NASA hasn't been to the surface of the Moon in any meaningful way since the 70s. So, you're correct, but how is that relevant? Obviously all discussions about

NASA hasn't been to the surface of the Moon in any meaningful way since the 70s. So, you're correct, but how is that relevant? Obviously all discussions about "NASA plans to do X on the Moon" and "if NASA's doing X on the Moon, we've worked out that they can use Y to accomplish X" are hypothetical at this point. So, in that context, what's the relevance of your claim that "GPS cannot be used on the Moon". I agree that if you're going to insist on empirical evidence that no, we don't actually know if it works on the Moon. But if that's your goalposts then I'd think you'd worry more about the hypothetical astronaut reading that GPS position or GPS time having long since asphyxiated. After all we've got no empirical evidence that the space suits planned for use on the Moon actually work there, etc. It's all inferred at this point, we'll see about the experiment. But if I had to bet that signal propagation works the way we expect (GPS), v.s. say some joint failing when filled with lunar regolith (spacesuit), then my money's on the GPS experiment.