BIC (GRP)

NASA and the Max Planck Institute for Extraterrestrial Physics (MPE), Munich, Germany, conducted the Barium Ion Cloud (BIC) project, a cooperative experiment involving the release and study of a barium cloud at 31500 km altitude near the equatorial plane.

The MPE-built spacecraft contained a canister of 16 kg of a Barium (Ba) and Copper-Oxide (CuO) mixture, a two-axis magnetometer, and other payload instrumentation.

The objectives of the experiment were to investigate the interaction of the ionized barium cloud with the ambient medium and to deduce the properties of electric fields in the proximity of the release. Optical observation sites were established in North and South America to provide long base line triangulation data to map the evolution, growth, and motions of the cloud. In addition, various geophysical parameters were monitored by supplementary experiments near the base of the field line at Great Whale Geophysical Station, Canada, and Byrd Station, Antarctica.

It was launched from the NASA, Wallops Island, facilities into a probe trajectory by a four-stage NASA Scout rocket. The release was made near local magnetic midnight on 21 September 1971 at a height of about 31000 km in the magnetosphere at 18.5° magnetic latitude and 5.6 R_E distance. The barium atoms were rapidly photoionized and remained visible for more than 1 hour. During the initial period the ion cloud expanded spherically creating a magnetic cavity. Its expansion perpendicular to the field was soon inhibited by the ambient magnetic field, and 60 s after release the ion cloud assumed the shape of a spindle oriented along the field. While growing mainly along the magnetic field, the cloud continued moving perpendicular to B with the velocity of the spacecraft at injection. However, the plasma distribution became soon asymmetric with a striated trail growing in the southeastward direction.