Large Synoptic Survey Telescope
Encyclopedia
The Large Synoptic Survey Telescope (LSST) is a planned wide-field "survey" reflecting
telescope
that will photograph the available sky every three nights. The LSST is currently in its design and development phase and will achieve engineering first light four years after construction starts. Full science operations for the ten-year survey will begin two years after that, toward the end of the decade.
The telescope will be located on the El Peñón peak of Cerro Pachón
, a 2682 metre high mountain in Coquimbo Region
, in northern Chile
, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.
and Moon
, as seen from the Earth
, are 0.5 degrees across, or 0.2 square degrees. Combined with its large aperture (and thus light-collecting ability), this will give it a spectacularly large etendue
of 319 m²degree².
To achieve this very wide undistorted field of view requires three mirrors, rather than the two used by most existing large telescopes: the primary mirror will be 8.4 meters in diameter, the secondary mirror will be 3.4 metres in diameter, and the tertiary mirror, located in a large hole in the primary, will be 5.0 metres in diameter. The large hole reduces the primary mirror's light collecting area to 35 m², equivalent to a 6.68 m diameter circle. (Multiplying this by the field of view produces an etendue of 336 m²degree²; the actual figure is reduced by vignetting
.)
The primary and tertiary mirrors are being constructed as a single piece of glass, the "M1M3 monolith".
A 3.2 gigapixel prime focus digital camera will take a 15-second exposure every 20 seconds.
Allowing for maintenance, bad weather, etc., the camera is expected to take over 200,000 pictures (1.28 petabyte
s uncompressed) per year, far more than can be reviewed by humans. Managing and effectively data mining
the enormous output of the telescope is expected to be the most technically difficult part of the project. Initial computer requirements are estimated at 100 teraflops of computing power and 15 petabyte
s of storage, rising as the project collects data.
It is also hoped that the vast volume of data produced will lead to additional serendipitous discoveries.
Synoptic
is an adjective from the same root as the noun "synopsis", and means "relating to data obtained nearly simultaneously over a large area."
Some of the data from the LSST (up to 30 Terabytes per night) will be made available by Google
as an up-to-date interactive night-sky map.
and Bill Gates
pledged $20 million and $10 million respectively to the project. The project continues to seek a National Science Foundation
grant of nearly $400 million.
The LSST was greatly encouraged by its selection as the highest-priority ground-based instrument in the 2010 Astronomy and Astrophysics Decadal Survey
Construction of the primary mirror, the most critical and time-consuming part of a large telescope's construction, is already well underway. The M1M3 monolith is being constructed at the University of Arizona
's Steward Observatory
Mirror Lab. Construction of the mold began in November 2007, mirror casting was begun in March 2008, and the mirror blank was declared "perfect" at the beginning of September 2008. , both M1 and M3 figures have been generated, and fine grinding is pending.
The secondary mirror blank has been constructed and coarse-ground to within 40 μm of the desired shape. It is in storage awaiting funding to complete it.
Site excavation began in earnest March 8, 2011, and a construction progress website maintains two webcams showing live construction progress.
Reflecting telescope
A reflecting telescope is an optical telescope which uses a single or combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century as an alternative to the refracting telescope which, at that time, was a design that suffered from...
telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
that will photograph the available sky every three nights. The LSST is currently in its design and development phase and will achieve engineering first light four years after construction starts. Full science operations for the ten-year survey will begin two years after that, toward the end of the decade.
The telescope will be located on the El Peñón peak of Cerro Pachón
Cerro Pachón
Cerro Pachón is a mountain located close to Chilean city of Vicuña and 10 km southeast of the Cerro Tololo Inter-American Observatory, at an altitude of 2,715 m over the sea level in the foothills of the Andes. The location is exceedingly dry, making it suitable for infrared observations....
, a 2682 metre high mountain in Coquimbo Region
Coquimbo Region
The IV Coquimbo Region is one of Chile's 15 first order administrative divisions. It is some 400 km north of the capital, Santiago.The capital and largest city is La Serena, other important cities include the seaport Coquimbo and the agricultural centre...
, in northern Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.
Overview
The LSST design is unique among large telescopes (8m-class primary mirrors) in having a very wide field of view: 3.5 degrees in diameter, or 9.6 square degrees. For comparison, both the SunSun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
and Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
, as seen from the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
, are 0.5 degrees across, or 0.2 square degrees. Combined with its large aperture (and thus light-collecting ability), this will give it a spectacularly large etendue
Etendue
Etendue or étendue is a property of pencils of rays in an optical system, which characterizes how "spread out" light is in area and angle. It may also be seen as a volume in phase space....
of 319 m²degree².
To achieve this very wide undistorted field of view requires three mirrors, rather than the two used by most existing large telescopes: the primary mirror will be 8.4 meters in diameter, the secondary mirror will be 3.4 metres in diameter, and the tertiary mirror, located in a large hole in the primary, will be 5.0 metres in diameter. The large hole reduces the primary mirror's light collecting area to 35 m², equivalent to a 6.68 m diameter circle. (Multiplying this by the field of view produces an etendue of 336 m²degree²; the actual figure is reduced by vignetting
Vignetting
In photography and optics, vignetting is a reduction of an image's brightness or saturation at the periphery compared to the image center. The word vignette, from the same root as vine, originally referred to a decorative border in a book. Later, the word came to be used for a photographic...
.)
The primary and tertiary mirrors are being constructed as a single piece of glass, the "M1M3 monolith".
A 3.2 gigapixel prime focus digital camera will take a 15-second exposure every 20 seconds.
Allowing for maintenance, bad weather, etc., the camera is expected to take over 200,000 pictures (1.28 petabyte
Petabyte
A petabyte is a unit of information equal to one quadrillion bytes, or 1000 terabytes. The unit symbol for the petabyte is PB...
s uncompressed) per year, far more than can be reviewed by humans. Managing and effectively data mining
Data mining
Data mining , a relatively young and interdisciplinary field of computer science is the process of discovering new patterns from large data sets involving methods at the intersection of artificial intelligence, machine learning, statistics and database systems...
the enormous output of the telescope is expected to be the most technically difficult part of the project. Initial computer requirements are estimated at 100 teraflops of computing power and 15 petabyte
Petabyte
A petabyte is a unit of information equal to one quadrillion bytes, or 1000 terabytes. The unit symbol for the petabyte is PB...
s of storage, rising as the project collects data.
Scientific goals
Particular scientific goals of the LSST include:- Measuring weak gravitational lensingWeak gravitational lensingWhile the presence of any mass bends the path of light passing near it, this effect rarely produces the giant arcs and multiple images associated with strong gravitational lensing. Most lines of sight in the universe are thoroughly in the weak lensing regime, in which the deflection is impossible...
in the deep sky to detect signatures of dark energyDark energyIn physical cosmology, astronomy and celestial mechanics, dark energy is a hypothetical form of energy that permeates all of space and tends to accelerate the expansion of the universe. Dark energy is the most accepted theory to explain recent observations that the universe appears to be expanding...
and dark matterDark matterIn astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly detected via optical or radio astronomy...
. - Mapping small objects in the solar system, particularly near-Earth asteroids and Kuiper beltKuiper beltThe Kuiper belt , sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune to approximately 50 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20 to 200 times as massive...
objects. - Detecting transient optical events such as novaNovaA nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
e and supernovaSupernovaA supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
e. - Mapping the Milky WayMilky WayThe Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
.
It is also hoped that the vast volume of data produced will lead to additional serendipitous discoveries.
Synoptic
Synoptic
Synoptic is derived from the Greek words σύν and ὄψις , and describes observations that give a broad view of a subject at a particular time. Specific uses include:*Synoptic scale meteorology*Synoptic Gospels*SynOptics...
is an adjective from the same root as the noun "synopsis", and means "relating to data obtained nearly simultaneously over a large area."
Some of the data from the LSST (up to 30 Terabytes per night) will be made available by Google
Google
Google Inc. is an American multinational public corporation invested in Internet search, cloud computing, and advertising technologies. Google hosts and develops a number of Internet-based services and products, and generates profit primarily from advertising through its AdWords program...
as an up-to-date interactive night-sky map.
Construction progress
In January, 2008 software billionaires Charles SimonyiCharles Simonyi
Charles Simonyi is a Hungarian-American computer software executive who, as head of Microsoft's application software group, oversaw the creation of Microsoft's flagship Office suite of applications. He now heads his own company, Intentional Software, with the aim of developing and marketing his...
and Bill Gates
Bill Gates
William Henry "Bill" Gates III is an American business magnate, investor, philanthropist, and author. Gates is the former CEO and current chairman of Microsoft, the software company he founded with Paul Allen...
pledged $20 million and $10 million respectively to the project. The project continues to seek a National Science Foundation
National Science Foundation
The National Science Foundation is a United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National Institutes of Health...
grant of nearly $400 million.
The LSST was greatly encouraged by its selection as the highest-priority ground-based instrument in the 2010 Astronomy and Astrophysics Decadal Survey
Construction of the primary mirror, the most critical and time-consuming part of a large telescope's construction, is already well underway. The M1M3 monolith is being constructed at the University of Arizona
University of Arizona
The University of Arizona is a land-grant and space-grant public institution of higher education and research located in Tucson, Arizona, United States. The University of Arizona was the first university in the state of Arizona, founded in 1885...
's Steward Observatory
Steward Observatory
The University of Arizona's Steward Observatorys main office is located on the University's campus and is closely tied to the Department of Astronomy. Established in 1916 by its first director, Andrew Ellicott Douglass, and a $60,000 bequest made by Lavinia Steward in memory of her late husband...
Mirror Lab. Construction of the mold began in November 2007, mirror casting was begun in March 2008, and the mirror blank was declared "perfect" at the beginning of September 2008. , both M1 and M3 figures have been generated, and fine grinding is pending.
The secondary mirror blank has been constructed and coarse-ground to within 40 μm of the desired shape. It is in storage awaiting funding to complete it.
Site excavation began in earnest March 8, 2011, and a construction progress website maintains two webcams showing live construction progress.
See also
- Pan-STARRSPan-STARRSThe Panoramic Survey Telescope and Rapid Response System is a planned array of astronomical cameras and telescopes and computing facility that will survey the sky on a continual basis, including accurate astrometry and photometry of detected objects...
- List of largest optical reflecting telescopes
- VLT Survey TelescopeVLT Survey TelescopeThe VLT Survey Telescope is the latest telescope to be added to ESO’s Paranal Observatory in the Atacama Desert of northern Chile. It is housed in an enclosure immediately adjacent to the four Very Large Telescope Unit Telescopes on the summit of Cerro Paranal. The VST is a wide-field survey...
External links
- Official home page
- LSST reports and documentation
- Science & Technology brief
- New Scientist SPACE Article
- LSST Tutorials for Experimental Particle Physicists is a detailed explanation of LSST's design (as of February 2006) and weak lensing science goals that does not assume a lot of astronomy background.
- The New Digital Sky is a video of a July 25, 2006 presentation at GoogleGoogleGoogle Inc. is an American multinational public corporation invested in Internet search, cloud computing, and advertising technologies. Google hosts and develops a number of Internet-based services and products, and generates profit primarily from advertising through its AdWords program...
about the LSST, particularly the data management issues. - HULIQ Google participation announcement, this is a comprehensive overview of the LSST., an updated and expanded overview.