The United States Air Force Operates a series of weather satellites through the Defense Military Satellite Program (DMSP). These satellites operate in a near-polar sunsynchronous orbit at a height of about 850 km and provide global coverage roughly twice daily. These satellites are similar to the NOAA series but carry different sensors (see avhrr). The sensors carried aboard the DMSP satellites that are supported by the TeraScan system are the:
Operation Linescan System (OLS) - ols Special Sensor Microwave Imager - ssmi Special Sensor Microwave Temperature Sounder - ssmt Special Sensor Microwave Water Vapor Sounder - ssmt SSJ4 - rtdin, rdsin.
The TeraScan telemetry processing software also extracts the Direct Mode Data Message (when available) which contains orbital element and other information for the DMSP and NOAA satellites (dmdm).
The four telemetry formats transmitted by the DMSP satellites and their corresponding TeraScan ingest functions are listed below:
RTD - real time data - rtdin
SDF - stored data fine - sdfin
RDS - real time smooth - rdsin
SDS - stored data smooth - rdsin
These telemetry formats are distinguished primarily by whether they are real time or stored (i.e. multi-orbit) data, and then how the OLS video data is transmitted. The OLS is a two channel radiometer with visible (0.4 - 1.1um) and infrared (10 - 12um) channels. Each has a nearly constant spatial resolution of 0.6km across the scan line. This produces about 12 lines of data per second with about 7300 samples per line per channel.
The RTD telemetry contains one OLS channel at full resolution (fine data) and one channel smoothed in the scan direction by a factor of five (smooth data). In general, the visible channel is transmitted as fine data and the infrared as smooth data for daytime overflights, vice versa for nighttime passes. High latitudes are special cases where, in general, the summer season is associated with fine visible data and the winter season fine infrared data. The RTD data also contains the special sensor data and the DMDM message.
The SDF telemetry contains both OLS channels at full (fine) resolution. It does not contain the special sensor data or DMDM message.
The RDS telemetry contains both OLS channels smoothed in both the line and sample directions by a factor of five, and thus both are considered smooth data. The RDS data also contains the special sensor data and the DMDM message.
The SDS telemetry is identical in content to the RDS telemetry.
The DMSP satellites are denoted by an "f" number, such as f-8, f-9, f-10, and f-11. Satellite f-9 has equatorial passing times at 12am and 12pm local time, while for the other three they are 6am and 6pm local time. Currently, DMSP reception is only available at US military sites where decryption devices exist or from the Antarctic, where due to the International Antarctic treaty, the data are transmitted in an unencrypted format.
avhrr, dmdm, ols, ssmi, ssmt, rtdin, rdsin, sdfin.
Last Update: $Date: 1999/05/10 21:17:13 $