote Sensing Satellite, paved the way for placed at 36000 Kms above the earth, at the development of myriad of advanced Indian orbital space and make it earth Satellites, launch vehicles and inter planetary pointing for communication Antennas within missions, executed under one agency ISRO. the specified accuracy in the three axis and APPLE Satellite the first Three Sun pointing of Solar arrays, both rotating in Axes Stabilized experimental geostationary sa different planes with satellite moving at earth tellite built by ISRO, was designed and built at rotational speed, which operation is known as the Industrial sheds of Peenya situated at the three axis body stabilization. Thanks to vision outskirts of Bangalore. The Solid propellant and passion of the then Project Director based Apogee Boost Motor to circularize Dr.R.M.Vasagam in not only conceiving a state APPLE's orbit was derived from fourth stage of of the art technology and configuration of a compact satellite of this kind, but also getting a free launch opportunity on the third experimental flight of Ariane launch vehicle, from ESA. The technologies of Bus and Payload systems needed to be qualified with in stringent project schedule, was a huge challenge and we the team did it exemplarily, thanks to work culture and dedication of different centers of ISRO, ably supported by the then Director of the lead centre Prof. U.R.Rao and encouragement by Prof. Satish Dhawan, the then chairman, ISRO/Secretary Dept of Space.

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 The dream and hard work culminated in the Apple was really a quintessential Satellite realization of the Satellite in record time with surpassing in every front and which lead the successful launch of APPLE Satellite, it’s on germination of INSAT and GSAT orbit positioning at 102 Deg East Longitude communication satellites of today. This would and Payload operations for Telecom and not have been possible but for the unique Audio/Video broadcast experiments which ISRO culture. That is, the infectious was a real saga and memorable event to enthusiasm and unbridled passion for Space remember even today. Science and Technology which has been the For us and the team at different work centers hallmark of this team’s knowledge, hard work responsible for design, fabrication, AIT, and dedication. Quality assurance and Test and evaluation of On this day we remember the following subsystems and Spacecraft, one can imagine colleagues and guides who are not with us the hardships/tribulations one had to today: undergo. The Qualification and acceptance of the various new technologies of Mechanical Prof.SatishDhavn system , Power, TTC and AOCS, the Inertial Prof.U.R.Rao systems like Momentum wheels, Solar array drives and Pyros, Solid ABM and Propulsion Col.N Pant system, Payload and the Integrated Satellite was a total effort of APPLE project supported Dr.Anantharam by every center’s team. The successful Dr.K.N.Shankara and few others integrated Satellite Thermo Vaccum test for 21 Days, Spacecraft Dynamic test in all up L.S.Satyamurthy,SRG,ISAC launch configuration and Antenna performance test on Bullock cart platform President, Suquino Telehealth and Vice before the shipment of Space craft to the President, Planet Aerospace Formerly: launch base at Korou was the grand finally of Director Antrix and Program Director, the project before launch. Telemedicine, ISRO Hq The mission operations team at ISAC and ISTRAC, for the first time, had other challenges like precise timing for commanding for one shot firing of the Solid ABM for Apogee boosting, post orbit determination, drift orbit manoeuvre, on station positioning and Station keeping operations, IOT and Payload operations. In the end the Apple satellite, except for non deployment one side Solar panel on north side resulting in modified thermal management, every subsystem performance including the Solid ABM, Indigenous Momentum wheel, Payload and other systems, was outstanding and satellite out lived beyond 2 years design life.

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES The pinnacle of the mission operations was the “Pitch Rotation” carried out every day for Dr.S.Rangarajan a few hours around local midnight to prevent sun rays falling on the earth sensor and raising As a member of the Mission Planning and its temperature beyond the allowed limits. Operations team for APPLE, I was part and Switching to a spin mode for a few hours and parcel of the excitements, agonies and reacquiring 3-axis stabilized mode for the rest triumphs of this project. The lessons learnt of the day allowed the Apple Utilisation here prepared me to tackle many Program (AUP) to continue the variety of contingencies in future missions. As the PD experiments, participated by premier told an informal gathering after the successful institutions and departments. initial phase operations, the L in APPLE stands for a “L” board satellite! Thus, my colleagues and I got the best On-Job When the north solar panel did not deploy, Training with a real satellite, better than any not only did it result in the loss of half the simulator, for more than 2 years with a power generated, but also led to a host of communication satellite in a geostationary consequent problems, including the blocking orbit, paving the way for the INSAT of part of the sensors and thermal problems programme. due to the non availability of north OSR for heat radiation. The mission team worked with Thanks, APPLE, you made me my career! all the subsystem experts and revised the procedures and operational sequences. E.g., Dr. S. Rangarajan • Innovative methods of computing the spin rate, Former Director, MCF • Successful Sun acquisition even when the sensor information was only partial, • Gradually arresting the post-ABM eastward drift by firing RCS thrusters, • Use of external network stations for TT&C

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES Sub carrier modulation. As it used error Detection only, Command transmission had 4 Sri.R K Rajangam frames repetition to increase command execution probability. Two types of commands viz. on/off and data commands are provided. Digital implementation of Non- Coherent FSK demodulation is used. Two step operations were built in for critical commands with a clear protocol. SPECIFICATIONS TTC Bit rate 100 bps (Telemetry, Tracking and Command) of Type of code BCH 31,16 APPLE works in VHF . Frame format 31 BITS Message format 4 Frame with 10 bit SPECIFICATIONS gap between each Word format frame Frame length 64words Modulation 16 bits Subcarrier frequency PCM /FSK /FM Word length 8 bits 3.125 AND 5.55 KHZ Sampling rate 2/4/16/32/ seconds No. Of commands FOR “0”& “1” on/off 255 Bit rate 256 bits/sec No. Of commands DATA 7 Frame sync code 24 bits No of subframe 8 Onboard timer 32 BITS with 8 ms TM and TC systems are realised using CMOS digital ICS to reduce the power consumption Modulation resolution to barest minimum. Both the system are fully PCM /PSK/ PM redundant and active all the time Subcarrier frequency 32 KHZ The communication system of APPLE worked in VHF. AM was selected for TC link and PM Frame length 64words for TM link. Four monopoles were used for TTC antenna to provide near omni radiation Word length 8 bits pattern. Sampling rate 2/4/16/32/ seconds On orbit performance of TTC system was Bit rate 256 bits/sec excellent and It has supported the mission throughout. Frame sync code 24 bits R.K.RAJANGAM No of subframe 8 Onboard timer 32 BITS with 8 ms Former DD, RCA, ISAC resolution Modulation PCM /PSK/ PM Subcarrier frequency 32 KHZ Telecommand provides uplink from ground to Spacecraft. For the first time, TC system of APPLE used error correcting code (BCH) for command link to provide error free commanding.TC data rate is 100 BPS and it used FSK (Frequency Shift Keying) as

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES into Space Odyssey and is steadily progressing towards the fifth position in the world with H.Bhojraj the initiation of great stalwarts like Prof. Sarabhai, Prof. Dhawan and Prof. U R Rao. My Journey with ISRO: I joined ISRO on In one of the regular review visits of Prof. November 7, 1972, after attending a Dhawan to Peenya, Dr Rao introduced me to recruitment interview held in October at the Prof Dhawan as: “He is the best painter”. Yes, Indian Institute of Science (IISc) and was the whole satellite including all subsystem headed by Dr S P Kosta. I remember Mr packages was painted by me with specified Thomas was asking me the Moment of Inertia thickness standard as per the Russian equation M/I=f/y=E/R and I feel that I was Standards with Russian paints (Thermal very fortunate to join ISRO which gave me Control Coatings). everything in my life. We are very grateful to For the APPLE spacecraft, I got assistance ISRO from Mr Sreenivasachar to do the painting which is technically called thermal control ARYABHATA, the first satellite of INDIA that coating. For the first time in APPLE, we used was fabricated in the PEENYA SHEDS by the flexible OSR and Multi-Layer Insulation almost the same team has propelled INDIA that was developed by Mr P P Gupta and Mr Rastogi. The APPLE satellite was the first three axes stabilised and a thermal balance test was approved in CNES Facility in Toulouse, France. The only eight-member team under the leadership of Mr H Narayanamurthy, toiled day and night for 37 days and completed the test successfully.

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 many foreign dignitaries and even presented my first Acupressure book to them. I thank Mr P.Ramachandran, who gave such brilliant ideas continuously during our weekly review meetings of the INSAT 2 series as Project Director, for encouraging me in my The Picture above: During the last phase of extracurricular activities. Even today our the test, Chairman ISRO, Prof Dhawan and Academy for Acupressure and Acupuncture Director. ISAC Prof. U R Rao visited CNES to (AAA) is involved in Acupressure research for review the results. Mr Narayanamurthy eyesight improvement at the National level. briefed them for two hours and they were I thank all my mentors for giving me their about to leave. We the team members were knowledge and support for our growth. there to say goodbye to them. I just took the initiative to go near Prof Dhawan and requested him for a group photo with them. He readily agreed and that the black and white photograph is a treasure for me now. After two years I met both of them and got their signature on that photograph. It gives us great satisfaction that we could work closely Signing off with Best Memories, with such great stalwarts in our life span. H BHOJRAJ, Thermal Testing and Fabrication Section I recall the recommendation letter given by Dr R M Vasagam for my MS admission to Arizona State University, USA and I got through the admission process as well. However, I could not join the course due to unforeseen family circumstances which I now consider as a blessing. Our PD (Project Director) Ramachandran is my wonderful supporter, not only in the technical field during the INSAT 2A project but also in my Acupressure journey. He introduced me to

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES that the test would safely pass through. APPLE provided an opportunity for young engineers Dr.M Sambasiva Rao like me, fresh from college, to build strong technical foundation for the career ahead. I am really thankful to ISRO for that. Dr.M.Sambasiva Rao, Structures Group, ISAC Dr.N Ramani Forty years after the launch of APPLE, the first It is great to reminisce the epoch-making day Indian Communication Spacecraft, it gives me when Apple mission took birth, 40 years ago. great pleasure to recollect my participation in It was first for ISRO in many ways. For the the Project. At that time, we already had mission team, it was the first time that it reasonably good Finite Element Structural planned and executed orbit manoeuvres. Analysis software, completely indigenously Though the mission was not a success in the developed and successfully applied to conventional sense, in provided great many spacecraft like Aryabhata, Bhaskara etc. challenges and many a learning opportunity. I Association with CNES helped us develop new consider myself very fortunate and cherish concepts like Modal Effective Masses and new the GOD given opportunity to have been a procedures for generating Low Order Models, part of a team of specialists engaged in a Coupled Load Analysis, Subsystem pioneering activity for our Nation. GOD Bless Specifications, Notching etc., to address the us all. complex dynamic load environment faced by the spacecraft. They were integrated into Dr.Ramani,ISAC indigenous as well as commercial software like NASTRAN, enhancing our analysis ---------- capability significantly. It was very useful in accurately predicting the structural performance of APPLE, which was sandwiched between Meteosat spacecraft at the top and CAT module at the bottom, in the LO3 Stack, to be launched by ARIANE. I remember it was a bit frightening to watch from a close distance, the passing through resonances of the tall LO3 Stack, during vibration testing. But we had confidence in our analysis results

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 responsible for the offline data processing, REMINISCENCES/MESSAGES orbit/attitude/manoeuvre processing and other processing requirements. APPLE was P.J.Bhat perhaps the first mission wherein, hardware Data Processing Systems for APPLE and software teams from different ISRO Mission centres worked together to realise the ground systems for real-time mission operations. The real-time software consisted of components from SHAR Computer Facilities (Environmental software for data acquisition and display) and ISRO Satellite Centre (Data processing). It was for the first time by ISRO that real-time displays were realized using the very basic ANSI CRT terminals. In the absence of any operating system on TCD-316, the total The Very early satellite missions of ISRO, software system was realized jointly by the namely, Aryabhata, Bhaskara and APPLE, have teams from SHAR and ISAC. Offline data provided platforms for learning towards processing systems were realized by ISAC building robust systems in different domains team on IRIS-55. The experience gained in this of satellite technology, which have fructified mission contributed to a large extent towards into very reliable indigenous systems realization of a fully fledged state of art commissioned for current missions. Ground SCHEMACS systems for IRS1A/INSAT-2A, based satellite data acquisition, health enhanced version of which have been monitoring, control and data processing supporting all the remote sensing, systems are not an exception to this fact. communication, science and interplanetary Today, ISRO has very robust and reliable missions at ISRAC and MCF. Other software systems established in this domain, systems for Orbit, Attitude, Manoeuvre, responsible for the smooth conduct of mission Station keeping etc. were realized by ISAC operations of all satellite missions from MCF teams on IRIS-55. Overall, it was a very and ISTRAC. This has been possible primarily valuable and useful experience especially for due to the very basic level of learning that we software teams at ISAC and SHAR, realizing had gone through, constrained by the very the software systems for APPLE mission. primitive computer resources during these P.J.Bhat,Mission,ISAC early missions. Specifically for APPLE mission, a totally indigenous 16 bit minicomputer TDC- 316 (built by ECIL, Hyderabad), with 32KB memory, was responsible for real-time telemetry (TM) data acquisition, processing, storage and subsystem wise real-time display of processed parameters. TM was received through an in-house developed hardware interface and stored on magnetic tapes. The tapes were physically moved to another mainframe computer IRIS-55, which was

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES Geostationary orbit and subsequent in orbit maintenance of APPLE. Dr.V.S.Iyengar  Experience thus gained was  Designation in APPLE Project: invaluable, provided the groundwork Operations Director. and shortened all aspects of realization of the indigenous (much  Function: Overall in charge of Mission more complicated ) combined Analysis and Mission Operations for communications and weather APPLE Satellite. satellites of INSAT Series  Associated with APPLE Project since Dr.V.S.Iyengar,Operations Manager inception. -----  Accompanied R.M.Vasagam and P.Ramachandran to ESA IN 1978 & 1979 for discussions of APPLE Launch window compatible with co passenger Meteor at and for Launch and early orbit phases support of ESA ground stations for APPLE.  Led the Indian Mission and Project teams for a (10 day) detailed discussion with ESA team ( in 1980 ) for ensuring compatibility and finalization of ESA support for APPLE.  Led the Mission team for developing the detailed time line and support plans & procedures documentation together with the Spacecraft system teams.  Oversaw the ground support operations from launch through orbit raising, drift and in orbit checkouts of APPLE and establishment on station in

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES development , each and every subsystem and the integrated payload were V.Ramaiah subjected to thorough endurance and APPLE COMMUNICATIONS PAYLOAD environmental tests. The existing environmental test chambers were not Four decades back, on June 19,1981 we big enough to accommodate the were witness to the successful launch of integrated payload. We devised Apple satellite from Kourou by Ariane an ingenious way of folding the donut launch vehicle to its designated location in shaped integrated payload panel for the geostationary orbit. testing using the existing environmental test chambers. With all these Space Applications Centre was concentrated efforts a fully qualified responsible for the supply of payload for payload was completed and delivered the Apple spacecraft. For this purpose a well in time for integration with the team led by Mr. Leo Lasrado was set up to satellite. Thereafter, the payload was design, develop, fabricate, test and supply subjected to tests at various stages a space qualified C-band communication including the integrated satellite level payload for the Apple satellite fully tests, combined stack tests in ESA complying with the Apple satellite facilities at Toulouse, tests during the imposed limits on the permissible launch campaign at Kourou and post payload weight and the delivery schedule. launch in orbit checkouts. The payload These restrictions left no leeway for performance remained flawless and committing any mistakes or occurrence of stable all through. Subsequent to the failures during various phases of the successful launch of the Apple satellite, development and testing of the payload. the payload was used for conducting The payload team had put in meticulous several technological and application and long hours of hard work to comply demonstration experiments over a period with all the specifications. For the of two years. integrated payload we had to make special efforts for meeting the The successful completion of the Apple requirements of thermal distribution (no payload project had provided a much hot spots) as well as compliance to the needed vent for the pent up tension EMI/EMC specifications. After initial and stress of four years of relentless hard work by the payload team and gave way for jubilation and immense satisfaction for a job well done. It was wonderful working under the able leadership of Dr.RM Vasagam, Project Director, Apple Project. V.Ramaiah, Deputy Project Director,APPLE Payload,SAC

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 REMINISCENCES/MESSAGES overall PA plan and periodically monitor implementation of the same through the PRODUCT ASSURANCE PROGRAMME FOR various phase of the programme. Amongst APPLE SPACECRAFT the various task elements, emphasis was on the following: Sri.S.G.Raghavan 1. PA support during the design phase in Generation and implementation of an terms of Parts and Materials integrated Product Assurance(PA) plan selection, reliability apportionment, encompassing quality, reliability and safety assessment of candidate assurance aspects for APPLE spacecraft to configurations and preliminary ensure that the performance and mission reliability estimates. Identification of objectives are fully met was a highly potential failure modes and their challenging one, considering the many new criticalities, assessment and indigenous technology developments had to elimination of single point failures. be appropriately evaluated in terms of design assurance, process and manufacturing 2. Preliminary Design review(PDR) controls, demonstration of adequate margins during development, Critical Design from environmental standpoint in the Review(CDR) post -qualification of absence of heritage in the earlier missions. sub-systems and integrated The protocols had to be evolved deriving from spacecraft, Pre-Shipment Review the limited expertise the Product Assurance post- flight model AIT and acceptance team had gained during the Aryabhatta and test phases and Mission Readiness Bhaskara programme. Review(MRR) were major milestones. An Apex Product Assurance Board (PAB) comprising of representatives for various 3. Generation of Approved Parts and Centres of ISRO developing various functional Materials list for the programme. modules and sub-systems for APPLE was appointed and mandated to formulate the 4. Generation of environmental test specifications in coordination with structural and thermal design experts at unit, sub-system and integrated spacecraft level. 5. Establishment of Qualification and validation procedures for all new and critical processes 6. PA surveillance during Assembly, Integration, Test and pre-launch phases 7. Non-conformance management. Parts & Materials management: Preferred Parts and Materials list was generated identifying qualified sources.

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 Parts Engineering support was a major aspect Microwave elements fabrication & assembly, of R&QA efforts for APPLE spacecraft. The high-precision attitude control and inertial chosen approach factoring then limited system components, hydrazine propulsion screening facilities available was: system components such as Titanium  Procurement of Class –S Components tankages, pressure regulators, thrusters , in the radiation-hardened version thermal elements like Optical Solar Reflectors based on the radiation- modeling etc. required considerable efforts in terms of and where they were not available process validation and proving the margins. provide local Tantalum shielding Structural inspection at HAL was carried out jointly with HAL inspection staff, using special  Screening/up screening of all passives inspection jigs fabricated at HAL. and transistors in-house at ISAC  Procurement of chips for hybrid Periodic training & certification of Technicians microcircuits and batch validation on for Soldering, conformal coating engaged in chip / wire bonding through Electronics fabrication, Chip mounting & wire environmental stress screening bonding; hermetic sealing of hybrid modules was carried out. Stringent stress-screening Screening of non-metallic and volatile off-line tests including on accelerated modes compounds like epoxies, polymeric materials where feasible, were established to verify the for thermal control, potting & conformal margins for most of the critical processes. compounds etc., for compliance to the Total Mass Loss and Collectible Condensable Mass Environmental testing & evaluation Loss requirements evaluation were carried The environmental test matrices were established for validation of functional units out in-house . The Materials Test facilities at package or module level, sub-system level and integrated spacecraft level. Sine & inclusive a Versatile Universal testing machine Random vibration test, thermal cycling followed by thermal vacuum was carried out with thermal cycling features, Thermal at unit level. Static tests for validating the structural design were carried out in-house. parametric measurement facilities, Ultrasonic and X-ray inspection facilities were augmented for material evaluation and Non- destructive testing. Fabrication & Process controls: Vibration tests were carried out in the There were many challenges in establishing structural model at STEX, SHAR. process control, inspection and non- destructive testing techniques for many new processes employed in APPLE. Customised Tools for Inspection, verification of the quality of inserts in Honey comb sandwich panels used for mounting the equipment, bond quality assessment using Fokker Bond testing and holographic techniques were successfully developed. Quality control of solar panels , C- Band reflectors using composites, process controls for high-density electronics packaging including hybrid micro circuits, RF &

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 Qualification Vibration tests in the stack-mode results comprehensively and corrective action integrated with the simulated co-passengers where required were appropriately of Ariane-3 were mandated by the launcher implemented. agency were carried out at SOPEMEA, a CNES Extensive QA support was provided at the facility at Toulouse and only on verification of launch site for operations including satisfactory structural integrity and other deployment tests on the assembled array, dynamics performance requirements as per propellant filling and pressurization the launch agency requirements, clearance operations, leak-checks, interface checks with was given for flight-model fabrication. the co-passengers, physical inspection on assembling the stack at the launch pad. QA surveillance of all electrical check-out and applicable functional checks on the spacecraft were an integral part of the pre-launch operations. Interaction with the QA agencies of the Co-Passengers also was done. Reliability Engineering: The reliability engineering efforts essentially consisted of:  Failure Modes, effects & criticality assessment  Parts Derating analysis The thermal design of the spacecraft was  Fault-tree analysis validated through Solar Simulation tests at SOPEMEA.  Reliability prediction Long-duration thermal vacuum tests were carried out in the larger space-simulation In Summary: chamber established during the APPLE programme for verifying the electrical The R&Q approach followed for the APPLE functioning of the spacecraft in different spacecraft paved way for formulating the thermal & operational modes. EMI & EMC guidelines for the Product Assurance validation tests were also carried out at ISAC. Management of the subsequent operational spacecraft programmes like The Flight model also had to be tested for IRS and Insat-2. The continuous evolution vibration at Toulouse in the stack mode prior of the methodologies in tune with the to transportation to then launch site at French complexity of the missions, operational, Guiana. life and reliability requirements have gone a long way in building the requisite R&QA The deployment tests of the solar array were expertise at ISRO and the testimony is the carried out before and after all environmental impressive track record of successful exposures in gravity compensated modes. missions for more than four decades. As we transcend to the “Better, faster, Test Review Board at sub-system level and cheaper” era of Spacecraft manufacture, integrated spacecraft level reviewed the test

APPLE SPACECRAFT COMPLETES 40 YEARS of LANDMARK On 19th June 2021 since launch on 19th June 1981 not necessarily meaning a trade-off among the three, innovation and good technical judgement require to be applied to those factors that eliminate the risk element to a good extent. Experience is a guide to efficiency and effectiveness in tailoring the right PA Programme on a continual basis to achieve the objectives. While all divisions of the Product Assurance at the various Centers significantly contributed to the success APPLE, the key managerial personnel who coordinated the efforts in various disciplines were Late Mr. K.R.Ramgopal (Chairman, PA Board), Mr.Siharan De (Parts Engineering), Dr.Sahu (Materials) Mr.L.S.Sathyamurthy(Test & Evaluation) and Mr. V.N.Purohit (Reliability)at ISAC,Mr. Kulkarni at SAC,and Mr.Seeniah & Mr.Thampi Pal at VSSC. S.G.Raghavan, Head, Mechanical QA, ISAC --------------