Step by step, the Stratospheric Observatory for Infrared Astronomy (SOFIA) is nearing its first flight. Last month the heavily modified 747SP aircraft, which will carry a 2.5-meter (98-inch) telescope above 99% of the atmosphere's infrared-absorbing water vapor, received a fresh coat of paint. The sparkling white livery — a striking tranformation from unpainted metal in shades of green, brown, and silver — was unveiled in a giant hangar at L-3 Communications in Waco, Texas, where the plane has spent the last few years being converted from an airliner to an airborne observatory. The new plumage also features the American and German flags as well as the logos of NASA and the Deutsches Zentrum für Luft- und Raumfahrt (DLR), the German space agency, which has partnered with its US counterpart to develop SOFIA and operate it over the next 20 years.

The key modification to the aircraft is the telescope bay and aperture door, which occupies much of the fuselage between the wings and tail. SOFIA also features new high-power engines, state-of-the-art avionics, and a control room where high-flying astronomers will operate the telescope and scientific instruments and where teachers will help prepare the next generation of researchers.

Initial test flights, scheduled to get under way by early 2007, will be conducted with the aperture door closed and will focus on proving the refurbished aircraft's airworthiness. Then, perhaps a year after the first closed-door flight, comes the real nail-biter: the first flight with the telescope exposed to the sky. Aircraft designers have "pushed the envelope" of aerodynamics to ensure that airflow inside the telescope bay will not be turbulent and that the pilots will have no problems handling the plane with the aperture door open. Once they know they've succeeded, they'll turn SOFIA over to the astronomers.