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Trends in Satellite Remote Sensing

K. R. Sridhara Murthi
Executive Director
Antrix Corporation, India

The satellite remote sensing scenario witnessed a great upheaval over the past one decade and it was dominated by the success of high-resolution satellites, in the commercial domain.
The anchor tenant role of the US Government coupled with the spurt in demand for such data on a continuous basis due to a changing geopolitical landscape, which had been clouded by conflicts have helped to sustain this activity. The classical model of systematic global coverage cycles for imaging have been augmented with limited, AOI (Area Of Interest) coverage with improved revisit capability, thanks to the highly agile spacecraft platforms that permitted diverse modes of imaging such as ‘push broom’, ‘step and stare’ and ‘paint brush’ modes providing images of high resolution. Another major development in recent past that helped in meeting the underserved needs for high resolution digital elevation models is the successful entry into operation of along track stereo imaging satellites such as India’s Cartosat-1 and Japan’s ALOS.

Turning to lower resolutions, a robust need also continues for medium resolution data, which received some set back in supply side due to the limitation of line-scan corrector’s performance on Landsat-7. However, SPOT system, IRS-1C and 1D satellites and Resourcesat-1 continued to address this segment with established track record.

Notwithstanding the relatively long planning horizons of the satellites or related sensor technologies, the prediction of future trends is fraught with some risk of over or understatement of what the market is going to be in future. A major reason for this is the bouncing back of aerial remote sensing segment, reinforced with new sets of sensors and with the promise of improved turn around and cheaper operational costs. The drive towards creation of mass market for information embedding image based inputs and delivery through Internet are other forces that make predictions difficult. Nevertheless, the satellite remote sensing activity is going to be highly vibrant in the coming years, if the number of new systems which are under planning and development is any indication.

Even while this article is going for print, a state of the art operational satellite Cartosat-2, capable of providing 1 meter resolution images, is undergoing preparation for launch at the India’s Satish Dhawan Space Center, SHAR, at Sriharikota. Cartosat-2 will mark the first of the series of very high resolution mapping satellites of India, with observational features comparable to its peers across the globe. Cartosat-2 is designed as an agile system, permitting diverse modes of operation and higher revisit capabilities than earlier satellites from India. The satellite sensor will provide a radiometric resolution of 10 bits and its data will be downlinked in ‘X’ band, thus facilitating many existing stations around the globe to be able to downlink data, with minimum additional investments.

The satellite will also have recording capability onboard, so as to allow imaging of areas not covered by International Ground Stations. The International stations will be equipped with a variety of software developed by Indian Space Research Organisation such as satellite orbit/attitude data interface, quick look browse, payload programming and data product generation softwares. Cartosat-2 along with its predecessors like IKONOS-II, Quikbird, Orbview-3 and EROS-B1 will strengthen the application scenario worldwide.

The advent of many new satellites in the high-resolution range will improve user service levels, besides bringing down costs. There will also be a trend to realise sub meter systems, as evident from the plans for GeoEye-1 (data of 41 cm GSD) and Wordlview-1 of Digital Globe (providing data of 47 cm GSD) and such future satellites from India, Europe and others. Public private partnerships will be a trend to be watched in this area.

The Advanced Wide Field Sensor on ResourceSat has led a trend to provide very wide coverage with improved resolution. Usefulness of this approach has been vindicated by growing demand for such data in a variety of resource management applications which need both seasonal currency of data and coverage of large areas.

Agricultural inventory and production forecasts are example of such an application. Such needs will be addressed in future by constellations of small satellites, with improved sensor technology. Rapid Eye constellation from Europe will provide larger coverage combined with fairly high resolution.