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In his Oral History, STS-63 commander James Wetherbee describes the final moments of the first Shuttle-Mir rendezvous.
He says, ". . . So now the two vehicles [were at the same altitude], flying at almost exactly the same speed. [Mir was traveling at] 17,500 miles an hour, and we [in the space shuttle] were going 17,500 miles an hour - minus three feet per second... So we're closing at three feet per second relative velocity. . ."
The shuttle had four different sensors to gauge what the spacecraft's' relative positions were. As expected, the sensors did not all agree on the distance. As Wetherbee puts it, "Two of them were lying and two of them were telling the truth. . ."
But Wetherbee says, "You couldn't have picked a better thing to happen on a test flight, [because one of our jobs] was to figure out which of the two sensors were lying and which of the two were accurate. . .
"So it was pretty tense there for a while, trying to figure out what the proper sensor was to use. [But as we had simulated many times on the ground, we chose the one that is the most reliable - the one that is the least complicated. We chose our human eyeballs. . ."
Mission specialist and computer expert Michael Foale determined the problems with the incorrect sensors and he was able to recalibrate them. "So," according to Wetherbee, "as we approached, we finally had a good feeling about where we were."
Related
Links:
James
Wetherbee Oral History (PDF)
Rendezvous
and Docking
STS-63
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Curator:
Kim Dismukes
Responsible NASA Official: John Ira Petty