Tracking antenna. Time-exposure image of star trails and an aurora borealis, or northern lights, display silhouetting a satellite-tracking antenna at Poker Flat Research Range (PFRR), Alaska, USA. The antenna tracks, and receives data from, polar- orbiting satellites. These satellites, and other equipment including meteorological balloons and sounding (non-orbiting) rockets, collect data on the Arctic atmosphere. Much of the research is on the aurorae, the light displays (visible at night) that result from the hundreds-of-kilometres-high atmospheric impacts of charged particles from the Sun. These particles are drawn to the polar regions by the Earth's magnetic field.