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Back in 2008 I wrote about celestial navigation on the Gemini and Apollo
space flights:

http://www.fer3.com/arc/m2.aspx?i=106262&y=200809

In that message I mentioned the Gemini 10 flight, during which Mike
Collins used a handheld sextant in an orbit determination experiment.
NASA has transcripts of the flight audio online:

http://www.jsc.nasa.gov/history/mission_trans/gemini10.htm

I downloaded the second file. I don't know what's in the first one.

In the transcript, Mike Collins is designated "P" and John Young "C". (I
think these stand for "pilot" and "commander".) The "Capcom", the man on
the ground who does all the talking to the crew, is "CC".

The sextant work was one of the first activities of the mission. At only
18:33 after liftoff Collins says, "I'm ready to start on the orbit
determination, as soon as I unstow this sextant".

At 21:49 Collins starts setting up the computer for the first star. It's
possible to figure out what some of the numbers mean. Value "92:" (or
"J-92") is right ascension in units of .01 degree. BUT, it's 64.64°
greater than the true RA. For example, the RA of Hamal in July 1966 was
2h05m16s, or 31.32°. Adding 64.64° gives 95.96°. In the transcript
Collins enters 09596.

Value "93:" is simply declination in units of .01°.

The poor definition of the horizon makes observations difficult, and the
mission schedule is tight. There are problems with the sextant too: "The
image will not split!" Toward the end of the observation period you can
sense the crew hurrying to stay on the timeline.

As Collins begins to reduce the observations there's a lot of button
pushing and pencil math as he talks to himself. ("They changed my chart
on me and I can't find anything."). And finally, after all that trouble,
the results are unsatisfactory and they use the navigational data from
Mission Control instead. Collins is unhappy, but Young shrugs off the
failure: "What the heck! If you can't see the stars, you can't see them.
I've been telling you this for six months."

-- 

   

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