SOFIA

THE ASTRONOMY PICTURE OF THE DAY FOR 2010 June 3

Jupiter from the Stratosphere

Credit: Infrared - NASA, USRA, DSI, Cornell Univ. / Visible - Anthony Wesley

Explanation: SOFIA, the Stratospheric Observatory for Infrared Astronomy, captured its "first light" images on May 26, from an altitude of 35,000 feet. While flying above most of planet Earth's infrared-absorbing water vapor, SOFIA's premier infrared views of the cosmos included this remarkable false-color image (right panel) of Jupiter. For comparison, on the left is a recent, ground-based visible light image. Both show our solar system's ruling gas giant without its dark southern equatorial belt (normally seen in the upper hemisphere in this orientation). That familiar feature faded from view early in May. But the bright white stripe in SOFIA's image is a region of Jupiter's clouds transparent to infrared light, offering a glimpse below the cloud tops.

The information below is from WIKIPEDIA:

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a joint project of NASA and the German Aerospace Center (DLR) for the construction and maintenance of an airborne telescope. Universities Space Research Association (USRA) was awarded the contract by NASA in 1996 for development, operation of the observatory and management of the American part while the DSI (Deutsches SOFIA Institut) manages the German part (mainly science and telescope related). SOFIA's telescope saw first light on May 26, 2010.

SOFIA

SOFIA Makes its First Flight on April 26, 2007

Organization

Location

Coordinates

Altitude

Telescopes

2.5 meter (98.4 inch) reflector

Facility

SOFIA is based on a Boeing 747SP wide-body aircraft that has been modified to carry a 2.5 meter diameter reflecting telescope in the aft section of the fuselage. This telescope is designed for infrared astronomy observations at altitudes of about 41,000 feet (about 12 km) in the stratosphere. The water vapor in the Earth's atmosphere blocks some infrared wavelengths from reaching the ground, but SOFIA's flight capability allows it to rise above almost all of the water vapor in the Earth's atmosphere. At the aircraft's cruising altitude, 85% of the full infrared range will be available.[1] The aircraft can also travel to almost any point on the Earth's surface, allowing observation from the northern and southern hemispheres.

Once ready for use, the expectation is for observing flights to be flown 3 or 4 nights a week for the next 20 years. SOFIA is now based at NASA's Dryden Aircraft Operations Facility at LA/Palmdale Regional Airport, California, while staff at NASA Ames Research Center, in Mountain View, California, operate the SOFIA Science Center where astronomical observation missions are planned for the flying observatory.

The Telescope

.SOFIA Telescope.

SOFIA uses a 2.5-meter reflector telescope, which has an oversized, 2.7 meter diameter primary mirror, as is common with most large infra-red telescopes.[2] The optical system uses a Cassegrain reflector design with a parabolic primary mirror and a remotely configurable hyperbolic secondary. In order for the telescope to fit into the fuselage, the primary is shaped to an f-number as low as 1.3. However, the resulting optical layout has an f-number of 19.7. A flat, tertiary, dichroic mirror is used to deflect the infrared part of the beam to the Nasmyth focus where it can be analyzed. An optical mirror located behind the tertiary mirror is used for a camera guidance system.[1]

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 main instruments are the FLITECAM, a near infrared camera covering 1–5 micrometres; FORCAST, covering the mid-infrared range of 5–40 micrometres, and HAWC, which spans the far infrared in the range 40–300 micrometres. The other five infrared instruments are spectrometers with various overlapping spectral ranges.[3] SOFIA’s telescope is by far the largest ever to be placed in an aircraft, although there are a number of larger ground-based research observatories. 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 open cavity housing the telescope 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 compartment is flooded with nitrogen gas in order to avoid condensation of moisture on the chilled instrument.[1]

DLR is responsible for the entire telescope assembly and design, whereas NASA is responsible for the plane only. 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. The consortium has a mirror coating facility in Moffett Field, allowing a fast recoating of the primary mirror.

The Aircraft

The 747SP, which now serves as NASA's 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 house the telescope.

The SOFIA aircraft is a widebody Boeing 747SP (manufacturers serial number 21441) with a distinguished history. It was originally acquired by Pan American World Airways and was delivered on May 6, 1977. The "SP" (Special Performance) designates that this is a special short-body version of the 747, designed for longer flights than the basic model.[4] 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 (N141UA) 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 May 6, 1977. Similarly, Lindbergh's grandson, Erik Lindbergh, re-christened the aircraft Clipper Lindbergh on May 21, 2007 at L-3's Waco facilities.[5]

The telescope is mounted in the aft part of the aircraft behind a pressurized bulkhead. The telecope's focal point is located at a science instruments suite in the pressurized section. In the center of the aircraft is the mission control and science operations section, while the forward section hosts the education and public outreach area.

Project Development

SOFIA comes out of the hangar with a new paint job in October 2006 in current NASA livery. It has also regained its original name Clipper Lindbergh.

An F/A-18 mission support aircraft shadows SOFIA during a functional check flight.

SOFIA with the telescope door open in flight.

The first use of an aircraft for performing infrared observations occurred in 1965 when Gerard P. Kuiper used the NASA Convair 990 to study Venus. Three years later, Frank Low used the Ames Learjet to perform observations of Jupiter and nebulae.[6] In 1969, planning began for mounting a 36-inch (910 mm) telescope on an airborne platform. The goal of this instrument was to perform astronomy from the stratosphere, where there was a much lower optical depth from water vapor absorbing infrared radiation. This project was named the Kuiper Airborne Observatory, and it was dedicated on May 21, 1975. The telescope became instrumental in numerous scientific studies, including the discovery of the ring system around the planet Uranus.[7]

The proposal for a larger aircraft-mounted telescope was officially presented in 1984, which called for a Boeing 747 to carry a three-meter telescope. The preliminary system concept was published in 1987 in the Red Book. It was agreed that Germany would contribute 20% of the total cost, and they would provide the telescope. However, the reunification of Germany and budget cuts at NASA led to a five-year slide in the project. NASA then contracted the work out to the Universities Space Research Association (USRA), and in 1996, NASA and DLR (the German Space Agency or Deutsches Zentrum fur Luft- und Raumfahrt) signed a memorandum of understanding for the building and operation of SOFIA.[8]

The SOFIA telescope's primary mirror was manufactured out of Zerodur, a glass-ceramic composite produced by Schott AG that has almost zero thermal expansion. REOSC, the optical department of the SAGEM Group in France, performed weight reduction by milling honeycomb-shaped pockets out of the back. They finished polishing the mirror on December 14, 1999, achieving an accuracy of 8.5 nm over the optical surface.[9] The hyperbolic-shaped secondary mirror was made out of silicon carbide, with polishing completed by May 2000.[1] During 2002, the main components of the telescope were assembled in Augsburg, Germany. These consisted of the primary mirror assembly, the main optical support and the suspension assembly. After successful integration tests were made to check the system, the components were shipped to Waco, Texas on board an Airbus Beluga aircraft. They arrived on September 4, 2002.[10] SOFIA completed its first ground-based "on-sky" test on August 18–19, 2004 by taking an image of the star Polaris.[11]

In February 2006, following delays, and costs which increased from US$185 million to $330 million,[12] NASA placed the project "under review" and suspended funding. On June 15, 2006, SOFIA passed the review when NASA concluded that there were no insurmountable technical or programmatic challenges to the continued development of SOFIA.[13][14]

The maiden flight of SOFIA took place on April 26, 2007 at the L-3 Integrated Systems' (L-3 IS) Waco, Texas facility.[15] 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 May 31, 2007. The first phase of loads and flight testing was used to check the aircraft characteristics with the external telescope cavity door closed. This phase was successfully completed by January, 2008 at NASA-Dryden F.R.C.[16]

On December 18, 2009, the SOFIA aircraft performed the first test flight in which the telescope door was fully opened. This phase lasted for two minutes of the 79 minute flight. Two daytime flights to test the operational capability of the telescope are scheduled for spring, 2010.[17] SOFIA's telescope saw first light on May 26, 2010, returning images showing M82's core and heat from Jupiter's formation escaping through its cloud cover.[18] Normal science observation flights should begin in 2011 and the observatory is slated for full capability by 2014.[16]

Scientific Research

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. While SOFIA aircraft operations are managed by NASA Dryden, NASA Ames Research Center in Mountain View, California, is home to the SOFIA Science Center.

See Also

References

External Links

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