Inside Outer Space
Physicist Luke Keller helped design the camera that is probing farther and deeper into our universe.
By Keith Davis
It was just past five o’clock on the morning of May 26 when associate professor of physics Luke Keller watched the chopped-and-channeled Boeing 747 finally touch down at NASA’s Dryden Aircraft Operations Facility in California.
“I was so excited,” Keller says. “I literally had goose bumps.”
Mounted in a nonpressurized compartment in the jumbo jet’s fuselage was a telescope nearly 10 feet in diameter and weighing the equivalent of two school buses. Known as SOFIA (Stratospheric Observatory for Infrared Astronomy), the 17-ton telescope was returning from its first mission, a six-hour flight that, if things went as planned, would bring back galactic images recorded at wavelengths beyond the capabilities of ground-based observatories and satellite-based telescopes.
“When I was starting a post-doc at Cornell in 1999, I joined a team of scientists and engineers in designing FORCAST, the infrared camera system that is now installed on the SOFIA telescope,” Keller says. “We fully expected to use our instrument by 2001. But the logistics and technical details of modifying the aircraft, making sure sensitive instruments work in turbulent flying conditions, reaching consensus with the various collaborating agencies, and bringing the aircraft into compliance with safety regulations have made for a gigantic undertaking. When I saw the plane landing in California last May, those goose bumps were worth waiting for.”
The excitement hardly diminished when Terry Herter, the Cornell University astronomy professor and leader of the FORCAST team, disembarked from the aircraft and handed Keller the thumb drive containing the data from the first flight. A coinvestigator on Herter’s Cornell-based team and the key contributor to designing FORCAST’s optics, Keller joined Herter and his FORCAST colleagues in processing the data and producing its first images. The effort took all of the next day, but Keller and his colleagues were beyond complaining about the extra work.
“After 11 years on the SOFIA project — and I was one of the more recent additions to the FORCAST team — it was truly a thrill to see those first images taking shape on our computers,” Keller says. “The delays have been disappointing, but we’re excited to finally be using SOFIA for astronomy.”
Indeed, successfully recording never-before-seen images of Jupiter and the galaxy M82 (see page 25) prompted NASA’s Astrophysics Division director Jon Morse to say, “With this flight, SOFIA begins a 20-year journey that will enable a wide variety of astronomical science observations not possible from other Earth- and space-borne observations. This first flight is a milestone achievement.”
Because the 747’s payload allows large and heavy instruments on board, SOFIA can capture images that space telescopes cannot. Several things make these images unique.One, FORCAST recorded the images at an altitude high in the Earth’s troposphere, where there was almost no water vapor to distort them. And, the images were taken using the infrared area of the spectrum instead of visible light.
“Infrared images are the only way to remotely look deep into the atmosphere of Jupiter or the very center of the M82 galaxy,” he explains, distinguishing infrared from visible light images that show only the surface details of objects — the “tip of the iceberg,” as he puts it. “Infrared light images show us what lies beneath.”
Being able to image astronomical objects and environments at different infrared wavelengths enables Keller and his colleagues to analyze physical characteristics such as temperature and chemical composition. Warm objects or regions in space that would look completely dark in visible light are visible on the infrared images, thus allowing scientists to watch dynamic processes taking place.
“SOFIA is going to give us key insights into the processes that form stars in the Milky Way, our home galaxy, as well as the processes that influence the formation and evolution of planets in star systems beyond our solar system,” says Keller.
A monumental undertaking, SOFIA is a collaboration of NASA; the Deutsches Zentrum für Luft und Raumfahrt, the German agency that designed and built the telescope; and teams of scientists and engineers at more than 30 universities, laboratories, and research centers. Six of Keller’s students also made contributions (see sidebar on page 26).
With the aircraft and the equipment having passed muster, Keller spent October and November in California with the in-flight science team, gathering and processing data from FORCAST. He also flew several astronomical missions on board the aircraft.
Over the next 20 years, additional instruments will be successively installed on the telescope, each one designed to investigate targeted infrared wavelengths using the latest technology. In addition, SOFIA’s management team, through its education and public outreach program, will invite educators and journalists on board, with the aim of giving teachers, students, and the general public a firsthand look at how scientific research is conducted. Eventually it will serve as a hands-on educational and training facility for future scientists.
“Astronomers and physicists are constantly looking for better ways to view space and learn about our environment beyond Earth’s atmosphere,” Keller says. “With SOFIA now in operation, we are going to see the universe in detail never before possible.”