Experiment Operations During Apollo EVAs

Experiment: Dust, Thermal, & Radiation Engineering Measurements Package

a.k.a. Lunar Dust Detector
Acronym: DTREM (LDD)


The DTREM Schematic.

PI/Engineer: James R. Bates/JSC
Other Contacts: S. C. Freden, B. J. O'Brien

Apollo Flight Nos.: (11), 12, 14, 15
Apollo Exp't No. M 515

Discipline: lunar dust

Weight: 0.27 kg
Dimensions:

Manufacturer: MSC (JSC)

Description/Purpose:
This engineering measurement was included on the central station of the ALSEPs to record the then-anticipated heavy dust accumulation from LM ascent or from any long-term cause. Subsequent findings showed the dust layer and resultant blowing of the dust to be less than expected, so the original configuration was expanded to include the effect of radiation degradation of the solar cells and their resultant drop in voltage output. It merely measured the power generation from solar cells as their illumination varied through the day/light cycle and due to dust coverage. It consisted of 3 different solar cells attached atop the structure and 3 temperature sensors (internal, cell, and external infrared temperatures). Three different types of solar cells were used: a bare cell without cover glass; a cell with 0.15 mm cover glass, and a cell with a cover glass which was also pre-irradiated with 1x10^15 electrons of 1 MeV energy. The short circuit current was measured due to its direct dependence on illumination. This was considered an engineering experiment rather than a science experiment, hence the M designation rather than S.

Unloading from the LM: Part of the ALSEP central stations

Transporting by foot or MET: See ALSEP - general

Loading/unloading tools/exp'ts on LRV: NA

Site selection: As part of the central station of the ALSEP.

Deploying experiment:
No action required separate from deploying the central station.

Check-out of experiment:
The data was received on Earth to verify operation.

Operation of experiment:
There was no real operation of the experiment, since it was passive, but data was collected by telemetry at the JSC. The A-14 instrument yielded data from 2/71 - 2/76. The A-15 instrument yielded data from 7/71 to 2/76. Although the data continued to be received for an additional 19 months, it was not processed due to budget cutbacks and these data are not retrievable.

Repairs to experiment: NA

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

Trenching: NA

Raking: NA

Drilling: NA

Coring: 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? No.

Was lighting a problem?
No. But, as described below, on-orbit observations of A-17 used the moon to occult the sun and provide the necessary lighting conditions to view the corona, zodiacal light, and possible lunar dust at high altitude.

Were the results visible to the crew? No.

Would you recommend any design changes? None made by crew.

Were any special tools required? No.

Was the orientation of the experiment (i.e. horizontal/vertical) important? Difficult? No.

Was the experiment successful? Yes.

Were there related experiments on other flights?
The power generated by the A-11 PSEP solar panels may have provided similar information, but the lifetime of the experiment was limited and the power output curves are not retrievable. On-orbit sketches from the A-17 crew (and others) were made of the lunar horizon before orbital sunrise. This was intended to look at the solar corona and zodiacal light. A glow along the horizon has been interpreted as evidence of lunar dust at high altitude (~10 km) that was caused by expulsion from the surface by photoelectric charging of the soil near the terminator. Also, one of the Lunakhod rovers had a UV/visible photometer which looked vertically and registered a glow for at least 2 hours after local sunset. This was interpreted as a dust cloud at least 200 m above the surface. Finally, Surveyor cameras registered a "horizon glow" after sunset that was deduced to be only several tens of centimeters above the surface. The LEAM provided data consistent with the detection of the transport of lunar surface fines.

Where was it stored during flight? with the ALSEP.

Were there any problems photographing the experiment?
No, but the high altitude dust described from orbit on A-17 did not register on film.

What pre-launch and cruise req'ts were there?
power, thermal, late access, early recovery? None.

What was different between training and actual EVA? See ALSEP, general.

What problems were due to the suit rather than the experiment? None.

Any experiences inside the LM of interest from the experiment/operations viewpoint? No.

References:

Preliminary Science Report for A-11, 14, 15.

Apollo Scientific Experiments Data Handbook, JSC-09166, NASA TM X-58131, August, 1974, In JSC History Office.

Personal communication, J. R. Bates/JSC

H. A. Zook and J. E. McCoy, Large Scale Lunar Horizon Glow and a High Altitude Lunar Dust Exosphere, Geophys. Res. Let., Vol. 18, No. 1, 2117-2120, 1991.

Criswell, D. R., Lunar dust motion, in; Proc. 3rd Lunar Sci. Conf., The MIT Press, Cambridge, MA, 2671-2680, 1972.

Rennilson, J. J. and D. R. Criswell, Surveyor observations of lunar horizon glow, The Moon 10, 121-142, 1974.

Apollo Program Summary Report, section 3.2.27 Lunar Dust Detector Experiment, JCS-09423, April, 1975.

ALSEP Termination Report, NASA Reference Publication 1036, April, 1979.