Design and development of an airborne microwave radiometer for atmospheric sensing

Abstract

Satellite-based passive microwave remote sensing is a valuable tool for global weather monitoring and prediction. This thesis presents the design and development of a low-cost airborne weather sensing instrument to independently validate a satellite-based sensor platform. The NPOESS Aircraft Sounder Testbed - K-band (NAST-K) is a passive microwave radiometer operating over approximately 200 MHz bandwidth centered at 23.8 GHz and 31.4 GHz, whose data can be used to find surface water, humidity, and temperature conditions. NAST-K flies along with the existing NAST-M instrument at an altitude of 18 km in the NASA ER-2 high altitude aircraft. The primary function of NASTK is to provide coverage of channels 1 and 2 of the Advanced Technology Microwave Sounder (ATMS) aboard the NPOESS Preparatory Project (NPP) satellite, scheduled to be launched in October 2011. The combined NAST-M/K system can validate the performance of ATMS on all channels with data products up to 17km, by underflying the satellite along the same ground track and collecting correlated data. NAST-K has fullwidth at half maximum beamwidths of 7.4° and 6.8° for the two channels respectively, which is approximately consistent with NAST-M. The effective spot size of NAST-K is 2.3km in diameter for the wider 23.8GHz channel at nadir, providing an areal resolution approximately 1000 times greater than ATMS. The major contributions of this thesis include the system-level design of NAST-K, the development of the video amplifier and embedded environmental monitor, and the analysis of the antenna system.