Preliminary results of the XSAT in-orbit IRIS calibration and validation campaign

Abstract

XSAT, a Singapore built Earth Earth Observation microsatellite was placed in polar orbit on 20th April 2011 and has completed its LEOP phase. It has now begun its primary mission of earth observation. The main EO payload is IRIS, a multispectral camera with red, green and near infrared bands and a specified ground sample distance of 10m. This paper describes the process of calibration and validation of IRIS. Two aspects of camera performance are examined: 1) The Modular Transfer Function (MTF) has been estimated with the sharp linear edge method. A man-made high contrast linear edge at the Pasir Panjang terminal has been selected to be the target object. From the target, an Edge Spread Function (ESF) is estimated by interpolating the image appropriately. The MTF is then obtained by differentiating the ESF. 2) Inter-pixel normalization. Sensors left without normalization would exhibit a visible amount of inter pixel variation for any given uniform illumination. This results in visible along-track striations. Normalization is the process of adjusting the individual pixel responses in order to minimize inter pixel variation. In this paper we present the process used to normalize pixel responses.