Hipparcos: The Star Machine

ESA's High Precision Parallax Collection Satellite (Hipparcos), was an astrometry mission that determined the precise position of over 100,000 stars. This video from 1989, prior to launch, clearly explains the scientific goals and the demonstrates with clear animations how Hipparcos measurements were carried out (principles of parallax). By the time the mission ended in 1993, Hipparcos had pinpointed the positions of more than one hundred thousand stars to high precision. Hipparcos confirmed Einstein's prediction of the effect of gravity on starlight and discovered that the Milky Way is changing shape.