The HSB Instrument
The Humidity Sounder for Brazil (HSB) is a 4-channel microwave moisture sounder implemented as a single module. Three channels are located near 183 GHz, while the fourth is a window channel at 150 GHz. Physically HSB is identical to AMSU-B, which is operated by NOAA on its most recent POES satellites, but HSB lacks the fifth channel (89 GHz) of AMSU-B. Like AIRS, HSB is a cross-track scanner, and it has only one parabolic scan antenna. Its scan speed as well as its footprints is similar to AIRS (three scans per 8 seconds and about 15 km at nadir, respectively). There is therefore one HSB footprint per AIRS footprint.
HSB ceased operation on February 5, 2003 due to a failure in the mirror scan motor electronics.
HSB instrument state
The HSB instrument failed on February 5, 2003. An anomaly investigation team concluded the most likely failure cause was a bad connection or solder joint in the motor drive electronics commutation circuit. The symptoms seen on orbit were replicated on an engineering model.