FIRST OBSERVATIONS FROM THE AIRBORNE HYPERSPECTRAL MICROWAVE SOUNDER COSMIR-H

R. Kroodsma¹, I. Adams¹, M. Fritts¹, A. Gambacorta¹, P. Mohammed^2,1, S. Nicholls^3,1

¹NASA Goddard Space Flight Center, ²Morgan State University, ³Science Systems and Applications Inc.

Spaceborne passive microwave sounders have been used for decades to retrieve temperature and humidity profiles on a global scale using selected frequencies near the 60-GHz or 118-GHz oxygen absorption lines for temperature profiling and 22.235 GHz and 183.31 GHz water vapor absorption lines for humidity profiling [1]. Current spaceborne passive microwave sounders sparsely sample the oxygen and water vapor absorption lines in the microwave spectrum, but recent analysis using simulated data shows that increasing the number of channels around these absorption lines may improve the accuracy and resolution of retrieved temperature and humidity profiles [2-5]. A hyperspectral microwave (HMW) sounder with hundreds or thousands of channels versus tens of channels gives high sensitivity to the thermodynamic structure not seen by the current program of record, e.g. ATMS (Advanced Technology Microwave Sounder).

NASA’s Goddard Space Flight Center (GSFC) developed an airborne HMW sensor by modifying the existing Conical Scanning Millimeter-wave Imaging Radiometer (CoSMIR) receivers with digital spectrometers. The new CoSMIR-Hyperspectral (CoSMIR-H) retained the dual-polarized (vertical and horizontal) window channels at 89 and 165 GHz and replaced the two 50-GHz channels and three 183-GHz channels with hyperspectral channels spanning a range of 8 GHz between 50.0 and 58.0 GHz near the 60-GHz oxygen absorption band and a range of 16 GHz between 175.31 and 191.31 GHz centered on the 183.31 GHz water vapor absorption line. The Pacific Microchip Corporation Application Specific Integrated Circuit (ASIC) spectrometers give CoSMIR-H 3.906-MHz spectral resolution in these frequency ranges [6]. The fine spectral resolution can be averaged to match the bandwidth of current spaceborne sounders for inter-comparison of measurements and to validate improvement in vertical resolution of retrievals.

CoSMIR-H flew in two campaigns in 2024 on the high-altitude NASA ER-2 aircraft out of Edwards Air Force Base, California, USA. The July 2024 engineering check flights campaign collected approximately 20 hours of observations and provided essential information about CoSMIR-H’s performance in-flight that allowed the team to optimize the sensor prior to flying again in a science campaign. CoSMIR-H was the primary instrument flying on the ER-2 during the WH2yMSIE (Westcoast and Heartland Hyperspectral Microwave Sensor Intensive Experiment) campaign in Oct-Nov 2024 and collected approximately 43 hours of observations [7]. Observations collected during WH2yMSIE were primarily clear sky over both ocean and land surfaces to perform calibration/validation (cal/val) for CoSMIR-H. There were two ER-2 underflights of the NOAA21 satellite to allow direct comparison between CoSMIR-H and ATMS (Advanced Technology Microwave Sounder) as well as multiple overflights of radiosonde launch locations to validate the hyperspectral measurements.

This presentation will briefly describe the CoSMIR-H instrument, highlight the observations collected during WH2yMSIE, and show calibration/validation (cal/val) of the observations. Overall, the cal/val analysis shows that CoSMIR-H performed extremely well during the campaign and provided quality HMW observations that can be used to demonstrate improvements in thermodynamic retrievals.

References

1. E. Kim, C.-H. J. Lyu, K. Anderson, R. V. Leslie, and W. J. Blackwell, “S-NPP ATMS instrument prelaunch and on-orbit performance evaluation,” J. Geophys. Res. Atmos., vol. 119, pp. 5653-5670, May 2014.

2. W. J. Blackwell, et al., “Hyperspectral microwave atmospheric sounding, IEEE Trans. Geosci. Remote Sens., vol. 49, no. 1, pp. 128-142, 2011.

3. S.-A. Boukabara and K. Garrett, “Benefits of a hyperspectral microwave sensor,” 2011 IEEE Sensors, Limerick, pp. 1881-1884, 2011.

4. F. Aires, C. Prigent, E. Orlandi, M. Milz, P. Eriksson, S. Crewell, C-C. Lin, and V. Kangas, “Microwave hyperspectral measurements for temperature and humidity atmospheric profiling from satellite: The clear-sky case,” J. Geophys. Res. Atmos., vol. 120, pp. 11334-11351, 2015.

5. A. Gambacorta, et al., “Advancing Atmospheric Thermodynamic Sounding from Space using Hyperspectral Microwave Measurements,” IEEE J. Sel. Topics Appl. Earth Observ. Remote Sens., 2023.

6. G. Baranauskas, P. Racette, D. Baranauskas, D. Zelenin and P. N. Mohammed, “A Commercially Available Digital Spectrometer ASIC,” IEEE J. Sel. Topics Appl. Earth Observ. Remote Sens., vol. 18, pp. 1853-1863, 2025.

7. A. Gambacorta, et al., “The West-Coast Hyperspectral Microwave Sensor Intensive Experiment (WHYMSIE),” Proc. 2024 IEEE International Geoscience and Remote Sensing Symposium, Athens, Greece, pp. 1430-1432, 7-12 July 2024.