Modified Boeing 747SP Houses 17-Metric-Ton Telescope

NASA's Stratospheric Observatory for Infrared Astronomy, or SOFIA, has begun a series of flight tests intended to confirm the structural integrity and performance of the highly modified Boeing 747SP aircraft.

The current tests, which began Thursday, are the first of several flight and ground-test phases required to verify that the unique airborne observatory is ready to perform its future astronomical science mission. Thursday's flight lasted just over five hours and was conducted by NASA's Dryden Flight Research Center in restricted test airspace northwest of Edwards Air Force Base in Southern California.

"The flight went very smoothly overall, and we accomplished (the test points) that I expected," said NASA research pilot Frank Batteas, pilot-in-command for Thursday's test mission. "The aircraft will be a very stable platform for its observatory mission."

A 17-metric-ton telescope was installed in SOFIA's aft fuselage during major modifications at L-3 Communications Integrated Systems facility in Waco, TX. A 16-foot-high telescope cavity door opening was cut into the fuselage during the installation process.

The first series of flight tests, conducted with the cavity door closed, are studying the aerodynamics, structural integrity, stability and control and handling qualities of the modified aircraft, according to NASA Dryden's SOFIA aircraft project manager John Carter. Later flights in the series will concentrate on the in-flight free-floating rotational motion and control of the German-built telescope.

Since its arrival at Dryden, the aircraft has been outfitted with test instrumentation critical for the initial series of flight tests. The aircraft has also been equipped with a telescope cavity environmental control system designed to keep the telescope dry when the door is closed and as the aircraft flies to the altitude required for operation of the observatory.

After door-closed flight testing is complete -- expected by year-end -- the SOFIA 747 will undergo installation and integration of the remaining elements of the observatory before door-open test flights, scheduled to begin in late 2008.

"The largest technical challenges are in 2008, with the remainder of the mission sub-system installation that will give the aircraft the ability to fly with the cavity door open," Carter said.

When fully operational, SOFIA's 2.5-meter infrared telescope will conduct celestial observations while flying at up to 45,000 feet altitude. This will place the instrument above almost 99 percent of the Earth's atmospheric water vapor, greatly enhancing its abilities to probe into space. The flying observatory is designed to detect the formation of stars in our galaxy, determine the chemical composition of the interstellar medium, and peer through the dust that hides the black hole at the center of the Milky Way.

After completing flight testing and further modifications, NASA plans to begin "first light" infrared observations of the universe in 2009.
This will enable the mission to begin obtaining results several years before the observatory reaches its full capacity in 2014. SOFIA will collect science data using a variety of specialized instruments developed by NASA and its German partners.

"SOFIA is making tremendous progress towards the initiation of science observations in 2009, and the initiation of flight testing is another milestone along the path to science observations," said Jon Morse, director of the Astrophysics Division in the Science Mission Directorate at NASA Headquarters, Washington. "Early observations will have significant science community involvement in order to initiate broad scientific use of this unique astronomical observatory."

The SOFIA program is a partnership of NASA and the German Aerospace Center. NASA Dryden manages the SOFIA program, with science elements of the program managed by the NASA Ames Research Center, Moffett Field, CA.

FMI: www.nasa.gov/sofia