Almost the same question as Could Schiaparelli's retroreflector array (still) be used? except for Beresheet.

Some important differences in this case:

  • Beresheet was far less "crashed" than Schiaparelli
  • There are fewer dust storms on the Moon than on Mars to burry things
  • The laser altimeter on the LRO is currently active, while the MRO uses radar for altimetry.
  • The Moon is within reach of powerful Earth lasers, whereas Mars is not
  • 2
    $\begingroup$ What was the estimated impact velocity of Beresheet again? I don't remember it exactly, but I'm pretty sure it was somewhere on the order of "smash everything into tiny pieces". $\endgroup$ – Ilmari Karonen Jun 1 '19 at 15:03
  • 1
    $\begingroup$ @IlmariKaronen look it up; you'll see it wasn't at all like that. $\endgroup$ – uhoh Jun 1 '19 at 16:49
  • 2
    $\begingroup$ I did, actually. 1000 m/s or so seems pretty fast to me; that's about the speed of a rifle bullet. I suppose some of the sturdier parts might have survived, particularly as it was a glancing impact, but I wouldn't personally bet much on it. $\endgroup$ – Ilmari Karonen Jun 1 '19 at 17:14
  • $\begingroup$ @IlmariKaronen I thought iI'd read that it was only a few hundred, but I'll have to check around to find it now. Where does 1000 m/s come from? The retroreflector looks pretty robust, I found a photo here but it certainly might rapidly disassemble at that speed. However it would be on top of the spacecraft which would then act as a giant "crumple zone" for it, so I wouldn't give up hope so quickly. $\endgroup$ – uhoh Jun 1 '19 at 22:18

The final impact velocity of Beresheet with the lunar surface has been estimated as around 1000 meters per second, comparable to the muzzle velocity of a rifle bullet. While the impact was glancing, it's still likely that the lander smashed into tiny pieces as soon as it touched the surface.

However, if the retroreflector array (or even any of its individual reflectors) somehow survived the impact, there's indeed a good chance that it can and will be found. The whole point of a retroreflector is that it's supposed to reflect any light hitting it back to the source, making it bright and easy to detect, and as you note, there are several powerful lasers on the Earth and around the Moon that could be used to try and light it up.

In fact, NASA seems to believe that there's at least a chance that the array may have survived, and is using the laser altimeter on the Lunar Reconnaissance Orbiter to look for it. Their biggest source of uncertainty, aside from the possibility that the array might simply have shattered, is apparently that it might have landed upside down with all the reflectors pointed at the surface. Still, the reflector array has apparently been designed with a 120° angle or reception, and with a laser in lunar orbit they can presumably try to illuminate the impact area from many directions, allowing possible detection even if just one of the reflectors is facing even slightly above the lunar horizon.

And if the reflector has survived and can be spotted once, presumably it can also be spotted again and even used for its intended purpose of ranging measurements. After all, aside from the occasional falling space rock and the even more occasional falling space probe, there's not much on the lunar surface that would spread dust or debris around, so things that are exposed and visible on the surface tend to stay that way for a good while.

Apparently, as of May 15, 2019, nobody's yet managed to spot the retroreflector array, but "efforts are ongoing."

| improve this answer | |
  • $\begingroup$ Thanks for the thorough and well-sourced answer! $\endgroup$ – uhoh Jun 1 '19 at 22:39

Your Answer

