 The spacecraft was placed into a highly elliptical orbit with apogee at 9 Earth radii and perigee at 1.8 Earth radii (geocentric), 86 degrees inclination, with a period of around 18 hours.The apogee was initially over the northern polar region, but has since been precessing south at about 16° per year.Sensors on the spacecraft gathered multi-wavelength imaging of the aurora, and measured the entry of plasma into the polar magnetosphere and the geomagnetic tail, the flow of plasma to and from the ionosphere, and the deposition of particle energy in the ionosphere and upper atmosphere.