How is the velocity of a spaceship measured?

Question

I get that with air crafts you can use a pitot tube to measure air speed, but what do you do if there is no air

In: Physics

Answer 1

Usually some combination of inertial guidance with star tracking and ground-based tracking via Doppler. the Deep Space Network antennas can measure spacecraft speeds accurately to within hundredths of a millimeter per second anywhere in the solar system.