|Abstract||The Canada Centre for Remote Sensing (CCRS) has been using the scene-statistics approach, originally implemented in 19751 for destriping LANDSAT MSS data, for the routine correction of LANDSAT Thematic
Mapper (TM) reflective band data. The 0.8% within-scene radiometric accuracy specified for Canadian production systems has been achieved for all but a small percentage of requested scenes2. A significant functionality of the processing methodology
includes the correction for dark signal (DC) level shifts as a function of both detector and scan line number, by utilizing background reference level measurements available during the calibration period of each mirror scanning sequence.
Additionally, forward and reverse mirror scans are treated independently. The effect of extended, bright targets such as snow, ice or clouds, is to cause a lowering of the background level by as much as 4 digital numbers (DN), with recovery times
equivalent to approximately 2000 pixels. Hence, in the vicinity of the target itself, localized banding in phase with forward and reverse mirror sweeps is evident. A two-fold impact to the CCRS processing system occurs when the bright targets are at
the edge of the scene, since the background reference level measured during the calibration period does not represent the offset for the imaging period of the sequence. The effects are, firstly, a more pronounced banding in those scan lines which
image the bright target, and secondly, a forward/reverse banding superimposed over the entire scene, causing these scenes to fail the accuracy criterion. An automated procedure has therefore been adopted to detect when the forward/reverse banding
would be outside specifications using the standard techniques. In such cases, forward and reverse mirror sweeps are then corrected with identical gain and offset correction parameters and the DC level shift corrections are applied. |