What I think is even crazier is the GRACE mission with two sattelites chasing each other (fittingly named Tom & Jerry):
They use the fact that higher densities of gravity on the earth below accelerate one sattelite before the other. So the way they measure gravity is by very accuratly measuring the fluctuations in the distances of the sattelites.
This is a feat in itself, the sattelites are 200 km apart and the fluctuations are on the scale of the strength of a hair.
Maybe there are better more precise ways of measuring local gravity from space, but this is just so clever.
They use the fact that higher densities of gravity on the earth below accelerate one sattelite before the other. So the way they measure gravity is by very accuratly measuring the fluctuations in the distances of the sattelites.
This is a feat in itself, the sattelites are 200 km apart and the fluctuations are on the scale of the strength of a hair.
Maybe there are better more precise ways of measuring local gravity from space, but this is just so clever.