The Indian Earth Observation (EO) system was commissioned with the launch of Indian Remote Sensing satellite, IRS-1A, in 1988. The EO definition, development, operation and its applications are overseen by the National Natural Resources Management System (NNRMS) for which DOS is the nodal agency. NNRMS is aimed at deriving optimum utilisation of the country's natural resources by systematic inventory using EO data in conjunction with conventional techniques. The Planning Committee of NNRMS(PC-NNRMS)provides guidelines for implemen-tation of the system and oversees the progress of remote sensing applications. Ten Standing Committees have been constituted for application of remote sensing in different areas. They are: (i) Agriculture and Soils, (ii) Bio-Resources, (iii)Geology and Mineral Resources, (iv) Water Resources, (v)Ocean Resources, (vi) Cartography and Mapping, (vii)Urban Management, (viii) Rural Development, (ix) Technology and Training and (x) Meteorology. Each of these Standing Committees is chaired by Secretary of the respective government departments and includes experts from major user departments/agencies.
The Indian Remote Sensing (IRS) satellite system has the world's largest constellation of remote sensing satellites in operation today. It provides space-based remote sensing data in a variety of spatial, spectral and temporal resolutions, meeting the needs of many applications.
Satellites in Operation
There are six remote sensing satellites in operation - IRS-1C, IRS-1D, IRS-P3, Oceansat-1, Resourcesat-1 and Technology Experiment Satellite, (TES). They are placed in polar sun-synchronous orbits.
Resourcesat-1 was launched on board PSLV-C5 in October 2003. It is placed in 820 km high polar Sun Synchronous Orbit. Resourcesat-1 carries three cameras, they are:
Resourcesat-1 also carries a Solid State Recorder to store the images taken by its cameras, which can be received later by the ground stations.
IRS-1C and IRS-1D
IRS-1C and IRS-1D launched in December 1995 and September 1997 respectively are identical satellites carrying three cameras, Panchromatic Camera (PAN), Linear Imaging Self Scanner (LISS-III) and Wide Field Sensor (WiFS) with following specifications:
IRS-P3 was launched in March 1996 on-board PSLV. It carries a Wide Field Sensor (WiFS), Modular Opto-electronics Scanner (MOS) developed by the German Space Agency, DLR, and an X-ray astronomy instrument. The payloads on this satellite are:
Wide Field Sensors (WiFS)
IRS-P3 also carries an X-ray scientific payload comprising three Pointed Proportional Counters (PPC) in the Energy range of 2-20 keV and an X-ray Sky Monitor (XSM) in the Energy range 2-8 keV. However, at present, IRS-P3 is used only for earth observation applications.
OCEANSAT-1, meant to study physical and biological aspects of oceanography, was launched on board PSLV-C2 in May 1999. It carries the following payloads:
Ocean Colour Monitor (OCM): OCM provides the best-ever spatial resolution for any oceanography mission:
At present, OCEANSAT-1 is used to collect data from its OCM.
TES was launched on board PSLV-C3 in October 2001. The satellite is intended to demonstrate and validate technologies that could be used in the future cartographic satellite missions. Some of the technologies demonstrated in TES are attitude and orbit control system, high torque reaction wheels, new reaction control system with optimised thrusters and a single propellant tank, light weight spacecraft structure, solid state recorder, X-band phased array antenna, improved satellite positioning system, miniaturised TTC and power system and two-mirror-on-axis camera optics. TES also carries a panchromatic camera with a spatial resolution of 1 m.
The satellite is primarily intended for advanced mapping applications. Cartosat-1 will have two panchromatic cameras with a spatial resolution of 2.5 m and a swath of 30 km each. The cameras are mounted with a tilt of +26 deg and _5 deg along track with respect to nadir to provide stereo pairs of images for generation of Digital Terrain Models (DTM)/Digital Elevation Models (DEM). The satellite will be placed in a sun synchronous polar orbit of 617 km. It will have a revisit capability of 5 days, which can be realised by steering the spacecraft about its roll axis by +26 degrees.
The new technologies that will get proven in Cartosat-1 will include improved version of star sensor, bus interface connecting control systems, star sensor, satellite positioning system and data handling.
During the year, all mainframe systems have been integrated and tested. Disassembled mode test has been completed for mainframe and payload systems. The payload, Data handling, Solid State Recorder and X band systems have been tested. Preparations are in progress for the integrated satellite test and thermovac test.
Cartosat-1 is planned for launch by PSLV in the first half of 2005.
CARTOSAT - 2
Cartosat-2 will be an advanced remote sensing satellite with a single panchromatic camera capable of providing scene-specific spot imageries for cartographic applications. The camera is designed to provide imageries with better than one metre spatial resolution and a swath of 10 km. The satellite will have high agility with capability to steer along and across the track up to + 45 degrees. It will be placed in a sun-synchronous polar orbit at an altitude of 630 km. It will have a revisit period of four days. The re-visit can be improved to one day with suitable orbit manoeuvres.
Several new technologies like two mirror on axis single camera, Carbon Fabric Reinforced Plastic based electro optic structure, lightweight, large size mirrors, JPEG like data compression, advanced solid state recorder, high-torque reaction wheels and high performance star sensors are being employed in Cartosat-2.
During the year, the flight structure of Cartosat-2 has been fabricated and thermally treated. Reaction control systems elements like tanks, filters, pressure transducers, latch valves and plumbing are being integrated. The qualification model payload has gone through environmental tests. The flight model assembly of lightweight mirrors is under integration.
Cartosat-2 is planned for launch in 2005-06.
Radar Imaging Satellite (RISAT)
Radar Imaging Satellite with night and day imaging capability as well as imaging under cloudy conditions, will be an important system to complement the band of electro-optical sensors launched on board Indian remote sensing satellite so far. RISAT will have a multi-mode, multi polarisation, agile Synthetic Aperture Radar (SAR) operating in C-band and providing 3-50 metres spatial resolution. Various modes such as Scan SAR and strip and spot modes are planned to provide images with coarse, fine and high spatial resolutions. RISAT will also incorporate algorithms and data products to serve the user community in many applications.
The new technologies in RISAT include: 160 x 4 Mbps data handling system, 50 Newton-meter-second reaction wheels, SAR antenna deployment mechanism and phased array antenna with dual polarisation.
During the year, the preliminary design review for electrical subsystems and Attitude and Orbit Control System elements has been completed. Installation of 3D measuring instrument for integration and alignment of SAR antenna has been completed.
Oceansat-2 is envisaged for providing continuity to Oceansat-1. It will carry Ocean Colour Monitor (OCM) and a Ku-band Pencil Beam Scatterometer. OCM will be similar to that of Oceansat-1. It will be an 8-band multi-spectral camera operating in the Visible _ Near IR spectral range. This camera provides an instantaneous geometric field of view of 360 m covering a swath of 1,420 km. The Scatterometer is a microwave radar for measuring the ocean surface wind velocity. It operates at 13.515 GHz providing a around resolution of 50 km.
During the year, flight model OCM payload fabrication has been initiated. Scatterometer configuration has been finalised.
Oceansat-2 will be launched into a near polar sun-synchronous orbit of 720 Km altitude by PSLV in 2006-07.
The 90 kg Twsat is a remote sensing micro satellite proposed for Third World countries. The payload will be a 3-band CCD camera with single optics and beam splitter. The 50 user terminals, which can receive payload data are to be installed in Indian universities and selected Third World countries. The design and development of this micro-satellite is expected to evolve a standard micro-satellite bus configuration, which can incorporate various payloads.
Initial configuration study was completed during the year.
During the year ISRO Telemetry, Tracking and Command Network (ISTRAC) continued to provide mission support to the Resourcesat-1, TES, Oceansat-1, IRS-1D, IRS-P3 and IRS-1C.
The Svalbard and Tromso stations of Kongsberg, Norway have been added to the TTC network to support data reception requirements of IRS missions. Modernisation of the TTC station at Bearslake has been completed. RESOURCESAT-1 entered into normal phase of operations during the year and mission operations are being carried out as per schedule. The payload operations are carried out over Shadnagar in India and Neustrelitz in Germany.
IRS-1D payload operations have been carried out over the Indian stations at Shadnagar as well as over 15 data reception stations around the world. The OCM payload of Oceansat-1 is operated over four international ground stations.
Satellite Data Acquisition and Processing
The National Remote Sensing Agency (NRSA) at Hyderabad acquires and processes remote sensing data and supplies value added products and application services to users. Being the nodal agency for reception, archival, processing and dissemination of remote sensing data in the country, NRSA ensures optimal utilisation of remote sensing data as well as helps spreading its benefits and awareness among the user community. NRSA also caters to the data demand from the neighbouring countries.
Data acquisition from Indian Remote Sensing Satellites, IRS-1C, IRS-1D, IRS-P3, Oceansat-1, TES and Resourcesat as well as US TERRA and NOAA satellites has continued during the year. The European ERS data is being acquired on user requests. Reception and processing facilities have been upgraded during the year to handle MODIS data from Aqua satellite.
The ground systems for reception, processing and product generation are being upgraded for the forthcoming missions like, Cartosat-1, Cartosat-2 and Risat. A new X-S Band composite feed system is being developed with improved specifications and performance. This will also be used for data in dual Polarisation in X-Band, needed for Risat. For Cartosat-1, new procedures have been worked out for quality verification and the facility has been established.
Data archival efficiency during the year continued to be more than 98 percent for all the missions. Data is recorded on digital media for the archival and quick look browse systems. The browse data along with ancillary data is transmitted over the Spacenet of ISRO from NRSA Earth Station at Shadnagar to the browsing facility at Balanagar, Hyderabad. The data on the browse archival system is available for users on internet for selection.
The payload programming facility has been automated by integrating it with data ordering and browse services.
The demand for data products from the users including state governments and foreign customers has increased significantly during the year with IRS data demand being the most. About 11,000 data products have been disseminated to both Indian as well as foreign users in state and central governments, private and academic sectors. The requirement of value-added products continues to see an upward trend. While the average turn-around-time of data products is around three days, the products are supplied within 24 hours in case of emergencies. Historic data of all satellites in NRSA's archives has been transcribed onto durable high-density digital media like CDs. OCM/NOAA data are being made available through the Internet to important users like IITs and Indian National Centre for Ocean Information Services.
RESOURCESAT-1 data products availability was announced to the users during January 2004.
As per the Remote Sensing Data Policy of the Government, NRSA is the national acquisition/distribution agency for all satellite data within India. NRSA is currently supplying data from Ikonos, Radarsat, Envisat and Quick Bird satellites. Distributors for IRS data are appointed in USA, Iran, Bangladesh, Sri Lanka and Singapore.
Aerial Remote Sensing
The Aerial Remote Sensing facility of NRSA offers a range of value-added services. With two aircraft with modern navigational aids, aerial cameras and sensors, state-of-the-art equipment and expertise, NRSA renders aerial remote sensing services such as aerial photography and digital mapping, infrastructure planning, scanner surveys, aero-magnetic surveys, large scale base mapping, topographic and cadastral mapping, etc. Facilities for Airborne Laser Terrain Mapping Digital Camera system have been established. A Network Attached Storage system has been installed and commissioned and a prototype of storage/archival of data has been designed and demonstrated for implementation.