Aquarius Radiometer: Pre-launch Performance and Calibration

The NASA-CONAE Aquarius/SAC-D observatory for measuring the changing global distribution of sea surface salinity at unprecedented accuracy from space is scheduled to launch in 2010 [1]. The Aquarius Instrument comprises a 1.4 GHz radiometer and a 1.2 GHz scatterometer, both of which share a common reflector antenna, feed network, and other electronics. The ability to measure sea surface salinity hinges upon the radiometer error meeting a stringent 0.15 K requirement after post-launch calibration. To do so, the inherent calibration stability of the radiometer antenna temperature measurement must be better than 0.13 K over 7 days. Additionally, pre-launch calibration must also compensate for subtle changes in RF component temperatures over the changing seasons for the duration of the mission.