What is the bumper mode on Landsat 5?
Early in 2002, The TM instrument onboard Landsat 5 lost synchronization between the scan mirror and calibration shutter, resulting in caterpillar tracks on imagery. In order to fix this problem, the USGS switched the TM instrument from the scan angle monitor (SAM) mode to backup bumper mirror mode in order to extend the useful life of the TM instrument. In SAM mode the telemetry data reports three time values; the active scan start time, the first (scan start to mid-scan) second (mid-scan to scan stop) time. While in bumper mode, the telemetry data contains values for the total scan mirror travel time between successive bumper impacts. The USGS team has developed an emulated SAM mode using the bumper mode (bumper mode theoretical basis). A check has already been engaged by ESA/ESRIN to assess the impacts of such change on the product quality. The European Landsat 5 products acquired in bumper mode, are processed in SAM mode. Thus, information written in the CEOS format (imagery file) a
