In particular, the mirrors on the 107'' and 82'' telescopes were cleaned shortly before the event. The McDonald 82'' telescope was also used to image the event. 100 second exposure images were taken of the south polar region shortly before the Lunar prospector struck the surface and were again taken shortly afterward. The idea was to subsequently subtract the images and look for evidence of an expanding vapor plume. The image is approx.
North is up.
The impact site is marked with an arrow. First we correct the CCD images with zero and flat-field frames. Zero frames are obtained through a series of short exposures with the camera shutter closed. We need zero frames to obtain the signal introduced by the readout electronics of each pixel and remove those values from raw images. Flat field frames give us information about the relative sensitivity of each pixel.