The Configurable Scanning Submillimeter-wave Instrument/Radiometer (CoSSIR) is an airborne 16-channel radiometer that was primarily developed for the measurement of ice clouds. Previously known as the Compact Scanning Submillimeter-wave Imaging Radiometer, CoSSIR was first flown in CRYSTAL-FACE (Cirrus Regional Study of Tropical Anvils and Cirrus Layers – Florida Area Cirrus Experiment) in 2002, followed by CR-AVE (Costa Rica Aura Validation Experiment) in 2006, and TC4 (Tropical Composition, Cloud and Climate Coupling Experiment) in 2007. For CRYSTAL-FACE and CR-AVE, CoSSIR had 15 channels centered at 183±1, 183±3, 183±6.6, 220, 380±.8, 380±1.8, 380±3.3, 380±6.2, 487.25±0.8, 487.25±1.2, 487.25±3.3, and 640 GHz, where the three 487 GHz channels were dual-polarized (vertical and horizontal). For TC4, the 487 GHz channels were removed, 640 GHz was made dual-polarized, and an 874 GHz channel was added. In 2022, CoSSIR was completely updated with new receivers under funds through the Airborne Instrument Technology Transition (AITT) to improve measurement accuracy and enable CoSSIR to be a stand-alone sensor that no longer shared a scan pedestal with its millimeter-wave sibling, CoSMIR. Frequencies were selected for CoSSIR to optimize snow and cloud ice profiling, and dual-polarization capability was added for all frequencies to provide information on particle size and shape. The updated CoSSIR flew for the first time in the Jan-Feb 2023 deployment of IMPACTS (Investigation of Microphysics and Precipitation for Atlantic Coast Threatening Snowstorms) and operated nominally for the entire campaign, collecting a wide variety of observations over different types of clouds and precipitation. CoSSIR also flew in the Airborne Lightning Observatory for FEGS and TGFs (ALOFT) campaign in July 2024 and collected observations over deep convective systems near Central America and Florida. All the receivers and radiometer electronics are housed in a small cylindrical scan head (21.5 cm in diameter and 28 cm in length) that is rotated by a two-axis gimbaled mechanism capable of generating a wide variety of scan profiles. Two calibration targets, one maintained at ambient (cold) temperature and another heated to a hot temperature of about 323 K, are closely coupled to the scan head and rotate with it about the azimuth axis. Radiometric signals from each channel are sampled at 10 ms intervals. These signals and housekeeping data are fed to the main computer in an external electronics box. (Top left) CoSSIR mounted on the scan pedestal, (top right) CoSSIR seen from below when installed in the ER-2. (Top) CoSSIR brightness temperature observations from an IMPACTS flight on February 17, 2023, over a rain/snow system over northern Maine and southern Quebec. CoSSIR Parameters Frequencies: 16 channels centered at 170.5, 177.3, 180.3, 182.3, 325±0.9, 325±3.55, 325±11.3, and 684 GHz, all dual-polarized (vertical and horizontal) Scan modes: Programmable for conical scan at angles between 0-53°, cross/along-track scan, or a combination of both In-flight Calibration: two external targets at ~323 K and at ambient temperature (typically 230-250 K, depending on aircraft cruising altitude) Scan head: a cylinder 21.5 cm in diameter and 28.0 cm long Field of view: ~4.3° beam width – gives a footprint at the surface of 1.5 km at nadir and 2.5x4.2 km at 53° off-nadir at ER-2 cruising altitude of 20 km Aircraft: Flown previously on the NASA WB-57 and ER-2 Data Products Level 1 quality-controlled, geolocated, calibrated brightness temperatures between 170 and 684 GHz with accuracy on the order of ±1 K. Through various retrieval algorithms, the acquired data can be used to estimate ice cloud parameters (ice water path and mean particle size), snowfall rates, and water vapor profiles (with known temperature profiles). CoSSIR Level 1 data from CRYSTAL-FACE, CR-AVE, TC4 are archived as listed below. IMPACTS data are available on the GHRC DAAC. ALOFT data are currently being calibrated. https://espoarchive.nasa.gov/archive/browse/crystalf/ER2 https://espoarchive.nasa.gov/archive/browse/cr_ave/WB57 https://espoarchive.nasa.gov/archive/browse/tc4/ER2 https://dx.doi.org/10.5067/IMPACTS/COSSIR/DATA101 Team Members Principal Investigator Ian Adams NASA Goddard Space Flight Center, Code 610 ian.s.adams@nasa.gov Co-Investigator Rachael Kroodsma NASA Goddard Space Flight Center, Code 612 rachael.a.kroodsma@nasa.gov Lead Engineer Matt Fritts NASA Goddard Space Flight Center, Code 555 matthew.a.fritts@nasa.gov References Evans, K. F., J. R. Wang, D. C. Starr, G. Heymsfield, L. Li, L. Tian, R. P. Lawson, A. J. Heymsfield, and A. Bansemer, 2012: Ice hydrometeor profile retrieval algorithm for high-frequency microwave radiometers: application to the CoSSIR instrument during TC4, Atmos. Meas. Tech., 5, 2277-2306. Wang, J. R., L. A. Chang, B. Monosmith, and Z. Zhang, 2008: Water vapor profiling from CoSSIR radiometric measurements, IEEE Trans. Geosci. Remote Sens., 46, 137-145. Evans, K. F., J. R. Wang, P. E. Racette, G. Heymsfield, and L. Li, 2005: Ice cloud retrievals and analysis with data from the Conical Scanning Submillimeter Imaging Radiometer and the Cloud Radar System during CRYSTAL–FACE, J. Appl. Meteor., 44, 839–859. CoSSIR Meso
