A procedure for making antenna pattern corrections to antenna temperatures
of the advanced microwave sounding unit-a (AMSU-A) is developed, Antenna ef
ficiencies, fractions of total power over three different solid-angle regio
ns subtended at the satellite by the earth (plus atmosphere below 20 km), c
old space, and the satellite platform, were calculated at 30 earth views an
d four possible cold space calibration positions, These calculated results
simplify the process for correcting antenna temperature measurements to ret
rieve the true brightness temperatures from AMSU-A data. Using the antenna
pattern data and a profile of atmospheric brightness temperature, a set of
antenna pattern corrections was simulated for each channel at the 30 earth
views and four possible cold space calibration positions. The results show
that these corrections can add 0.5 to 2.7 K to the antenna temperatures to
retrieve the brightness temperatures and that the cold space calibration te
mperatures may be raised to 2 K above the nominal cold sky temperature of 2
.73 K, Antenna pattern 3-dB beamwidths and main-beam efficiencies were also
calculated from the antenna pattern data.