Imaging Spectrometers/Radiometers
type: Concept

MERIS
in scheme: instruments
definition: The Medium Resolution Imaging Spectrometer (MERIS) is a core European Space Agency (ESA) instrument on the ENVISAT spacecraft (launched March 1, 2002). The primary objective of MERIS is to monitor ocean color and marine biophysical parameters in oceans and coastal regions with applications to land and atmospheric processes. MERIS is a passive push-broom optical system using Charge Coupled Devices (CCDs) at high spectral resolution (5-20 nm) in 15 channels from0.405 to 1.030 micrometers with a swath width of 1500 km. MERIS performed simultaneous spatial and spectral imaging. Spatial imaging is performed in a push-broom mode and spectral imaging is performed by diffraction grating dispersion. MERIS images are converted into electrical signals using CCDs. MERIS operates in two modes: Full Resolution (Direct Transmission) Mode and Low Resolution (Average Transmission) Mode. Full resolution mode uses 15 channels with a resolution of 0.25 x 0.25 km and a spectral resolution of 2.5 nm. Data will be relayed directly to the ground station in this mode and is not stored on-board. Low Resolution Mode uses 15 channels with a spatial resolution of 1 x 1 km and a spectral resolution of 2.5 nm. The MERIS imaging system consists of six overlapping optical modules, each with a 14 degree FOV. The FOV is deflected in the along-track direction by a depointing mirror. The ground imager receives light from the Earth and formed an Earth image on the entrance slit of the spectrometer. The spectrometer then dispersed the light onto an area array CCD. The spectrometer is comprised of a refracting block and a concave reflecting diffraction grating. All 15 MERIS channels are programmable in width and wavelength. On-board calibration is performed by seperate light sources and through the use of the depointing mirror as a shutter. All of the mechanical, thermal electronic and optical devices are mounted externally to the platform. MERIS is operated synergistically with the RA-2, ASAT, and AATSR …
type: Concept