Stratospheric Observatory for Infrared Astronomy

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For other uses of "Sofia", see Sofia (disambiguation).
The 747SP which now serves as NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) on a test flight in 1997. Still mostly in United Airlines livery, a black square was painted on the aft fuselage to indicate the area that would eventually house the telescope.
The 747SP which now serves as NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) on a test flight in 1997. Still mostly in United Airlines livery, a black square was painted on the aft fuselage to indicate the area that would eventually house the telescope.
SOFIA comes out of the hangar with a new paint job in October 2006 in a Pan Am inspired livery. It has also regained its original name Clipper Lindbergh.
SOFIA comes out of the hangar with a new paint job in October 2006 in a Pan Am inspired livery. It has also regained its original name Clipper Lindbergh.
SOFIA makes first flight on 26 April 2007
SOFIA makes first flight on 26 April 2007

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 (Deutsches SOFIA Institut) manage the German part (mainly science and telescope related).

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[edit] Overview

SOFIA is a Boeing 747SP airliner, formerly flown commercially by United Airlines and Pan Am, 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 at wavelengths from 1–655 micrometres and high-speed optical astronomy at wavelengths from 0.3–1.1 micrometres.

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 Dryden Flight Research Center at Edwards AFB, California (near Lancaster, CA).

[edit] The telescope

SOFIA telescope.
SOFIA telescope.

SOFIA uses a 2.5-meter reflector telescope, which has an oversized primary mirror (2.7 meters in diameter) in common with most large infra-red telescopes. 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.

The project also has its own mirror coating facility in Moffett Field allowing a fast recoating of the primary mirror.

DLR is responsible for the entire telescope assembly (whereas NASA is responsible for the plane). The manufacturing of the telescope was subcontracted to European industry (The telescope is German, the mirror is French-made and the secondary mirror mechanism is Swiss-made).

For each mission one interchangeable science instrument 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.

The telescope is housed in an open cavity that will be exposed to high-speed turbulent winds. In addition the vibrations and motions of the aircraft introduce observing difficulties. The telescope was designed to be very light-weight, and the mount includes a system to isolate the instrument from vibration. The telescope cabin must be pre-cooled prior to aircraft takeoff so that the telescope matches the external temperature (thus avoiding thermally-induced shape changes). Prior to landing the cabin is flooded with nitrogen gas in order to avoid condensation of moisture on the chilled instrument. [1]

[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.[2] United Airlines purchased the plane in February 1986, and removed it from active service in December 1995. Two years later, NASA purchased it from United for use by the SOFIA project. A series of "baseline" flight tests were conducted in 1997 prior to heavy modification of the aircraft by L-3 Communications Integrated Systems of Waco, Texas for its new role as a flying astronomical observatory. A dismantled section from another 747SP was used as a full-size mock-up to ensure proper modification.

Pan Am had named this aircraft Clipper Lindbergh in honor of the famous aviator Charles Lindbergh. The aircraft was personally christened by Lindbergh's widow, Anne Morrow Lindbergh, on the occasion of the 50th anniversary of her husband's historic flight from New York to Paris in 1927, although the aircraft had been officially placed into service on 6 May 1977. Similarly, Lindbergh's grandson, Erik Lindbergh, re-christened the aircraft Clipper Lindbergh on 21 May 2007 at L-3's Waco facilities.

The maiden flight of SOFIA took place on 26 April, 2007. After a brief test program was conducted in Waco to partially expand the flight envelope and perform post-maintenance checks, the aircraft was moved to Edwards Air Force Base on 31 May 2007, where the bulk of the flight testing will take place. When testing is completed, SOFIA will be operated and maintained by Evergreen International Airlines at NASA's Ames Research Center in Moffett Field (in "Silicon Valley" near San Jose, California).[3]

[edit] Project development

SOFIA completed its first ground-based "on-sky" test on 18–19 August 2004 by taking an image of the star Polaris.

In February 2006, following delays, and costs which increased from US$185 million to $330 million,[4], NASA placed the project "under review" and suspended funding. On the 15 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][6]

SOFIA's first test flight was completed on 26 April 2007 at L-3 Integrated Systems' (L-3 IS) Waco, Texas facility.[7] The first school children to see it were students from Waco Montessori School.

SOFIA is currently undergoing loads and flight testing at NASA-Dryden F.R.C.

[edit] References

  1. ^ Krabbe, Alfred (March, 2007). "SOFIA telescope" (PDF). Proceedings of SPIE: Astronomical Telescopes and Instrumentation: 276–281, Munich, Germany: SPIE — The International Society for Optical Engineering. Retrieved on 2007-06-07. 
  2. ^ The SOFIA Boeing 747SP.
  3. ^ Evergreen International Airlines Awarded Contract To Operate And Maintain The SOFIA Aircraft (2004-07-22).
  4. ^ Maggie McKee (2006-02-13). NASA leaves jumbo-jet telescope on the runway. NewScientist.com news service.
  5. ^ NASA Astronomical Observatory Passes Hurdle (2006-06-15). NASA Headquarters press release 06-240
  6. ^ Brian Berger (2006-05-30). NASA Expected To Save SOFIA. Space News Business Report.
  7. ^ SOFIA Airborne Observatory Completes First Test Flight (2007-04-26).

[edit] External links

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[edit] See also