The Level 1C algorithms calculate calibrated brightness temperature values so that the brightness temperature form an individual sensor is consistent with the brightness temperature from other passive-microwave sensors.  Currently, the GPM Microwave Imager (GMI) is the reference instrument for calibrating the other sensors. The 1C data product is the lowest level passive-microwave data product that most researchers are interested in examining, although some instruments have more primitive data products available from the GPM project. 

The Level 1C algorithms contain the following major components:

  • Orbitization
  • Satellite intercalibration
  • Quality control
  • Ancillary data calculations.

The algorithm theoretical basis document (ATBD) cited below describes the general implementation of the algorithm and appendices describe sensor-specific details.  The following instruments are described: GMI, Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), Special Sensor Microwave Imager/Sounder (SSMI/S), Advanced Microwave Scanning Radiometer 2 (AMSR2), Advanced Technology Microwave Sounder (ATMS), Sondeur Atmospherique du Profil d'Humidite Intertropicale par Radiometrie (SAPHIR), and Microwave Humidity Sounder (MHS). 

Processing Level
Dates Covered
1987 - 2009 (SSMI), 1997 - Present (varies by instrument)
Data Simple Description
Calibrated brightness temperature for GPM GMI, TRMM TMI, and constellation microwave radiometers
Minimum Latency
20 minutes (GMI near real-time); 4 hours (GMI research); 6 hours to 7 days (various instruments)
Spatial Resolution
5km x 8km (GMI 89GHz channels)
Varies by satellite and instrument channel
Current Algorithm Version