SPACE APPLICATION CENTRE - A PERSPECTIVE
K.N.Shankara
Director, SAC
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Introduction |
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As the lead centre for harnessing space technology for national development, Space Applications Centre (SAC) has been conceiving and demonstrating new applications using space technology and helping to operationalise these. Established in 1972, it is one of the lead Centers of the Indian Space Research Organisation. The centre is also engaged in the areas of development of sensors in optical, IR and microwave regions for remote sensing of earth resource, meteorology and oceanography; transponders for telecommunications and TV broadcasting, ground hardware/software and application methodologies in close interaction with user community in the country. For successfully carrying out these activities, the centre has developed necessary infrastructure in a campus spread over 95 acres of land with a staff of about 2200 including technical/scientific and administrative manpower. Recently a new campus at Bopal, about 8 kilometers west of the present campus has also become operational.
To effectively discharge the above responsibilities SAC is organized into various areas and groups.<>The areas and groups are also periodically reorganized to cater to the new projects and activities.
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Satellite Communication |
Anticipating the important role of space communications in nation building, an Experimental Satellite Communication Earth Station (ESCES) was established in 1967 at Ahmedabad (now part o SAC). It was an experimental Earth Station and training centre where scientists and engineers of India and other developing countries could receive training and first hand experience in the design, development and operations of an earth station for communications and broadcasting. A large number of international training courses have been conducted since then.
A unique experiment called the Satellite Instructional Television Experiment (SITE), was conducted during 1975-76 utilising the American ATS-6 satellite. It involved telecasting educational programmes aimed at socio-economic upliftment of rural India, to 2400 villages-spread over six states - through experimental Direct Reception Sets. SITE was followed by a communication techniques developmental project called Satellite Telecommunications Experiments projects (STEP), carried out with the Franco-German satellite, Symphony.
The first experimental communication satellite APPLE, designed, fabricated and qualified at SAC, It was launched onboard the first experimental flight of the Arianne. An exhaustive communications application programme called the APPLE Utilisation Programme (AUP) was also conceived and carried out simultaneously.
The INSAT-1 series of satellites was custom designed and made as per the unique requirements of the country by US company. The INSAT 2A, 2B, 2C, 2D, and 2E, launched in the years 1992, 1993, 1995, 1997 and 1997 and 1999 respectively, were designed, fabricated and qualified in house. These had various combinations of C, Ext. C, Ku and S band transponders with varying degrees of e.i.r.p. Some of these also carried meteorological payload VHRR, payload for search & Rescue, etc. It is worth noting here that eleven transponders onboard the INSAT2E were leased to the international INTELSAT group even before its launch.
With development of these communication transponders, several new technologies, such as thin wall invar multiplexes, solid State Power Amplifiers, integrated receivers, etc have been developed. New design capabilities have also been developed both in hardware and software for improved antenna coverage, cross polarization and better beam shaping, onboard regenerative payload, etc. Work on definition and realization of future generation communication satellites in INSAT-4 series and for satellite payloads to be launched on board experimental flights of Geosychronous Satellite Launch Vehicle (GSLV), called the GSATs, has been in full swing. Most of the INSAT-3 series satellites have been launched.
The GSAT-2, carrying 4 C band, 2 Ku band India beam transponders and 1 MSS payload, is scheduled to be launched in first half of 2003. GSAT-3 (EDUSAT) will carry 5 Ku band transponders to provide coverage through 5 regional beams with spatial frequency reuse in addition to 2 Ku band and 6 Ext. C band transponders for all India coverage. The GSAT-4 will include 8 channels each in Ka band regenerative and bent pipe payloads and the navigation payload.
Under the SATCOM and IT applications programme, the development of all hardware and software like DSDB receiver for digital sound and data broadcast and hybrid internet, envisaged under GAP-1, has been successfully completed and demonstrations carried out using INSAT. A number of spin-off applications of DSDB for information dissemination were also developed and demonstrated. Users like the All India Radio (AIR) and India Meteorology Department (IMD) have evinced keen interest in the use of DSDB for their progrmmes. In the area of Mobile Communication, the handheld MSS was integrated with GPS and demonstrated for fleet management applications. MSS was also interfaced with DCP and tested successfully with INSAT.
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Remote Sensing Activities |
The utilisation aerial and Landsat imagery for resources application in early 70s paved way for initiation of the remote sensing activities in the country. Activities were also carried in the field of meteorology with available data from foreign satellites and from indigenously developed airborne thermal Scanner. All the remote sensing activities so far can be divided into three Phases, viz, Experimental Phase, Semi-Operational and Operational Phase.
The first phase saw the development of airborne thermal sensors such as Infrared (IR) scanner, multispectral scanner, linear Charge Coupled Device (CCD) camera, Side Looking Radar, Colour Infrared (CIR) based photographic systems and a number of photo interpretation and ground truth equipment which were later productions through technology transfer. Landsat data were fully utilized since 1973 to learn space based Remote Sensing applications. For all these sensors, efforts were made to also define and develop data products systems.
Based on above initial work, a strong applications programme was evolved around these instruments. Foundations for space borne sensors were laid during this period. Under Satellite for Earth Observation (SEO) programme, 2 satellites were launched and called Bhaskara satellites after their Launch onboard Russian launch Vehicle, Bhaskara carried a 1 km resolution 2 band TV camera system and a three channel microwave radiometer. These were designed, developed and successfully qualified in house. The programme formed the basis for the advanced sensor development leading to operational applications Users were also sensitized for utilizing remote sensing data from satellite based sensors.
The second phase in 1980s witnessed the results of earlier efforts of experimental satellites. The IRS 1A programme was successfully launched and the users started receiving multispectral imagery with 36m resolution. Professionalism was brought into the design of sensors, data products and applications projects. Major applications in agriculture, hydrology, geology and other areas were defined in close interaction with user agencies and the IRS utilization programme was carried out successfully. These efforts led to semi-operational applications of IRS 1A data.
Over these years, groups had acquired adequate expertise in high resolution sensor design, digital image handling and analysis, design of applications missions and execution of the same in close interaction with user agencies and in coordination with other ISRO/DOS centres and units. Strong foundation was also laid for airborne SAR system development, its data processing and applications. Meteorology and Oceanographic studies were carried out with data in optical and microwave region from foreign satellites.
The advanced activities carried out during the third phase in 1990s put India at par with many other advanced nations through the design of high resolution sensors in the optical and microwave regions including a successfully flown airborne SAR system and a very sophisticated application programme tuned to our country's needs. The 5.8 m resolution Pan Camera of IRC 1C & 1D revolutionized the applications concept in the country. Being the best resolution civilian sensor in the world at that time, it attracted he attention of foreign users which resulted in the global reception of IRS data through he agreement with American Company, Space Imaging/EOSAT. A variety of data products to meet the needs of user community were defined and developed. These are being used worldwide The design and launch of the IRS-TES with 1 m resolution has gone a long way in redefining remote sensing with several new applications. Several new remote sensing satellites like Cartosat-1 & II, Resource sat, METSAT, etc. are also getting ready for launch.
Radar Imaging Satellite (RISAT) will have all weather and day-night observation capability. Slated for launch in 2006, it will carry a band Synthetic Aperture Radar (SAR).
The applications programme got a fillip under several of the ISRO's innovative programmes like Integrated Mission for Sustainable Development (IMSD) in which SAC played a significant role. Applications in Agriculture like Crop Acreage and Production Estimation CAPE) were operationalised which was accepted by the Agriculture Ministry as a major component in their scheme of crop production estimation. The latest collaborative programme with the user agencies, FASAL is another achievement in this direction. Numerous applications were demonstrated to utilize the sensor combination of medium resolution LISS-III sensor; high resolution Pan Camera and coarse resolution but highly repetitive WiFS imagery. Such a combination of sensors does not exist in any other operational remote sensing programme. Further, SAC scientists trained a number of scientists in user departments on advanced concepts in RS applications.
As part of continuing support to Disaster Management in the country DOS has initiated several actions towards operational use of space data. These include near real time flood monitoring, National Agriculture Drought assessment and Monitoring (NADAMS), Land Slide Hazard Zonation mapping, communication support to Disaster Management and airborne survey using airborne SAR, digital camera, etc. SAC has been playing important role in many of these activities.
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Meteorological & Oceanographic Activities |
The Meteorological activities at SAC basically involve payload design and fabrication and applications using the data received from such satellites. The successful ventures outlined in the previous paragraphs enabled ISRO to evolve an ambitious Remote Sensing and Meteorology programme for the country tot have a unique constellation of satellites for resources and environmental applications. Bhaskara I and II were the first Indian Meteorological satellites which carried microwave radiometer called SAMIR to provide information on sea state and atmospheric water vapour content for use in meteorological studies.
In the initial phase of met applications data from Bhaskara were supplemented by data from NOAA, SEASAT, ERS etc. Meteorological components from INSAT, starting from 1982 have now become fully operational. Over the years the resolution available from VHRR onboard INSATs has become better. The CCD camera also onboard some of the INSATs and inclusion of water vapour channel in the new VHRRs have added advantage. Exclusive meteorological payload would be carried ON BOARD met sat. The INSAT-3D, to be launched soon should carry 6 channel imager and 19 channel sounder giving vertical profile of temperature and humidity in the atmosphere.
The first exclusive meteorological satellite KALPANA-1 was launched by ISRO's PSLV on Sept. 12, 2002. It carried a VHRR and a data relay transmitter. SAC has also launched the Oceansat-1 in May, 1999. It has an Ocean Colour Monitor (OCM), an optical sensor with 8 narrow spectral bands with high resolution and higher dynamic range and Multi frequency Microwave Scanning Radiometer (MSMR). These sensors have high receptivity of 2 days and hence are most suited for dynamic events in coastal and mid ocean regions. Oceanographic applications including improved techniques for delineating primary fishing zones and monitoring ocean parameters like Sea Surface Temperature (SST), wind speed etc. are planned. Another major activity underway is the Meghatropiques project, a collaborative programme with CNES, France. It would carry microwave instrumentation and is scheduled for launch in 2006-07.
SAC has also taken up many Applications projects under Announcement of Opportunity scheme of several international missions like ERS, TRMM, ADEOS, ENVISAT, etc. SAC has state of the art. General Circulation Models for experimentation with satellite data. Prediction of weather in the extended range and prediction of Ocean state in the short range are the fields of active research. Research work is being carried out on retrieval of parameters like rainfall, soil moisture, sea surface temperature, sea surface winds, etc.
Laboratory models of advanced microwave sensors such as Scatter meter and Altimeter have already been developed and the space qualified models will be developed for Oceansat-II programme. A major application programme is defined under DOD's funding at SAC for development of applications packages to derive oceanographic and atmospheric parameters using space borne sensors.
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Support Groups |
The success story of above programmes is written in the very active and efficient Electronics and Mechanical Support Services Groups in the Centre. These Groups provide support in almost all the fields such as fabrication facilities, Microwave Integrated Circuits, Chemical facilities and Quality Control. These are also responsible for the operation, maintenance an establishment of the electronic test, mechanical vibration test and thermo vacuum test facilities. A separate group is responsible for the maintenance and calibration of the equipment.
There is an independent Systems Reliability Group at SAC that ensures that the required quality objectives are met by examining all the work in terms of electronic design, mechanical design, component selections, component applications, material selection, material applications, process selection, process qualification, software, etc. For this purpose there are well equipped laboratories and facilities that carry all the necessary tests including destructive physical and chemical analysis and X-ray tests.
SAC has now grown into a unique centre of space technology and applications with multidisciplinary teams consisting of experts in the files of state of the art satellite payload design, fabrication and qualification, Earth station technology and various applications in communications, remote sensing and meteorology.
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