Apollo Lunar Surface
Experiment Package (ALSEP)
Surface Electrical Properties
(SEP) Experiment
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Nice photo, the only one I've ever seen of both elements
of the SEP: the rover, with it's receiver mounted on the back, and
the transmitter behind it on the ground (red arrow).
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Close up of the SEP transmitter in deployed configuration
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Above Left - Apollo 17 LMP Jack Schmidt practices
deploying the SEP receiver antenna on LRV mockup
Above Right - SEP transmitter in preflight photo
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Above Left - Diagram of SEP transmitter in deployed
configuration
Above Right - Diagram of the SEP receiver DSEA box.
Failure of the Velcro caused over heating of the unit
Also, you can refer to my Lunar Roving Vehicle
gallery for other pictures of this equipment
Apollo Experiment Number: S 204
Apollo Missions: 17
Wt: 16 kg
Dim:
Transmitter package was ~ knee high after deployment,
had a solar panel which was ~60 X 25 cm, and used 2 sets of dipole antennae
which were 70 m long and were deployed E - W and N - S by the crew
Receiver box (Data Storage Electronics Assembly or DSEA)
on LRV geopallet: 23 cm3
Receiver antenna: ~2.5 meters tall
This interesting experiment used two separate
instruments to transmit and measure radio waves propagating through the
lunar regolith. The purpose was to obtain data to develop a model
of how the lunar surface reflected and absorbed radar waves at the surface
(vs in orbit). These data were to be used to help calibrate data
taken from orbit by the CSM SIM experiments, and to determine the layering
of the surface and look for the possible presence of water.
A transmitter was set up approximately 100 meters
east of the LM. The transmitter used 2 long wire antennae on reels
that were layed out in both the east - west and north - south axis.
To properly align these antennae, the crew used the compass on the LRV,
then drove it across the deployment area in a straight line to mark out
the directions to unreel the wire. A problem quickly ensued when
the solar panel on the transmitter would not open properly. The crew
taped it open. Also, one of the crew dropped the antennae reels onto
the ground and thereby confused which was supposed to be deployed in which
direction.
The receiver and it's electronics package was carried
on the back of the rover, mounted on the geopallet. It consisted
of a square, gold foil covered box and a triangular shaped, 4 element antenna.
Another problem occurred when the electronics package
thermal covering would not stay closed, allowing lunar dust to be kicked
up by the LRV wheels onto it's radiator, which caused the unit to overheat.
Also, one of the crew accidentally left the unit switched on standby.
Consequently, useful data was only obtained from the unit at 2 stops during
the second EVA. Also, the CSM recorded data from the transmitter
during 2 overhead passes, using the Lunar Sounder Experiment equipment
in the SIM bay.
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