LAMOST
The Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST), also known as the Guo Shoujing Telescope (Chinese: 郭守敬望远镜) after the 13th-century Chinese astronomer,[1] is a meridian reflecting Schmidt telescope, located in Xinglong Station, Hebei Province, China. Undertaken by the Chinese Academy of Science, the telescope is planned to conduct a 5-year spectroscopic survey of 10 million Milky Way stars, as well as millions of galaxies. The project's budget is RMB 235 million yuan.
 The LAMOST telescope | |
| Part of | Xinglong Station  |
|---|---|
| Location(s) | People's Republic of China |
| Coordinates | 40°23′45″N 117°34′33″E |
| Altitude | 960 m (3,150 ft) |
| Wavelength | 370 nm (810 THz)-900 nm (330 THz) |
| Built | September 2001–October 2008 |
| Telescope style | optical telescope Schmidt camera |
| Diameter | 4 m (13 ft 1 in) |
| Secondary diameter | 6 m (19 ft 8 in) |
| Collecting area | 18.86 m2 (203.0 sq ft) |
| Focal length | 20 m (65 ft 7 in) |
  Location of LAMOST | |
 Related media on Wikimedia Commons | |
Optics
LAMOST is configured as a reflective Schmidt telescope with active optics. There are two mirrors, each made up of a number of 1.1-metre (p-p) hexagonal deformable segments. The first mirror, MA (24 segments, fitting in a 5.72×4.4 m rectangle) is a Schmidt corrector plate in a dome at ground level.[2] The almost-flat mirror MA reflects the light to the south, up a large slanted tunnel (25° above horizontal) to the larger spherical focusing mirror MB (37 segments, fitting in a 6.67×6.09 m rectangle). This directs light to a focal plane 1.75 metres in diameter corresponding to a five-degree field of view. The focal plane is tiled with 4000 fibre-positioning units, each feeding an optical fibre which transfers light to one of sixteen 250-channel spectrographs below.
Looking at the image opposite, MB is at the top of the left-hand supporting column of the tower, MA is in the left of the two domes at the right of the image (the rightmost, grey dome is an unrelated telescope), and the spectrographs are inside the right-hand column of the tower.
Each spectrograph has two 4k×4k CCD cameras, using e2v CCD chips, with 'blue' (370–590 nm) and 'red' (570–900 nm) sides; the telescope can also be used in a higher spectral resolution mode where the range is 510–540 and 830–890 nm.[2]
Using active optics technique to control its reflecting corrector makes it a unique astronomical instrument in combining large aperture with wide field of view. The available large focal plane may accommodate up to thousands of fibers, by which the collected light of distant and faint celestial objects down to 20.5 magnitude is fed into the spectrographs, promising a very high spectrum acquiring rate of ten-thousands of spectra per night.
Scientific goals
The telescope is to conduct a wide-field survey, called the "LAMOST Experiment for Galactic Understanding and Evolution," or LEGUE. Particular scientific goals of the LAMOST include:
- An extra-galactic spectroscopic survey to shed light on the large scale structure of the universe
- A stellar spectroscopic survey, including a search for metal-poor stars in the galactic halo, to provide information on the structure of our Galaxy
- Cross-identification of multi-waveband surveys
It is also hoped that the vast volume of data produced will lead to additional serendipitous discoveries. Early commissioning observations have been able to confirm spectroscopically a new method of identifying quasars based on their infrared color.[3] An overarching goal of the telescope is to bring Chinese astronomy into the 21st century, taking a leading role in wide-field spectroscopy and in the fields of large-scale and large-sample astronomy and astrophysics.
Early results
A 2011 conference presentation [4]:10–12 suggests that there was initially a problem with accuracy of the fibre positioners causing poor throughput, but that this was rectified by adding another calibration step.
The same presentation also points out that the telescope's location, only 115 km (71 mi) NW of Beijing,[4]:9 is far from ideal, being in an area with high levels of both atmospheric and light pollution. The telescope has generally been disappointing,[5] with the site receiving only 120 clear nights per year.[6]
References
- “郭守敬望远镜”冠名仪式在国家天文台兴隆观测站举行 (Guo Shoujing Telescope naming ceremony held at Xinglong Station, BAO) (in Chinese), National Astronomical Observatory of China (BAO), 2010-04-20.
- Yongheng ZHAO (2009-03-27). "Preparing first light of LAMOST" (PDF).
- Xue-Bing Wu; Zhendong Jia; Zhaoyu Chen; Wenwen Zuo; Yongheng Zhao; Ali Luo; Zhongrui Bai; Jianjun Chen; Haotong Zhang (2010). "Eight new quasars discovered by LAMOST in one extragalactic field". Research in Astronomy and Astrophysics. 10 (8): 745–752. arXiv:1006.0143. Bibcode:2010RAA....10..745W. doi:10.1088/1674-4527/10/8/004. S2CID 118606164.
- Martin Smith (2011-06-04). "Progress and plans for Chinese surveys" (PDF).
- Huang, Yongming (11 August 2017). "Spat over design of new Chinese telescope goes public". News from Science.
Chen, an astronomer at Peking University in Beijing, notes ... LAMOST 'is not very successful,' he adds ... its performance doesn’t match that of the 2.5-meter Sloan Digital Sky Survey telescope at Apache Point Observatory in New Mexico.
- Normile, Dennis (14 June 2017). "Spat threatens China's plans to build world's largest telescope". News from Science.
They note that LAMOST has fallen short of its primary goal: observing faint galaxies beyond the Milky Way. [Xiangqun] Cui says the issue is not with the telescope, but with increasing dust and humidity at the site, which now gets only 120 clear nights a year, down from more than 200 when LAMOST was being planned.