ランドサットMSSセンサに起因するラインスタート異常に関する一検討

抄録

MSS's aboard Landsat 2 and 3, which retired from operational service on March 31, '83, experienced line start anomaly over several periods of months to a year in their operation.
Line start anomaly is a trouble wherein start timing of data sampling within each mirror scanning is delayed and the western 27 percent of the data line is lost. In image, this late start data line appears displaced from normal data lines. The image displacement degrades the image usefulness greatly. Line start anomaly also affects the calibration data which are generated following the image data. As the frequence of the line start anomaly occurence increases, calibration data begin to be delayed with respect to the end of the image data and finally reach to the maximum dislocation where the latter part of the calibration data is damaged by the next image data line. Damaged calibration data result in anomalous radiometric correction, if they are used.
In an attempt to recover the line start anomaly data, Landsat ground stations in the world devised various methods which include new hardware installation and software modification. But the most of the methods have drawbacks in that they can not cope with the damaged calibration data and that a buffer memory is required, etc. A method proposed in this paper is the one adopted at Earth Observation Center (EOC), Japan. The method eliminates the aforementioned shortcomings and has proven itself very effective through its practice at EOC.
This paper first introduces the mechanism of the line start anomaly and various recovery methods adopted by other ground station and then give a comparison on advantages and disadvantages of each method. Finally the description of the Japanese method is presented and some examples of its practice are shown.