LAUNCH VEHICLE TECHNOLOGY
LAUNCH VEHICLE TECHNOLOGY
SLV-3: In the area of launch vehicle technology, from the successful launching of first Indian Satellite Launch Vehicle SLV-3 in 1980, the nation is on the threshold of realising large, cost effective operational launch vehicles required for IRS and INSAT classes of satellites. The successful launch of SLV-3 in 1980, that put 40-kg Rohini satellite into a low earth orbit, made India the sixth country to have the capability to orbit her own satellite. The next two launches of SLV-3 were made in May 1981 and April 1983. The 22.7 metre tall SLV-3 was a four stage all solid propellant vehicle and had a lift off weight of 17 tonnes. SLV-3 programme was terminated after four flights.
ASLV: The Augmented Satellite Launch Vehicle (ASLV) was infact developed for placing a 150 kg satellite (SROSS) into a 100 km orbit. The first two developmental flights of ASLV, ASLV- D1 in 1987 and ASLV-D 2 in 1988, failed. However they validated a number of technology elements relating to the launch vehicle. The third development flight of ASLV (ASLV-D3) was successfully launched on 20 May 1992 and it injected 106 kg SROSS satellite into orbit. ASLV- D4 was launched on 4 May 1994 and it successfully placed SROSS-C2 satellite, similar to SROSS C, into a low earth orbit. The 23.5 m tall ASLV has a lift off-weight of 39 tonnes. It is a five stage rocket using solid fuel.
PSLV: The first developmental flight of Polar Satellite Launch Vehicle (PSLV), capable of launching 1000 kg class of satellites into a polar sun synchronous orbit, took place on 20 September 1993. The largest rocket built by India so far failed to put IRS-1E into orbit due to a control software implementation error. The second developmental launch of PSLV, PSLV-D2, on 15 October 1994 successfully placed the IRS-P2 satellite in the intended orbit. The successful launch of PSLV-D3, the country’s third and last developmental flight of PSLV from SHAR on 21 March 1996 catapulted this country into a force to reckon with in the global satellite launch vehicle market.
With a lift-off weight of about 283 tonnes, the PSLV-D3 had four stages. The first stag^ one of the largest solid propellant boosters in the world, had indigenously produced hydroxyl-terminated poly-butadiene (HTPB) as fuel and ammonium perchlorate as the oxidiser. The second stage employed indigenously manufactured vikas engine and liquid propellant, unsymmetrical dimethyl hydrazine (UDMHS) as fuel and nitrogen tetroxide (N2O4) as oxidiser. The third stagey used HTPB based solid propellant. The fourth stage had a twin engine configuration using liquid propellant, monomethyl hydrazine and another grade of nitrogen tetroxide as oxidiser.
The successful launch of PSLV-D3 has marked an end to the dependence on other countries for launch of indigenous IRS class satellites. India can now very well consider commercial launch offers by the end of 1997. ISRO can try as many as four launches from SHAR every year. PSLV development programme has lent a fillip to India’s Geosynchronous Satellite Launch Vehicle (GSLV) which has similar technical systems.
GSLV: Development of Geosynchronous Satellite Launch Vehicle, (GSLV), incorporating the proven modules of the PSLV along with a 12 tonne cryogenic rocket motor was initiated in 1990 in order to achieve total self-reliance for launching 2.5 tonne INSAT class of satellites in geostationary orbit. Its first launch is expected by 1998. GSLV will be developed in two stages. In the first stage of development, GSLV Mark I will be developed which will have the core vehicle as PSLV and four liquid second stages of PSLV replacing the solid motors as the first stage strapons. In the second stage, GSLV Mark-II will be developed with the upper two stages (i.e. third and fourth stage) of Mark-I replaced by a cryogenic engine. Initially India was to acquire the cryogenic engine and technology from Russian Space Agency, Glavkosmos. But under US pressure and Missile Technology Control Regime (MTCR) restrictions Russia declined to honour the deal. So ISRO started on its own to develop a cryogenic engine. It would have taken many years to manufacture such an engine. But in early 1994 ISRO and Glavkosmos renewed negotiations and reached an agreement whereby Russia is to provide four mock-up models in lieu of technology, besides three boosters. Meanwhile, ISRO has developed a small one tonne cryogenic engine.
REMOTE SENSING SATELLITES
Remote sensing is a process of indirectly gathering information about the earth’s surface without actual contact with the object or area being : investigated. Remote sensing is done from air-borne or space platform by measuring the electromagnetic radiations of the sun that are reflected, scattered or re-emitted by the objects on the surface of the earth. Visual infrared and microwave portions of electromagnetic spectrum are used in remote sensing. The characteristic spectral signatures of terrestrial bodies are detected by remote sensors aboard satellites or aircrafts.
India is already a member of the exclusive club of nations capable of designing and operating remote sensing satellites. China, France, USA, Russia, Canada and European Space Agency are the other members of the club which compete and cooperate in the market for satellite knowhow and data.
Remote sensing in India is under the umbrella of the National Natural Resources Management System (NNRMS) for which Department of Space is the nodal agency. The remote sensing now covers diverse fields such as crop acreage and yield estimation, drought warning and assessment, flood control and damage assessment, land use/land, cover information, agro climatic planning, wasteland management, water resources management, underground water exploration, prediction of snow melt, run-off management of watersheds and command areas, fisheries development, urban development, mineral prospecting, forest resources survey, etc.
The NNRMS with its headquarter in Bangalore is the guiding spirit behind the Indian remote sensing programme. It is a unique system in which data from remote sensing are integrated with conventional sources for effectively managing the country’s natural resources. The main objectives of NNRMS are:
- establishing a national natural resources information system
- infrastructure and manpower development by helping the users of remote sensing data in establishing infrastructure, supplying equipment for data processing and analysis; and
- application projects in major resources sectors such as agriculture, land use, water resources, forestry, geology, marine resources and environment.
Indian Remote Sensing Satellites (IRS): With a three years life, IRS-1A was the first operational satellite of the Indian Remote Sensing Satellites and was put into a polar sun synchronous orbit in March 1988. It is now used when more frequent data is required. The second operational satellite of IRS series, IRS-1B was launched on 29 August 1991. IRS-1E, launched in September 1993 by India’s own launcher PSLV-D1 proved a failure due to technical snag in the rocket developed after the launch. IRS-P2 was put into orbit in October 1994 by the PSLV-D2. IRS-1Cwas successfully put into orbit in December 1995. JRS-P3 was launched in March 1996 by the PSLV-D3.
CHRONOLOGY OF IRS
IRS-1A, IRS-IB, IRS-P2, IRC-1C and IRS-P3 have greatly enhanced the scope for more repetitive data for monitoring dynamic features associated with natural resources and environment. The IRS- 1C has a marked improvement over its predecessors IRS-1A and IRS-IB. It incorporates advanced features that provide better spatial resolution, additional spectral bands, stereoscopic imaging, wide field coverage and more frequent revisit capabilities than its predecessors. In terms of imagery resolution IRS-1C is today the best civilian satellite in the world. It also records data when they are not being transmitted in real time.
Remote sensing satellites belonging to the IRS-P series are meant for advanced technology probing missions, especially in the area of oceanography, cartography and environment monitoring. The IRS- P3 satellite carries two remote sensing payloads and a payload for X-ray astronomy. One of the remote sensing payloads is a Wide Field Sensor (WiFS), similar to that of IRS-1C but with an additional short wave infrared band. This band being sensitive to moisture content in vegetation, provides additional data for crop condition assessment. Its other applications include snow and cloud cover differentiation, snow-melt run-off studies, flood damage assessment and geological studies. The second payload is a modular opto-electronic scanner of the German space agency DLR, primarily for use in ocean related studies. Data from both these payloads will be useful for plant applications like vegetation index monitoring (to study forest cover or foodgrain crop estimation), biomass and desertification studies, atmospheric studies such as aerosol or cloud analysis, optical turbidity (pollution monitoring), cloud and snow discrimination and water vapour content in the atmosphere. The X-ray payload is used to study time variability and spectral characteristics of cosmic X-ray sources and detection of transient X- ray sources.
The National Remote Sensing Agency (NRSA), Hyderabad is an agency that acquires or receives data from the IRS series satellites and other satellites like LANDSAT 4 and 5, METSAT, SPOT and ERS-1. Multispectral scanner and Thematic Mapper data from the US LANDSAT-5 satellite and meteorological data from NOAA satellite are also being acquired regularly.
The data obtained from IRS is being used extensively in various application projects like land use, land cover mapping for agroclimatic zonal planning, crop acreage and yield estimation, drought monitoring and assessment, irrigation and command area development, flood mapping, snow mapping, ground water prospect zone mapping, environment impact assessment, forestry, ocean resources management, geological mapping, integrated mission for sustainable development, etc.
ISRO-EOSAT Agreement: From July 1996 the US company EOSAT has begun acquiring data from India’s IRS-1C, considered the world’s most powerful civilian remote sensing satellite currently in orbit. Data from IRS-1C is also being acquired by the Neutaliz, Station of the GAF in Germany while several other ground stations around the world are expected to follow suit shortly. The data processing system developed by ISRO will ultimately link upto a network of 22 ground stations for worldwide IRS data collection.
In 1995 ISRO had signed an agreement with EOSAT, giving the company, based in Norman, Oklahoma, USA, worldwide marketing rights of IRS data for ten years. The data provided by IRS- 1C are of high resolution imagery, normally available only to military satellites. With the IRS- 1C data being marketed commercially, India has become a serious competitor in the market for space-based data so far dominated by the US LANDSAT-5, the French SPOT series, Europe’s ERS-1 and the Russian Resurs-F satellite.
IRS-P3 is the first indigenously launched remote sensing satellite whose data will be distributed globally through the American EOSAT company under a ten-year contract signed with ISRO’s corporate wing, Antrix Corporation in 1995. In order to ensure continuity of data coming from IRS-P3, another more powerful satellite IRS-P4 will also be launched soon.
ISRO has scheduled the launch of INSAT-3C and PSLV in August, 2001. The Polar Satellite Launch Vehicle (PSLV) will carry three satellites, including 2 foreign ones. They are: India’s TES (Technology Experiments Satellite), ‘PROBA’ belonging to a Belgium company and ‘BIRD’ of the German space agency, DLR.
The second development flight of the Geosynchronous Satellite Launch Vehicle (GSLV) is scheduled for third or fourth quarter of next year. ISRO will start testing the indigenous cryogenic engine for GSLV in about two months and its duration will be increased subsequently. ISRO hoped to use indigenous cryogenic engine in the third and fourth flights of GSLV and was looking at alternative configuration for GSLV to launch 3.5 ton spacecraft. The indigenous cryogenic engine was expected to be ready in 2½ years.
ISRO to develop launch vehicles to carry higher payloads
ISRO has drawn up a proposal to develop launch vehicles for carrying payloads of up to five tons. Dr. Kasturirangan said that efforts were on to increase payload capacity of the launch vehicles. Normally, the payload portion in the total weight of the launch vehicle was 0.5%. The ISRO had been able to increase it to 0.7 to 0.8%. India is developing it own capabilities. If the country has the capability to assimilate other technologies, it can speed up our own programs. The rocket would be capable of carrying 250 kg more of payload than the Russian stage.