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    Space station sextant returned to Earth
    From: Paul Hirose
    Date: 2021 Jan 16, 14:03 -0800

    The recent SpaceX Dragon mission returned two tons of cargo from the
    space station, including the sextant in the navigation experiment.
    A paper on the NASA "Sextant Navigation for Exploration Missions"
    project was presented at an American Astronautical Society conference in
    "Astronauts on board the International Space Station (ISS) tested a
    hand-held sextant to demonstrate potential use on future human
    exploration missions such as Orion and Gateway. The investigation,
    designed to aid in the development of emergency navigation methods for
    future crewed spacecraft, took place from June-December 2018. A sextant
    provides manual capability to perform star/planet-limb sightings and
    estimate vehicle state during loss of communication or other
    contingencies. Its simplicity and independence from primary systems make
    it useful as an emergency survival backup or confirming measurement
    source. The concept of using a sextant has heritage in Gemini, Apollo,
    and Skylab. This paper discusses the instrument selection, flight
    certification, crew training, product development, experiment execution,
    and data analysis. Preflight training consisted of a hands-on session
    with the instrument and practice in a Cupola mock-up with star field
    projector dome. The experiment itself consisted of several sessions with
    sextant sightings in the ISS Cupola module by two crew members.
    Sightings were taken on star pairs, star/moon limb, and moon diameter.
    The sessions were designed to demonstrate star identification and
    acquisition, sighting stability, accuracy, and lunar sights. Results are
    presented which demonstrate sightings within the accuracy goal of 60
    arcseconds, even in the presence of window refraction effects and
    minimal crew training. The crew members provided valuable feedback on
    sighting products and microgravity stability techniques."
    Holt GN, Wood BA. Sextant Navigation on the International Space Station:
    A human space exploration demo. 42nd Annual AAS Guidance, Navigation and
    Control Conference, Breckenridge, CO. 2019 February 3; AAS 19-06415
    Paul Hirose

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