More than 500 sounding rockets have been launched from Esrange since the start in 1966. A sounding rocket makes a short flight in space, returning to earth via parachute landing without orbiting the earth. Thanks to the large impact zone, which is completely uninhabited, maximum altitudes of 900 km can be reached without jeopardizing safety. Also considerably lower altitudes can be of interest to researchers, depending on their aims. The initial aim was to study the northern lights at an altitude of 100-200 km and this particular altitude is difficult to reach in any other way. Other important fields of research are microgravity, aeronomy, astronomy, atmospheric physics, space physics and meteorology.