Scott Manley and I agree that altitude signal shouldn't matter if navigation is correct. Athena simply risked touchdown, and it didn't find a flat spot, it found a hole.
He's saying modern spacecraft can null out the horizontal velocity to land, but without an altimeter, you don't necessarily know when to do so, nor when to give the thrusters a little boost to avoid an obstacle you're about to hit, like a plateau.
He's saying modern spacecraft can null out the horizontal velocity to land, but without an altimeter, you don't necessarily know when to do so, nor when to give the thrusters a little boost to avoid an obstacle you're about to hit, like a plateau.