How do I design a microwave radiometer for earth observation from a satellite?

A microwave radiometer for satellite Earth observation is a passive RF receiver that measures the natural microwave emission (thermal radiation) from the Earth's surface and atmosphere to determine physical parameters such as sea surface temperature, soil moisture, atmospheric water vapor, ice coverage, and ocean salinity. The design focuses on: operating frequency (selected based on the geophysical parameter of interest: 1.4 GHz for soil moisture and ocean salinity because water has a very large dielectric effect at L-band; 6.8-10.7 GHz for sea surface temperature; 23.8 GHz for water vapor; 36.5 GHz for sea ice and rain; 89 GHz for precipitation and cloud properties), receiver architecture (total-power or Dicke-switched radiometer that measures the weak thermal noise power received from the Earth; the total received power is P = kTB where k is Boltzmann's constant, T is the brightness temperature of the scene, and B is the bandwidth), ultra-low receiver noise temperature (10-50 K using cryogenic or ambient-temperature InP HEMT LNAs, since the signal being measured is the thermal noise itself and the receiver's own noise must be as low as possible), precise calibration (frequent calibration against known-temperature references: a hot load at ambient temperature approximately 300 K and a cold load viewing deep space approximately 2.7 K, to convert measured power to absolute brightness temperature with 0.1-0.5 K accuracy), and antenna (large reflector or phased array providing the desired spatial resolution: a 6 meter antenna at 1.4 GHz achieves approximately 40 km resolution from 700 km orbit).