A NASA satellite deployed in April 1984 by the space shuttle Challenger to collect long-term data on the space environment and its effects on space systems and operations. It was retrieved in January 1990 by the space shuttle Columbia. LDEF carried 57 experiments, which involved more than 200 principal investigators from 7 NASA centres, 33 companies, 21 universities, 9 US Department of Defense laboratories, and 8 foreign countries. The results, kept in the LDEF Archive System at the Langley Research Center, have led to research in such fields as radiation, meteoroids and debris, and contamination.