Apparently the Moon was in its Waxing Crescent phase as Armstrong and Aldrin stood on its surface. Was the Moon’s phase one of the things NASA considered when planning to Apollo missions? Best I can figure, sending them up there during a New Moon wouldn’t have made any sense, since getting communications between the astronauts on the surface and Mission Control would have been problematic, unless we sent them to the far side, which we did not (based on my limited understanding of astronomy). Also, were Armstrong and Aldrin on a part of the Moon that people on the Earth could have seen at the time?
They went to the near side and they had to do it during the lunar day so, yes, the phase of the moon mattered.
Previous threads covered this as well.
The angle of the sun relative to the lunar surface was the most important part of the timing. They needed a sun angle that provided good surface illumination so as to be able to see the surface detail, and thus land safely. An overhead sun would lead to a flat illumination, and to low an angle is no good either. So about 30 degrees above the horizon (if I remember ok) was chosen.
Once that is determined the location of the landing fixes phase of the moon needed, and thus the launch date. If you look at the date of each launch, find it the phase of the moon, and then check the longitude of the landing site, you will get the same difference each time.
All the landing sites were on the near side.
Why would this have been problematic for communications? The only problem is that the astronauts wouldn’t be able to see anything, not that they wouldn’t have direct line-of-sight. (Which also wouldn’t matter, since communication from the surface of the Moon was first relayed to the lunar orbiter.)
Actually is wasn’t. The command module was in orbit around the moon, and was on the far side, and out of all communication range for close to half the mission. The lander communicated directly with the Earth, and sometimes actually relayed messages to the command module via mission control. There were times in the descent where the two were close together, as the LM decelerated out of orbit to the surface the CM ran ahead, but it was possible for the CM to relay messages to the LM in the early stages, which was important when getting the link from the LM to Earth stable. But once on the way down, the LM communicated directly with the Earth, and continued to do so once landed.
Once on the lunar surface, one of the early tasks was setting up a larger communications antenna, so that higher bandwidth comms were possible. The lunar rover also had it’s own high gain antenna for direct communication with the Earth. This was all possible because the Earth side communication systems were huge. The NASA’s Deep Space Network used an extensive set of large dish antenna at locations around the Earth to allow for continuous communications.
Ooh thank you - that’s great info!
At new Moon, the Moon is within a few degrees of the Sun. A solar flare might produce enough radio noise to interfere with the communications.
It wouldn’t have been totally dark. There would be a full Earth in the sky which would be much brighter than the full Moon as seen from Earth. Not sure if it’d have been bright enough to reliably land the craft. My guess is that it would have been.
But it would also have been from directly overhead, which would kill eyeball terrain recognition (which is enhanced by moderate shadows), in addition to being a lot dimmer that sunlight.
Nope. The full Moon is not always directly overhead and not always even close to it. It can be fairly low in the sky. The same is true of the full Earth as seen from the Moon.
Exactly how high in the sky a full Earth would be depends on the latitude of the landing site and what time of the year it is.
Yeah, you would be able to see by Earthshine. But if you’re spending all that money to send people all that way, you don’t just want them to see; you want them to see as well as they possibly can. Which means daylight. And since you can, after all, choose the location and timing of your landing, why not?
What would have been really cool is if they landed right before a lunar eclipse. But the technical requirements as said precluded that. Another issue would have been overheating I believe.
And longitude. Landing on the equator of the moon but close to the edge of the near side would produce a low-in-the-sky blue marble.
True, but Apollo 12 got a taste of that while they were on the way back from the moon: