The LEAM instrument as deployed at the Apollo 17 ALSEP site (AS-17-134-20500). The central station is directly behind it, the RTG to the right of that, and the LSG to the left of the central station. Discarded pallets and trash are also visible.
The LEAM instrument as deployed at the Apollo 17 ALSEP site (AS-17-134-20500).
The central station is directly behind it, the RTG to the right of that,
and the LSG to the left of the central station. Discarded pallets and trash
are also visible.
PI/Engineer: Otto E. Berg, Goddard Space Flight Center
Other Contacts:
F. F. Richardson, H. Burton; Goddard Space Flight Center
Apollo Flight Nos.: 17
Apollo Exp't No.: S 202
Discipline: lunar geology, cratering, micrometeorites
Weight: 7.4 kg
Dimensions: 32.3 x 30.5 x 19.8 cm, stowed
Manufacturer: Bendix
Description/Purpose:
The objectives of the LEAM experiment were to detect secondary particles
that had been ejected by meteorite impacts on the lunar surface and to
detect primary micrometeorites themselves. The 3 classes of particles encountered
by the LEAM included lunar ejecta, interstellar grains, and cometary debris,
all of which can be considered under the title of cosmic dust. The experiment
measures particle speed, radiant direction, particle momentum, and particle
kinetic energy. The particle detectors of the instrument were multi-layered
arrays that were capable of measuring the velocity and energy of incident
particles. It consisted of 3 sensors - East, West, and Up. It stood on
4 legs and was connected to the ALSEP central station by a cable.
Unloading from the LM: As part of the ALSEP.
Transporting by foot or MET: As part of the ALSEP.
Loading/unloading tools/exp'ts on LRV: NA
Site selection: As part of the ALSEP.
Deploying experiment:
As part of ALSEP. The crew had to
connect a cable to the central station, remove the instrument from the
subpallet, locate it 25 feet SE of the central station, release the legs,
and place in on the surface within 5 degrees of level and 5 degrees of
alignment, using a bubble and sun dial. As requested, the east sensor was
directed 25 degrees North of East to accommodate interstellar grains. It
was protected by 2 dust covers that were removed by ground command using
a redundant squib system.
Check-out of experiment:
After deployment, it was commanded "on" from Earth for calibration,
then turned off until after LM ascent and detonation of the surface charges
of the LSP experiment.
Operation of experiment:
Operated from JSC via the ALSEP command system. The dust covers over
the sensors were commanded to release in the lunar night, but did not;
perhaps because of the cold. They did release sometime during dawn of the
second lunation.
Repairs to experiment: None required or attempted.
Recovery/take-down of experiment: NA
Stowing experiment for return: NA
Loading/unloading samples on LRV: NA
Loading of exp't/samples into the LM: NA
Stowing of package once in the LM: NA
Sampling operations - soil, rocks: NA
Navigating/recognizing landmarks: NA
Were there any hazards in the experiment?
i.e. hazardous materials (explosive, radioactive, toxic), sharp
objects, high voltages, massive, bulky, tripping hazards, temperatures?
The dust covers were removed by ground command using a redundant squib
system. These were adequately interlocked against misfiring. High voltages
were used in the instrument, but were not commanded on while the crew was
nearby.
Was lighting a problem? No.
Were the results visible to the crew?
Only alignment and level.
Would you recommend any design changes?
The thermal control provisions for the unit did not maintain the operating
temperature below the qualification test maximum level during the lunar
day because the thermal conditions at the A-17 site were different than
those of the design site (level plain at the equator). However, the unit
operated during 100 % of each lunar night and 30 % of each lunar day.
Were any special tools required? UHT for deployment
Was the orientation of the experiment (i.e. horizontal/vertical)
important? Difficult?
Orientation was important so that the radian, or source direction,
of the impacting particle could be determined. This allowed differentiation
between interstellar grains and other types of cosmic dust. A bubble level
and the shadow of a gnomon on a compass rose were used.
Was the experiment successful?
Yes, but unusual data events followed by laboratory investigations
with the spare LEAM unit indicated that the instrument was responding to
the transport of lunar surface fines.
Were there related experiments on other flights?
Pioneer 8 and 9, which measured cosmic dust and micrometeorites in
Earth orbit, were forerunners of the LEAM experiment. The dust particle
flux striking the LEAM experiment increased dramatically some tens of hours
before sunrise. It was argued that this was due to electrostatically transported
dust. See also M 515: Lunar Dust Detector.
Where was it stored during flight? As part of the ALSEP.
Were there any problems photographing the experiment? No
What pre-launch and cruise req'ts were there?
power, thermal, late access, early recovery?
What was different between training and actual EVA? No comments by crew.
What problems were due to the suit rather than the experiment? No comments by crew.
Any experiences inside the LM of interest from the experiment/operations viewpoint? No comments by crew.
References:
A-17 Preliminary Science Report
A-17 Mission Report
Apollo 17 Final Lunar Surface Procedures, Vol. 1: Nominal Plans, MSC, 11/6/72
Apollo Lunar Surface Experiments Package - Apollo 17 ALSEP (Array E) Familiarization Course - Handout for class of 1 September 1972, in JSC History Office
Apollo Scientific Experiments Data Handbook, JSC-09166, NASA TM X-58131, August, 1974, In JSC History Office.
Berg, O. E., H. Wolf, and J. Rhee, Lunar soil movement registered by the Apollo 17 cosmic dust experiment, in: Interplanetary Dust and Zodiacal Light, H. Elsasser and H. Fechtig, eds., Springer-Verlag, New Youk, 233-237, 1976.
Berg, O. E., F. F. Richardson, J. W. Rhee, and S. Auer, Preliminary results of a cosmic dust experiment on the Moon, Geophy. Res. Lett. 1, 289-290, 1974.
Apollo Program Summary Report, section 3.2.25 Lunar Ejecta and Meteorites Experiment, JCS-09423, April, 1975.
ALSEP Termination Report, NASA Reference Publication 1036, April, 1979.