EYE IN THE SKY A Lowell Observatory scientist is contributing a key instrument to an airborne telescope that will place astronomers high above Earth's distorting atmosphere. By GARY GHIOTO Sun Staff Reporter The spiral staircase is still there, but the piano bar is missing in a Boeing 747 being fitted to house the largest airborne telescope ever built--more powerful than many ground-based telescopes and larger than the Hubble Space Telescope. If all goes according to plan, the plane will fly to Germany this fall to be fitted with a high-precision mirror that will make the Stratospheric Observatory for Infrared Astronomy, or SOFIA, the largest telescope ever to leave the ground. And a vital component of SOFIA is a 600-pound camera being built by Ted Dunham, an instrument scientist at Flagstaff's Lowell Observatory, who will fly aboard the flying observatory on which NASA and its German counterpart expect to spend about $375 million. "I've always liked airplanes and astronomy," said Dunham chuckling, "And as my wife's grandfather used to say, 'What could be more better?'" Dunham, who came to Lowell Observatory four years ago from NASA, began his astronomical career as a graduate student flying aboard the Kuiper Airborne Observatory, a Lockheed C-141 that operated from 1974 to 1995. On one flight out of Perth, Australia, in 1977, Dunham's crew played a key role in an historic discovery that also included Robert Millis, director of Lowell Observatory. "On that flight we happened to stumble on the rings of Uranus. Bob Millis was observing with a telescope in Perth at that time. That was really cool. That's probably the reason I stuck with airborne astronomy because it's so much fun." After graduate school, Dunham became a project scientist for NASA assigned to the Kuiper Airborne Observatory that was grounded five years ago to be replaced by SOFIA. Once operational at the end of 2002 or early 2003, SOFIA will be the largest airborne observatory ever. At more than 8 feet in diameter, the mirror of the SOFIA telescope is slightly larger than Hubble and almost the same size as the famous Hooker telescope at Mount Wilson, Calif.. Dunham made this comparison between the optical system aboard the Kuiper flying telescope and SOFIA: "This one is about three times as big in diameter and pretty much 10 times the collecting area. It's a big step up, a huge step up." The largest optical telescope, the Keck telescope 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 earth-bound telescopes. Flying at 550 mph with the door open, the 40-below-zero temperature of the stratosphere matches that of the unpressurized telescope compartment, which is refrigerated before takeoff to prevent condensation from forming on the optics. Scientists sit next to the telescope on the other side of a 30-inch thick pressure bulkhead that protects them from the near vacuum and fatal cold of the stratosphere. Cruising between 41,000 and 45,000 feet, SOFIA will rise above 99 percent of the atmosphere. Astronomers will open a huge portal cut behind the aircraft's left wing to expose the telescope's mirror and mounting. At that altitude, clouds or pesky water vapor aren't around to hamper or ruin delicate observations, said Dunham. SOFIA should allow astronomers to peer deep into vast dust clouds to witness the birth of stars in the far reaches of the heavens. Scientists will be able to observe galaxies and quasars billions of light-years away and study the very early universe, as well as the local neighborhood of planets, moons and asteroids. Lowell Observatory's contribution to the instrument systems aboard the 747 is HIPO, short for High Speed Imaging Photometer for Occultations. HIPO is a camera with two independent optical systems bolstered by charged coupled devices, integrated circuits that act as film. The CCDs, similar to those found in home video cameras, will be cooled to minus-120 degrees centigrade, which greatly enhances the camera's ability to record faint celestial objects. Lowell astronomers and others will use HIPO to observe occultations. Occultations occur when a planet moves across a star, effectively eclipsing the distant point of light. If the planet has an atmosphere, the light of the star being eclipsed fades and shimmers as it is refracted by atmospheric gases. The same thing happens here on Earth when the Sun seems to flatten against the western horizon at sunset. Astronomers measure the light curve from the distant star to calculate a temperature profile in the planet's atmosphere, explained Dunham. "So without actually going there, you can measure the temperature of the atmosphere of an outer planet, for example, at a number of different altitudes," he said. "We look at this as kind of a poor man's space probe," added Dunham. Besides giving Lowell astronomers data about planetary atmospheres, occultations also provide an incredibly accurate measuring tool. For example, when a star is eclipsed by the rings of Saturn, astronomers can calculate their position in the heavens by a few tens of meters, Dunham said. Aboard SOFIA, the Lowell imaging system will be able to fly almost anywhere to observe occultations as they occur. Ground-based telescopes need to be in the right place at the right time to observe occultations. "The key ingredient with SOFIA is that you can locate yourself anywhere on the Earth. It doesn't matter where the occultation chooses to happen. Usually you are stuck being wherever you happen to have an observatory. But SOFIA gives us a 2 1/2-meter telescope we can put anywhere, within the limits of political reality. We won't be flying over Iraq," he said. SOFIA will fly high above commercial air routes, across empty oceans and desolate regions of the Earth in search of occultations and many other types of celestial phenomenon. "The oceans are not a problem. It's a killer when you have a beautiful event over the ocean and you don't have an airplane...so the mobility is really probably the most important thing. But equally important is the fact that it's never cloudy. And occultations only happen once, so if you miss it, that's tough luck," Dunham added. An anticipated $35 million per year will be needed to operate the observatory. Dunham expects to fly aboard SOFIA several times a year. The HIPO camera will be offered to other scientists and can be used on ground-based telescopes, too. One component of SOFIA that excites astronomers like Dunham is the education and public outreach program. "Among other things, the plan is to fly teachers on a lot of flights. There is seating up in the first-class section across from some equipment racks," he said. As a joint project between NASA and the German Aerospace Center, scientists and engineers are modifying the airplane at a Raytheon Air Integration Systems Inc. hangar in Waco, Texas. Its primary base will be NASA's Ames Research Center at Moffett Field, Calif., about 40 miles south of San Francisco. It will be flown and maintained by United Airlines under operational control of the Universities Space Research Association, under contract by NASA. Scientists occasionally will fly to the Southern Hemisphere to observe the center of the Milky Way, satellite galaxies of the Milky Way, or discoveries that require urgent investigation in the infrared spectrum, such as a supernova.