HYPERSPECTRAL MICROWAVE SATELLITE OBSERVATIONS: INFORMATION CONTENT AND CHANNEL SELECTION FOR NUMERICAL WEATHER PREDICTION DATA ASSIMILATION APPLICATIONS
Marzo 25, 2026HISRAMS RADIOMETRIC CALIBRATION AND ENVIRONMENTAL BIASES
Marzo 25, 2026S. Reising1, A. Mohamed2, O. Pradhan2, A. Babenko2, S. T. Brown2, A. B. Tanner2, P. Kangaslahti2, R. Thomas1, S. Farzana1, M. Abedin1, A. Whitney1
1Colorado State University, 2NASA/Caltech Jet Propulsion Laboratory
The 2017 National Academies’ Earth Science Decadal Survey has identified the planetary boundary layer (PBL) as a new frontier for remote sensing that requires investment in new technologies, retrieval approaches and observational techniques. Current passive microwave systems and those planned to be launched over the next decade are not optimized for the frequency-resolving flexibility and resilience necessary for near-surface atmospheric remote sensing. These conventional microwave sounders typically rely on difficult-to-tune analog back-ends with total power detectors and are therefore limited to only a few tens of spectral channels. This limitation results in under sampling of the vertical atmospheric temperature and moisture profile and increases retrieval errors. Additional drawbacks include potential passband variability between detectors, susceptibility to a changing radio frequency interference environment and limited use of the available spectral bandwidth at each vertical sounding level. On the other hand, next-generation software-defined spectrometers based on high-speed digitizer circuits, or so-called “hyperspectral” radiometers, have the capability to overcome these limitations. Such systems are well poised to meet the needs of the atmospheric science community while taking advantage of the maturation of analog and digital components for high-frequency system design.
NOAA-sponsored radiometer technology development and demonstration activities are ongoing at JPL in close collaboration with Colorado State University (CSU) and World View Enterprises. The stratospheric balloon instrument is an upgraded version of the CSU High-frequency Airborne Microwave and Millimeter-wave Radiometer (HAMMR). HAMMR-HD (high definition) preserves the original three narrowband channels from 18.7 to 34 GHz. In addition, HAMMR-HD includes wide-bandwidth (18 GHz) coverage with high spectral resolution (~4-6 MHz) near each of the 60 GHz oxygen (O2) absorption complex, and the 118 GHz O2 and 183 GHz water vapor absorption lines. Additionally, two SMICES (Smart Ice Cloud Sensing) radiometers will be integrated into HAMMR-HD to perform brightness temperature observations at 250 GHz, 310 GHz and 670 GHz. HAMMR-HD will be mounted onto a high-altitude (~20 km) balloon for acquisition of up to 30 days of brightness temperature observations. The HAMMR-HD instrument will provide a rich data set on both the upper atmosphere and the planetary boundary layer (PBL) by sampling the full microwave spectrum from 18-200 GHz over a variety of atmospheric scenes.
This work includes design principles of very wide-band millimeter-wave radio frequency (RF) front ends (> 40-GHz frequency span) as well as high speed ASIC-based digital back-ends (18-GHz frequency spans) and associated calibration challenges. We will also present extensive sub-system characterization with spectral response, white noise characteristics, and flicker (1/f) noise performance and their respective effects on instrument sensitivity and operational concepts. This includes end-to-end laboratory testing results demonstrating new hyperspectral technology across the spectrum. Lastly, outdoor performance during clear skies will be discussed, along with associated radiometric calibration requirements and techniques.
