"It's just gone."

  

Edgar Mitchell moves across the lunar surface as he looks over a traverse 

map while exploring the Fra Mauro region. Credit: NASA/Alan Shepard

I have been studying the technical details of lunar exploration for a while now.  I think the archives have important information that will help Artemis explorers and mission planners.

While reading through the "Apollo 14 Technical Crew Debriefing" from 1971, I found some interesting comments from lunar module pilot Ed Mitchell about visibility on the lunar surface.

"In looking out the window from the LM [Lunar Module], I had a very definite impression of the relief. I think we stated several times that the relief was greater than we expected. However, I observed that when we got on the lunar surface, subsequent to that, that your observation of the relief changes with Sun angle.

The Sun wipes out, or seems to smooth out, a lot of relief that you see at certain Sun angles and that you just don't see at other Sun angles. Or maybe the visor distorts it in some way. But sometimes you see a very good sized, crater, a depression ahead of you. You look at it at a different angle and it's just gone.

When you turn your head a different way, you don't see it. So, perhaps there's a bit of distortion in the visors. You're never quite sure whether it's visor distortion or whether it's Sun angle or what it is that causes you to see these things or not to see them at a particular point in time."

Source: Apollo 14 Technical Crew Debriefing, February 17, 1971, https://www.hq.nasa.gov/alsj/a14/a14-techdebrief.pdf

 

This aligns with similar startling observations from Apollo 16 commander John Young posted here: https://outwardspace.blogspot.com/2021/09/apollo-16-invisible-obstacles.html

Visibility issues related to a combination of sun angle and/or visor distortion may pose a hazard to future lunar explorers.  

Depending on the landing site, a mission lasting one lunar day (about 30 Earth days) will expose Artemis astronauts to every possible sun angle, including possible weeks of darkness.