In normal Landsat data processing, blackbody and shutter temperatures are extracted from the Payload Correction Data (PCD) and used to estimate per-scan gains and biases necessary for the radiometric calibration of the instrument's thermal band data.
In case of TM no-PCD data, where the blackbody and shutter temperatures are not available, the temperature information is obtained from lifetime Look-Up-Tables (LUTs) of blackbody and shutter temperatures generated using a database of trended temperatures stored during radiometric processing of all TM scenes with valid PCD information. Note: There is no difference in the radiometric processing of the TM reflective bands (bands 1-5 and 7), when comparing standard TM data and no-PCD.
Radiometric comparison of the standard TM PCD-based scenes and the LUT-based no-PCD scenes reveals the difference in radiance is 1) scene dependent, and 2) generally within a small percentage.
Below, a comparison of an area within WRS-2 path 38 row 38 from January 1985 to December 1998 shows that the difference in radiance is within 3 percent, except for a few scenes acquired within few days of outgassing events where the difference is as high as 28 percent. For PCD-based TM data, the average difference is .11 percent.
