Abstract
The radiometric calibration stability of Landsat 5 (L5) Thematic Mapper (TM), Landsat 7 (L7) Enhanced Thematic Mapper Plus (ETM+) and Landsat 8 (L8) Operation Land Imager (OLI) is continuously monitored, trended, and updated using various on-board and vicarious calibration techniques. The on-board calibrators in L5 TM and L7 ETM+ were deemed unreliable after a few years of on orbit operations, therefore methods based on analysis of Pseudo Invariant Calibration Site (PICS) responses have been used to assess and update the temporal gain changes of these instruments. Long term trending from PICS, primarily located in the Saharan region, indicate that long term degradations are less than 0.05% per year in L7 ETM+ bands and less than 0.2% per year in L5 TM bands. On the other hand, L8 OLI has well behaved on-board calibrators that are used to assess the stability of the instrument while PICS are used as a complementary method. Statistics derived from these on-board calibrators indicate that all bands in OLI are stable to within 0.05% per year, except the Coastal Aerosol Band where all on-board calibrators indicated a systematic degradation of about 0.2% per year. Recently, the US Geological Survey (USGS) Earth Resources Observation and Science (EROS) addressed this degradation within the Landsat Collection 1 product generation. PICS statistics from L8 OLI indicated trends that differ from the on-board calibrator trends by about 0.35%. Further analyses of L7 ETM+ trends show that due to PICS variability more than four years’ worth of PICS data are needed to better estimate the long term stability of the Landsat sensors.
Assessing Long Term Stability of Landsat 5 TM, Landsat 7 ETM+ and Landsat 8 OLI
The radiometric calibration stability of Landsat 5 (L5) Thematic Mapper (TM), Landsat 7 (L7) Enhanced Thematic Mapper Plus (ETM+) and Landsat 8 (L8) Operation Land Imager (OLI) is continuously monitored, trended, and updated using various on-board and vicarious calibration techniques. The on-board calibrators in L5 TM and L7 ETM+ were deemed unreliable after a few years of on orbit operations, therefore methods based on analysis of Pseudo Invariant Calibration Site (PICS) responses have been used to assess and update the temporal gain changes of these instruments. Long term trending from PICS, primarily located in the Saharan region, indicate that long term degradations are less than 0.05% per year in L7 ETM+ bands and less than 0.2% per year in L5 TM bands. On the other hand, L8 OLI has well behaved on-board calibrators that are used to assess the stability of the instrument while PICS are used as a complementary method. Statistics derived from these on-board calibrators indicate that all bands in OLI are stable to within 0.05% per year, except the Coastal Aerosol Band where all on-board calibrators indicated a systematic degradation of about 0.2% per year. Recently, the US Geological Survey (USGS) Earth Resources Observation and Science (EROS) addressed this degradation within the Landsat Collection 1 product generation. PICS statistics from L8 OLI indicated trends that differ from the on-board calibrator trends by about 0.35%. Further analyses of L7 ETM+ trends show that due to PICS variability more than four years’ worth of PICS data are needed to better estimate the long term stability of the Landsat sensors.