Momentum wheels are reaction wheels. I'm not sure why the wikipedia article on them thinks differently-- Hubble wasn't gyrostablized at all, it's a telescope, i

Momentum wheels are reaction wheels. I'm not sure why the wikipedia article on them thinks differently-- Hubble wasn't gyrostablized at all, it's a telescope, it can't be allowed to spin. Hubble also masses eleven times that of Kepler. (11,000kg vs 1,000kg) I don't know the actual numbers, but attitude control systems possibly take up a larger percentage of spacecraft mass on Kepler than it does on Hubble.