May 16 1979
From The Space Library
NASA reported that the multispectral scanner on Landsat 3 had begun sending defective images at random; the pulse to trigger a line-start signal was not working. The scanner images, line-by-line transmissions of views from an oscillating mirror, would form a continuous line unless arranged one under the other by line-start and line-end scan pulses. GSFC engineers noticed that lines normally printed under the preceding line to fill in a picture were either missing a start signal or lacking about a fourth of the line. Last fall they had solved a similar problem by switching to a backup system, the one now malfunctioning.
Since its launch March 15, 1978, Landsat 3 had transmitted more than 91,000 scenes each representing an area 185 square kilometers of Earth's surface, used to produce either photographs or computer tapes. The equipment needed to correct for the missing data would not be available until later in 1979, the agency said; however, most Landsat 3 data were still accurate, and Landsat-2. was still "going strong" after producing more than 325,000 scanner scenes since 1975. (NASA Release 79-67)
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