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Q:

I haven't seen any rockets on the Hubble or on Kepler. How do they move? Do they just point at the same spot for years and years?

A:

Scientists and engineers can move space telescopes using small gyroscopes inside the device because huge rockets are expensive, limited, and could damage the instruments. 

 

The Hubble uses gyroscopes called reaction wheels to change its orientation. When they are turned on, it creates angular momentum, and forces the telescope to rotate in the opposite direction, thanks to Newton's third law of motion.

 

Kepler, however, has a fixed field of view, meaning it will point at the same corner of space for a long time, though it also has thrusters and reaction wheels.

Categories: Flight Dynamics