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When landed on the moon, the ladder seems to be in the shadow for each Apollo mission.

For example, on this photo, the ladder is not in the side exposed to the Sun. (the astronaut go out of the LM in the shadow of the LM).

Why did the NASA choose to land the LM in that direction (exit (and the ladder) in the shadow of the LM)?

NASA photo AS11-40-5869; Buzz Aldrin in the moonhttps://upload.wikimedia.org/wikipedia/commons/a/a5/AldrinOnMoon.jpg

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    $\begingroup$ Bonus: Whenever the Luna Rover is stationary the shadows of the sun-side wheels never fall on the far-side wheels. This is by design and not an astounding coincidence. [Somebody will probably now produce a photos falsifying this :-) , but that was the aim.] $\endgroup$
    – Russell McMahon
    Commented Jul 8, 2019 at 6:53
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    $\begingroup$ Bonus two: The shadow of the LEM is projected on both Aldrin and the lunar ground, why can't we see the ground? $\endgroup$
    – user19132
    Commented Jul 8, 2019 at 9:21
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    $\begingroup$ @qqjkztd I think you lack some photographic background. It is not uncommon that the dynamic range of a camera make shadow dark enough to not be able to see details on it while white objects (the astronaut) light by a small reflector (here, the moon regolith) is bright enough to be seen (you can easily find reconstitution made with Lego on photographs' blogs and try to reproduce it yourself) $\endgroup$
    – Manu H
    Commented Jul 8, 2019 at 9:27
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    $\begingroup$ @qqjkztd This image shows the original plus a lightened version. I suspect that the black shadow has been further darkened - can't have original photos when they can be improved with editing. (I may be wrong). The 'black" is a very dark blue and is not quite homogeneous, but dies not have the variability I'd expect. [I often enough lighten up photos in this manner to check for editing]. || That said, the ground is horizontal and less liable to be highly illuminated by low angle reflected light. $\endgroup$
    – Russell McMahon
    Commented Jul 8, 2019 at 10:43
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    $\begingroup$ || PhD thesis - Dynamic thermal modeling for moving objects on the Moon || p7 lower - ... During Apollo 14 the MET was used to transport instruments and equipment ... MET was designed to sustain minimal temperatures as low as 216 K. ... during surface operations one wheel fell below that threshold temperature only because it was shadowed by the other parts of the MET ... The Astronauts had to adopt to this unforeseen condition in order not to loose the MET. ... by positioning the MET Stack Overflow no shadow was casted on the wheels. $\endgroup$
    – Russell McMahon
    Commented Jul 8, 2019 at 11:12

1 Answer 1

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All the lunar landings were performed with the sun low in the sky behind the LM, between 5º and 14º above the horizon at the landing site. This provided several advantages:

  • The sun wouldn't be in the crew’s eyes during any portion of the descent (they’d start out oriented feet forward, lying on their backs looking upward, during the braking phase, and progressively pitch downward from that orientation to standing vertically looking forward during the final portion of descent)
  • The terrain would cast sharp shadows, which made it easier to see the shape of the surface
  • The shadow of the LM itself would be cast on the ground ahead in the final moments of descent, which would help the commander judge the LM's altitude.

The descent ladder, being on the front leg of the ship, was therefore always in shadow after touchdown.

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    $\begingroup$ The third bullet point there is the key one - pilots would rather use shadows to judge altitude rather than blindly trusting doppler radar to indicate the descent rate and altitude of the LM. From what I've read, no landing was ever performed under autonomous control. Lovell intended to, but of course that never happened. It make sense for the ladder to be under the only windows on the ascent stage - ergo the ladder is on the dark side. $\endgroup$
    – user21233
    Commented Jul 8, 2019 at 10:42
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    $\begingroup$ @Snow: That was my thinking exactly, from KSP landings. I always use the shadow. $\endgroup$
    – dotancohen
    Commented Jul 8, 2019 at 11:22
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    $\begingroup$ The cabin was very small, and the astronauts stood just behind the window to improve their downward view. There was nowhere else for the exit hatch to be placed. $\endgroup$
    – Russell Borogove
    Commented Jul 8, 2019 at 13:00
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    $\begingroup$ The low sun makes a lot of sense from the point of view of revealing surface relief during the descent. This meant the landing had to be made in the lunar morning or evening. Morning was always chosen because, in the event of any mishap, that gave them the maximum amount of daylight to resolve the issue. $\endgroup$
    – Oscar Bravo
    Commented Jul 8, 2019 at 13:50
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    $\begingroup$ @CGCampbell, it still makes sense to want to maximize the amount of daylight in case of a problem, even when the period from dawn to dusk lasts 348 hours. I'd rather have 324 hours to work on something if I'm stranded on another world, than just 24 hours. (Or rather, I'd prefer my useful working period to be determined by O2, and not daylight.) $\endgroup$
    – Ghedipunk
    Commented Jul 8, 2019 at 17:42

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