<title>POLDER on-ground stray light analysis, calibration, and correction</title>

Abstract

POLDER is a CNES instrument on-board ADEOS polar orbiting satellite, which was successfully launched in August 1996. POLDER entered in its nominal acquisition phase in November 1996, and had been acquiring data till the loss of ADEOS in June 1997. POLDER spare model will be launched on-board ADEOS II in August 1999. This instrument is a multispectral imaging radiometer/polarimeter designed to collect global and repetitive observations of the solar radiation reflected by the Earth/atmosphere system, with a wide field of view (2400 km) and a moderate geometric resolution (6 km). Due to the wide field of view (around 50 degrees) and the important spectral range (from 443 nm to 910 nm), two different types of stray light phenomena have been identified during the radiometric on ground calibration. One is a local effect, that takes place around a light source, the second one is a global one, i.e. that a located light source creates stray light on the whole CCD detector. This paper first presents the analysis and characterization of these phenomena by means of instrumental measurements and a software simulation of the optics, then it describes the stray light calibration methods, and concludes with the correction method and its results.