The Special Sensor Microwave Imager / Sounder (SSMIS) is a 24-channel, 21-frequency, linearly polarized passive microwave radiometer system. The instrument is flown on board the United States Air Force Defense Meteorological Satellite Program (DMSP) F-16, F-17, F-18 and F-19 satellites, which were launched in October 2003, November 2006, October 2009, and April 2014, respectively.[1] It is the successor to the Special Sensor Microwave/Imager (SSM/I). The SSMIS on the F19 satellite stopped producing useful data in February 2016.[2]
The Department of Defense announced it would cut off access to SSMIS data useful for calculating depth of sea ice and location of hurricanes, as of July 31, 2025.[3]
In late July 2025, the Department of Defense announced it will keep the SSMIS data flowing until the sensor fails or the program formally ends in September 2026. [4]
Instrument characteristics
The SSMIS sensor is a passive conically scanning microwave radiometer that combines and extends the current imaging and sounding capabilities of three previously separate DMSP microwave sensors: the SSM/T-1 temperature sounder, the SSMI/T- 2 moisture sounder, and the SSM/I. The SSMIS instrument measures microwave energy at 24 discrete frequencies from 19 to 183 GHz with a swath width of 1700 km.[5] The first SSMIS was launched aboard the DMSP-16 satellite on 18 October 2003. Due to a manufacturing mistake, the polarization for the channels at 50.3, 52.8, 53.6, 54.4 and 55.5 of the first unit of SSMIS (the one flying on DMSP-16) was reversed. Those five channels detect the vertical polarization rather than the Horizontal polarization detected by the successive units of SSMIS.[6]
| Channel # | Frequency (GHz) | Polarization | Along-track resolution (km) | Cross-track resolution (km) | Spatial sampling (km x km) | Instrument noise (K) |
|---|---|---|---|---|---|---|
| 12 | 19.35 | horizontal | 73 | 47 | 45×74 | 0.35 |
| 13 | 19.35 | vertical | 73 | 47 | 45×74 | 0.35 |
| 14 | 22.235 | vertical | 73 | 47 | 45×74 | 0.45 |
| 15 | 37.0 | horizontal | 41 | 31 | 28×45 | 0.22 |
| 16 | 37.0 | vertical | 41 | 31 | 28×45 | 0.22 |
| 1 | 50.3 | horizontal | 17.6 | 27.3 | 37.5 | 0.34 |
| 2 | 52.8 | horizontal | 17.6 | 27.3 | 37.5 | 0.32 |
| 3 | 53.596 | horizontal | 17.6 | 27.3 | 37.5 | 0.33 |
| 4 | 54.4 | horizontal | 17.6 | 27.3 | 37.5 | 0.33 |
| 5 | 55.5 | horizontal | 17.6 | 27.3 | 37.5 | 0.34 |
| 6 | 57.29 | right circular | 17.6 | 27.3 | 37.5 | 0.41 |
| 7 | 59.4 | right circular | 17.6 | 27.3 | 37.5 | 0.40 |
| 19 | 63.283248 ± 0.285271 | right circular | 17.6 | 27.3 | 75 | 2.7 |
| 20 | 60.792668 ± 0.357892 | right circular | 17.6 | 27.3 | 75 | 2.7 |
| 21 | 60.792668 ± 0.357892 ± 0.002 | right circular | 17.6 | 27.3 | 75 | 1.9 |
| 22 | 60.792668 ± 0.357892 ± 0.0055 | right circular | 17.6 | 27.3 | 75 | 1.3 |
| 23 | 60.792668 ± 0.357892 ± 0.016 | right circular | 17.6 | 27.3 | 75 | 0.8 |
| 24 | 60.792668 ± 0.357892 ± 0.050 | right circular | 17.6 | 27.3 | 75 | 0.9 |
| 18 | 91.665 | horizontal | 14 | 13 | 13×16 | 0.19 |
| 17 | 91.665 | vertical | 14 | 13 | 13×16 | 0.19 |
| 8 | 150 | horizontal | 14 | 13 | 13×16 | 0.53 |
| 11 | 183.311 ± 1 | horizontal | 14 | 13 | 13×16 | 0.38 |
| 10 | 183.311 ± 3 | horizontal | 14 | 13 | 13×16 | 0.39 |
| 9 | 183.311 ± 6.6 | horizontal | 14 | 13 | 13×16 | 0.56 |
References
- ^ “Special Sensor Microwave/Imager (SSM/I) and Special Sensor Microwave Imager Sounder (SSMIS)”. World Meteorological Office Observing Systems Capability Analysis and Review Tool. Retrieved 27 July 2021.
- ^ “Air Force Says DMSP-19 Weather Satellite is ‘About Dead’“. Space.com. 17 March 2016.
- ^ “US military cuts climate scientists off from vital satellite sea-ice data”. Space.com. 6 July 2025.
- ^ “Defense Department will continue providing critical weather satellite data to NOAA”. abcnews.go.com. 30 July 2025.
- ^ “SSMI and SSMIS Monitoring and Documentation”. National Environmental Satellite, Data, and Information Service (NESDIS), NOAA. Retrieved 24 December 2010.
- ^ [“Intercalibration between special Sensor Microwave Imager/Sounder and Special Sensor microwave Imager”; B. Yan and F. Weng; IEEE TGRS, 2008, 46, 984]
- ^ Kunkee, David B.; Poe, Gene A.; Boucher, Donald J.; Swadley, Steven D.; Hong, Ye; Wessel, John E.; Uliana, Enzo A. (April 2008). “Design and Evaluation of the First Special Sensor Microwave Imager/Sounder”. IEEE Transactions on Geoscience and Remote Sensing. 46 (4): 863–883. Bibcode:2008ITGRS..46..863K. doi:10.1109/TGRS.2008.917980. ISSN 1558-0644. S2CID 47668.