The Advanced Microwave Sounding Unit – A1 (AMSU-A1) is one of the complement of American instruments provided by NOAA to fly on MetOp-A, -B and –C.
The AMSU-A1 measures scene radiance in the microwave spectrum. The data from this instrument is used in conjunction with the High-resolution Infrared Sounder (HIRS) instrument to calculate the global atmospheric temperature and humidity profiles from the Earth's surface to the upper stratosphere, at approximately 2-millibar pressure altitude (48 km). The data is used to provide precipitation and surface measurements including snow cover, sea-ice concentration and soil moisture.
The instrument is a cross-track scanning total-power radiometer and is divided into two separate modules:
- AMSU Module A-1 with channels 3 to 15
- AMSU Module A-2 with channels 1 and 2
Each module operates and interfaces with the spacecraft independently. Often both instrument modules are presented under the generic name of AMSU-A. AMSU-A1 and -2 were developed by Northrop Grumman (formerly Aerojet), Los Angeles, USA.
The AMSU-A instrument has an IFOV of 3.3° at the half-power points providing a nominal spatial resolution at nadir of 48 km (29.8 mi). The antenna provides a cross-track scan, scanning ± 48.3° from nadir with a total of 30 Earth fields-of-view per scan line. The instrument completes one scan every 8 seconds. The footprint (resolution at nadir) is 50 km. The swath width is approximately 2000 km.
Courtesy NOAA-L brochure, NOAA Observation of the Earth and its Environment – Survey of Missions and Sensors by: Dr H.J. Kramer