Imaging Spectrometers/Radiometers
type: Concept

AVNIR
type: Concept
in scheme: instruments
definition: AVNIR is a high spatial resolution optical sensor for observing land and coastal zones in visible and near-infrared regions. AVNIR has 4 spectral bands with a 16m spatial resolution and 1 panchromatic band with an 8 m spatial resolution. The AVNIR data will be useful for environmental awareness and monitoring of such phenomena as desertification, destruction of tropical forests, and pollution of coastal zones as well as for resource exploration, land use, etc. AVNIR's field of view (FOV) is about 80km, picked up by lines of small pixels. Its FOV scans the entire earth's surface as the satellite moves. There are only a few other similar sensors, such as TM on LANDSAT. Among AVNIR's sensors are features which give the sensors high spatial resolution, a pointing function to change the observation field by +-40 degrees along the cross track, a 0.4rim band useful for coastal zones and lakes, an optical calibration function which uses solar light and lamps, as well as others. AVNIR is composed of two units, the Scanning Radiometer Unit (SRU) which is mainly composed of optical components and the Electronic Unit (ELU) which includes mainly electronic components. Optics in SRU adopts a Catadioptric Schmidt optical system to reduce aberration in a wide field of view. Large mirrors used in Optics and Pointing Mechanism Assembly are ultralight mirrors weighing 50 to 70% less than conventional mirrors, made from low expansion material. CFRP with low thermal and moisture expansion properties is used as the truss structural material in order to make Optics light yet extremely precise in orbit. The large linear-array CCDs with 5,000 and 10,000 pixels are used as detectors and deliver high spatial resolution. Observation data is compressed in the Image Processing Assembly by about 10% in order to reduce the transmission data rate. [Summary provided by the Japan Aerospace Exploration Agency.] Group: Instrument_Details Entry_ID: AVNIR Group: Instrument_Identification Instrument_Categ…