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Landing Time

18 June 1996: Oh no! I'm still  working on this one one.  At least I fixed the broken links this time.  I also added some notes to the little pictures at the end so you can see where I'm going with this.  Thanks for your patience.

Scope of this Section

Here we're concerned about what time of day we land on the moon, rather than the overall program schedule which tells what year we conduct the first manned lunar landing. The program schedule for the overall Artemis Project is in Section 1: Project Overview.

Considerations for the Time of Landing

The main issue for choosing a time for the landing is lighting at the landing site. We want the pilot to have a good view of his target, with craters and other obstructions clearly visible, and we don't want him to have the sun in his eyes.

Another consideration for the landing time is crew factors. We want to schedule to landing for a time when the crew will be alert, at their peak performance. We can adjust the crew schedule to some extent so that the landing occurs in the early morning relative to their internal biological clocks, but we can push the human body only so far. So the time of landing will drive the whole mission all the way back to trasnlunar injection. Fortunately, the time of flight to the moon and major mission activities allow us quite a bit of flexibility for scheduling around human factors, which in turn allows us to choose the landing time based on lighting at the landing site.

Besides the technical issue of proper lighting for the pilot's view out the window, we have to consider photography. We're in show business, so it wouldn't do to have a dark image or the camera pointed directly into the sun while recording the landing. Again, we're fortunate: the same conditions that lead to good lighting for piloting also are excellent for photography.

Lighting for the Pilot

Notes for finishing up this part:

  • Crater Geometry
    We're getting into a bit of geometry here.

    Sun too high If the sun is too high in the sky, all the surface details in the craters are washed out and the pilot can't see hazards.

    Sun too low If the sun angle is too low, the shadow of the crater rim fills the floor of the crater, and again, the pilot can't see where he's going.

    Sun just rightDepending on the type of crater and the height of the walls, a sun angle between 5 and 20 degrees seems just right. Shadows show distinct detail of objects on the crater floor, and craters stand out in bold relief. The pilot can use the lunar surface for landing cues and hazards are clearly visible.

    Link to Apollo Landing Time page


    Earth Orbit to Lunar Surface

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