NSSDC Master Catalog Display
Experiment
Suprathermal Ion Detector Experiment (SIDE)
NSSDC ID: 69-099C-05
Mission Name: Apollo 12 LM/ALSEP
Principal Investigator: Freeman
Description
This experiment, part of the ALSEP package, measured positive ions
reaching the lunar surface, including magnetospheric ions and those
generated from ultraviolet ionization of the lunar atmosphere and from
the free-streaming solar wind/lunar surface interaction. Similar
instruments, differing only in look direction and mass range, were
also flown on Apollo 14 and 15. Flux, number density, velocity, and
energy/unit charge were determined. A low-energy curved-plate mass
analyzer (MA), with a velocity filter of crossed -E and -B fields
determined the ion flux in 20 mass channels up to 1000 amu per charge
for 6 energies over the range 0.2 to 48.6 eV. Another analyzer, the
total ion detector (TID), did not have a velocity filter and detected
higher energy ions in 20 steps over the range 10 to 3500 eV. A mass
spectrum (from MA) and an energy spectrum (from TID) were obtained
each 24 s in normal mode. The potential of the entrance apertures
relative to a grid deployed on the lunar surface was normally varied
through 24 steps at 2.58 min/step, in order to monitor the lunar
surface potential. The detectors looked upward, 15 deg from local
vertical, in a plane parallel to the lunar equator. The sensors looked
approximately 38.4 deg to the right of Earth, so solar wind ions were
not directly observeable while the moon was outside the magnetosphere.
Streaming ions in the downstream dawn-side magnetosheath were
observed, as were ions upstream from the bow shock. An instrument
description and preliminary report is given by Freeman, Balsiger, and
Hills as section 6 of the Apollo 12 Preliminary Science Report, NASA
SP-235, 1970.
Discipline(s)
Planetary Science/Fields and Particles
Space Physics/Magnetospheric Studies
Personnel Information
Data Set Information
Mission Information
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Dr. James Thieman, thieman@nssdca.gsfc.nasa.gov, (301)286-9790
National Space Science Data Center, Code 633.2
NASA/Goddard Space Flight Center, Greenbelt, MD 20771
NASA Official: J. H. King, king@nssdca.gsfc.nasa.gov
Last Updated: 1996-12-19
Output Generated: 1997-09-24
Programming by: E. V. Bell, II