GIS News - Cover Story

October 2001 : EO Satellite boom

The successful launch of the Technology Experiment Satellite (TES) by the Polar Satellite Launch Vehicle (PSLV-3) along with two other satellite-BIRD for Germany and Project for On-Board autonomy (PROBA) for Belgium, from the SHAR is a mission made possible by ISRO. (http://www.isro.org/pslvc3/pslvc3_1.htm)

The TES is a major technological advancement for India especially in the field of Earth Observation. "TES is a one metre resolution system. We can now look more closely at buildings, vehicles, flood areas, etc. anywhere on the earth." said Mr. Kasturirangan, Chairman ISRO.

The capability of 1 metre high resolution has raised the expectation of high-resolution imagery becoming available for civilian projects in India at economical cost. Although there are speculations regarding the use of the satellite for military purposes only like the US military. Indian Army has been asking for a satellite with 1 metre resolution, especially after Kargil war in 1999, although ISRO's IRS-1C and 1D are still operational and provide 5.8 metre resolution images with PAN Cameras they are not very helpful in monitoring intruders in border areas.

TES unlike PAN is fixed and the entire satellite has to be turned. Getting 1-metre resolution requires the TES to be counter rotated in the opposite direction as its movement. This keeps the camera pointed at the same place longer and allows sufficient light to reach the electronic imaging devices. The same technique has been used in the Israeli satellite EROS-1A, which gives image of 1.8-metre resolution.

As per the available information on EROS, it carries a camera with a focal plane of CCD (Charge Coupled Device) detectors with 7,800 pixels per line, and produces a panchromatic image with a resolution of 1.8 m. The EROS A-class satellites provide a swath of at least 12.5 km in width. The EROS system utilizes a "push broom" technique, as if the satellite were sweeping the areas to be imaged in long strokes. The EROS satellite camera is rigidly attached to the satellite bus (main structure), so pointing the satellite aims the camera. The EROS A1 sensor scans asynchronously, allowing the satellite to move at a faster ground speed than its rate of imaging. The satellite tilts backward to take the images at an almost constant predetermined angular speed, enabling the detectors to dwell longer over each area. In this way the sensor is able to get more light, and improve contrast and signal-to-noise ratio - important conditions for optimal imaging. (http://www.ccrs.nrcan.gc.ca/ccrs/tekrd/eros/erosteke.html)

October witnessed an upsurge in the launch and availability of sub-meter resolution imagery from various satellites. QuickBird high-resolution satellite by DigitalGlobe was launched on 18 Oct 2001. Once operational, QuickBird will begin acquiring 61-centimetre (2 foot) resolution Panchromatic and 2.44-metre (8 foot) multispectral (colour) imagery. At 61-centimetre resolution, buildings, roads, bridges and other detailed infrastructure becomes visible. (http://www.digitalglobe.com/?goto=news/news_10_18_2001)

LAND INFO International, provider of digital geospatial information across the world now offers 0.95-meter, 1.56-meter, and 2-meter resolution imagery generated from Russia's DK-1, DK-2 and KVR-1000 satellites, respectively. This panchromatic (black/white) imagery is available for the United States and across the world. Prices start as low as $22 per square kilometre. Archived data is as recent as 1999 for major USA and international cities. Special custom tasking services are also available. (http://www.landinfo.com/1_russian.htm)

On the military front US, who already had six spy satellites, added one more spay satellite a week after the September 11, 2001 attack. Four of these are called Keyholes, which take photographic images estimated to be six to ten times better than 1 metre resolution imagery available from IKONOS.