Great Observatories program
The
The
in 2000 after a gyroscope failed.The
into an elliptical high-Earth orbit, and was initially named the Advanced X-ray Astronomical Facility (AXAF).The
The Hubble Space Telescope and Chandra X-ray Observatory continue to operate as of April 2024.
Origins of the Great Observatory program
The concept of a Great Observatory program was first proposed in the 1979
Great Observatories
Hubble Space Telescope
The history of the Hubble Space Telescope can be traced back to 1946, when the astronomer Lyman Spitzer wrote the paper Astronomical advantages of an extraterrestrial observatory.[6] Spitzer devoted much of his career to pushing for a space telescope.
The 1966–1972 Orbiting Astronomical Observatory missions demonstrated the important role space-based observations could play in astronomy. In 1968, NASA developed firm plans for a space-based reflecting telescope with a 3-meter mirror, known provisionally as the Large Orbiting Telescope or Large Space Telescope (LST), with a launch slated for 1979.[7] Congress eventually approved funding of US$36 million for 1978, and the design of the LST began in earnest, aiming for a launch date of 1983. During the early 1980s, the telescope was named after Edwin Hubble.
Hubble was originally intended to be retrieved and returned to
Compton Gamma Ray Observatory
Gamma rays had been examined above the atmosphere by several early space missions. During its
Chandra X-ray Observatory
In 1976 the Chandra X-ray Observatory (called AXAF at the time) was proposed to NASA by Riccardo Giacconi and Harvey Tananbaum. Preliminary work began the following year at Marshall Space Flight Center (MSFC) and the Smithsonian Astrophysical Observatory (SAO). In the meantime, in 1978, NASA launched the first imaging X-ray telescope, Einstein Observatory (HEAO-2), into orbit. Work continued on the Chandra project through the 1980s and 1990s. In 1992, to reduce costs, the spacecraft was redesigned. Four of the twelve planned mirrors were eliminated, as were two of the six scientific instruments. Chandra's planned orbit was changed to an elliptical one, reaching one third of the way to the Moon's at its farthest point. This eliminated the possibility of improvement or repair by the Space Shuttle but put the observatory above the Earth's radiation belts for most of its orbit.
Spitzer Space Telescope
By the early 1970s, astronomers began to consider the possibility of placing an infrared telescope above the obscuring effects of
The launch of the
Spitzer was the only one of the Great Observatories not launched by the Space Shuttle. It was originally intended to be so launched, but after the
Timeline
Timeline of NASA Great Observatories Program |
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Strengths
Since the Earth's atmosphere prevents
Each observatory was designed to push the state of technology in its region of the electromagnetic spectrum. Compton was much larger than any gamma-ray instruments flown on the previous
Chandra similarly had no ground predecessors. It followed the three NASA HEAO Program satellites, notably the highly successful Einstein Observatory, which was the first to demonstrate the power of grazing-incidence, focusing X-ray optics, giving spatial resolution an order of magnitude better than collimated instruments (comparable to optical telescopes), with an enormous improvement in sensitivity. Chandra's large size, high orbit, and sensitive CCDs allowed observations of very faint X-ray sources.
Spitzer also observes at wavelength largely inaccessible to ground telescopes. It was preceded in space by NASA's smaller IRAS mission and European Space Agency (ESA)'s large ISO telescope. Spitzer's instruments took advantage of the rapid advances in infrared detector technology since IRAS, combined with its large aperture, favorable fields of view, and long life. Science returns were accordingly outstanding.[citation needed] Infrared observations are necessary for very distant astronomical objects where all the visible light is redshifted to infrared wavelengths, for cool objects which emit little visible light, and for regions optically obscured by dust.
Synergies
Aside from inherent mission capabilities (particularly sensitivities, which cannot be replicated by ground observatories), the Great Observatories program allows missions to interact for greater science return. Different objects shine in different wavelengths, but training two or more observatories on an object allows a deeper understanding.
High-energy studies (in X-rays and gamma rays) have had only moderate imaging resolutions so far. Studying X-ray and gamma-ray objects with Hubble, as well as Chandra and Compton, gives accurate size and positional data. In particular, Hubble's resolution can often discern whether the target is a standalone object, or part of a parent galaxy, and if a bright object is in the nucleus, arms, or halo of a spiral galaxy. Similarly, the smaller aperture of Spitzer means that Hubble can add finer spatial information to a Spitzer image. Reported in March 2016, Spitzer and Hubble were used to discover the most distant-known galaxy, GN-z11. This object was seen as it appeared 13.4 billion years ago.[15][16] (List of the most distant astronomical objects)
Ultraviolet studies with Hubble also reveal the temporal states of high-energy objects. X-rays and gamma rays are harder to detect with current technologies than visible and ultraviolet. Therefore, Chandra and Compton needed long integration times to gather enough photons. However, objects which shine in X-rays and gamma rays can be small, and can vary on timescales of minutes or seconds. Such objects then call for followup with Hubble or the Rossi X-ray Timing Explorer, which can measure details in angular seconds or fractions of a second, due to different designs. Rossi's last full year of operation was 2011.
The ability of Spitzer to see through dust and thick gases is good for galactic nuclei observations. Massive objects at the hearts of galaxies shine in X-rays, gamma rays, and radio waves, but infrared studies into these clouded regions can reveal the number and positions of objects.
Hubble, meanwhile, has neither the field of view nor the available time to study all interesting objects. Worthwhile targets are often found with ground telescopes, which are cheaper, or with smaller space observatories, which are sometimes expressly designed to cover large areas of the sky. Also, the other three Great Observatories have found interesting new objects, which merit diversion of Hubble.
One example of observatory synergy is Solar System and asteroid studies. Small bodies, such as small moons and asteroids, are too small and/or distant to be directly resolved even by Hubble; their image appears as a diffraction pattern determined by brightness, not size. However, the minimum size can be deduced by Hubble through knowledge of the body's albedo. The maximum size can be determined by Spitzer through knowledge of the body's temperature, which is largely known from its orbit. Thus, the body's true size is bracketed. Further spectroscopy by Spitzer can determine the chemical composition of the object's surface, which limits its possible albedos, and therefore sharpens the low size estimate.
At the opposite end of the cosmic distance ladder, observations made with Hubble, Spitzer and Chandra have been combined in the Great Observatories Origins Deep Survey to yield a multi-wavelength picture of galaxy formation and evolution in the early Universe.
Impact
All four telescopes have had a substantial impact on astronomy. The opening up of new wavebands to high resolution, high sensitivity observations by the Compton, Chandra and Spitzer has revolutionized our understanding of a wide range of astronomical objects, and has led to the detection of thousands of new, interesting objects. Hubble has had a much larger public and media impact than the other telescopes, although at optical wavelengths Hubble has provided a more modest improvement in sensitivity and resolution over existing instruments. Hubble's capability for uniform high-quality imaging of any astronomical object at any time has allowed accurate surveys and comparisons of large numbers of astronomical objects. The Hubble Deep Field observations have been very important for studies of distant galaxies, as they provide rest-frame ultraviolet images of these objects with a similar number of pixels across the galaxies as previous ultraviolet images of closer galaxies, allowing direct comparison.
Successors to Great Observatories
- The James Webb Space Telescope (JWST) launched in December 2021 and works simultaneously with Hubble.[17] Its segmented, deployable mirror is over twice as wide as the Hubble's, increasing angular resolution noticeably, and sensitivity dramatically. Unlike Hubble, JWST observes in the infrared, in order to penetrate dust at cosmological distances. This means it continues some Spitzer capabilities, while some Hubble capabilities are lost in the visible and especially the ultraviolet wavelengths. JWST exceeds Spitzer's performance in near-infrared. The European Space Agency's Herschel Space Observatory, operational from 2009 to 2013, has exceeded Spitzer in the far-infrared. The SOFIA (Stratospheric Observatory for Infrared Astronomy) airborne platform observed in near- and mid-infrared. SOFIA had a larger aperture than Spitzer, but lower relative sensitivity.
- The Swift, launched in 2004, and previously by HETE-2, launched in 2000.
- The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), launched in 2002, observes in some Compton and Chandra wavelengths, but is pointed at the Sun at all times. Occasionally it observes high-energy objects which happen to be in the view around the Sun.
- Another large, high-energy observatory is INTEGRAL, Europe's INTErnational Gamma Ray Astrophysics Laboratory, launched in 2002. It observes in similar frequencies to Compton. INTEGRAL uses a fundamentally different telescope technology, coded-aperture masks. Thus, its capabilities are complementary to Compton and Fermi.
Later programs
- The Einstein Great Observatories, to differentiate them from the current generation. However, they are not a part of the Great Observatories program.[19]
- The International Solar-Terrestrial Physics Science Initiative (ISTP), in the spirit of the Great Observatories program, is a group of instruments to study the Sun and related electromagnetic phenomena near Earth.[20]
Next Great Observatory
This section needs to be updated. The reason given is: Refers to reports being turned in in 2019 and selection taking place in 2021.(April 2024) |
In 2016,
See also
- Beyond Einstein program
- Herschel Space Telescope(Far infrared space observatory, 2009–2013)
- List of space telescopes
Notes and references
- ^ "A Strategy for Space Astronomy and Astrophysics for the 1980s". Washington, DC: The National Academies Press.
- ^ Stern, David P. (12 December 2004). "Seeing the Sun in a New Light". From Stargazers to Starships. NASA Goddard Space Flight Center. Retrieved 7 December 2007. This article incorporates text from this source, which is in the public domain.
- ^ Roman, Nancy Grace (2001). "Exploring the Universe: Space-Based Astronomy and Astrophysics" (PDF). Exploring the Cosmos. NASA. Archived from the original (PDF) on 27 May 2005. Retrieved 8 December 2007. This article incorporates text from this source, which is in the public domain.
- ^ Harwit, Martin; Neal, Valerie (9 January 1986). "The Great Observatories for Space Astrophysics" (PDF). NASA document number 21M585. NASA.
- ^ Harwit, Martin; Neal, Valerie (1 January 1991). "The Great Observatories for Space Astrophysics" (PDF). NASA document number NP-128. NASA.
- ^ Spitzer, L., REPORT TO PROJECT RAND: Astronomical Advantages of an Extra-Terrestrial Observatory, reprinted in Astronomy Quarterly volume 7, p. 131, 1990
- ^ Spitzer, Lyman S (1979), "History of the Space Telescope", Quarterly Journal of the Royal Astronomical Society, v. 20, p. 29
- ^ "NASA Updates Space Shuttle Target Launch Dates". NASA. Archived from the original on 8 May 2017. Retrieved 22 May 2008.
- ^ Boyle, Alan (31 October 2006). "NASA gives green light to Hubble rescue". NBC News. Retrieved 10 January 2007.
- ^ "Gamma-Ray Astronomy in the Compton Era: The Instruments". Gamma-Ray Astronomy in the Compton Era. NASA (GSFC). Archived from the original on 24 February 2009. Retrieved 7 December 2007. This article incorporates text from this source, which is in the public domain.
- ^ Harwood, William. "NASA space telescope heads for fiery crash into Pacific". Spaceflight Now. Retrieved 2 February 2020.
- ^ Watanabe, Susan (22 November 2007). "Studying the Universe in Infrared". NASA. Archived from the original on 7 July 2019. Retrieved 8 December 2007. This article incorporates text from this source, which is in the public domain.
- ^ Kwok, Johnny (Fall 2006). "Finding a Way: The Spitzer Space Telescope Story". Academy Sharing Knowledge. NASA. Archived from the original on 8 September 2007. Retrieved 9 December 2007. This article incorporates text from this source, which is in the public domain.
- ^ Note: Gamma-rays from space can be detected indirectly from the ground by a technique known as Imaging Air Cherenkov Technique or IACT for short. It was pioneered by the Whipple Observatory in 1968 and several newer telescopes have been built in various countries since then.
- ^ "Hubble Team Breaks Cosmic Distance Record". Spitzer Space Telescope. NASA. 3 March 2016. Retrieved 14 December 2016. This article incorporates text from this source, which is in the public domain.}
- ^ Landau, Elizabeth (25 August 2016). "Spitzer Space Telescope Begins "Beyond" Phase". NASA. Retrieved 9 December 2016. This article incorporates text from this source, which is in the public domain.
- ^ "About the James Webb Space Telescope". Goddard Space Flight Center. NASA. Retrieved 20 December 2018. This article incorporates text from this source, which is in the public domain.
- ^ "NASA's Shuttle and Rocket Missions — Launch Schedule". NASA. 5 June 2008. This article incorporates text from this source, which is in the public domain.
- ^ "Great Observatories". Beyond Einstein. NASA. Archived from the original on 3 November 2007. Retrieved 28 November 2007. This article incorporates text from this source, which is in the public domain.
- ^ Acuña, Mario H.; Keith W. Ogilvie; Robert A. Hoffman; Donald H. Fairfield; Steven A. Curtis; James L. Green; William H. Mish; the GGS Science Teams (1 May 1997). "The GGS Program". ISTP-GGS/SOLARMAX Proposal. Goddard Space Flight Center. Retrieved 3 December 2007. This article incorporates text from this source, which is in the public domain.
- ^ a b Scoles, Sarah (30 March 2016). "NASA Considers Its Next Flagship Space Telescope". Scientific American. Retrieved 15 October 2017.
Further reading
- Armus, L.; et al. (2021). "Great Observatories: The Past and Future of Panchromatic Astrophysics". arXiv:2104.00023 [astro-ph.IM].
External links
- "Preflight Videos (STS-93)". NASA. 9 April 2002. Archived from the original on 9 December 2007. Retrieved 27 November 2007.
A detailed description of NASA's Great Observatories, including STS-93 primary payload, the Chandra X-ray Observatory
- STS-125: Final Shuttle Mission to Hubble Space Telescope Archived 16 July 2015 at the Wayback Machine
- Great Observatories Interactive using WorldWide Telescope