Radiometric Responses of the Multispectral Imager SLIM 6 for Dark and Bright Target

Abstract

ALSAT-1 is the first Algerian satellite put into orbit. It was launched November 2002, 28th at 6:07 GMT into a 700 KM sun-synchronous orbit. Alsat-1 payload (SLIM-6) is a multispectral imager, with two banks of 3 channels. Each is equipped with a CCD sensor and an optical convergent associated electronic circuit. The image quality of ALSAT-1 depends on the quality of imager and design. For the control, we must detect and analyze changes in the radiometric quality of the camera caused by aging instruments and satellite. This analysis should be periodic to locate the defects on raw reference images. The aim of our study was to analyze the sensitivity of each channel, using reference images (scenes with a uniform background radiation): images taken at night, images over the ocean, or images of snowy areas; were taken by Alsat-1 between early 2004 and late 2006. In this purpose we used several assessment methods based on mathematical and algorithmic tools. These includes objective assessment and many of subjective method (visual analysis, use of statistical indicator).