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Advanced Microwave Sounding Unit-A (AMSU-A)

The Advanced Microwave Sounding Unit-A (AMSU-A) and the Advanced Microwave Wave Sounding Unit B are planned for NOAA K, L and M. AMSU-A, a US instrument, and an upgrade of AMSU-B, the Microwave Humidity Sounder (MHS), procured and developed by EUMETSAT, are planned to fly on METOP. The prime role of these Microwave Sounders is to provide temperature and humidity sounding under completely overcast conditions and to aid the cloud detection for the companion IR sounding instrument. The temperature sounding exploits mainly the band of oxygen at 50 GHz.

The 3 dB instantaneous footprint for AMSU-A channels is 3.3° (45 km). Calibration repeatability is 0.3 K. AMSU-A scans across track in a ‘stop and stare’ mode at a scan rate of 8 sec. The circular instantaneous field of view has a diameter of 45 km at nadir. The covered swath is about ± 1027 km. There are 30 mirror positions per scan.

AMSU-A channel characteristics (spec)

 Channel  Central Frequency (GHz) # of Pass Bands Bandwidth  (MHz) NeDT (K) Calib Acc. (K) pol. ang. (° )
AMSU-A2
1 23.8
1
± 135 0.3  2.0 90-q 
2 31.4
1
± 90 0.3  2.0 90-q 
AMSU-A1
3 50.3 
1
± 90 0.4  1.5 90-q 
4 52.8 
1
± 200 0.25  1.5 90-q 
5 53.596 ± 0.115 
2
± 85 0.25  1.5 nospec
6 54.40 
1
± 200 0.25  1.5 nospec
7 54.94
1
± 200 0.25  1.5 nospec
8 55.50 
1
± 165 0.25  1.5 nospec
9 FLO = 57.290344
1
± 165 0.25  1.5 nospec
10 FLO ± 0.217
2
± 39 0.4  1.5 nospec
11 FLO ± 0.3222 

± 0.048 
4
± 18 0.4  1.5 nospec
12 FLO ± 0.3222 

± 0.022
4
± 8 0.6  1.5 nospec
13 FLO ± 0.3222

± 0.010 
4
± 4 0.8  1.5 nospec
14 FLO ± 0.3222 

± 0.0045
4
± 1.5 1.2  1.5 nospec
15 89.0
1
± 3000 0.5  2.0 90-q