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Ironically, Orbiter's shot of Copernicus was merely a byproduct of its assignment to photograph 13 possible lunar landing sites for astronauts. Of the 211 photographs it has taken while orbiting the moon, Copernicus and twelve others were shot for "housekeeping"—to advance the roll of film and keep the camera in working order during long intervals when Orbiter was not over one of the possible landing sites. Though NASA did not release any of the other housekeeping shots by week's end, an astronomer who was allowed to see them reported that those taken while the satellite flew over the moon's back side showed "an eerie character that we've never seen before."
A built-in darkroom aided Orbiter's remarkable performance. Unlike Ranger spacecraft, or the Surveyor that made a soft landing and televised relatively coarse pictures directly to earth, Orbiter focused the images from its medium and high-resolution lenses onto a fine-grain strip of film. After each section of the film was exposed, it was passed over a drum and pressed against a web treated with chemicals that developed it. After drying, the negative was scanned electronically, one narrow (one-tenth of an inch) strip at a time. Because each strip was electronically divided into 17,000 horizontal lines, enough picture information could be radioed back to earth to reconstruct prints showing almost as much detail as the original.
Orbiter is scheduled to complete the tedious transmission of its pictures by Dec. 10. Shortly afterward, having carried out a practically perfect mission, it will be ordered to fire its retrorocket, drop out of orbit and plunge to destruction on the moon below.