Goals: The spacecraft's main objectives were to study the plasma, particle, and magnetic-field environment of the Moon and map the lunar gravity field.
Accomplishments: The subsatellite, deployed by the Apollo 15 crew shortly before they left lunar orbit, provided about six months of data coverage before electronics failures in February 1972 caused the loss of most of the data channels. Nevertheless, all mission objectives were fulfilled. Measurements supported Explorer 35's finding that the Moon acts as a physical barrier to the solar wind, creating a "hole" in the flow of charged particles.
This was the first orbiter deployed by humans from a spacecraft (right).