Catching Sunbeams at Tranquility Base
Painting Completed December 2013
|The Solar Wind Composition (SWC)
experiment was designed to measure elemental and
isotopic abundances of helium, neon and argon in the
solar wind, and to investigate time variations in the
solar wind composition. Considering that the
collecting device was aluminum foil similar to foil we
use in our kitchens, it was a simple, but very smart
experiment. It was science that was easy for the
public to understand. It was simple to deploy,
retrieve and return to Earth. It demonstrated evidence
of international cooperation as the SWC was proposed,
designed and constructed by a team of Swiss
scientists. This is exactly what NASA needed for the
first ever moonwalk.
The Solar-Wind Collector (SWC) experiment consists of a five-section telescoping pole and an aluminum foil sheet about 12 inches (30cm) wide and about 55 inches (140cm) long, rolled up on a reel. Buzz has just pushed the pole into the lunar soil, attached the reel, unrolled and positioned the foil sheet perpendicular to the sun's rays so helium, neon and argon ions can penetrate the surface of the foil.
Buzz would later say, "I found that the shaft extended and locked into position easily... it went down (in the ground) about 4 or 5 inches. It wasn't quite as stable as I would have liked it to have been, but it was adequate to hold it in a vertical position... the shadow that was cast by the solar wind afforded a good check (when the foil was) perpendicular to the Sun."
About 77 minutes later, Buzz retrieved the SWC. He said, "the reel disengaged from its staff quite easily. When it rolled up, it had a tendency to sneak off to the side and crinkle on the edges... I then remembered they really didn't care about exact neatness, all they wanted was the material back, because they were going to cut it up in little pieces anyway."
Back on Earth the foil was analyzed using an ultra-high vacuum mass spectrometer. The experimental results were published in various scientific journals, PhD theses and NASA science reports. It was found that the lunar environment did not significantly affect the solar wind composition measured at the lunar surface, and the SWC results are representative of the solar wind prevailing in interplanetary space at the time of foil exposure.
After Neil and Buzz returned to Earth, Buzz briefed Pete and Me on the details of the deployment and recovery of the SWC as they knew we would be carrying one on our Apollo 12 mission. In fact, the Solar Wind Composition experiment was successfully flown on the Apollo 14, 15, and 16 missions as well.