DTA10 MERIS/OLCI CAMERAS

MERIS Spain

The MERIS instrument is a spectro-imager of medium resolution, operated in push-broom mode. It is fitted onto the ESA ENVISAT satellite. The Earth's surface can be analysed within a spectral range of 400nm to 1050nm, with a spatial resolution of 260m at nadir and a swath width of 1200km. Up to 15 spectral bands can be selected in the whole spectrum with a width of 1.25nm to 30nm.

SODERN’s contribution to MERIS is very significant as it includes the major part of the imaging chain, namely the 5 optical modules and the complete analogue imaging chain.

MERIS / OLCI camera

To cover its 68° field of view, the MERIS instrument consists of 5 identical Optical Modules mounted in fan-shape on an optical bench. Each module is composed of a catadioptric lens imaging the Earth's surface on the entrance slit of a spectrometer. With diffraction grating, this Earth line image is then spectrally spread in the range 400nm ­ 1050nm on the columns of a CCD array.

Each optical module is equipped with a focal plane assembly (FPA) to form a camera. The FPA is part of the Analogue Imaging Chain which is comprised of:

• 5 FPA, each equipped with a back-thinned illuminated CCD matrix and a front-end electronics. The CCD is accurately positioned with respect to the optical module focal plane. A thermoelectric Peltier cooler sets the detector operating temperature at -25°C ± 100 mK,
• 5 detection boxes (BD) which supply the FPA with the electrical signals to operate the CCD,
• the video electronics unit (VEU) which processes the analogue signal coming from the FPA and digitises it on 12 bits,
• the detection supply unit (DSU) to supply power to all these electronic devices.

In the frame of the GMES european initiative, SODERN will now supply the OLCI cameras for the SENTINEL 3 satellites. This development relies on similar cameras developped for MERIS on ENVISAT that give excellent in-flight results.