Suitability of the amazon rain forest as an on-orbit, microwave radiometric calibration target

Passive microwave sensors known as radiometers are calibrated receivers that make absolute measurements of weak natural blackbody noise power emissions to infer geophysical properties of the Earth´s atmosphere and surface. Because of the high accuracy needed in measuring these geophysical parameters, frequent on-orbit radiometric calibrations over natural surfaces with stable radiometric emissions are highly desirable. This paper discusses the suitability of the Amazon rain forest as such a radiometric calibration target. Results of analysis of on-orbit microwave radiometer measurements from the Amazon are presented to demonstrate repeatable temporal and spatial emission signatures that can be used for radiometric calibration.