Initial evaluation of AMSU-B in-orbit data

The NOAA-K polar-orbiting satellite was launched on 13(th) May 1998. On board are a number of new instruments, including the microwave sounders AMSU-A and AMSU-B. The UK Met Office were responsible for the procurement and characterisation of AMSU-B and have a continuing role in supporting the program. The first AMSU-B flight model was activated in orbit on 20(th) May 1998. This paper describes the initial tests that were conducted on the instrument and gives some preliminary results. Functionally the instrument appeared to work well, but major discrepancies were apparent for two channels between measured and predicted brightness temperatures. The problem has been traced to RF interference from spacecraft transmitters; characterisation of the errors is still in progress. Finally, a technique is outlined, and preliminary results presented, for measuring the co-channel alignment between the 89 GHz channels on AMSU-A and AMSU-B.