Once again, I wonder: why hasn't there ever been a decent science fiction novel (that I know of) about the far side of the Moon? I mean, there are good astronomical reasons for having a base there, but if orbiting communications satellites stopped working, it would be about the loneliest place in the local corner of the universe. Surely the potential isolation could be a good setting for a story?
Anyhow, that's all by way of preamble to noting that
Science magazine has an article about possible astronomical uses for the far side, from low frequency radio telescopes:
Charting the dark ages' 21-centimeter radiation “is
essential. It has to be done at some point,” says radio astronomer Heino
Falcke of Radboud University in Nijmegen, the Netherlands, who works on
the Low Frequency Array (LOFAR), a vast radio telescope spread across
northern Europe. The problem is that after 13 billion years of cosmic
expansion, photons from the dark ages arrive at Earth stretched to
frequencies below 50 MHz, where they not only have to contend with the
ionosphere, but also with confounding signals from ham radio, aviation,
and long-distance communications. LOFAR, for example, has struggled to
detect the 21-centimeter signal from that epoch (
Science, 7 November 2014, p.
688).
The Hydrogen Epoch of Reionization Array, which Hewitt and others are
building in South Africa, may have a better shot. But Falcke and others
are looking to the Moon.
Burns's 35-year campaign for a
lunar radio telescope won him NASA funding in 2008 to form a team called
LUNAR to work out how to build it. The researchers designed a lunar
telescope array that would include hundreds of simple dipole antennas
laid flat on the ground. They demonstrated how autonomous rovers could
lay out strips of conducting film to act as antennas. In a 2013
experiment, astronauts on the International Space Station remotely
guided a rover that laid out antenna strips on a simulated moonscape at
the NASA Ames Research Center in Mountain View, California, to show how a
future crew onboard NASA's proposed Moon-orbiting Lunar Gateway station
could supervise construction.
to optical:
One solution, proposed by a NASA-funded team last decade,
is to build a liquid mirror. The idea is simple: Construct a large
shallow circular dish, fill it with a liquid, and set it gently
spinning. Centrifugal force will pull the surface into a parabolic
shape. Liquid mirror telescopes on Earth use mercury, which is naturally
reflective. The biggest so far was the 6-meter Large Zenith Telescope
in British Columbia in Canada. That testbed telescope, built in 2003 and
now decommissioned, paved the way for the 4-meter International Liquid
Mirror Telescope, which will take its first view of the sky from the
Devasthal Observatory in India later this year. Although a liquid mirror
is limited to looking straight up, the rotation of Earth—or the
Moon—scans it across the sky.
Mercury won't work on the
Moon—it would evaporate in the lunar vacuum and is too heavy to
transport from Earth. In its place, the NASA team came up with a class
of organic compounds called ionic liquids, essentially molten salts,
that would remain liquid in the frigid lunar night. Ionic liquids are
not reflective, but could be glazed with silver to make an ideal
reflecting surface. Superconducting bearings could levitate the dish and
keep it spinning frictionlessly. “In principle there is no limit on the
size,” says team member Ermanno Borra of Laval University in Quebec
City, Canada. “This would be totally impossible in space, but not that
expensive on the Moon.”
The Canadian Space Agency (CSA)
followed up the NASA study by looking at the practicalities of building
such a scope. “There were no showstoppers and the mechanical tolerances
were more relaxed than for a space telescope,” says Paul Hickson of the
University of British Columbia in Vancouver. A 20-meter telescope, CSA
concluded, would require no more than 3.5 tons of material to be
transported to the surface. An even larger instrument, as big as 100
meters across, “would be in a class of its own,” Hickson says, able to
study the very first stars that formed and coalesced into galaxies at
the end of the dark ages.