Title: Technology Development for a Hyperspectral Microwave Atmospheric Sounder
Presenting Author: Bill Blackwell
Organization: MIT Lincoln Laboratory
Co-Author(s): Chris Galbraith, Idahosa Osaretin, and Erik Thompson -MIT Lincoln Laboratory; Paul Racette and Larry Hilliard - NASA Goddard Space Flight Center

Abstract:
The MIT Lincoln Laboratory and NASA Goddard Space Flight Center have partnered to develop a Hyperspectral Microwave Atmospheric Sounder (HyMAS). Funded through ESTO’s Advanced Component Technology program, the hyperspectral radiometer uses six receivers and a compact Low Temperature Co-fired Ceramic (LTCC) Intermediate Frequency Processor (IFP) to sample 52 channels about the 118.75-GHz Oxygen and 183.31-GHz Water Vapor absorption lines. The channel passbands are selected to correspond to closely spaced temperature and humidity weighting functions. Simulations indicate this ‘hyperspectral’ microwave set of channels will yield all-weather sounding capability comparable to hyperspectral infrared sounders in clear air with vertical resolution up to 1 km.

HyMAS comprises four 118 GHz and two 183 GHz receivers, three dual-polarized lens antennas, the IFP, power supply, thermal control, and data handling system. Each receiver includes a dielectric resonator oscillator, single-sideband mixer, and an integrated IF amplifier. Each of the six down-converted IFs spans 18 – 29 GHz which are passed to the IFP. The IFP uses highly integrated microwave amplifier-multiplexer-detector blocks implemented in LTCC and other circuits made in standard printed circuit board (PCB) technology, and is a key technological advancement enabling the novel hyperspectral capability of HyMAS in a super compact design. The IFP amplifies, filters, detects and digitizes the six IF passbands into the 52 channels of aggregated data. The IFP will use a Serial Peripheral Interface (SPI) for passing the digitized data to the scanhead computer. The entire IFP is packaged within a volume of 10 x 10 x 1 cm^3.

HyMAS will be the third in a series of radiometer scanheads that share a common scanning pedestal with the Conical Scanning Microwave Imaging Radiometer (CoSMIR) and Compact Scanning Submillimeter-wave Imaging Radiometer (CoSSIR). The instrument pedestal uses an azimuth over elevation mechanism to achieve across track and conical scanning with period calibration using two blackbody references. The instrument package is compatible with NASA’s DC-8, WB-57, and ER-2 high-altitude aircraft that are well suited for atmospheric research. Successful completion of this project will result in the HyMAS scanhead ready flight demonstration.