this post was submitted on 06 Mar 2025
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interesting. its not just about the moon:
"LuGRE’s groundbreaking success opens the door for future NASA Artemis missions and other space explorations to use GNSS (Global Navigation Satellite System) signals. This means they can accurately figure out their position, speed, and time without human help. It’s a huge leap forward for navigation systems on the Moon and Mars!"
this should be pretty huge. think about the various failed landings and such you have seen in the news.:
"Traditionally, NASA engineers use a combination of onboard sensors and Earth-based tracking signals to track spacecraft. LuGRE’s demonstration shows that GNSS signals can autonomously aid navigation, even at the Moon’s distance."
so this really changes space exploration as or more significant to the reusable rocket stages.
They were only able to receive signals from the bare minimum to achieve a solution (4 GPS and 1 Galileo). Their achieved accuracy was +/- 1.5km and +/- 2m/s. That is good enough in astronomic scales to get you to a planet, but it isn't going to help failed landings or autonomous landings.
I don't think there was any new tech involved, just a receiver put on a moon lander to see if it could detect signals. And this won't really do anything for Mars for two reasons: 1) the signal strength would be too small for any reasonable antenna to detect GPS L1/L5 at Mars distances, and 2) the distance would make the geometry be unusable to trilaterate a solution... think about a triangle where two lengths are 100 million miles and the third length is 100 miles. That is a completely worthless geometry for trilateration of a position solution. Even if we could somehow detect a GPS signal at Mars, best case is we get atomic clock time.
If they can get rockets to mars, what’s to prevent them from deploying GPS satellites around Mars? Then just have the spacecraft switch to receiving those signals instead as it get close enough
Nothing to prevent it except money. The issue with PNT satellites around Mars is how many satellites would have to be sent (smaller planet and less accuracy needed, so maybe we could get away with 12 instead of 24), plus the ground command and control stations plus monitoring stations. The ground part is probably the most critical piece of why GPS is so accurate, and I'm not sure we could do that from Earth. Definitely couldn't do the monitoring from Earth.
We'd have to be able to build an accurate ephemeris table for the Mars satellites, have accurate clock updates, monitor the signals being transmitted to do updates, etc. While we could do the commanding and controlling from Earth, I don't know if we could do the things from Earth that make GPS accurate. So not only would we have to send 12 satellites to Mars, we'd have to build monitoring stations on Mars to do the ground portion. Technically doable, just not financially feasible when we have star trackers and other navigation systems that work well enough for now.
Nice. That’s the detail I was hoping someone would have! Thank you