SATELLITE SYSTEMS

Indian satellite systems fall into two categories; Remote-Sensing & Communications. The main programs being;

• Apple

• Aryabhata

• Bhaskara

• INSAT-1 series

• INSAT-2 series

• IRS-Series

• Rohini

• Sross

IRS - Indian Remote Sensing satellite

The Indian Remote Sensing satellite system is India's first domestic dedicated earth resources satellite program and an element of the National Natural Resource Management System. IRS is an Indian program to develop an indigenous capability to image earth, particularly India. Its mission is ground water exploration, land use, forest & flood mapping, inventory of surface  water. The first satellite in the IRS series (IRS-1A) was launched by a Soviet Vostok booster. As of December 1997, seven IRS family satellites have been launched; IRS-1A, -IB, -1E, -P2, -1C, -P3, -1D (in order of launch). Two more satellite are planned to be launched before the end of the century, these include IRS-P4 (to be called Ocean Sat) to be launched in early 1998 and the IRS-P (to be called Carto Sat) before 1999. Both satellites are planned to be launched aboard the PSLV.

IRS-1A: The IRS-1A was launched on 17 March 1988 from Tyuratam. Weight was 950kg. A four-band imaging system, with CCD cameras returned overlapping 73m & 36.5m res images from sun-synchronous orbit. The series extends the work of earlier satellites in conducting forestry surveys, snow cover & flood control work, location of underground water supplies, determination of salinity, of water used for agricultural irrigation and land management. All three imaging systems have been opertional since 7 April 1988. Over 700,000 scenes had been returned by mid-1996. The satellite carried a real time LISS-2A/B data downlink with a transfer rate of 10.4Mbit/s. The data is down-linked to the 10 metre dish at Shadnagar on 20W X-band & LISS 1 data on 5W S-band at 5.4Mbit/s. There is no onboard recorder. Satellite control is exercised from Bangalore, with the Lucknow station providing backup.

LISS-1: Four 2048 element linear CCD imagers with spectral filters. The total unit mass is 38.5 kg. Focal length 162.2cm, field of view 9.4°, generating resolution of 72.5m and 148 km swath width, framing LISS-2 image pairs.

LISS-2A/B: Eight 2048 element linear CCD imagers with spectral filters. Focal length 324.4mm, field of view 4.7° each, generating resolution of 36.5m & 74 km swath width. The two 80.5kg units are positioned either side of LISS-1 and view either side of the ground track with a 3km lateral overlap; two pairs thus cover a single LISS-1 frame.

IRS-1B: Launched on 29 August 1991 from Tyuratam, aboard a SL-2 Vostok. Declared operational 16 September 1991. Its orbit was 857x919km, 99.25°. Sun-synchronous. Other specifications are same as the IRS-1A.

IRS-1C: Launched on 28 December 1995 from Baikonur into a retrograde (99º inclination). It's orbit was 816km/816km (sun-synchronous). The IRS-1C acquires the highest spatial resolution remote sensing data commercially available today. The 5 metre panchromatic data is especially useful for urban planning and mapping, the 25 metre multi-spectral data is good for vegetation monitoring and natural resource planning; and the 180 metre wide-field data band has a 740km swath and 5-day repeat coverage which is excellent for large-area vegetation monitoring.

Communications: Satellite control is exercised from Bangalore, with the Lucknow station providing backup. Recorded data is down-linked on the 40W 8 GHz X-band link. Three cameras all utilize push-boom CCD units, continuing and expanding the IRS-1A/B imagers. IRS-1C data are currently being received at three ground stations: Shadnagar in India; Norman in Oakland and Neustrelitzl in Germany.

The IRS-1C satellite

Shadnagar covers all of India, Pakistan, Afghanistan, Bangladesh, Burma and Thailand, and portions of Iran, Oman, Cambodia and Laos. Norman acquires data of nearly all of North America, including from southern Canada, Mexico and most of Central America. Neustrelitz covers Europe, and portions of western Asia and northern Africa. Space Imaging EOSAT has complete coverage several times over of IRS-1B data for the Norman footprint and is beginning to build the IRS-1C archive.

IRS-1C has on-board recorders for data collection outside the range of ground station, to further increase data availability. Space Imaging EOSAT is rapidly expanding the IRS ground station network. Germany is now receiving IRS-1C data and is processing this data since mid-1996. Ground stations in Australia, Japan, Thailand, South Africa and Ecuador are be receiving and recording data since the end of 1996, and as many as 10 others are on-line in 1997. Another means to expand the global archive of available data is Space Imaging EOSAT's capability to deploy portable ground stations worldwide to collect IRS (as well as Landsat, ERS, and SPOT) data.

PAN: The IRS-1C's high-resolution digital panchromatic data is the is the best imagery commercially available today. The Pan sensor on IRS-1C is the first commercial satellite imagery to break the 10 metre barrier and offer regular repeat coverage. Compared to aerial photography, IRS-1C PAN data save users time and money. Its generous scene size (70 x 70 km) eliminates the time-consuming need to mosaic dozens of individual aerial photos. And because it is digital data, IRS-1C Pan images are immediately ready for loading into your image processing or GIS system.

The high resolution makes it an excellent tool for creating and maintaining up-to-date thematic maps of even the most remote area of our planet. In addition, with off-nadir viewing, repeat coverage is available as often as every five days, enabling users to monitor rapidly evolving environmental situations, and stereoscopic coverage can be acquired (with off-track viewing up to +/- 26º). Unlike most aerial photography, IRS-1C Pan data is already digital, so you can easily combine it with other data. Merged with multi-spectral data, pan data adds spatial detail to thematic maps. In a GIS, Pan data is an excellent base on which to display other data layers. With stereo capability, digital terrain models can be created for 3-D analysis.

LISS-III (Linear Imaging and Self Scanning sensor): A multi-spectral sensor with a spatial resolution of 23.5m, operating in the visible, near infra-red bands and 70.5m resolution in the short wave infra-red band, with a swath of 141Km.

WiFS: A Wide Field Sensor sensor with a spatial resolution of 188m, two spectral bands in the visible and near infra-red regions, with a swath of 810 Km.

More detailed spectral sensor information at: http://www.euromap.de/docs/doc_002.html

IRS-P2: Launched on 15 October 1994 from Sriharikota aboard the PSLV-D2. The IRS-P2, has completed one year of successful operation in orbit. Specifications are the same as the IRS-1C.

IRS-P3: Launched on 21 March 1996 from Sriharikota aboard the PSLV-D3. This was the third test launch of the PSLV. The satellite's perigee/apogee was 802km/848km and inclination was 98.8° 

The payload consists of two imaging sensors and one non-imaging sensor. The Wide Field Sensor (WiFS) sensor is providing data with a spatial resolution of 188m in three spectral bands, in the visible and near infra-red regions, with a swath of 810 Km. The other two sensors on-board are a Modular Opto-electronic Scanner (MOS) and an Xray astronomy payload. WiFS and MOS data products are being disseminated to users.

The IRS-1D satellite

IRS-1D: Launched in September 1997, IRS-1D was launched from Sriharikota using the PSLV. However the PSLV placed in an elliptical orbit, instead of a circular orbit. The snag was partly fixed. It is being used to map and monitor calamities. Specifications are the same as the IRC-1C satellite.

More detailed spectral sensor information at: http://www.euromap.de/docs/doc_003.html

IRS-P4: Also known as the Oceansat-1, the IRS-P4, has a Multi-frequency Scanning Microwave Radiometre (MSMR) and a nine-band Ocean Colour Monitor (OCM). The satellite's sensors will have a resolution of 250 metres at nadir and will have a swath width of 1500 km with a receptivity of two days. It was launched in a polar sun-synchronous orbit at 720 km away from the earth. It was launched successfully into space on 26 May 1999 by PSLV-C2 and is currently in orbit. The main application of this satellite is for gathering information related to water vapour and carrying out ocean colour monitoring. The data collected from ocean colour monitoring will be used for conducting a fisheries survey and development of a fisheries forecast model based on the data.

The satellite will record the chlorophyll concentrations in the oceans which will help predict biological productivity in the oceans. Some of the important applications of the ocean colour monitoring are identification of potential fishing zones in coastal waters, exploration of deep sea fishery resources, primary production model and fish stock assessment and selection and monitoring of algal blooms. Besides these, the monitoring will be useful in coastal processes like sediment dynamics, dynamics of estuaries and tidal inlets, prediction of shore time changes, circulation & dispersal pattern, up-welling of coastal and oceanic fronts and surface currents. The satellite will have a great impact on environment studies as it will prove to be of great use in learning about marine pollution and oil slicks. Also important will be its use in coral reef studies.

IRS-P5: Also known as the Cartosat, the IRS-P5, has been intended for cartographic applications. Two PAN Cameras one fore-mounted with a tilt of +26 deg and the other Aft-mounted with a tilt of -5 deg from the yaw axis with a resolution of 2.5 metres. It would be mainly useful for map making and terrain modelling. Would be launched on PSLV-C6. Reports suggest 2004/05.

CARTOSAT-1 in space (artistic rending). (Source: ISRO)
CARTOSAT-1 during assembly and testing (Source: ISRO)	Electro-optical module configuration of pan camera  (Source: ISRO)

Good source of information in a paper published by ISRO
1. http://www.gisdevelopment.net/technology/rs/techrs023.htm
2. http://www.gisdevelopment.net/technology/rs/techrs023a.htm
3. http://www.gisdevelopment.net/technology/rs/techrs023b.htm
4. http://www.gisdevelopment.net/technology/rs/techrs023c.htm
5. http://www.gisdevelopment.net/technology/rs/techrs023d.htm

IRS-P6: Also known as the Resorcesat-1.

Resourcesat-1, mounted on top of the PSLV-C5's fourth stage. (Source: ISRO)	Resourcesat-1 in space (artistic rending). (Source: ISRO)
Isometric view of IRS-P6 (compact) (Source: ISRO)	Isometric view of IRS-P6 (deployed) (Source: ISRO)
LISS-IV Camera (Source: ISRO)	LISS - III Camera (Source: ISRO)
AWiFS - A Camera (Source: ISRO)	Coverage due to LISS-IV off-nadir capability (Source: ISRO)

Of the 12 remote sensing satellites sent up by ISRO till date, Resourcesat-1 is the most sophisticated as well as the heaviest. The satellite will continue the remote sensing data services provided by IRS-1C and IRS-1D that have outlived their design life, and also enhance the data quality.

The 3 axis stabilized satellite has:
1. A high-resolution linear imaging self-scanner (LISS-4) operating in three spectral bands in the visible and near infrared region (VNIR) with 5.8-metre spatial resolution and steerable up to 26 degree across track in order to obtain stereoscopic imagery and achieve a five-day revisit capability;
2. A medium resolution LISS-3 operating in three spectral bands in VNIR and one in short-wave infrared (SWIR) band with 23.5-metre spatial resolution and;
3. An advanced wide-field sensor (AWiFS) operating in three spectral bands in VNIR and one band in SWIR with 56-metre spatial resolution.
4. A solid state recorder with a capacity of 120 giga bits(15GB) to store the images taken by the cameras, which could be read out later to the ground stations.
5. Solar panels that generate 1250Watt power.

Source: ISRO http://www.isro.org/pslvc5/index.html

More spectral  sensor information at:       http://www.euromap.de/docs/doc_005.html
IRS-P6 Data User handbook:                 http://www.euromap.de/download/P6_data_user_handbook.pdf

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