Development of a high stability L-band radiometer for ocean salinity measurements

Future sea surface salinity missions will require L- band radiometers to have calibration stabilities of ≤ 0.05 K over 2 days. This research program has focused on determining the optimum radiometer requirements and configuration to achieve this objective. System configuration and component perform- ance have been evaluated with radiometer test beds at both JPL and GSFC. The GSFC testbed uses a cryogenic chamber that allows long-term characterization at radiometric temperatures in the range of 70 - 120 K. The research has addressed areas including component characterization as a function of tempera- ture, system linearity, optimum noise diode injection calibration and precision temperature control of components.