Explorer 22 (known as S-66 pre-launch; also called BE-2 or Beacon Explorer B) was a small American ionospheric research satellite launched October 9, 1964, part of NASA's Explorers Program. It was instrumented with an electrostatic probe, four radio beacons for ionospheric research, a passive laser tracking reflector, and two radio beacons for Doppler navigation experiments. Its objective was to provide enhanced geodetic measurements of the Earth as well as data on the total electron content in the Earth's atmosphere and in the satellite's immediate vicinity.