According to the NASA Johnson video Space to Ground: A Star to Steer By: 08/10/2018:

A tool that once helped sailors cross vast oceans for centuries is now being put to the test in space. The crew has been testing out a sextant, a device with a small telescope-like sight that can take precise measurements between pairs of stars. These were actually used in the early days of human spaceflight on programs like Gemini and Apollo. And mission planners are once again looking at how they can be used for emergency navigation needs on deep-space exploration vehicles like Orion.

As for the title: And all I ask is a tall ship and a star to steer her by; 12 Teleplay by Dorothy Catherine Fontana, poem by John Masefield.

I show some screenshots below.

Question: What is the nature of the sextant tests on the ISS for Orion cis-lunar emergency navigation? I'm guessing that the idea is to use measurements of the separation between a star and a position on either the Earth or the Moon, rather than between two stars. Is there a description or a report?

In real practice, in an emergency, I'm guessing that you'd probably need an ephemeris printout, pen and paper, or a small handheld computer to do useful navigation using this technique assuming that you are beyond near Earth orbit and experiencing an emergency. It would be great to read about these procedures if there's anything written about it.

Shown in the NASA Johnson video using a sextant aboard the ISS are NASA Astronaut Serena M. Auñón-Chancellor M.D. (per comments and here) and German ESA astronaut Alexander Gerst (from here).


sextant tests on ISS

sextant tests on ISS

  • $\begingroup$ The other crewmember is Serena Aunon-Chancellor. Google for "space station highlights week of June 25 2018" on www.nasa.gov. $\endgroup$ Aug 12, 2018 at 3:51
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    $\begingroup$ Links about the Apollo sextant: 1. astronomy.com/news/2018/06/the-story-of-the-apollo-sextant 2. ion.org/museum/item_view.cfm?cid=6&scid=5&iid=293 $\endgroup$
    – Heopps
    Aug 12, 2018 at 7:06
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    $\begingroup$ @OrganicMarble thank you, and duly noted above. $\endgroup$
    – uhoh
    Aug 12, 2018 at 9:01
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    $\begingroup$ @Heopps those are great links, than you! $\endgroup$
    – uhoh
    Aug 12, 2018 at 9:01
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    $\begingroup$ A measurement of the angle between pairs of stars may be used to check your sextant as well as your measurement skills. The angular distance of pairs of stars many light years away is constant and does not depend on your position on Earth or in orbit. If you measured the tabulated angular disances of several pairs with good precision, your sextant and your usage of it should be OK. $\endgroup$
    – Uwe
    Nov 2, 2018 at 10:44


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