Analysis conducted by two Landsat 7 Science Team investigator groups using ground and aircraft measurements indicated a bias in the Thermal band (Band 6) calibration of the Landsat 7 Enhanced Thematic Mapper Plus (ETM+) Level-1 (L1) data processed by the Landsat Product Generation System (LPGS) at the USGS Earth Resources Observation and Science (EROS) Center. This bias apparently results from limitations in the prelaunch calibration of the ETM+ sensor.
The magnitude of the correction is currently estimated to be 0.31 W/(m^2 sr um) or about 3-4 percent radiance error at typical surface temperatures. This apparent systematic error in band 6 radiance calibration translates into estimated temperatures derived from Landsat 7 ETM+ being about 3 degrees C too high for typical Earth surface temperatures.
The current recommended correction is for users to subtract this value (0.31 W/(m^2 sr mm)) from the radiances obtained from Level-1 Radiometrically Corrected (L1R) and Level-1 Geometrically Corrected (L1G) data products generated since launch by the LPGS for both high and low gain band 6 data. Results to date indicate the sensor and calibration are stable with time and that this bias correction is a constant. The Landsat Image Assessment System (IAS) team at EROS, Landsat 7 Science Office Personnel at Goddard Space Flight Center (GSFC) and the Science Team Members are examining ways to improve the calibration in the processing system.