Frequently Asked Questions

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Question:
When does distortion become a significant factor in off-nadir versus nadir collects?

Answer:
There is no measurement of distortion available. For clarification, nadir generally refers to being within the spacecraft's flight path. For descending acquisitions (daylight) in the nadir path, the instruments are nominally imaging the eastern area of the path. The amount of distortion depends on where from nadir the target is located. If the target is located in the western area of the path, there will be less distortion imaging from the adjacent path to the west than from the nadir path. In other words, the spacecraft would manuever less to capture this angle than the western roll that would be required to image the same location from within the path. True nadir acquistions are very rare, less than 1% of the time. Only targets that are in the eastern part of the WRS path can be acquired at true nadir.