Particles and Fields Subsatellite

PFS-1

Mission Profile

Particles and Fields Subsatellite (PFS-1) was a small 36 kg scientific satellite released into lunar orbit by the Apollo 15 Command and Service Module on 4 August 1971 to measure the Moon's magnetic field, gravitational anomalies, and the solar wind particle environment at lunar distance. The subsatellite was ejected from the Scientific Instrument Module bay in the Service Module and operated autonomously in lunar orbit for 35 days before crashing into the Moon due to lunar orbital perturbations. A second identical PFS-2 was deployed during Apollo 16, and the data from both contributed to mapping of the Moon's complex and surprisingly patchy magnetic fields and surface electrical properties.