As reported on the USGS Landsat website: “On April 1, 2007, the Landsat 7 mission will begin imaging in an alternate mirror-scanning control mode from the original Scan Angle Monitor (SAM) process that has been used since the satellite was launched in 1999. This change, known as Bumper Mode, is necessary due to a predictable physical wear of the mirror bumpers mounted within the Enhanced Thematic Mapper Plus (ETM+) imaging system. Landsat 7 data users should notice little or no change as a result of this transition. Five years ago, the Landsat 5 Thematic Mapper (TM) scanner was successfully converted to this alternate imaging mode, and customers have reported no problems related to that change.”

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