Wikipedia

Multi-Object Spectrometer

A multi-object spectrometer is a type of optical spectrometer capable of simultaneously acquiring the spectra of multiple separate objects in its field of view.[1] It is used in astronomical spectroscopy and is related to long-slit spectroscopy.[2] This technique became available in the 1980s.[3]

Basic principle of multi-object spectroscopy
Basic principle of multi-object spectroscopy

Description

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The term multi-object spectrograph is commonly used for spectrographs using a bundle of fibers to image part of the field. The entrance of the fibers is at the focal plane of the imaging instrument. The bundle is then reshaped; the individual fibers are aligned at the entrance slit of a spectrometer, dispersing the light on a detector.[1]

This technique is closely related to integral field spectrography (IFS), more specifically to fiber-IFS. It is a form of snapshot hyperspectral imaging, itself a part of imaging spectroscopy.

Apertures

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External image
  Photographs of the Configurable Slit Unit on MOSFIRE Left: full picture, in a configuration for imaging. Right: close-up on the knife-edge slits.[4][5]

Typically, the apertures of multi-object spectrographs can be modified to fit the needs of the given observation.[6]

For example, the MOSFIRE (Multi-Object Spectrometer for Infra-Red Exploration )[7] instrument on the W. M. Keck Observatory contains the Configurable Slit Unit (CSU)[8] allowing arbitrary positioning of up to forty-six 18 cm slits by moving opposable bars.[5]

Some fiber-fed spectroscopes, such as the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) can move the fibers to desired position. The LAMOST moves its 4000 fibers separately within designated areas for the requirements of a measurement, and can correct positioning errors in real time.[9]

The James Webb Space Telescope uses a fixed Micro-Shutter Assembly (MSA), an array of nearly 250000 5.1 mm by 11.7 mm shutters that can independently be opened or closed to change the ___location of the open slits on the device.[10]

Uses in telescopes

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Ground-based instruments

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Instruments with multi-object spectrometry capabilities are available on most 8-10 meter-class ground-based observatories.[6] For example, the Large Binocular Telescope,[11] W. M. Keck Observatory,[12] Gran Telescopio Canarias,[13] Gemini Observatory,[14] New Technology Telescope,[15] William Herschel Telescope,[16] UK Schmidt Telescope[17] and LAMOST[3] include such system.

Four instruments in the Very Large Telescope, including the KMOS (K-band multi-object spectrograph)[18] and the VIMOS (Visible Multi Object Spectrograph)[19] instruments, have multi-object spectroscopic capabilities.

Space-based instruments

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The Hubble Space Telescope has been operating the NICMOS (Near Infrared Camera and Multi-Object Spectrometer)[20] from 1997 to 1999 and from 2002 to 2008.

The James Webb Space Telescope's NIRSpec (Near-Infrared Spectrograph) instrument is a multi-object spectrometer.[21]

References

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  1. ^ a b "multi-object spectrograph". astro.vaporia.com. Retrieved 2023-08-07.
  2. ^ "Multi Object Spectroscopy (decommissioned)". eso.org. European Southern Observatory. Retrieved 2023-08-07.
  3. ^ a b Chu, Yaoquan. The Large Sky Area Multi-Object Fibre Spectroscopy Telescope ( LAMOST) Project. Conference of the Working Group of IAU Commission 9 on “Wide-Field Imaging” held in Athens, Greece, May 20–25, 1996. Springer Dordrecht. doi:10.1007/978-94-011-5722-3_9.
  4. ^ Goodrich, Bob; Adkins, Sean (2011). "The Imminent Arrival of MOSFIRE, Keck's New Infrared, Multi-Object, Imaging Spectrograph". Keck Observers' Newsletter (10).
  5. ^ a b McLean, Ian S.; Steidel, Charles C.; Harland, Epps; Matthews, Keith; Adkins, Sean; Konidaris, Nicholas; Weber, Bob; Aliado, Ted; Brims, George; Canfield, John; Cromer, John; Fucik, Jason; Kulas, Kristin; Mace, Greg; Magnone, Ken; Rodriguez, Hector; Wang, Eric; Weiss, Jason (2010-07-20). McLean, Ian S.; Ramsay, Suzanne K.; Takami, Hideki (eds.). "Design and development of MOSFIRE: the multi-object spectrometer for infrared exploration at the Keck Observatory" (PDF). SPIE Conference Proceedings. Ground-based and Airborne Instrumentation for Astronomy III. 7735. SPIE: 77351E. Bibcode:2010SPIE.7735E..1EM. doi:10.1117/12.856715. S2CID 122823326.
  6. ^ a b "JWST Multi-Object Spectroscopy". JWST User Documentation. 2022-10-17. Retrieved 2023-08-07.
  7. ^ "MOSFIRE Home Page". www2.keck.hawaii.edu. 2020-10-07. Retrieved 2023-08-07.
  8. ^ "Multi-Object Spectrometer for Infra-Red Exploration First Light Obtained: April 4, 2012". irlab.astro.ucla.edu. Retrieved 2023-08-07.
  9. ^ "Fiber positioning". lamost.org. 2012-08-14. Retrieved 2023-08-07.
  10. ^ "NIRSpec Micro-Shutter Assembly". jwst-docs.stsci.edu. 2023-04-24. Retrieved 2023-08-07.
  11. ^ "Instruments - an overview". Large Binocular Telescope Observatory. Retrieved 2023-08-07.
  12. ^ "Keck I And Keck II Telescopes". W. M. Keck Observatory. Retrieved 2023-08-07.
  13. ^ "MEGARA". Gran Telescopio CANARIAS. 2023-05-08. Retrieved 2023-08-07.
  14. ^ "The GMOS (Gemini Multi-Object Spectrograph) project at the ATC". 2003-09-12. Retrieved 2023-08-07.
  15. ^ "EFOSC Overview". eso.org. European Southern Observatory. Retrieved 2023-08-07.
  16. ^ "WEAVE - instrumental overview". ing.iac.es. 2023-07-05. Retrieved 2023-08-07.
  17. ^ "The UK Schmidt Telescope". aat.anu.edu.au. 21 May 2014. Retrieved 2023-08-07.
  18. ^ "KMOS - K-band Multi Object Spectrograph". eso.org. European Southern Observatory. Retrieved 2023-08-07.
  19. ^ "VIMOS - VIsible MultiObject Spectrograph". eso.org. European Southern Observatory. Retrieved 2023-08-07.
  20. ^ "Hubble's Instruments: NICMOS - Near Infrared Camera and Multi-Object Spectrometer". esahubble.org. Retrieved 2023-08-07.
  21. ^ "NIRSpec Multi-Object Spectroscopy". JWST User Documentation. 2023-04-24. Retrieved 2023-08-07.
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