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Instrument: AMSU-A : Advanced Microwave Sounding Unit-A
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Associated Platforms

Spectral/Frequency Information
Wavelength Keyword: Microwave
Number Channels: 15 Channels (13 for AMSU-A1, 2 for AMSU-A2)
Spectral/Frequency Coverage/Range: 23 - 90 GHz (50-90 GHz for AMSU-A1, 23-32 GHz for AMSU-A2)

Related Data Sets
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The objectives of the Advanced Microwave Sounding Unit (AMSU) instrument are to (1) provide atmospheric temperature sounding from the surface up to 40 km, (2) obtain estimates of total column water vapor in the atmosphere, and (3) detect the presence of precipitation. AMSU-A is a 15-channel microwave sounder that obtains temperature profiles in the upper atmosphere and provides a cloud-filtering capability for the AIRS infrared channels for increased accuracy of tropospheric temperature observations. The fifteen AMSU-A channels have a 3.3° beam width, resulting in a nominal horizontal spatial resolution of 40.5 km at nadir.

Channels 3 to 14 on AMSU-A are situated on the low-frequency side of the oxygen resonance band (50 ~ 60 GHz) and are used for temperature sounding. Successive channels in this band are situated at frequencies with increasing opacity and therefore respond to radiation from increasing altitudes. Channel 1, located on the first (weak) water vapor resonance line, is used to obtain estimates of total column water vapor in the atmosphere. Channel 2 (at 31 GHz) is used to indicate the presence of rain. Channel 15 on AMSU-A, at 89 GHz, is used as an indicator for precipitation, using the fact that at 89 GHz ice more strongly scatters radiation than it absorbs or emits radiation.

The AMSU is currently operational on the NOAA-15 polar orbiting satellite (launched 13 May 1998), the NOAA-16 polar orbiting satellite (launched 21 September 2000), the NASA EOS Aqua (formally PM-1) spacecraft (launched 4 May 2002), the NOAA-17 polar orbiting satellite (launched 21 May 2002), the NOAA-18 polar orbiting satellite (launched 20 May 2005), the NOAA-19 polar orbiting satellite (launched 06 February 2009), and the METOP-B satellite (launched 17 September 2012). The NOAA AMSU configuration consists of the 15-channel AMSU-A and a 5 channel AMSU-B for a total of 20 channels.

Key AMSU-A Facts
Heritage: Microwave Sounding Unit (MSU)
Aperture: 13.2 cm on AMSU-A1 (two apertures); 27.4 cm on AMSU-A2 (one aperture)
Swath Width: 1690 km
Coverage: Global coverage every 1 - 2 days
Spatial Resolution: 40.5 km at nadir
Dimensions: 72 cm x 34 cm x 59 cm for AMSU-A1; 73 cm x 61 cm x 86 cm for AMSU-A2
Mass: 91 kg (49 kg for AMSU-A1, 42 kg for AMSU-A2)
Power: 101 W (77 W for AMSU-A1, 24 W for AMSU-A2)
Duty Cycle: 100%
FOV: ± 49.5° cross-track from nadir
Instrument IFOV: 3.3° (40.5 km at nadir) for both units
Scan Period: 8 s
Scan Sampling: 30 x 3.3°, in 6 s
Design Life: 3 years

Online Resources

Instrument Logistics
Data Rate: 2.0 kbps (1.5 kbps for AMSU-A1, 0.5 kbps for AMSU-A2)
Instrument Start Date: 2002-08-31
Instrument Owner: USA/NASA