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AQUA

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aqua

Launched in a sun-synchronous orbit on 4 May 2002 Aqua is the second satellite in NASA's Earth Observing System (EOS). Aqua, Latin for water, is a NASA Earth Science satellite mission named for the large amount of information that the mission is collecting about the Earth's water cycle, including evaporation from the oceans, water vapor in the atmosphere, clouds, precipitation, soil moisture, sea ice, land ice, and snow cover on the land and ice.

 

Instruments
  • AIRS – Atmospheric Infrared Sounder
  • AMSR-E – Advanced Microwave Scanning Radiometer for EOS
  • AMSU-A – Advanced Microwave Sounding Unit
  • CERES – Clouds and the Earth's Radiant Energy System
  • HSB – Humidity Sounder for Brazil
  • MODIS – Moderate Resolution Imaging Spectroradiometer. MODIS delivers sea surface temperature (SST), atmospheric temperature, cloud temperature, cloud altitude, water vapor, ocean color and aerosol data. The MODIS instruments on board the Terra and Aqua EOS satellites acquire data with global coverage every 1-2 days.
MODIS Instrument

The MODIS instrument provides high radiometric sensitivity (12 bit) in 36 spectral bands ranging in wavelength from 0.4 µm to 14.4 µm. The responses are custom tailored to the individual needs of the user community and provide exceptionally low out-of-band response. Two bands are imaged at a nominal resolution of 250 m at nadir, with five bands at 500 m, and the remaining 29 bands at 1 km. A ±55-degree scanning pattern at the EOS orbit of 705 km achieves a 2,330-km swath and provides global coverage every one to two days.

A high-performance passive radiative cooler provides cooling to 83K for the 20 infrared spectral bands on two HgCdTe Focal Plane Assemblies (FPAs). Novel photodiode-silicon readout technology for the visible and near infrared provide unsurpassed quantum efficiency and low-noise readout with exceptional dynamic range. Analog programmable gain and offset and FPA clock and bias electronics are located near the FPAs in two dedicated electronics modules, the Space-viewing Analog Module (SAM) and the Forward-viewing Analog Module (FAM). A third module, the Main Electronics Module (MEM) provides power, control systems, command and telemetry, and calibration electronics.

The system also includes four on-board calibrators as well as a view to space: a Solar Diffuser (SD), a v-groove Blackbody (BB), a Spectroradiometric calibration assembly (SRCA), and a Solar Diffuser Stability Monitor (SDSM).

Primary Use Band Bandwidth1 Spectral
Radiance2
Required
SNR3
Land/Cloud/Aerosols
Boundaries
1 620 - 670 21.8 128
2 841 - 876 24.7 201
Land/Cloud/Aerosols
Properties
3 459 - 479 35.3 243
4 545 - 565 29.0 228
5 1230 - 1250 5.4 74
6 1628 - 1652 7.3 275
7 2105 - 2155 1.0 110
Ocean Color/
Phytoplankton/
Biogeochemistry
8 405 - 420 44.9 880
9 438 - 448 41.9 838
10 483 - 493 32.1 802
11 526 - 536 27.9 754
12 546 - 556 21.0 750
13 662 - 672 9.5 910
14 673 - 683 8.7 1087
15 743 - 753 10.2 586
16 862 - 877 6.2 516
Atmospheric
Water Vapor
17 890 - 920 10.0 167
18 931 - 941 3.6 57
19 915 - 965 15.0 250

Primary Use Band Bandwidth1 Spectral
Radiance2
Required
NE[delta]T(K)4
Surface/Cloud
Temperature
20 3.660 - 3.840 0.45(300K) 0.05
21 3.929 - 3.989 2.38(335K) 2.00
22 3.929 - 3.989 0.67(300K) 0.07
23 4.020 - 4.080 0.79(300K) 0.07
Atmospheric
Temperature
24 4.433 - 4.498 0.17(250K) 0.25
25 4.482 - 4.549 0.59(275K) 0.25
Cirrus Clouds
Water Vapor
26 1.360 - 1.390 6.00 150(SNR)
27 6.535 - 6.895 1.16(240K) 0.25
28 7.175 - 7.475 2.18(250K) 0.25
Cloud Properties 29 8.400 - 8.700 9.58(300K) 0.05
Ozone 30 9.580 - 9.880 3.69(250K) 0.25
Surface/Cloud
Temperature
31 10.780 - 11.280 9.55(300K) 0.05
32 11.770 - 12.270 8.94(300K) 0.05
Cloud Top
Altitude
33 13.185 - 13.485 4.52(260K) 0.25
34 13.485 - 13.785 3.76(250K) 0.25
35 13.785 - 14.085 3.11(240K) 0.25
36 14.085 - 14.385 2.08(220K) 0.35

1 Bands 1 to 19 are in nm; Bands 20 to 36 are in µm
2 Spectral Radiance values are (W/m2 -µm-sr)
3 SNR = Signal-to-noise ratio
4 NE(delta)T = Noise-equivalent temperature difference

Note: Performance goal is 30-40% better than required