Space scientists are evaluating use of Moon-based instruments to study the Earth. Lunar situated sensors at an Earth observatory could yield distinctive observations of our home world, its vegetation, polar caps, as well as monitor Sun/Earth interactions.
One early prospect is to inspect the Earth from the Moon to appraise sensitive gear and procedures helpful in spotting Earth-like planets circling other stars.
Planting Earth-looking science instruments on the Moon is not a new idea.
Back in 1972, Apollo 16 was the fifth mission to land men on the Moon and return them back here to terra firma.
While bounding about the lunar landscape, astronauts snagged rock and soil samples, took pictures and performed research tasks that included use of an ultraviolet camera/spectrograph — the first astronomical and Earth observations taken from the Moon's surface.
But more recently, a NASA Advisory Council subcommittee has taken on the task to consider the merit of gazing at the Earth from the Moon. That review has been spurred by the space agency's big picture plan for returning humans to the Moon by 2020 — one element of the Vision for Space Exploration set in motion by U.S. President George W. Bush in early 2004.
Whole Earth cataloging
Late last year, a sub-panel group of the NASA Advisory Council (NAC) reviewed and consolidated a list of Earth Science objectives that could be carried out from the Moon's surface. In their down-to-earth view, Moon-based spectrometers of varying resolution operating over a wide range of wavelengths could perform valuable work.
"A general Earth Observatory on the Moon would be of considerable value. This Earth Observatory would have specific technological and energy requirements, and require significant investments in new technology, which NASA would need to determine in consultation with the Earth Science community," the NAC study group reported.
NAC members are also discussing a Moon-based Earth Observatory that is Internet accessible to the scientific community as well as the public.
That Internet link would offer a continuously monitored, hyper-spectral, single frame sight of the whole Earth.
Furthermore, by making use of data fusion technology, Earth imagery from Moon could be instantly integrated with real-time heliophysics and aeronomical data. Potentially, this mixing of information sets could lend a hand in deciphering the complex interactions of space phenomena with Earth weather processes.
There's also NAC member opinion about inspecting Earth's photometric signature of plant life from the Moon. By studying the biologically altered reflected light from the Earth, such looks may be helpful in fine-tuning skills in the search for Earth-like, extrasolar planets.
Durability of equipment
The Moon presents a useful and stable platform for obtaining unique, simultaneous views of the Earth and Sun explained Jay Herman, a project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md.
Still, setting up science gear on the lunar surface, powering them, and protecting hardware from the Moon's vicious day/night temperature swings is no piece of cake, he told SPACE.com.
Herman said that lunar dust is also a troublesome issue.
"It's quite abrasive. So keeping it out of movable joints ... it'll damage equipment very quickly. That's a major problem," he advised.
The real question in placing precision optical paraphernalia on the Moon is the durability of that equipment, Herman suggested.
Also, just how much attention such gear would need from space suited moonwalkers needs to be addressed, be it for initial deployment and setup to instrument pointing and final checkout.
Engineering around such problems would seem doable, Herman said.
Equipment on the Moon could address the relationship between solar activity and the structure and dynamics of Earth's atmosphere from the surface to the thermosphere-ionosphere, for a range of seasons, solar radiation and energetic particle inputs, Herman explained.
At the same time, Sun-scanning instruments could independently provide new information on the processes governing solar activity using wavelengths from the visible to soft x-rays.
Indeed, the output from such science observations from the Moon, Herman added, could help piece together the saga behind Sun-Earth weather relationships and long-term climate factors.
But to get a better handle on the types of science equipment that might be stationed on the Moon, Herman suggested first installing relatively inexpensive suitcase-sized instruments on the lunar surface.
"That would be sort of the first step toward seeing whether the Moon is actually a suitable place for instrumentation ... say for larger telescopes," Herman said. "These would be small, economical instruments to observe the Earth or the Sun, or both."
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