Large Synoptic Survey Telescope

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"LSST" redirects here. For the Lincolnshire School of Science and Technology, see The Priory LSST.
Large Synoptic Survey Telescope
Organization LSST Corporation
Location(s) El Peñón, Chile

30°14′40.7″S 70°44′57.9″W / 30.244639°S 70.749417°W / -30.244639; -70.749417Coordinates: 30°14′40.7″S 70°44′57.9″W / 30.244639°S 70.749417°W / -30.244639; -70.749417

Altitude 2,663 m (8,737 ft), top of pier[1][4]
Wavelength 320–1060 nm[5]
Built 2014–2019 (planned)
First light 2019[6]
Telescope style Three-mirror anastigmat, Paul-Baker / Mersenne-Schmidt wide-angle[7]
Diameter 8.360 m (5.116 m inner)
(27.43 ft [16.78 ft inner])[8]
Secondary dia. 3.420 m (1.800 m inner)[8]
Tertiary dia. 5.016 m (1.100 m inner)[8]
Angular resolution 0.7″ median seeing limit
0.2″ pixel size[5]
Collecting area 35 square metres (376.7 sq ft)[5]
Focal length 10.31 m (f/1.23) overall
9.9175 m (f/1.186) primary
Mounting altitude/azimuth
Commons page Related media on Wikimedia Commons

The Large Synoptic Survey Telescope (LSST) is a wide-field survey reflecting telescope under construction that will photograph the entire available sky every few nights.[9] Site construction began on April 14, 2015,[10] with engineering first light anticipated in 2019, science first light in 2021, and full operations for a ten-year survey commencing in January 2022.[11][12]

The telescope is 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.[13]

On July 18, 2012, with approval of the US National Science Board, the National Science Foundation (NSF) announced its intention to advance the LSST to the final design stage.[14] This action permits the NSF Director to include funds for LSST construction in a future budget request.

The project officially began construction 1 August 2014 when the NSF authorized the FY2014 portion ($27.5M) of its construction budget.[15] The ceremonial laying of the first stone was performed on 14 April 2015.[16]


Comparison of nominal sizes of primary mirrors of the Large synoptic Survey Telescope (the light-green ring with the large center opening near the center of the diagram) and some notable optical telescopes (click for detail)

The LSST design is unique among large telescopes (8 m-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 Sun and the Moon, as seen from 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 m2∙degree2.[5]

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 (M1) will be 8.4 metres (28 ft) in diameter, the secondary mirror (M2) will be 3.4 metres (11.2 ft) in diameter, and the tertiary mirror (M3), located in a large hole in the primary, will be 5.0 metres (16 ft) in diameter. The large hole reduces the primary mirror's light collecting area to 35 square metres (376.7 sq ft), equivalent to a 6.68-metre-diameter (21.9 ft) circle.[5] (Multiplying this by the field of view produces an etendue of 336 m2∙degree2; the actual figure is reduced by vignetting.)

The primary and tertiary mirrors (M1 and M3) are being constructed as a single piece of glass, the "M1M3 monolith".

A 3.2-gigapixel prime focus[note 1] digital camera will take a 15-second exposure every 20 seconds.[5] Repointing such a large telescope (including settling time) within 5 seconds requires an exceptionally short and stiff structure. This in turn implies a very small f-number, which requires very precise focusing of the camera.

Allowing for maintenance, bad weather and other contingencies, the camera is expected to take over 200,000 pictures (1.28 petabytes 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.[17][18] Initial computer requirements are estimated at 100 teraflops of computing power and 15 petabytes of storage, rising as the project collects data.[19]

Scientific goals[edit]

Particular scientific goals of the LSST include:

It is also hoped that the vast volume of data produced will lead to additional serendipitous discoveries.

Synoptic is derived from the Greek words σύν (syn "together") and ὄψις (opsis "view"), and describes observations that give a broad view of a subject at a particular time.

Some of the data from the LSST (up to 30 terabytes per night[17]) will be made available by Google as an up-to-date interactive night-sky map.[20]

Construction progress[edit]

LSST construction is underway, with the NSF funding authorized as of 1 August 2014.[15]

Early development was funded by a number of small grants, with major contributions in January 2008 by software billionaires Charles Simonyi and Bill Gates of $20 and $10 million respectively.[21] $7.5 million is included in the U.S. President's FY2013 NSF budget request.[22] The Department of Energy is expected to fund construction of the digital camera component by the SLAC National Accelerator Laboratory, as part of its mission to understand dark energy.[23]

The LSST was greatly encouraged by its selection as the highest-priority ground-based instrument in the 2010 Astronomy and Astrophysics Decadal Survey.[24]

The primary mirror, the most critical and time-consuming part of a large telescope's construction, was made over a 7-year period by the University of Arizona's Steward Observatory Mirror Lab.[25] Construction of the mold began in November 2007,[26] mirror casting was begun in March 2008,[27] and the mirror blank was declared "perfect" at the beginning of September 2008.[28] In January 2011, both M1 and M3 figures had completed generation and fine grinding, and polishing had begun on M3.

The mirror was completed in December 2014[29] and, after testing, formally accepted on 13 February 2015.[30] It was then placed in the mirror transport box and stored in an airplane hangar[31] until it is shipped to Chile.[32]

The secondary mirror was manufactured by Corning of ultra low expansion glass and coarse-ground to within 40 μm of the desired shape.[3] In November 2009, the blank was shipped to Harvard University for storage[33] until funding to complete it was available. On October 21, 2014, the secondary mirror blank was delivered from Harvard to Exelis for fine grinding.[34]

Site excavation began in earnest March 8, 2011,[35] and the site had been leveled by the end of 2011.[36] Also during that time, the design continued to evolve, with significant improvements to the mirror support system, stray-light baffles, wind screen, and calibration screen.

In November 2014, the LSST camera project, which is separately funded by the Energy Department, passed its "critical decision 2" design review and is progressing toward full funding.[37]


  1. ^ The camera is actually at the tertiary focus, not the prime focus, but being located at a "trapped focus" in front of the primary mirror, the associated technical problems are similar to those of a conventional prime-focus survey camera.

See also[edit]


  1. ^ a b Eric E. Mamajek (2012-10-10), Accurate Geodetic Coordinates for Observatories on Cerro Tololo and Cerro Pachon, p. 13, retrieved 2012-10-12  Measured GPS position for future site of LSST pier is WGS84 30°14′40.68″S, 70°44′57.90″W, with ±0.10" uncertainty in each coordinate.
  2. ^ Charles F. Claver et al. (2007-03-19), LSST Reference Design (PDF), LSST Corporation, pp. 64–65, retrieved 2008-12-10  The map on p. 64 shows the Universal Transverse Mercator location of the centre of the telescope pier at approximately 6653188.9 N, 331859.5 E, in zone 19J. However, those UTM coordinates appear to be using the PSAD56 (La Canoa) datum, as other assumptions do not lead to a peak. This is apparently widely used in South American UTM grids. The coordinates above translate to WGS84 30°14′39.6″S 70°44′57.8″W / 30.244333°S 70.749389°W / -30.244333; -70.749389.
  3. ^ a b Victor Krabbendam et al. (2011-01-11). "LSST Telescope and Optics Status" (PDF). American Astronomical Society 217th Meeting (poster). Seattle, Washington. Retrieved 2011-01-16.  This updated plan shows the revised telescope centre at 6653188.0 N, 331859.1 E (PSAD56 datum). This is the same WGS84 location to the resolution shown.
  4. ^ LSST Summit Facilities, 2009-08-14, retrieved 2009-08-21 
  5. ^ a b c d e f LSST Basic Configuration, LSST Corporation, retrieved 2008-01-28 
  6. ^
  7. ^ Willstrop, R. V. (October 1, 1984), "The Mersenne-Schmidt: A three-mirror survey telescope", Monthly Notices of the Royal Astronomical Society 210 (3): 597–609, Bibcode:1984MNRAS.210..597W, doi:10.1093/mnras/210.3.597, ISSN 0035-8711, retrieved 2008-01-23 
  8. ^ a b c Gressler, William (June 2, 2009), LSST Optical Design Summary (PDF), LSE-11, retrieved 2011-03-01 
  9. ^ LSST Observatory - FAQ
  10. ^ "The Large Synoptic Survey Telescope: Unlocking the secrets of dark matter and dark energy". May 29, 2015. Retrieved 3 June 2015. 
  11. ^ LSST Timeline
  12. ^ Krabbendam, Victor (2012-08-13), "LSST Project and Technical Overview", LSST All Hands Meeting (PDF), Tucson, Arizona, retrieved 2012-09-05 
  13. ^ Press Release LSSTC-04: Site in Northern Chile Selected for Large Synoptic Survey Telescope
  14. ^ NSF Press Release 12-137
  15. ^ a b Kahn, Steven; Krabbendam, Victor (August 2014). "LSST Construction Authorization" (Press release). Lsst Corp. 
  16. ^ "LSST First Stone" (Press release). LSST Corporation. 14 April 2015. 
  17. ^ a b Matt Stephens (2008-10-03), Mapping the universe at 30 Terabytes a night: Jeff Kantor, on building and managing a 150 Petabyte database, The Register, retrieved 2008-10-03 
  18. ^ Matt Stephens (2010-11-26), Petabyte-chomping big sky telescope sucks down baby code, The Register, retrieved 2011-01-16 
  19. ^ Boon, Miriam (2010-10-18), "Astronomical Computing", Symmetry Breaking, retrieved 2010-10-26 
  20. ^ "Google Joins Large Synoptic Survey Telescope (LSST) Project". January 10, 2007. Retrieved 29 April 2013.
  21. ^ Dennis Overbye (January 3, 2008). "Donors Bring Big Telescope a Step Closer". The New York Times. Retrieved 2008-01-03. 
  22. ^ "LSST Project Office Update". March 2012. Retrieved 2012-04-07. 
  23. ^ "World’s largest digital camera gets green light". 2011-11-08. Retrieved 2012-04-07. /
  24. ^ Large Synoptic Survey Telescope gets Top Ranking, "a Treasure Trove of Discovery", LSST Corporation, 2010-08-16, retrieved 2011-01-16 
  25. ^ Steward Observatory Mirror Lab Awarded Contract for Large Synoptic Survey Telescope Mirror
  26. ^ LSST Observatory - Site Photos
  27. ^ LSST High Fire Event
  28. ^ Giant Furnace Opens to Reveal 'Perfect' LSST Mirror Blank (PDF), LSST Corporation, 2009-09-02, retrieved 2011-01-16 
  29. ^ (December 2014). "LSST E-News - Volume 7 Number 4". Retrieved 2014-12-06. 
  30. ^ (April 2015). "M1M3 Milestone Achieved". LSST E-News 8 (1). Retrieved 2015-05-04. 
  31. ^ Beal, Tom (28 February 2015). "Big mirror about to move from UA lab". Arisona Daily Star. Retrieved 2015-05-04. 
  32. ^ Jepsen, Kathryn (January 12, 2015). "Mirror, mirror: After more than six years of grinding and polishing, the first-ever dual-surface mirror for a major telescope is complete". Symmetry. Retrieved 2015-02-01. 
  33. ^ "LSST M2 Substrate Complete and Shipped", LSST E-News 2 (4), January 2010 
  34. ^ "LSST M2 Substrate Received by Exelis", LSST E-News 7 (4), December 2014 
  35. ^ Cerro Pachón First Blast, LSST Corporation, March 8, 2011, retrieved 2011-04-23, ‘First Blast’, detonated on the El Peñón summit March 8th at 8:56:00 (MST) in preparation for the LSST 
  36. ^ Victor Krabbendam et al. (2012-01-09). "Developments in Telescope and Site" (PDF). American Astronomical Society 219th Meeting (poster). Austin, Texas. Retrieved 2012-01-16. 
  37. ^ "Successful DOE CD-2 Review for the LSST Camera!", LSST E-News 7 (4), December 2014 

External links[edit]