Science Instruments Ready for SOFIA Airborne Telescope

Scientists are busy preparing for the "First Light" flight of NASA's Stratospheric Observatory for Infrared Astronomy, or SOFIA, a highly modified Boeing 747SP with a 2.5-meter (8.2-foot) diameter infrared telescope installed in its rear fuselage. The first-light astronomical observation flights are now tentatively scheduled for Spring 2010 from NASA's Dryden Aircraft Operations Facility in Palmdale, Calif.

A team of international partners is developing eight instruments that will enable SOFIA to study the universe primarily in the infrared spectral band, but with capabilities extending from wavelengths of 0.3 to 1600 microns, across ultraviolet, visible, infrared, and sub-millimeter ranges.

"Working with our German colleagues, we are eagerly anticipating SOFIA's First Light flight," said Erick Young, SOFIA's recently appointed director of Science and Mission Operations. "SOFIA will be a discovery engine for the next 20 years, and our collaborator teams have spent a number of years perfecting these powerful scientific instruments."

Four of the new instruments are now ready for use on the airborne observatory. They include:

• The Faint Object infraRed Camera for the SOFIA Telescope, or FORCAST, a mid-infrared camera developed at New York's Cornell University that operates at wavelengths of 5-40 microns;
• A heterodyne spectrometer called the German Receiver for Astronomy at Terahertz Frequencies or GREAT, which operates at 60-200 microns. GREAT was developed at the Max Planck Institute for Radioastronomy, Bonn, Germany;
• The Lowell Observatory's High-Speed Imaging Photometer for Occultations, or HIPO, which operates in the 0.3 to 1.1 micron range;
• The Far-Infrared Field-Imaging Line Spectrometer, or FIFI LS, that operates from 42 to 210 microns. FIFI LS was developed at the Max Planck Institute for Extraterrestrial Physics, in Garching, Germany.

Several other instruments will be installed later. They include:

• The CAltech Submillimeter Interstellar Medium Investigations Receiver, or CASIMIR, another heterodyne spectrometer. CASIMIR operates in the 250-600 micron range, and is being built at the California Institute of Technology in Pasadena;
• The High-resolution Airborne Wideband Camera or HAWC, a far-infrared bolometer camera that functions in the 50-240 micron range, developed by the University of Chicago;
• Echelon-Cross-Echelle Spectrograph, or EXES, an echelon spectrometer under construction at the University of California in Davis that operates between five and 28 microns; and
• The First Light Infrared Test Experiment CAMera, or FLITECAM, a near-infrared camera in the one-to-five micron range being developed at the University of California in Los Angeles.

Three of the first nine instruments have been thoroughly tested on ground-based telescopes – HIPO at the Lowell Observatory in Flagstaff, Ariz., FLITECAM at the University of California's Lick Observatory, and FORCAST on Caltech's Mt. Palomar five-meter telescope. HIPO has also been mounted on SOFIA's telescope and used to observe celestial objects from the ground to test the observatory's systems during line operations in Palmdale in late 2008. FORCAST is slated for installation for SOFIA's First Light flight, when photons from a celestial object come down the telescope tube for the first time while the aircraft is airborne.

GREAT, which has been tested in a lab environment, awaits its flight opportunity where it will be able to demonstrate its capabilities. This spectrometer has not yet been tested onboard SOFIA because it analyzes infrared wavelengths that are entirely inaccessible from the ground.

The German-built 2.5-meter infrared telescope is nestled in its cavity in the SOFIA airborne observatory. (NASA Photo / Tom Tschida) SOFIA will fly with one instrument fitted to the telescope for each airborne observation period.

When flying science missions, SOFIA cruises between 39,000 and 45,000 feet at a speed of Mach 0.8 – about 520 mph – on seven- to nine-hour observing flights. When in full operation, the observatory will typically fly three nights per week for approximately 1,000 hours of observing time each year.

SOFIA's telescope weighs 34,000 pounds and was built in Germany by MAN Technologie AG and Kayser-Threde GmbH. It has an elevation range of 20 to 60 degrees above the horizon, and a clear, undistorted field-of-view diameter of 8 arc minutes – about a quarter the diameter of the full moon.

SOFIA is the successor to NASA's extremely successful Kuiper Airborne Observatory, a modified Lockheed C-141 fitted with a one-meter infrared telescope that operated from NASA's Ames Research Center in Mountain View, Calif., from 1974 to 1995.The Kuiper observatory discovered the rings around the planet Uranus, the atmosphere surrounding the planet Pluto, and the presence of water vapor in the interstellar medium.

The new SOFIA observatory is a joint NASA and German Space Agency (Deutsches Zentrum fur Luft- und Raumfahrt, or DLR) program. The development program is currently managed at NASA's Dryden Flight Research Center, Edwards, Calif. with the aircraft based at the Dryden Aircraft Operations Facility in Palmdale. NASA's Ames Research Center manages SOFIA science and mission operations in cooperation with the Universities Space Research Association and the Deutsches SOFIA Institute in Stuttgart, Germany.