Operating instruments: AIRS, AMSU, CERES, MODIS, and AMSR-E, the latter at a reduced rotation rate appropriate for cross-calibration purposes rather than for science.
The focus of the Aqua mission is the multi-disciplinary study of the Earth's water cycle, including the interrelated processes (atmosphere, oceans, and land surface) and their relationship to Earth system changes. The data sets of Aqua provide information on cloud formation, precipitation, and radiative properties, air-sea fluxes of energy, carbon, and moisture (AIRS, AMSU, AMSR-E, HSB, CERES, MODIS); and sea ice concentrations and extents (AMSR-E).
INTRUMENTS
The Atmospheric Infrared Sounder (AIRS) is an advanced sounder containing 2378 infrared channels and four visible/near-infrared channels, aimed at obtaining highly accurate temperature profiles within the atmosphere plus a variety of additional Earth/atmosphere products. AIRS is the highlighted instrument in the AIRS/AMSU-A/HSB triplet centered on measuring accurate temperature and humidity profiles throughout the atmosphere.
The Advanced Microwave Sounding Unit (AMSU-A), a 15-channel microwave sounder designed primarily to obtain temperature profiles in the upper atmosphere (especially the stratosphere) and to provide a cloud-filtering capability for tropospheric temperature observations. The first AMSU was launched in May 1998 on board the National Oceanic and Atmospheric Administration's (NOAA's) NOAA 15 satellite. The EOS AMSU-A is part of a closely coupled triplet of instruments that include the AIRS and HSB.
The Humidity Sounder for Brazil (HSB), a 4-channel microwave sounder provided by Brazil aimed at obtaining humidity profiles throughout the atmosphere. The HSB is the instrument in the AIRS/AMSU-A/HSB triplet that allows humidity measurements even under conditions of heavy cloudiness and haze. The HSB provided high quality data until February 2003.
The Advanced Microwave Scanning Radiometer for EOS (AMSR-E) is a twelve-channel, six-frequency, total power passive-microwave radiometer system. It measures brightness temperatures at 6.925, 10.65, 18.7, 23.8, 36.5, and 89.0 GHz. Vertically and horizontally polarized measurements are taken at all channels. The Earth-emitted microwave radiation is collected by an offset parabolic reflector 1.6 meters in diameter that scans across the Earth along an imaginary conical surface, maintaining a constant Earth incidence angle of 55° and providing a swath width array of six feedhorns which then carry the radiation to radiometers for measurement. Calibration is accomplished with observations of cosmic background radiation and an on-board warm target. Spatial resolution of the individual measurements varies from 5.4 km at 89.0 GHz to 56 km at 6.9 GHz.
The Moderate Resolution Imaging Spectroradiometer (MODIS), is a 36-band spectroradiometer measuring visible and infrared radiation and obtaining data that are being used to derive products ranging from vegetation, land surface cover, and ocean chlorophyll fluorescence to cloud and aerosol properties, fire occurrence, snow cover on the land, and sea ice cover on the oceans. The first MODIS instrument was launched on board the Terra satellite in December 1999, and the second was launched on Aqua in May 2002.
The Cloud's and the Earth's Radiant Energy System (CERES) is a 3-channel radiometer measuring reflected solar radiation in the 0.3-5 µm wavelength band, emitted terrestrial radiation in the 8-12 µm band, and total radiation from 0.3 µm to beyond 100 µm. These data are being used to measure the Earth's total thermal radiation budget, and, in combination with MODIS data, detailed information about clouds. The first CERES instrument was launched on the Tropical Rainfall Measuring Mission (TRMM) satellite in November 1997; the second and third CERES instuments were launched on the Terra satellite in December 1999; and the fourth and fifth CERES instruments are on board the Aqua satellite.