Geometric correction of data from CCD payload of INSAT 2E

Geometric correction of data from CCD payload of INSAT 2E

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N. Padmanabhan and S. B. Gurjar
DPSD/SIPG/SIIPA, Space Applications Centre
Jodhpur Tekra, Ahmedabad – 380 015

INSAT 2E, which was launched in 1999, has apart from the communication transponders, a three-band charge coupled device (CCD) based imager. This instrument provides co-registered images of the Earth in the visible, near infrared and short wave infrared regions of the spectrum. The subsatellite point ground resolution of these images is about 1km x 1km. The central wavelengths and band widths of the spectral bands as well as the dynamic range and saturation radiance set points are so selected that the images can be used both for meteorological and Earth resources remote sensing applications. The payload has a basic telescope and scan mechanism for imaging. It is for the first time such a payload has been flown on a geostationary satellite. The application potential of this payload is enormous. It can image a vast area of the Earth in twenty-five minutes in the three spectral bands. The imaging direction can be varied on command from the ground, to obtain the images of the different regions of the globe. To make the data available useful for resource applications, it is imperative that the data be corrected for all the errors inherent in such an imaging. This paper describes the mathematical model for generating geometrically corrected products from such a payload. Starting from the basic mathematical model of the payload geometry, the paper culminates in describing the software developed for generating geocoded products for any area of interest. The input to the software is the area of interest given in terms of the corner latitudes and longitudes. Apart from generating the Geocoded products the software also gives the sun azimuth and elevation angles as also the satellite azimuth and elevation angles at various points of the area of interest.