The Indian Space Programme

by Gurbir Singh

  Automatic weather data collection: INSAT-1B collected data from remote locations, including rivers and oceans. ISRO provided 1,000 Automated Weather Stations (AWS), one of which was located in the Indian Base Station in Antarctic: The Indian Meteorological Department provided another 679 AWS and 969 Automatic Rain Gauge stations.

  Early Warning System: 100 receivers for the disaster warning system were located in the cyclone-prone areas of Andrea Pradesh and Tamil Nadu.

  Relay of national TV across India: Television programmes from the national broadcaster Doordarshan, initially limited to the capital and large metropolitan areas, were retransmitted via INSAT-1B providing a wider national coverage not possible without a satellite.

  Wider educational reach: Programmes retransmitted for universities, schools and 2,000 community-based direct broadcast (SITE like provision) televisions.

  Increased television content: the number of TV stations grew from 11 to 250 in the first three years of INSAT-1B operations.[711]

  INSAT-1B performed as designed, exceeding it’s planned seven years of life and was eventually terminated in August 1993 when all its onboard propellant was consumed. To ensure that there was no break in the space-based services inaugurated by INSAT-1B,

  ISRO ordered INSAT-1C in 1983 to replace the lost INSAT-1A with a launch scheduled for 1987. In the absence of INSAT-1A, INSAT-1B was potentially a Single Point of Failure. If INSAT-1B failed, no single satellite could replace it. Its functions would have to be met by leasing of services from multiple satellites already in orbit. The meteorological function could be replaced by images from Japan’s or European satellite. Communication services could be delivered by Canadian or US satellites but TV was a challenge. TV broadcast would require technical modifications to receivers in ground stations in India to accommodate the different frequencies in use.[712] In addition to avoid this single point of failure and to cater for growth in demand, an order for INSAT-1D was signed with FACC in 1985 for launch in 1989. With this provision, ISRO bought more time to build its infrastructure for launching INSAT-class satellites.

  Figure 12‑5 INSAT-1B at the Kennedy Space Centre. 2 June 1983. Credit NASA

  Had the schedule gone to plan, INSAT-1C would have been launched by an Indian astronaut from the Space Shuttle. In the end, INSAT-1C built by FACC was launched by ESA’s Ariane launcher in 1988. It was not successful. A fault with the power supply a month after launch and other failures terminated the mission a year after launch. INSAT-1D launch was delayed by two incidents. It was damaged during launch preparations when a crane failed, and it was damaged again during the San Francisco earthquake of 1989. It was repaired each time and successfully launched in June 1990. It operated successfully for over a decade until May 2002 when it lost attitude control. INSAT-1D was the last of the INSAT-1 series.

  The INSAT-1 series comprised of four satellites, of which two failed. An analyst working in the US on behalf of the INSAT-1 series concluded that the INSAT-1 design was fundamentally flawed. FACC had “sold India a failed proposal originally rejected by the US Air Force on the basis that it was too risky and potentially prone to failure.”[713] The complex operational demands for navigation, communication and meteorology services were undermined by inherent design weaknesses. INSAT-1B and INSAT-1D remained operational for the planned lifetime but only because of the additional effort from Indian satellite operators.

  INSAT 2 Series

  The INSAT-1 series was built by FACC in the US. In 1984, U.R. Rao took over as chairman of ISRO, and he was best placed with the vision and hands-on experience to shift ISRO’s strategic goals to build large complex satellites in India. Starting with INSAT-2 launched in 1992, ISRO has built its own spacecraft ever since. The five satellites in the INSAT-2 series (INSAT-2A to INSAT-2E) were similar to the INSAT-1 series but provided enhanced services, including higher-resolution sensors for meteorology, larger number of transponders for communication and extended TV coverage to include Southeast Asia and the Middle East. In addition, the INSAT-2 series included new services for search and rescue,[714] mobile telephone support and dedicated channels for business customers. INSAT-2C and INSAT-2D[715] did not carry any meteorological payload, but INSAT-2E was fitted with an enhanced resolution camera for meteorology and was compatible with US satellite-service provider Intelsat. From 36,000 km, the sensors for the meteorological payloads in the INSAT satellites provided images of around a kilometre resolution of the constantly changing weather patterns over India.

  However, INSAT was not ideal to fully explore India’s natural resources, unlike satellites optimised for EO that operate from a lower orbit and can provide higher-resolution images and information sufficiently detailed to drive government. At the outset, ISRO engineers lacked self-confidence in the face of limited facilities and zero experience in satellite building. The group that built IRS-1A wanted to call it “pre-operational” and the INSAT-2A team for the first INSAT to be built in India wanted to use the suffix TS for Test Satellite, that is, INSAT-2TS. In each case, their faith in their ability grew, and the modified naming convention was dropped.[716]

  All satellites in the INSAT-2 series and beyond have been built and operated entirely by ISRO in India. Although the contract with FACC for INSAT-1 excluded any technology transfer, building on the experience of Aryabhata, Bhaskara, APPLE and SROSS, ISRO developed sufficient in-house the expertise for designing and building satellites and honed its satellite-production process, as well as quality control and operational procedures.

  The ISAC in Bangalore is the hub where spacecraft are realised. Starting with a basic structure, subsystems are gradually added for control, power, telemetry and communications, and eventually, a complete satellite emerges. The system for attitude control (reaction wheels, gyroscopes and momentum wheels) and antenna reflectors are produced at VSSC in Thiruvananthapuram. Transponders and cameras used for meteorological imaging (visible and infrared) are produced at the SAC in Ahmedabad. The propulsion system for the large apogee motor that takes satellites from the initial GTO to GEO and the liquid-fuel-based RCS used for attitude control and station-keeping are produced at the LPSC. These systems and components are integrated as a single spacecraft at ISAC.

  After the first decade of building its own satellites, ISRO’s techniques, technologies and procedures had achieved a substantial level of maturity. For example:

  30% of Aryabhata’s mass was solid metal. Replacing solid metal with honeycomb structures brought it down to just 7.5% for INSAT-2.

  Aryabhata, Bhaskara and SROSS used body-mounted solar cells. Since APPLE onwards, ISRO has used solar panels. Solar panels are more efficient in generating electricity, even though designing, building, deploying and operating them rely on complex subsystems.

  The increased amount of time in eclipse (in shadow during each orbit), satellites in LEO require a 50% higher battery and solar array capacity compared to satellites in GEO or GSO, which are in shadow only around 90 times a year.[717] Initially, ISRO procured solar panels but later developed in-house capability to manufacture space-qualified solar panels with a capacity to handle high-degree of temperature variations (from -100°C to +100°C) 240,000 times. It has also built the capability for nickel-cadmium batteries that could withstand extreme temperature variation and reliably manage multiple recharge cycles.

  Application Specific Integrated Circuits helped to reduce the quantity and complexity of wiring. The resulting miniaturised electronic units and mass reduction extended a satellite’s operating life.

  Traditionally, solar cells have been silicon-based. ISRO moved to gallium-arsenic solar cells that have greater efficiency.

  Nickel hydrogen (Ni-H) batteries, which have a much longer life than the usual nickel-cadmium batteries.

  Enhanced communication capacity was a common feature on everything that followed INSAT-1. INSAT-2A had twice the communication capacity of INSAT-1A. INSAT-1A payload included two C- and three S-band transponders and VHRR. INSAT-2A contained 18 C-band and two
S-band transponders, VHRR and a search and rescue payload. INSAT2-A was designed with an upper limit on its mass and physical size. Although US’s Delta or ESA’s Ariane 4 could launch heavier spacecraft, INSAT-2's mass specification of 2,000 kg was determined by ISRO with an eye on launching its own GSLV-Mk1 (designed for a payload of 2,000 kg) when it came online. During the 1990s, GSLV was still in development. Over time, the mass of communication satellites has increased, along with capacity, to well beyond the 2,000 kg of ISRO's 1990s design.

  Since the start of the INSAT programme, the number of satellite-based societal, commercial and strategic applications have increased. New services included Mobile Satellite Service (MSS), Satellite-aided Search and Rescue, early warning systems for flood, typhoon and tsunami and fleet-monitoring applications. The demand for satellite-based services, especially in the consumer sector, has seen particularly strong growth. The number of registered TV channels has grown to 821 as has the number of DTH operators; between them, they serve a customer base of 50 million users.

  The demand for MSS has also grown. MSS is a mobile cellular network, but the repeaters are in space, which allows a small portable handheld device to communicate from anywhere on Earth using satellite services. MSS payload was flown on INSAT-3C. Low speed satellite-based internet access from Very Small Aperture Terminals (VSATs) is used in the financial, transport, and predominantly in the shipping sectors. In India, the VSAT user base has grown to about 1,70,000 installations.[718]

  Since it was established in 1969, ISRO has built, launched or operated over 80 unique spacecraft, almost half of which are currently in operation. India’s EO programme, including its weather satellites, is contributing to modernise its national infrastructure. Communication satellites have driven growth in media, industry and the business sector. Yet, with only 260 transponders in C, Ext C and Ku bands, the demand still significantly exceeds supply. Through its science, student and education satellites, ISRO hopes to foster interest and develop the skilled personnel it will need in the future.

  Education and Defence

  Satellite-based technology is ideally suited to bringing education to large numbers of individuals distributed across a vast geographical area. Disparate communities can be involved in a shared learning experience (for example, lectures by specialist speakers and from academic establishments) via satellite. This technology is cost-effective, and its novel delivery technique can itself enhance learning compared to traditional methods. The Educational Satellite (EDUSAT) launched in 2004 has stimulated the demand for tele-education. ISRO's ambition is to cover primary, secondary and higher education using this technology. Currently, it has established about 80 networks across the country connecting 56,164 classrooms with 4,943 satellite interactive terminals, where students can interact with the speaker, and 51,221 receive-only terminals covering the full range from the primary to professional education.[719]

  ISRO learnt from some missions more than others. The Technology Experiment Satellite (TES), launched in 2001, incorporated new technologies, including the attitude and orbit control system, using a single propellant tank, high-torque reaction wheels, solid-state data recorder, improved satellite position system and miniaturised power and communication subsystems. It was built in just two years motivated by the 1999 incursion by Pakistan’s military into the Indian-administered section of the Kargil sector of the state of Jammu and Kashmir.[720]

  Access to slots in the GEO is determined by the International Telecommunications Union. India has the following GEO slots, all east of the Greenwich Meridian (32°, 48°, 55°, 72°, 74°, 82°, 83°, 93°, 102° and 111°). At present, India has more GEO satellites than slots. To accommodate them all, several are co-located, sharing the same GEO positions. To ensure safe separation, each satellite is maintained at the centre of an exclusive 150-km box of space. Although this is convenient as it eliminates the need to acquire additional GEO slots, MCF operations must work to a higher degree of precision to avoid collisions.[721]

  Satellite Assisted Search and Rescue

  ISRO is a member of the international COSPAS-SARSAT programme that provides distress alert and location service through Search and Rescue satellite systems. COSPAS-SARSAT was established in 1979 when the USSR's COSPAS (Cosmicheskaya Sistyema Poiska Avariynich Sudov, meaning Space System for Search of Vessels in Distress) and Search and Rescue Satellite Assisted Tracking (SARSAT) developed jointly by the US, France and Canada were merged. Since then, COSPAS-SARSAT has grown. It now covers 60% of the Earth’s land surface and is comprised of 11 satellites and 76 ground stations in 50 countries.

  Distress signals transmitted from anywhere on Earth by emergency locator transmitters on aircraft, ships and those owned by private individuals configured to use the internationally recognised 406 MHz frequency are detected by the COSPAS-SARSAT satellite network in orbit. A space-based search and rescue system consists of four elements: (i) the transmitter or beacon, which when activated initiates an alert signal[722] (ii) an orbiting satellite capable of detecting that signal and relay to the ground (iii) and a ground station capable of receiving that signal and (iv) a ground-based rescue coordination authority to perform a rescue on the ground, air or sea. Globally, there are an estimated 1,770,000 beacons, of which 1,380,000 are uniquely registered against aircraft, ships or stand-alone units for personal use.

  From September 1982 to December 2014, 39,565 persons were assisted through 11,070 search and rescue incidents. In India, the statistics for up to 2013 record that the COSPAS-SARSAT supported the rescue of 1,917 lives in 75 incidents.[723] A total of 42 countries offer services such as user, ground or space segments in the COSPAS-SARSAT system. Each international region is responsible for its component of COSPAS-SARSAT operating to a single global standard. In September 2015, COSPAS-SARSAT reported the operational infrastructure as:

  Five satellites in low polar orbit, also known as Low Earth Orbit Search and Rescue (LEOSAR).

  Seven satellites in GEO (for example, INSAT-3D).

  54 Local User Terminals (LUT), Earth station antennas, receiving signals transmitted by LEOSAR satellites.

  23 LUTs, including one in Bangalore and another in Lucknow, receiving signals transmitted by GEOSAR satellites.

  31 Mission Control Centres, including one in Bangalore, distributing distress alerts to SAR services.

  1.7 million 406-MHz beacons estimated to be in service worldwide.[724]

  Figure 12‑6 COSPAS-SARSAT System. Credit COSPAS-SARSAT

  India’s first contribution was INSAT-1D that carried a COSPAS-SARSAT payload in 1990.[725] All satellites of the INSAT-2 series, except INSAT-2C, also carried a COSPAS-SARSAT payload. None of the INSAT-1 or INSAT-2 satellites are operational today. By the end of 2016, INSAT-3D and INSAT-3DR had a COSPAS-SARSAT payloads. In India, 13,300 beacons had been registered by 700 user agencies by March 2013.

  Users of COSPAS-SARSAT in India on ships, aircraft or personal beacons (any that operate at 406 MHz) can trigger alerts once activated.[726] Two LUTs based in Bangalore and Lucknow listen in to the satellites for alerts. The LUTs are supported by the Indian Mission Control Centre (INMCC), also in Bangalore, that relays the coordinates of the beacon generating the alert to the Coast Guard, Navy and Air Force or ground-based civilian rescue organisations responsible for carrying out the rescue.[727]

  Rescue operations in India are coordinated with four rescue centres located in Mumbai, Chennai, Delhi and Kolkata and operated by the Airports Authority of India via the INMCC in Bangalore. The LUTs located in India provide coverage for the Indian Ocean region and seven other countries, Bangladesh, Bhutan, Maldives, Nepal, Sri Lanka, Seychelles and Tanzania. The Indian INMCC/LUTs had started operations in 1986 and, by 2002, were involved in rescuing about 1,300 individuals.[728]

  ISRO now has the complete infrastructure, on the ground and in space, to provide end-to-end services required for operating space-based assets. Although international collaboration has been and will continue to be an element of its activities,
ISRO is self-sufficient. The services delivered by ISRO’s satellites, built in and operated from India, touch the lives of most of its 1.3 billion population daily. More than any other element of India’s space programme, its satellite programme is a realisation of the vision of its founding fathers, Jawaharlal Nehru, Homi Bhabha and Vikram Sarabhai.

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  Chapter Thirteen

  Indian Regional Navigation Satellite System

  T he concept of a satellite-based navigation service arose from observing the world’s first satellite, Sputnik. Researchers at the Applied Physical Laboratory in Baltimore recognised that if measurements could be made of Sputnik’s orbit as it passed overhead, its entire orbit could be calculated. Dr Frank T. McClure (1916–1973) went further and concluded that the converse was also true.[729] If the position of the satellite in orbit was known, then the location of the observer on Earth could be calculated. In 1960, the first navigation satellite was launched. It was called Transit or NAVSAT and used by the US Navy to provide location information for its nuclear-armed submarines.[730] Today, there are over a hundred satellites in Earth orbit designed to provide precision location anywhere on Earth at any time.

  A navigation satellite in space incorporates a high-precision onboard clock that continuously transmits signals to Earth from which its position can be calculated. Every satellite navigation (satnav) receiver, whether in a mobile phone, a tablet or a car, also has an accurate built-in clock. The satnav receiver measures the time difference between when the signal was sent by the satellite and when it was received. By combining the signal from at least four satellites in space and its in-built clock, the receiver can calculate its position anywhere on the surface of the Earth.