Moderate-resolution Imaging Spectroradiometer

MODIS ( Moderate -resolution Imaging Spectroradiometer ) is a scientific instrument for measuring electromagnetic radiation. The translation of the term refers to an imaging spectrometer radio medium resolution. MODIS was by NASA on the Terra satellite (1999) and Aqua ( 2002) shot into orbit.

The instruments are designed to detect large-scale, geodynamic processes to deliver including changes in cloud cover and the radiation budget, but also information about the deeper atmosphere or oceans. The MODIS instrument provides high radiometric sensitivity (12 bit) in 36 spectral bands in the range from 0.4 to 14.4 microns. The response has been specially adapted to the needs of users and speaking very low signals on different frequency bands. In two bands is acquired nadir at a nominal resolution of 250m, in five frequency bands recording with 500m resolution and the remaining 29 bands work carried one kilometer resolution. Through a 55 -degree recording pattern in the EOS- orbital altitude of 705 km, a 2330 km wide strip is detected, so that the earth's surface every two days is completely absorbed.

Construction

In the assembly of the receiving mirror, a rotating, double-sided mirror is used to cover a range of ± 55 ° can. It is driven by a motor which will operate continuously throughout the estimated life of the equipment (6 years). The optical system consists of an afocal zweispiegeligen off-axis telescope, which directs energy to four refractive objective assemblies. These are the VIS, NIR, SWIR / MWIR and LWIR, covering the spectral ranges from 0.4 to 14.4 microns.

A passive high-performance water block for the 20 infrared spectral bands on two HgCdTe focal plane assemblies ( FPA for focal plane assembly) an operating temperature of 83K safe. A novel silicon- based photovoltaic cell readout technology for the visible light and near-infrared light leads to a hitherto not achieved quantum efficiency with low noise and exceptional dynamic range. Gain and zero point are analogous programmable. Amplifier electronics and timing are located in dedicated electronic modules in the immediate vicinity of the FPAs, the room viewing Analog Module (Space -viewing Analog Module, FAM ) and the forward -looking analog module (Forward -viewing Analog Module, FAM). The third module, the main electronics module controls the power supply, the system monitors, telemetry commands and performs activities and includes the calibration electronics.

The system also has four on-board calibrators and also takes a look into space: They are: A solar diffuser (SD ), a V -groove blackbody, a spectroradiometer - calibration assembly ( SRCA ) and a unit for monitoring stability of the solar radiation (Solar diffuser stability monitor SDSM ).

The first MODIS flight instrument (PFM for Proto Flight Model) is on board the Terra EOS AM-1 satellite. Terra was successfully put into operation on 18 December 1999. The second MODIS flight instrument, Flight Model 1 or FM1, is part of the Aqua EOS PM-1 satellite; it was successfully put into operation on May 4, 2002.

Specifications

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