The Apollo 15 and Apollo 16 missions carried a small subsatellite designed to be released in lunar orbit just prior to the beginning of the astronauts' return flight to earth. Powered by six solar panels in 11 silver-cadmium batteries, the so-called "Particles and Fields subsatellites" contained three instruments: a magnetometer, an S-band transponder, and charged particle detectors. Instruments were designed to measure the strength and direction of interplanetary and terrestrial magnetic field, to detect variations in the lunar gravity field, and measure proton and electric flux from the solar wind.

The artifact here is the qualification model for the Particles and Fields subsatellite. It underwent extensive tests and demonstrations prior to the launch of the actual satellites. It was transferred from NASA to the Smithsonian in 1975.

[Apollo 16 Particle and Fields Subsatellite Mission to Earth's Moon]

Mission Type: Orbiter

Launch Vehicle: Saturn V SA-511

Launch Site: Eastern Test Range / launch complex 39A, Cape Canaveral, Fla., USA

Spacecraft Mass: 42 kg

Spacecraft Instruments: 1) magnetometer; 2) S-band transponder; and 3) charged-particle detectors

Spacecraft Dimensions: hexagonal cylinder 78 cm long and about 36 cm across opposite corners of the hexagon, plus 3 equally spaced booms, each 1.5 m long

Spacecraft Power: 6 solar panels and 11 silver-cadmium batteries

Maximum Power: 24 W

Maximum Data Rate: 128 bits/sec

References:

Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, Monographs in Aerospace History No. 24, by Asif A. Siddiqi

National Space Science Data Center, http://nssdc.gsfc.nasa.gov/

Solar System Log by Andrew Wilson, published 1987 by Jane's Publishing Co. Ltd.

Nearly identical to its predecessor, the Apollo 16 Particle and Fields Subsatellite was ejected from the Apollo 16 Command and Service Module (CSM) about 4 hours prior to the crew's trans-Earth injection burn, which sent them home from the Moon.

Because of problems with the Apollo CSM main engine, the crew was forced to release the subsatellite in a low lunar orbit of 100 x 100 kilometers at 10° inclination. The orbit was rapidly altered by gravitational perturbations, and the probe crashed onto the lunar surface after 34 days in orbit rather than the planned one year. Impact point was at 10.2° north latitude and 112° east longitude at 21:00 UT on 29 May 1972. However, because of its low orbit, the spacecraft did return some valuable low-altitude data.