Experiment Operations During Apollo EVAs

Experiment: Solar Wind Composition

Acronym: SWC


The SWC foil deployed on Apollo 11. Notice the identification of which side should be in the shade at the bottom of the foil (AS-11-40-5873).

The SWC foil on Apollo 16 had some sections of platinum, which allowed for easier cleaning operations on Earth. Note the identity of the sun side near the bottom (AS-16-117-18849).

PI/Engineer: J. Geiss, Univ. of Bern
Other Contacts:
P. Signer, F. Buehler, J. Meister, P. Eberhardt

Apollo Flight Nos.: 11, 12, 14, 15, & 16
Apollo Exp't No.: S 080

Discipline: solar wind, solar physics

Weight: Total 430 g (foil 130 g); 450 g on A-16
Dimensions: Foil Sheet: 30 cm x 140 cm (130 cm exposed, 15 microns thick)
Pole: 4 cm diameter 40 cm long, stowed (1.5 m long, deployed)

Manufacturer: University of Bern, Swiss Nat'l Science Foundation

Description/Purpose:
The SWC experiment consisted of an aluminum metal foil which was deployed to trap the solar wind so as to measure the ion types and energies of the solar wind on the lunar surface. The area of the foil was 4000 cm2. It was deployed on a five-section telescopic pole and unrolled. The reel of foil was stored inside the collapsed pole. Purity of the foil was critical to avoid contamination of the lunar samples and background contamination of the experiment itself. The A-16 experiment was composed of both aluminum and platinum foils. The platinum foil allowed for treatment with dilute hydrofluoric acid before sample analysis on Earth to remove dust contamination and the resulting uncertainties.

Unloading from the LM: No comments by crew.

Transporting by foot or MET: Hand carried.

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

Site selection: Near the LM, in the sun.

Deploying experiment:
The telescopic pole was extended and the five sections locked automatically. The reel was then pulled out, and the foil was unrolled and fastened to a hook near the lower end of the pole. The pole was pressed upright into the ground, but it did not necessarily have to be perfectly vertical. Pictures from A-12 clearly show it leaning ~10 degrees, perhaps to provide more area perpendicular to the sun. Pictures from A-14, 15, and 16 show it to be within a few degrees of vertical. On A-11, it was possible to penetrate the lunar surface only ~4 or 5 inches with the pole. One side of the foil was marked with the word SUN, which was pointed at the sun. A typical timeline from A-15 shows ~7 minutes for deploying the experiment.

Check-out of experiment: None required.

Operation of experiment:
Exposed for 77 minutes on A-11, 18 h, 42 minutes on A-12, 21 hours on A-14, 41 hours , 8 minutes on A-15, and 45 h, 5 minutes on A-16.

Repairs to experiment: See recovery/take down.

Recovery/take-down of experiment:
The reel was spring-loaded to facilitate rewinding of the foil. It was detached from the telescopic pole, placed in a teflon bag, and placed in a sample return container. The pole was not returned. A typical timeline from A-15 shows ~4 minutes for retrieving the foil and placing it in the bag.

On A-12, the foil rolled up the first ~1.5 ft. After that, it would crinkle rather than roll. Using great care, they tried to roll up the foil, but on the 5th attempt a crack appeared in the crinkle area. They finally used their hands to roll it, and as a result the foil was soiled by the dirt adhering to their gloves. After it was rolled, they discovered that it was too big to fit into the container that was to be used to return it, and had to crush it with their hands. Upon inspection during the EVA 2 they decided that the foil tended to "set" and that it would not roll up because the set was stronger than the tension of the roller.

On A-14, about half the foil rolled up automatically, the rest was done manually. On A-15, the foil was rolled manually when it failed to roll mechanically. There was no reported difficulty recovering the A-16 foil.

Stowing experiment for return:
Placed in a Teflon bag, then into the sample return container. On A-15, it was transferred to the LM via the equipment transfer bag (still in its Telfon bag) and may have been kept separate from other samples to minimize dust contamination.

Loading/unloading samples on LRV: NA

Loading of exp't/samples into the LM: With the sample return container.

Stowing of package once in the LM: With the sample return container.

Sampling operations - soil, rocks:
The foil had to be ultrasonically cleaned before analysis on Earth. Part of the sheet was then melted in an ultra-high vacuum system and the gasses released were analyzed with a mass spectrometer. The platinum portions of the A-16 foil were cleaned with aqueous HF before analysis.

Trenching: NA

Raking: NA

Drilling:
Emplacing the shaft into the ground by hammering was difficult due to the compacted nature of the subsurface.

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.

Were the results visible to the crew?: No.

Would you recommend any design changes?:
No comments by crew. The foil was changed for A-16 to include a platinum section to determine whether HF acid could be used to remove any dust from the surface before analysis.

Were any special tools required?:
A hammer was sometimes required to drive the shaft into the ground.

Was the orientation of the experiment (i.e. horizontal/vertical) important? Difficult?
The metal foil needed to be oriented perpendicular to the sun so as to capture the solar wind most efficiently. On A-14, 15, and 16 the reel handle was color coded to give the exact angular position during exposure of the reel and the portion of the foil rolled around it to yield the angular distribution of the arriving solar wind.

Was the experiment successful?: Yes.

Were there related experiments on other flights?:
Yes. Some satellite measurements of solar wind and plasma and magnetic field strengths are relevant, i.e. Explorer 35, Vela 3A and 3B See also S 035 - Solar Wind Spectrometer. On A-17, there was a greatly scaled down version of the Al and Pt foils included as part of the Lunar Surface Cosmic Ray Experiment (LSCRE). Also, the lunar regolith itself has trapped the solar wind over the eons, but is an uncertain "instrument." Still, analysis of volatiles released upon heating of the regolith is used to provide insight into the solar wind.

Where was it stored during flight?: LM MESA (Modularized Equipment Stowage Assembly) in Quad IV.

Were there any problems photographing the experiment?: No.

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

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:

Preliminary Science Reports for A-11, 12, 14, 15, & 16

Mission Reports for A-11, 12, 14, 15, 16

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

Final Apollo 11 Lunar Surface Operations Plan, JSC, June 27, 1969

Apollo Program Summary Report, section 3.2.22 Solar Wind Composition Experiment, JCS-09423, April, 1975.

Apollo Program Summary Report, section 3.2.29 Particle Implantation Studies, JCS-09423, April, 1975.