The LROC NAC was designed with a very large dynamic range because the Moon is a very contrasty target (bright materials next to dark materials). You can think of each line overlapping quite a bit, so correcting the image geometry is simply a matter of averaging pixels in the line direction, which has the side benefit of increasing the signal-to-noise ratio ( SNR) of the image. As acquired, the image consists of 5064 pixels across (up and down here) and 52224 lines, here rotated 90° and reduced to 93 pixels by 952 lines.ĭue to the short line time (exposure), the raw image is very distorted in the down-track dimension (left-to-right in the figure above). Raw NAC image showing the original distorted geometry. The line exposure time was set at the lowest possible value to prevent bright clouds from saturating the CCD (charge coupled device) sensor. 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 NAC builds up an image line-by-line rather than the more typical 'instantaneous' framing camera (i.e. The LROC 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). 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 shadow of the Moon is centered over Hopkinsville, Kentucky (18:25:30.386 UTC or 1:25:30 pm Central Daylight Time in Kentucky E1257979198R, NASA/GSFC/Arizona State University).Īs 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). Earth as seen from the Moon during the total eclipse on 21 August 2017.

Central time lunar eclipse 2017