Spitzer Space Telescope
From Wikipedia, the free encyclopedia
| Spitzer Space Telescope | |
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The Spitzer Space Telescope prior to launch
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| General information | |
| Alternative names | formerly the Space Infrared Telescope Facility (SIRTF) |
| NSSDC ID | 2003-038A |
| Organization | NASA / JPL / Caltech |
| Major contractors | Lockheed Martin Ball Aerospace |
| Launch date | August 25, 2003[1] |
| Launched from | Cape Canaveral, Florida[1] |
| Launch vehicle | Delta II 7920H ELV[1] |
| Mission length | 2.5 to 5+ years[1] |
| Mass | 950 kg (2090 lb)[1] |
| Type of orbit | Heliocentric[1] |
| Orbit period | 1 year |
| Location | Orbiting the Sun |
| Telescope style | Ritchey-Chrétien[2] |
| Wavelength | 3 to 180 micrometers[1] |
| Diameter | 0.85 m[1] |
| Focal length | 10.2 m |
| Instruments | |
| IRAC | infrared camera |
| IRS | infrared spectrometer |
| MIPS | far infrared detector arrays |
| Website www.spitzer.caltech.edu/ |
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The Spitzer Space Telescope (formerly the Space Infrared Telescope Facility, SIRTF) is an infrared space observatory. It is the fourth and final of NASA's Great Observatories.
The planned "nominal mission" length was 2.5 years with a pre-launch expectation that mission life could extend to 5 or slightly more years until the onboard liquid helium supply was exhausted. As of late 2007, it is expected that this will occur in April 2009. Continued operation of the IRAC detector (the only instrument operable in a warm telescope) is possible, but faces uncertain funding.
In keeping with NASA tradition, the telescope was renamed after successful demonstration of operation, on December 18, 2003. Unlike most telescopes which are named after famous deceased astronomers by a board of scientists, the name for SIRTF was obtained from a contest open to the general public (to the delight of science educators).
The name chosen was that of Dr. Lyman Spitzer, Jr., the first to propose placing telescopes in space, in the mid-1940s.
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The US$ 800 million[3] Spitzer was launched on Monday 25 August 2003 at 1:35:39 (EDT) from Cape Canaveral Air Force Station on a Delta II 7920H ELV rocket. It follows a rather unusual orbit, heliocentric instead of geocentric, following earth in its orbit, and drifting away from Earth at approximately 0.1 astronomical unit per year (a so-called "earth-trailing" orbit). The primary mirror is 85 cm in diameter, f/12 (i. e. the focal length is 12 times the diameter of the primary mirror) and made of beryllium and cooled to 5.5 K. The satellite contains three instruments that will allow it to perform imaging and photometry from 3 to 180 micrometers, spectroscopy from 5 to 40 micrometers, and spectrophotometry from 5 to 100 micrometers.
[edit] History
By the early 1970s, astronomers began to consider the possibility of placing an infrared telescope above the obscuring effects of Earth's atmosphere. Most of the early concepts, such as the Shuttle InfraRed Observatory, envisioned repeated flights aboard the NASA Space Shuttle. This approach was developed in an era when the Shuttle program was presumed to be capable of supporting weekly flights of up to 30 days duration.
In 1979, a National Research Council of the National Academy of Sciences report, A Strategy for Space Astronomy and Astrophysics for the 1980's, identified a Shuttle Infrared Telescope Facility (SIRTF) as "one of two major astrophysics facilities [to be developed] for Spacelab," a Shuttle-borne platform. Anticipating the exciting results from an upcoming Explorer satellite and from the Shuttle mission, the report also favored the "study and development of ... long-duration spaceflights of infrared telescopes cooled to cryogenic temperatures."
A May 1983 NASA proposal described SIRTF as becoming envisaged as an attached Shuttle mission with an evolving scientific payload. Several flights were anticipated with a probable transition into a more extended mode of operation, possibly in association with a future space platform or space station. The SIRTF would be a 1-meter class, cryogenically cooled, multi-user facility consisting of a telescope and associated focal plane instruments. It would be launched on the Space Shuttle and remain attached to the Shuttle as a Spacelab payload during astronomical observations, after which it would be returned to Earth for refurbishment prior to re-flight. The first flight of SIRTF was expected to occur about 1990, with the second flight anticipated to be approximately one year after the first flight.
The launch of the Infrared Astronomical Satellite, an Explorer-class satellite designed to conduct the first infrared survey of the sky whetted the appetites of scientists worldwide for a follow-up mission capitalizing on the rapid improvements in infrared detector technology. By September 1983 NASA was considering the "possibility of a long duration [free-flyer] SIRTF mission." The Spacelab-2 flight aboard STS-51-F confirmed the Shuttle environment was not well suited to an onboard infrared telescope, thus a free flying design was better.[4][5]
Spitzer is the only one of the Great Observatories not launched by the Space Shuttle. It was originally intended to, but after the Challenger disaster, the Centaur LH2/LOX upper stage that would have been required to push it into its intended orbit was banned from Shuttle use. The satellite underwent a series of redesigns during the 1990s, primarily due to budget considerations. This resulted in a much smaller, although still fully capable, mission which could use the smaller Delta launch vehicle. One of the most important aspects of this redesign was the use of the earth-trailing orbit. Cryogenic satellites in earth orbit are exposed to a tremendous heat load from the earth. By placing the satellite in solar, and not earth, orbit, and through the use of innovative passive cooling (such as the sun-shield), the total amount of cryogenic helium needed to cool the satellite was drastically reduced, resulting in an overall smaller, lighter package. This orbit also has the benefit of simplifying the telescope pointing, but does require the Deep Space Network for communications.
The primary instrument package (telescope and cryogenic chamber) was developed by Ball Aerospace & Technologies Corp., in Boulder, CO. The individual instruments were developed jointly by industrial, academic, and government institutions, the principals being Cornell, the University of Arizona, the Smithsonian Astrophysical Observatory, Ball Aerospace, and Goddard Spaceflight Center. The spacecraft was built by Lockheed Martin. The mission is operated and managed by the Jet Propulsion Laboratory and the Spitzer Science Center, located on the Caltech campus in Pasadena, CA.
[edit] Instruments
Spitzer has three instruments on-board:
- IRAC (Infrared Array Camera), an infrared camera which operates simultaneously on four wavelengths (3.6 µm, 4.5 µm, 5.8 µm and 8 µm). Each module uses a 256 × 256 pixel detector -- the short wavelength pair use indium antimonide technology, the long wavelength pair use arsenic-doped silicon impurity band conduction technology.
- IRS (Infrared Spectrograph), an infrared spectrometer with four sub-modules which operate at the wavelengths 5.3-14 µm (low resolution), 10-19.5 µm (high resolution), 14-40 µm (low resolution), and 19-37 µm (high resolution). Each module uses a 128x128 pixel detector -- the short wavelength pair use arsenic-doped silicon blocked impurity band technology, the long wavelength pair use antimony-doped silicon blocked impurity band technology.
- MIPS (Multiband Imaging Photometer for Spitzer), three detector arrays in the far infrared (128 × 128 pixels at 24 µm, 32 × 32 pixels at 70 µm, 2 × 20 pixels at 160 µm). The 24 µm detector is identical to one of the IRS short wavelength modules. The 70 µm detector uses gallium-doped germanium technology, and the 160 µm detector also uses gallium-doped germanium, but with mechanical stress added to each pixel to lower the bandgap and extend sensitivity to this long wavelength.
Earlier infrared observations had been made by both space-based and ground-based observatories. Ground-based observatories have the drawback that at infrared wavelengths or frequencies, both the Earth's atmosphere and the telescope itself will radiate (glow) strongly. Additionally, the atmosphere is opaque at most infrared wavelengths. This necessitates lengthy exposure times and greatly decreases the ability to detect faint objects. It could be described as trying to observe the stars at noon. Previous space-based satellites (such as IRAS, the Infrared Astronomical Satellite, and ISO, the Infrared Space Observatory) were operational during the 1980s and 1990s and great advances in astronomical technology have been made since then.
[edit] Results
The first images taken by SST were designed to show off the abilities of the telescope and showed a glowing stellar nursery; a swirling, dusty galaxy; a disc of planet-forming debris; and organic material in the distant universe. Since then, monthly press releases have shown off Spitzer's capabilities, as the NASA and ESA images do for the HST.
As one of its most noteworthy observations, in 2005, SST became the first telescope to directly capture the light from extrasolar planets, namely the "hot Jupiters" HD 209458b and TrES-1. (It did not resolve that light into actual images though.)[6] This was the first time extrasolar planets had actually been visually seen, and earlier observations had been indirectly made by drawing conclusions from behaviors of the star the planets were orbiting. The telescope also discovered in April 2005 that Cohen-kuhi Tau/4 had a planetary disk that was vastly younger and contained less mass than previously theorized, leading to new understandings of how planets are formed.
While some time on the telescope is reserved for participating institutions and crucial projects, astronomers around the world also have the opportunity to submit proposals for observing time. Important targets include forming stars (young stellar objects, or YSOs), planets, and other galaxies. Images are freely available for educational and journalistic purposes.
In 2004, it was reported that Spitzer had spotted a faintly glowing body that may be the youngest star ever seen. The telescope was trained on a core of gas and dust known as L1014 which had previously appeared completely dark to ground-based observatories and to ISO (Infrared Space Observatory), a predecessor to Spitzer. The advanced technology of Spitzer revealed a bright red hot spot in the middle of L1014.
Scientists from the University of Texas at Austin who discovered the object believe the hot spot to be an example of early star development with the young star collecting gas and dust from the cloud around it. Early speculation about the hot spot was that it might have been the faint light of another core that lies 10 times further from Earth but along the same line of sight as L1014. Follow-up observation from ground-based near-infrared observatories detected a faint fan-shaped glow in the same location as the object found by Spitzer. That glow is too feeble to have come from the more distant core leading to the conclusion that the object is located within L1014. (Young et al., 2004)
In 2005, astronomers from the University of Wisconsin at Madison and Whitewater determined, on the basis of 400 hours of observation on the Spitzer Space Telescope, that the Milky Way Galaxy has a more substantial bar structure across its core than previously recognized.
Also in 2005, astronomers Alexander Kashlinsky and John Mather of NASA's Goddard Space Flight Center reported that one of Spitzer's earliest images may have captured the light of the first stars in the universe. An image of a quasar in the Draco constellation, intended only to help calibrate the telescope, was found to contain an infrared glow after the light of known objects was removed. Kashlinsky and Mather are convinced that the numerous blobs in this glow are the light of stars that formed as early as 100 million years after the big bang, red shifted by cosmic expansion.[7]
In March of 2006, astronomers reported an 80 light year-long nebula near the center of the Milky Way Galaxy, the Double Helix Nebula, which is, as the name implies, twisted into a double spiral shape. This is thought to be evidence of massive magnetic fields generated by the gas disc orbiting the supermassive black hole at the galaxy's center, 300 light years from the nebula and 25,000 light years from Earth. This nebula was discovered by the Spitzer Space Telescope, and published in the magazine Nature on March 16th, 2006.
In May 2007, astronomers successfully mapped HD 189733 b atmospheric temperature, thus obtaining the first map of some kind of an extrasolar planet.
Since September 2006 the telescope participates in a series of surveys called the Gould Belt Survey, observing the Gould’s Belt region in multiple wavelengths. The first set of observations by the Spitzer Space Telescope were completed from September 21, 2006 through September 27th. Resulting from these observation, the team of astronomers led by Dr. Robert Gutermuth, of the Harvard-Smithsonian Center for Astrophysics reported the discovery of Serpens South, a cluster of 50 young stars in the Serpens constellation.
On June 3 2008, scientists unveiled the largest, most detailed infra-red portrait of the Milky Way, created by stitching together more than 800,000 snapshots, at the 212th meeting of the American Astronomical Society in St.Louis, Missouri.[8][9]
[edit] See also
- COBE
- DIRBE
- Great Observatories program
- Herschel
- Infrared astronomy
- IRAS
- Infrared Space Observatory
- Space telescope
[edit] References
- ^ a b c d e f g h NASA:Spitzer Space Telescope. Fast Facts. Retrieved on 2007-04-22.
- ^ NASA:Spitzer Space Telescope. Spitzer's Telescope. Retrieved on 2007-04-22.
- ^ Spaceflight Now | Breaking News | First images from Spitzer Space Telescope unveiled
- ^ Watanabe, Susan (2007-11-22). Studying the Universe in Infrared. NASA. Retrieved on 2007-12-08.
- ^ Kwok, Johnny (Fall 2006). Finding a Way: The Spitzer Space Telescope Story. Academy Sharing Knowledge. NASA. Retrieved on 2007-12-09.
- ^ Press Release: NASA's Spitzer Marks Beginning of New Age of Planetary Science
- ^ Infrared Glow of First Stars Found: Scientific American
- ^ Press Release: Spitzer Captures Stellar Coming of Age in Our Galaxy
- ^ Released Images and Videos of Milky Way Mosaic
[edit] External links
- Spitzer official site
- Spitzer Space Telescope Profile by NASA's Solar System Exploration
- Spitzer images: http://www.spitzer.caltech.edu/Media/mediaimages/index.shtml
- Spitzer newsroom: http://www.spitzer.caltech.edu/Media/index.shtml
- Spitzer podcasts: http://www.spitzer.caltech.edu/features/podcasts/index.shtml
- Spitzer video podcasts: http://www.spitzer.caltech.edu/features/hiddenuniverse/index.shtml
- Simulation of Spitzer's orbit
