Apollo 15 Subsatellite

Type

Orbiter

Launch

Aug. 4, 1971

Target

Earth's Moon

Objective

Study the Moon's environment

Launch Date	Aug. 4, 1971
Launch Site	Cape Canaveral, Florida, USA \| Launch Complex 39A
Destination	Earth’s Moon
Type	Orbiter
Status	Successful
Nation	United States
Alternate Names	1971-063D, P + F S, Apollo 15D, PFS-1, Particles and Fields Subsatellite, 05377

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.

In Depth

This small satellite was deployed by the Apollo 15 crew shortly before leaving lunar orbit. The probe was designed around a 35.6-centimeter-diameter hexagonal structure that was equipped with three instrument booms. Power supply came from solar panels and chemical batteries.

The instruments measured the strength and direction of interplanetary and terrestrial magnetic fields, detected variations in the lunar gravity field, and measured proton and electron flux. The satellite confirmed Explorer 35’s finding that while Earth’s magnetic field deflects the incoming solar wind into a tail, the Moon acts as a physical barrier due to its weak field and creates a “hole” in the wind.

An electronic failure on Feb. 3, 1972 formally ended the mission. Although it originally had a one-year design life, all mission objectives were fulfilled.