Absolute calibration of the Landsat Thematic Mapper using the Internal Calibrator

Abstract

In order to assess the accuracy and usefulness of the Internal Calibrator of the Landsat 4 and 5 Thematic Mappers and characterize the radiometric calibration of the instruments themselves, several hundred scenes were extracted from the Landsat TM archive at the EROS Data Center, Sioux Falls, South Dakota. These scenes formed the basis of the TM Calibration Archive System and have been used to characterize the instruments at several different time scales. From analysis of these data, well-known instrument artifacts have been accurately characterized and new anomalies have been discovered. Only results from the reflective bands are presented. At the end of each scan of the TM, a shutter passes in front of the focal planes removing all radiant energy from the detectors as well as exposing the detectors to radiance from the calibration lamps for a short period of time. From this information, estimates of detector gain and bias can be determined. However, the data recorded by the detectors is corrupted by instrument artifacts that must be removed to optimize accuracy. The most significant artifacts are Scan Correlated Shift (SCS), Memory Effect (ME), and Coherent Noise (CN). Once these artifacts have been removed from the calibration file, it can be processed to determine pulse stability parameters, integrated pulse values, and bias. As a final step, temperature-related variability can be compensated by normalizing all detector pulse measurements to a constant temperature. Except where otherwise noted, the data presented follow these processing steps. For each scene processed, integrated pulse values were calculated on a scan-by-scan basis for each detector. These values were then avenged together to obtain one data point for the entire scene.