Landsat 7 ETM+ SLC-Off Products
An instrument malfunction occurred onboard Landsat 7 on 31 May 2003. The problem was caused by the failure of the Scan Line Corrector (SLC), which compensates for the forward motion of the satellite. The Landsat 7 Enhanced Thematic Mapper Plus (ETM+) is still capable of acquiring useful image data with the SLC turned off, particularly within the central portion of any given scene. Landsat 7 ETM+ will therefore continue to acquire image data in the SLC-Off mode.
The scene edge of an SLC-Off scene will contain alternating scan lines of missing data. The location of Earth surface features not imaged will vary for any two scenes of the same area and these scan gaps will not be visible on the browse image preview in the Geoscience Australia Navigator Catalogue.
The primary difference between an SLC-Off Landsat 7 product compared to data collected prior to the anomaly, will be the presence of duplicated data in the SLC-Off image for Raw data (USGS Level or equivalent) and Raw image (USGS Level 1T equivalent). In the case of systematic products (image). Precision products (Orthocorrected Image), our processing systems replace the duplicated image data with null values (zero fill).