Improved receiver architecture for future L-band radiometer missions

Microwave radiometer measurements are viable technique for measurement of soil moisture and ocean salinity. Therefore, there is a strong interest in new L-band remote sensing radiometers. For example, European Space Agency´s SMOS (soil moisture and ocean salinity) satellite is currently under development. SMOS applies Noise Injection Radiometer subsystem for the measurement of the average brightness temperature of the scene. This paper proposes the use of reference channel control method for the future L-band radiometer missions, e.g., for potential SMOS follow-on mission. According to analysis, significant improvement in radiometric resolution (up to 40%) would be achieved compared to traditional antenna channel noise injection architecture. The proposed system is based on the use of an active cold load (ACL) as cold reference.