GALEX satellite. Artwork of the Galaxy Evolution Explorer (GALEX) satellite in orbit as the Sun appears from behind the Earth. GALEX is equipped with ultraviolet (UV) sensors that are able to distinguish young and old stars more accurately than optical and other sensors. It was launched in April 2003 and is designed for a 29-month mission. The solar panels are deployed here to obtain power from the Sun. GALEX collects data when it is in the Earth's shadow. A full range of UV observations is only possible in space, as the Earth's ozone layer absorbs most UV radiation from space. The UV sensors are at the end of the probe that is seen here.