Fesen proposes use of high-altitude airships for astronomy
Dartmouth astronomy professor Robert Fesen
appreciates NASA's Hubble
Telescope, which he says has proven to be a terrific astronomical
observatory since it was launched in 1990. But, he says, there may be a vastly
cheaper way to obtain nearly as sharp images of stars and galaxies that doesn't
require space shuttle flights or teams of astronauts to launch or repair
it.
Robert Fesen
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Fesen has written a new report advocating the use of newly developed
military and telecommunications high-altitude, station-keeping vehicles. He
suggests that the time has come to develop and launch what he calls a
"Hubble Junior" by placing a relatively modest-size telescope on one
of these stratospheric platforms to conduct astronomical observations.
"A lot of the basic technology exists to make this happen," he
says. "High-altitude airships are currently being developed for
telecommunications and for the military. I want people to begin thinking about
the possibility of doing first-rate optical science like that done from Hubble
but at stratospheric altitudes like that flown by the U2 airplane and at a cost
of a few million dollars rather than a few billion."
Six years ago, he and colleagues from NASA, Johns Hopkins University, and
the Southwest Research Institute, did a feasibility study on this very topic.
They determined that it was indeed possible, as long as the payload (the
electronics, the mirror for the telescope, and the pointing system) wasn't too
heavy. Since then, the technology has greatly advanced, making the notion of
using a high-altitude airship for a stratospheric astronomical observatory a
real possibility.
An airship, says Fesen, is a propeller-driven balloon. Two blimp-shaped
balloons strapped together in catamaran fashion and solar powered could fly at
altitudes of 75,000 to 85,000 feet, or about twice that of commercial
airplanes. A one-half to one-meter size telescope mirror (about 20 to 40
inches) lofted to these altitudes would place it above more than 95 percent of
the Earth's atmosphere, thereby affording nearly razor sharp images of planets,
stars, and galaxies.
An illustration of a SwRI catamaran airship, a type of high-altitude catamaran
that could carry an astronomical telescope. (Image courtesy of Southwest
Research Institute.)
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Fesen is a big fan and a user of the Hubble Telescope. Its 2.4-meter mirror
captures beautifully sharp images from its 300-mile-from-Earth orbit. But, he
says that a Hubble Junior, at an altitude of just 85,000 feet (16 miles), which
would place it above the clouds and weather that plague earthbound telescopes,
could also acquire nearly as crisp and clear images as Hubble does.
"A 1-meter mirror telescope Hubble Junior, although not as powerful as
the real Hubble, could complement Hubble's contributions to our understanding
of the heavens. And since it would be more nimble because it's closer to home
and simpler to operate, a Hubble Junior could react faster to and follow
unexpected supernova explosions, close flybys of asteroids, and other transient
astronomical events," he says.
Fesen presented his paper, a road map of where the science is and what the
possibilities are, at a conference sponsored by SPIE, the International Society for Optical
Engineering, in late May. He has since posted his paper online.
"What I did was just outline the recipe," he says. "It's now
time to start cooking."
By SUSAN KNAPP
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