Flying Lab to Study Early Universe
While many Boeing 747s are slowly being retired, the version that sits in a hangar about 100 miles south of Dallas is getting a face lift of astronomical proportions.
The former passenger jet, which first flew in 1977, has been set aside for a stratospheric mission: to look at the universe.
After engineers cut a hole in the side of the aircraft, it will house the largest airborne telescope ever built--more powerful than many ground-based telescopes and larger than the Hubble Space Telescope.
The Stratospheric Observatory for Infrared Astronomy, or SOFIA, will allow astronomers to peer deep into vast dust clouds to witness the birth of stars, observe galaxies and quasars billions of light-years away and study the very early universe.
Infrared is an invisible part of the electromagnetic spectrum that is sensed by humans as heat. Clouds of gases and dust, where new stars are born, are often difficult--if not impossible--to see in visible light.
Among other missions, scientists plan to fly the revamped jet to the Southern Hemisphere to observe the center of the Milky Way, satellite galaxies of the Milky Way or phenomena that require urgent investigation in the infrared spectrum, such as supernovas.
The National Aeronautics and Space Administration and the German Aerospace Center expect to spend about $375 million developing SOFIA. Slightly more than 100 missions a year are planned over 20 years. The plane is being modified at a Raytheon Air Integration Systems Inc. hangar in Waco.
The plane will rise above 99% of the atmosphere. Cruising at 41,000 to 45,000 feet at night, astronomers will open a huge portal behind the aircraft’s left wing to expose the telescope’s mirror and mounting.
SOFIA will cruise at 550 mph with the door open, and the minus-40 degrees of the atmosphere should match that of the unpressurized telescope compartment, which is refrigerated before takeoff to prevent condensation from forming on the optics. A 30-inch-thick pressure bulkhead will protect scientists from the near vacuum and fatal cold of the stratosphere.
Once operational at the end of 2002 or early 2003, SOFIA will be the largest airborne observatory, replacing the Kuiper Airborne Observatory, which flew aboard a Lockheed C-141 from 1974 to 1995.
At 8.25 feet in diameter, the mirror of the SOFIA telescope is slightly larger than Hubble, almost the same size as the Hooker telescope at Mt. Wilson, Calif., and about eight times larger in surface area than Kuiper.
The largest optical telescope, the Keck at Mauna Kea, Hawaii, is 33 feet in diameter and four times that of SOFIA, but moisture in the atmosphere severely limits Keck’s ability to study infrared targets, a problem for all ground telescopes.
“Water just loves to absorb infrared radiation,” said Eric Becklin, an astronomy professor at UCLA and SOFIA’s lead scientist. “SOFIA flies above most of the absorbing water and catches the photons before they get absorbed.”
The plane’s primary base will be NASA’s Ames Research Center at Moffett Field, about 40 miles south of San Francisco.
Because SOFIA is airborne, maintaining or altering a mission can be done quickly and inexpensively, as opposed to launching a shuttle to service it, said professor John Lacy, who specializes in infrared astronomy and spectroscopy at the University of Texas at Austin.
