The parallax method is the fundamental calibration step for distance determination in astrophysics ; however, the accuracy of ground-based telescope measurements of parallax angle is limited to about 0.01″, and thus to stars no more than 100 pc distant. This is because the Earth's atmosphere limits the sharpness of a star's image. Space-based telescopes are not limited by this effect and can accurately measure distances to objects beyond the limit of ground-based observations. Between 1989 and 1993, the Hipparcos satellite, launched by the European Space Agency (ESA), measured parallaxes for about 100 000 stars with an astrometric precision of about 0.97 mas, and obtained accurate measurements for stellar distances of stars up to 1000 pc away.