Stratospheric Observatory for Infrared Astronomy
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The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a joint project of NASA and the German Aerospace Center (DLR). Universities Space Research Association (USRA) was awarded the prime contract by NASA in 1996 for development, operation of the observatory and management of the American part while the DSI (Deustch SOFIA Institute) manage the german part (mainly science and telescope related).
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[edit] Concept
SOFIA is a Boeing 747SP airliner modified to carry a 2.5 meter diameter reflecting telescope for infrared astronomy observations at altitudes of about 41,000 feet (~12 km) in the stratosphere. Its flight capability will allow it to rise above almost all of the water vapor in the Earth's atmosphere (allowing observations at some infrared wavelengths which are blocked by the atmosphere before reaching ground-based facilities), as well as travel to almost any point on the earth's surface for observations. The telescope looks out of a large door in the side of the fuselage near the airplane's tail, and will initially carry nine instruments for infrared astronomy in wavelengths from 0.35–655 micrometres.
[edit] Objective
The primary science objectives of SOFIA are to study the composition of planetary atmospheres and surfaces; to investigate the structure, evolution and composition of comets; to determine the physics and chemistry of the interstellar medium; and to explore the formation of stars and other stellar objects.
Once ready for use, it is hoped that observing flights will be flown 3 or 4 nights a week for the next 20 years. SOFIA will be based at NASA's Ames Research Center at Moffett Field, California (near San Jose, CA).
[edit] Current Status
19 August 2006 SOFIA completed aircraft system tests including engine and taxi tests at Waco Airport.[1] October 2006 SOFIA came out the hangar with a new paint job. The first flight is slated to be only a few months away.[2]
[edit] The Telescope
SOFIA uses a reflector telescope which uses a mirror to concentrate and focus the incoming light. When it comes to large telescopes, reflectors have proven to be much more practical than refractor telescopes because they are much easier and less expensive to build and use.
The project also has its own mirror coating fascillity in Moffett Field allowing a fast recoating of the primary mirror.
The primary mirror, located near the bottom of the telescope, is 2.7 meters (almost 9 feet) across. It is however usually referred to as a 2.5-meter meter telescope, rather than 2.7 meters, because the optical design requires that only about 90% of the mirror’s reflecting surface (called the "effective aperture") can be used at any one time. Although SOFIA’s telescope is by far the largest ever to be placed in an aircraft, compared to normal ground-based research observatories it is only medium-sized.
DLR is responsible for the entire telescope assembly (when NASA is reponsible by the plane). The manufacturing of the telescope was subcontracted to the Germany and european industry (The telescope is German, the mirror is French-made and the secondary mirror mechanism is Swiss-made).
For each mission one changeable science instruments will be attached to the telescope. Two groups of general purpose instruments are available. In addition an investigator can also design and build a special purpose instrument.
[edit] The Aircraft
The SOFIA aircraft is a Boeing 747SP with a distinguished history. It was originally acquired by Pan American World Airways and was delivered in May 1977. The "SP" designates that this is a special short-body version of the 747, designed for longer flights than the basic model.[3]
Pan Am named this aircraft - the Clipper Lindbergh - in honor of the famous aviator Charles Lindbergh. The aircraft was personally christened by Lindbergh's widow, Anne Morrow Lindbergh, and it was officially placed it into service on 6 May 1977. This was the 50th anniversary of Lindbergh's historic first solo flight from New York to Paris in 1927.
United Airlines purchased this plane in February 1986 and removed it from active service after nine years in December 1995. NASA purchased it from United in 1997 for the SOFIA project. The aircraft is being heavily modified for its new role as a flying astronomical observatory by L-3 Communications Integrated Systems of Waco, Texas. A dismantled section from another 747SP was used as a full-size mock-up to ensure proper modification.
When it returns to service as SOFIA, the 747SP will be operated and maintained by Evergreen International Airlines at NASA's Ames Research Center in Moffett Field, CA (on the silicon valley near San Jose).[4]
An interesting remark about the 747 is that it kept its name ... 'the Clipper Lindbergh'
[edit] Project Development
SOFIA completed its first ground-based "on-sky" test on 18–19 August 2004 by taking a picture of the star Polaris.
In February 2006 NASA placed the project "under review" and suspended funding. On the 15th of June 2006 SOFIA passed the review when NASA concluded that there were no insurmountable technical or programmatic challenges to the continued development of SOFIA[5].
