Lunar-Based vs. Lunar-Orbit Telescopes Discussed at Astrophysics Meeting

BALTIMORE — Now that NASA has developed a blueprint for whisking the next generation of astronauts back to the Moon, it’s time to figure out what to do when they get there and why .

At a workshop titled “Astrophysics Enabled by the Return to the Moon” held Nov. 28-30 at the Space Telescope Science Institute here on the campus of the Johns Hopkins University, astrophysicists discussed such ideas as setting up telescopes on the lunar surface — or possibly in lunar orbit.

“The main purpose is to really for the first time in many years have a very diverse group of astrophysicists come together and talk about whether it makes sense to do astrophysics from the Moon now that we’ve got NASA committed to sending people there and putting up infrastructure there,” said Laurie Leshin, director of sciences and exploration at the Goddard Space Flight Center in Greenbelt, Md.

“It’s a great time to have that conversation so it’s sort of the first conversation, not the last conversation about this,” Leshin said.

Presentations highlighted both the assets and liabilities of lunar-based science. Whereas Earth-based telescopes are subject to atmospheric distortion, the Moon’s lack of atmosphere would provide better range and sensitivity for skywatching.

One idea is to set up a liquid-mirror telescope on the Moon. Such telescopes spin to create a parabola at the telescope’s surface. The handful of these telescopes on Earth are limited in size because the spinning creates wind that disrupts the mirror-like surface.

By placing infrastructure on the Moon, future missions could rely on the already established equipment, meaning less payloa d to lug there. Setting up camp on the Moon would require oxygen and water. Lunar water has not yet been found, but is believed possibly to be present in the form of water ice at the lunar poles in craters where the sun never shines. In areas such as hilltops where there is plenty of sunshine, scientists said the constant sunlight could be used to produce electricity with solar voltaic cells.

Scientists are also in the process of designing spacesuits with the flexibility needed for extended wear on longer lunar missions.

There are plenty of hurdles to ponder, scientists said. The Moon is covered with a layer of fine particles with the consistency of talcum powder that is several feet thick. That material can generate dense dust clouds. Unlike the household variety, lunar dust is glass-like with a core of iron, giving it magnetic properties. Figuring out ways to ensure dust-free instruments would be a major priority for astronomers.

Another issue is levitated dust, which occurs when the sun’s energy causes dust grains to become electrically charged.

“I think we need to continue to evaluate whether the Moon is usable for astronomy or not,” said Paul Spudis of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. “And finally we need to fill in the missing pieces of knowledge and specifically we need to characterize this dust levitation and find out — does this occur and what the real magnitude of the effect is.”

Scientists also are considering whether lunar-based astrophysics is better than orbiting instruments, said Harley Thronson, a chief scientist for exploration at NASA’s Goddard Space Flight Center.

“Free space might be more suitable for some types of astronomy, and the surface of the Moon may be more suitable for others,” Thronson said.

Scott Horowitz, NASA associate administrator for the Exploration Systems Mission Directorate, told the group the space agency is still early in the design stage for the next Moon rockets and vehicles but wants significant capability to transport scientific instruments, living quarters and other cargo to the Moon. “We’re building a pickup truck and we’re going to fill the bed with whatever we can,” he said, noting that about one quarter of the mass of the estimated 125 metric-ton launch vehicle NASA is planning for lunar missions will be available for payload.

“We’re still trading off how much is available on the exploration lander for scientific payload, we still don’t know the exact number,” Horowitz said.

The Associated Press contributed to this article.