"Go to your exam, try out Hubble contacts, and get your prescription."
Hubble Servicing Mission 1, NASA
"After Hubble's deployment in 1990, scientist realized that the telescope's primary mirror had a flaw called spherical aberration. The outer edge of the mirror was ground too flat by a depth of 2.2 microns (roughly equal to one-fiftieth the thickness of a human hair). This aberration resulted in images that were fuzzy because some of the light from the objects being studied was being scattered. COSTAR (the Corrective Optics Space Telescope Axial Replacement) was developed as an effective means of countering the effects of the flawed shape of the mirror. COSTAR was a telephone booth-sized instrument which placed 5 pairs of corrective mirrors, some as small as a nickel coin, in front of the Faint Object Camera, the Faint Object Spectrograph and the Goddard High Resolution Spectrograph."
Keith's note: On their visit a doctor page they refer to "Dr. Edwin". As in Edwin Hubble. Get it?
from NASA Watch http://ift.tt/2sVrGKB
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