If you were on the Moon during last week’s solar eclipse, you would have seen the Moon’s shadow moving across Earth. This image was taken by the Lunar Reconnaissance Orbiter (LRO) satellite. From Arizona State University’s Lunar Reconnaissance Orbiter Camera (LROC) site:
As LRO crossed the lunar south pole heading north at 1600 meters per second (3579 mph), the shadow of the Moon was racing across the United States at 670 meters per second (1500 mph). A few minutes later, LRO began a slow 180° turn to look back at the Earth and capture an image of the eclipse very near the location of maximum length of totality. The LROC Narrow Angle Camera (NAC) began scanning the Earth at 18:25:30 UTC and completed the image 18 seconds later (UTC is 4 hours ahead of Eastern Daylight Time, or 7 hours ahead of Pacific Daylight Time).
The NAC builds up an image line-by-line rather than the more typical “instantaneous” framing camera (i.e. your cell phone camera). Each line of the image is exposed for 0.338 milliseconds, and since the camera acquires 52224 lines, the total time to acquire the image is about 18 seconds. The line exposure time was set at the lowest possible value to prevent bright clouds from saturating the CCD (charge coupled device) sensor.
Rendering of the Lunar Reconnaissance Orbiter:
LROC Narrow Angle Camera (NAC):
