The calibration accuracy of Landsat 7 ETM+ and Landsat 5 TM data is under responsibility of the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC), U. S. Geological Survey (USGS) Earth Resources Observation and Science Center (EROS) and South Dakota State University (SDSU). The calibration has always relied on the Landsat Calibration Validation Science Team (CVST), including people from NASA GSFC, USGS EROS, SDSU, NASA Jet Propulsion Laboratory (JPL), University of Arizona (U of A) and Rochester Institute of Science and Technology (RIT).
Initially developed for Landsat 7, the Image Assessment System (IAS) has been progressively improved in order to process data from previous Landsat missions, in particular Landsat 5.
For what concerns the characterization and calibration procedures, the IAS includes analysis tools and a trending database to record calibration information. By collecting a lot of data, IAS is notably used in order to estimate scan mirror parameters (geometric calibration), to monitor and model absolute/relative gain behaviour (radiometric calibration).
The IAS is also in charge of updating the Calibration Parameter Files (CPFs) for TM and ETM+ (available here) which is subsequently used by processing systems, in particular the ESA processing system, for Level 1 image product generation.
In 2013, the proposed calibration procedure has been updated on the ESA side, to comply with recommendations done by the USGS. The lifetime gain model has been derived from the instrument's response to pseudo invariant desert sites and from cross calibration with the Landsat 7 ETM+. This procedure is applied to all archived TM data.
Details on the USGS calibration activities can be found here.
Landsat TM/ETM+ Links