SSM/I Level IC Development
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Sensor Description:
SSM/I was first launched on board the Defense Meteorological Satellite Program (DMSP) F8 satellite in June of 1987. The DMSP series satellites are in sun-synchronous polar orbits at an altitude of approximately 830 km. The instrument is a seven channel linearly polarized passive microwave radiometer operating at frequencies of 19.36, 22.235, 37.0, and 85.5 GHz. Detailed specifications for the spacecraft and instrument are given by Hollinger et al. [1987] and Hollinger [1989, 1991].
Table 1. SSM/I characteristics ::
| Center Frequencies(GHz) | 19.35 | 19.35 | 22.235 | 37.0 | 37.0 | 85.5 | 85.5 | |
| Polarization | V | H | V | V | H | V | H | |
| Bandwidth (MHz) | 250 | 250 | 250 | 1000 | 1000 | 1500 | 1500 | |
| Sensitivity (K) | 0.6 | 0.6 | 0.6 | 0.6 | 0.6 | 1.1 | 1.1 | |
| IFOV (km x km) | 69 x 43 | 69 x 43 | 60 x 40 | 37 x 28 | 37 x 29 | 15 x 13 | 15 x 13 | |
| Sampling Interval (km x km) | 25 x 25 | 25 x 25 | 25 x 25 | 25 x 25 | 25 x 25 | 12.5 x 12.5 | 12.5 x 12.5 | |
| Integration Time (msec) | 7.95 | 7.95 | 7.95 | 7.95 | 7.95 | 3.89 | 3.89 | |
| Main Beam Efficiency (%) | 96.1 | 96.5 | 95.5 | 91.4 | 94.0 | 93.2 | 91.1 | |
| Beamwidth (half-power, degrees) | 1.87 | 1.87 | 1.65 | 1.10 | 1.10 | 0.43 | 0.45 |
Source Data:
The source for the Level 1C data is the Temperature Data Record (TDR) data produced by the Navy's Fleet Numerical Meteorology and Oceanography Center (FNMOC). The TDR data is archived and publicly available from NOAA's Comprehensive Large Array-data Stewardship System (CLASS).
Quality Control:
There are significant issues with the TDR data resulting in nonphysical antenna temperatures, mislocated scans, and geolocation problems. Unless these bad data are eliminated they can result in significant errors in the rainfall estimates. To address this issue a number of quality control procedures were implemented.
Details on Quality Control Procedures (Version 2005) Cross-Track Bias Correction:
It has been determined that the glare suppression system-B (GSS-B) scatters cosmic background energy into the SSM/I field-of-view (FOV) [Colton and Poe, 1999]. While this primarily affects those FOVs towards the end of the scan, the impact is significant resulting in a falloff of up to several Kelvin. Colton and Poe [1999] also note that there is a possible falloff at the beginning of the scan due to sidelobe energy from the reflective spacecraft surface. Colton and Poe [1999] suggest that this energy loss towards the end of the scan can be corrected for by multiplying the antenna pattern correction (APC) coefficients by a pixel-dependent factor, defined as unity plus the ratio of the deviations at each beam position normalized to the average brightness temperature of the central uncontaminated beam positions.
Details on Cross-Track Bias Correction (Version 2005) Converting TAs to TBs:
The antenna pattern correction procedure described by Colton and Poe [1999] was used to convert the antenna temperatures (TAs) to brightness temperatures (TBs). There is a modification to the coefficients provided by Colton and Poe [1999], however, in that the coefficients for F13 have also been used for F14 and F15. This was done to maintain compatability with the FNMOC processesing. As a result, the TBs have been verified to exactly match those in the FNMOC sensor data record (SDR) files. The rational for the change in the F14 and F15 coefficients was provided by Gene Poe.
APC coefficient table Satellite Intercalibration
Information on the satellite intercalibration is dependent on the version. The table below provides links to the calibration information for the SSM/I Level 1C versions produced to date.
Additional Documentation/References:
| – | Colton, M. C., and G. A. Poe, 1999: Intersensor calibration of DMSP SSM/I's: F8 to F-14, 1987-1997, IEEE Trans. Geosci. Rem. Sens., 37, 418-439. |
| – | Hollinger, J., R. Lo, and G. Poe, Special Sensor Microwave/Imager User's Guide, Navel Research Laboratory, Washington, D.C., Sep. 14, 1987. |
| – | Hollinger, J. DMSP Special Sensor Microwave/Imager Calibration/Validation, Naval Research Laboratory, Washington, D.C., Vol 1, July 20, 1989. |
| – | Hollinger, J. DMSP Special Sensor Microwave/Imager Calibration/Validation, Naval Research Laboratory, Washington, D.C., Vol 2, May 20, 1991. |
Related Links:
NOAA Comprehensive Large Array-data Stewardship System (CLASS)