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Solar System Exploration
Apollo 15 Particle and Fields Subsatellite
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Apollo 15D
Apollo 15 Particle and Fields Subsatellite Mission to Earth's Moon

Mission Type: Orbiter
Launch Vehicle: Apollo 15 CSM-112 (itself launched by Saturn V SA-510)
Launch Site: Eastern Test Range / launch complex 39A, Cape Canaveral, USA
Spacecraft Mass: 35.6 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
S-Band Data Rate: 128 bits/sec
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,

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

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 3 February 1972 formally ended the mission. Although it originally had a one-year design life, all mission objectives were fulfilled.

Key Dates
26 Jul 1971:  Launch
4 Aug 1971:  Deployment by Apollo 15 Crew (20:13:19 UT)
Status: Successful
Fast Facts
Apollo 15D Facts This was the first orbiter deployed by humans from a spacecraft (right).

Apollo 15 carried astronauts David Scott and James Irwin to the Moon. Alfred Worden piloted the command module in orbit.

A similar subsatellite was carried aboard Apollo 16.
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Last Updated: 29 Sep 2010