1,000 gigabytes of observational data
The original launch plan for Hipparchos called for a geo-stationary orbit. However, a booster engine failure resulted in the satellite achieving an elliptical geo-orbit instead. Exhaustive efforts by ground controllers enabled Hipparchos to carry out its mission of fixed-star observation, relaying some 1,000 gigabytes of observational data over an approximate three-year period until failure of the satellite's solar panel in June 1993. Due to the effect of Hipparchos not being able to achieve its originally intended geo-stationary orbit, however, observation data collected by the satellite was extremely complex, requiring a great deal of time and cost in analysis. Nevertheless, a portion of this analyzed data became available for use in August 1997. Furthermore, this highly precise data compared to that available in the past is anticipated to have a major impact on the fields of positional astronomy and astrophysics.
over an approximate 3-year period