Experiment Operations During Apollo EVAs

Experiment: Solar Wind Spectrometer

(a.k.a. Medium Energy Solar Wind Experiment)
Acronym: SWS (SWE)


The SWS as deployed on Apollo 15. The dust covers are still in place, to be removed after LM ascent by command from Earth. The louvered side was oriented north (on the side not visible in this view) for thermal control (AS-15-86-11593).

PI/Engineer: Conway W. Snyder, Jet Propulsion Lab
Other Contacts:
Douglas R. Clay & Marcia Neugebauer, JPL

Apollo Flight Nos.: 12, 15
Apollo Exp't No.: S 035

Discipline: Solar wind, Solar physics, Earth Sciences-magnetosphere

Weight: 5.3 kg
Dimensions: 27.9 x 22.9 x 10.2 cm, stowed (35.6 x 22.9 x 43.2 cm, deployed)

Manufacturer: JPL/Electro-Optical Systems Pasadena, CA (Bendix - Integration into ALSEP)

Description/Purpose:
The sensor in the SWS is a Faraday cup that measures the charged-particle flux entering the cup. An array of 7 cups was used to be sensitive in any direction and to ascertain the angular distribution - one pointed vertically and the others arrayed around it at 60 degrees off-vertical and to each other.

The purpose was (1) to compare the solar wind properties at the lunar surface with those measured in space near the moon, (2) To determine whether there were any subtle effects of the Moon on the solar wind properties, and to relate these to properties of the Moon, (3) to study the motion of waves or discontinuities in the solar wind by measuring the time intervals between the observation of changes in plasma properties at the Moon and at the Earth, (4) to make inferences as to the length, breadth, and structure of the magnetospheric tail of the Earth from continuous measurements made for 4 or 5 days around the time of full Moon.

Unloading from the LM: As part of ALSEP.

Transporting by foot or MET: As part of ALSEP.

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

Site selection: As part of ALSEP, 12 to 15 feet N of the central station.

Deploying experiment:
Four Boyd bolts were turned with the UHT to release it from the ALSEP subpallet. It was then carried with the UHT 4 m to the north. Four legs were then extended and locked, then the unit was placed on the surface and aligned using the shadow cast on the sensor head. The crewman checked that the thermal door was open and facing away from the central station. It was deployed without difficulty on A-12 and 15, although the Boyd bolt fasteners that held it to the subpallet were hard to remove on A-15. The covers were left on and were removed after LM ascent on command from Earth. The louvered side was oriented north for thermal control. A typical timeline from A-15 shows ~4 minutes for deploying the experiment.

Check-out of experiment: From Earth.

Operation of experiment: From JSC via the ALSEP command system.

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

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?: None made by crew.

Were any special tools required?: UHT

Was the orientation of the experiment (i.e. horizontal/vertical) important? Difficult?
The astronaut had to level it to within 5 degrees of horizontal about the N-S axis. He also had to align the unit about the vertical axis so that the shadow cast by the N edge of the sensors ran parallel to the edge of the sun shield. Post-flight photos were used to determine that the A-12 orientation was less than 3 degrees off level and off N-S alignment, which was said to be within tolerance. It was self leveling about the E-W axis. By touching the bottom of the unit with the UHT, the astronaut could see that it hung free.

Was the experiment successful?: Yes.

Were there related experiments on other flights?:
The Solar Wind Composition experiment (S 080) was flown on all Apollo landing missions except A-17.

Where was it stored during flight?: With ALSEP subpallets.

Were there any problems photographing the experiment?: No.

What pre-launch and cruise req'ts were there? power, thermal, late access, early recovery?:
No comments by crew.

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-12, 15

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

Final Apollo 12 Lunar Surface Operations Plan, JSC, October 23, 1969

Apollo Program Summary Report, section 3.2.21 Solar Wind Spectrometer Experiment, JCS-09423, April, 1975.