Characterization and calibration of a high-resolution multi-spectral airborne digital camera

This paper presents the characterization and calibration of a new digital modular camera call PELICAN (French acronym for "Plateforme Et Logiciels Informatiques de Cameras Aeroportees Numeriques"). This system has been developed in 2003 as an IGN-ONERA-CNES cooperation project. The basic configuration is a set of four optical heads each equipped with a 4096 × 4096 pixels CCD detector working in the visible and near IR spectral range (from 400 nm to 950 nm). This sensor provides synchronous images achieved with a TDI-like control of the CCD to avoid smearing, thanks to GPS data. This paper gives an overview of the instrument, its calibration facility and our approach of calibration. The first step consists of modeling the sensor. It conducts to the calibration equation and the proper number of correction point to acquire. Characterization includes all the necessary measurements to validate the previous model. This process also gives us accurate visions of the sensor use extent. After a possible model adjustment, we acquire flat-field images in the whole range of configuration. These images provide an inter-pixel sensitivity matrix. We also perform a spectral sensitivity measurement and an acquisition on calibrated source. These last steps allow calculation of the absolute sensitivity. As an example of the versatility of the system, first results from an experiment over urban area (Capitoul campaign) are described. For this airborne campaign held in February 2004, the system simultaneously acquires images of eight narrow spectral bands of 20 nm width, with a 20 cm spatial resolution.