NASA's SOFIA: The Airborne Telescope Prepares to Take Flight

By Edna DeVore
Director of Education and Public Outreach
posted: 07:00 am ET
09 May 2002



NASA'S SOFIA, the Stratospheric Observatory for Infrared Astronomy, is the world's largest portable telescope specializing in infrared astronomy (IR). IR can be thought of as the "light" emitted by objects not hot enough to shine in visible light. We humans emit IR - it is the heat from our bodies. Astronomically speaking, IR observing allows scientists to study the dust between stars, the formation of stars and new solar systems, the chemistry of the universe, and the deep universe where the most distant galaxies are seen in infrared light. When research missions begin, SOFIA, a modified Boeing 747SP will carry a 2.5-meter telescope up to the stratosphere to observe a universe invisible from ground-based telescopes.

SOFIA will host a complement of scientists, computer engineers, graduate students, and educators on nightlong research missions. When the observatory lands at NASA Ames Research Center's Moffett Federal Airfield, this tired group will exit the aircraft with new data and images of the infrared universe. Research missions begin in late 2004.

Often, I present talks and workshops on infrared astronomy and SOFIA for educators and the public, and I frequently hear the same, amazed questions from the audience.

Why put a telescope in an airplane? Why are we mounting a telescope in an airplane--a moving platform--instead of mounting it securely to the ground atop some remote, dark mountain, or sending it to space? The reasons are straightforward: the water in Earth's atmosphere absorbs almost all of the infrared energy from objects in the universe. All that IR energy can travel millions of light years through space to be stopped by the last 5 miles of Earth's atmosphere. A few infrared windows--parts of the electromagnetic spectrum--are available to the ground, and are well observed by projects like 2 MASS, the 2 Micron All Sky Survey. The fact that 99% of the water is concentrated in the lower atmosphere, up to about 40,000 feet elevation makes it possible to create an airborne observatory for IR astronomy. By flying above the water in the stratosphere (humidity less than 1%), a whole new infrared universe opens up to view.

Why not just put the telescope in space? Scientifically, SOFIA can do much of the IR astronomy that is also accessible from space, but with the advantage of being a ground-based observatory. SOFIA is akin to a space mission that lands every morning. Science instruments (cameras, spectrometers, photometers, etc.) can be mounted to the telescope while the aircraft is in the hangar and can be changed out, repaired, or replaced with newer technology on the ground. Because of this flexibility, the observatory life span is projected at 20 years. Cryogenics can be replenished for each flight. SOFIA's sister mission, SIRTF (Space Infrared Telescope Facility) will be a space-based infrared telescope and scientists anticipate that SIRTF will work for up to 5 years before its cooling system runs out of helium and the telescope warms up. These two NASA missions are truly complementary.

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