Gemini Multi-Object Spectrograph (GMOS)

Gemini Instrument Support Structure + instruments

The back end of the Gemini North telescope, tilted down, showing the suite of scientific instruments mounted on the Instrument Support Structure (ISS). GMOS is on the right-hand port. 

The GMOS instruments include GMOS-N at the Gemini North telescope on Maunakea in Hawai‘i and GMOS-S at Gemini South on Cerro Pachón in Chile. Their construction was a collaboration between the Astronomy Technology Centre at the Royal Observatory Edinburgh and the University of Durham in the UK, and the Herzberg Institute of Astrophysics in Canada. They are the International Gemini Observatory’s twin workhorse instruments for observations at visible wavelengths. They can be used as either a spectrograph or an imager. While there are slight differences, the information here applies to both instruments. 

GMOS instruments detect light in the 0.36–1.03 micrometer wavelength range and operate in four modes: three spectroscopic modes — long slit mode, multi-object mode, which captures spectra from many objects simultaneously, integral field spectroscopy mode, which collects spectra from a two-dimensional area of the sky — and an imaging mode. This versatility allows for a wide range of astronomical observations.

The mechanical system is designed to minimize tilts between optical components so that the only effect of flexure is a slow motion of the detector perpendicular to the optical path. This allows the detector to simply be repositioned to compensate for any warping of the instrument due to gravity in real time, keeping the images as sharp as possible.

More on GMOS.

Image: The Gemini Multi-Object Spectrographs (GMOS) mounted on Gemini South on Cerro Pachón in Chile.

The Gemini Multi-Object Spectrograph (GMOS) mounted on Gemini South on Cerro Pachón in Chile.
Credit: CTIO/NOIRLab/NSF/AURA/D. Munizaga

Science Highlights of GMOS-N

Science Highlights of GMOS-S

Quick Facts

  • GMOS-N was delivered in July 2001 and its twin, GMOS-S, was delivered in December 2002.
  • Because GMOS-N and GMOS-S are so similar, the choice between them is usually based on which one can see the target best at the time of observation.
  • Hundreds of objects can fit in a single multi-slit mask image, though a typical galaxy survey will only contain about 50.

 

Gemini Multi-Object Spectrograph


The technical information for astronomical observations is available at the NOIRLab Gemini Observatory webpage.

Site

GMOS-N: Maunakea, Hawai‘i

GMOS-S: Cerro Pachón, Chile

Telescopes

International Gemini Observatory North/South

Type

Spectrograph/Imager

Wavelength range

360−1030 nm

Spatial sampling

0.0807 arcsec per pixel

Detector format

one science detector composed of three 2048 x 4176-pixel CCDs in a row with two small gaps

Detector total size 

GMOS-N: 6278 x 4176 pixels (mosaiced — after tiling)


GMOS-S: 6266 x 4176 pixels

(mosaiced)

Spectral resolution

R up to 10,000 with 0.25-arcsec slits 

Field of view

Slit mode: 5.5 x 5.5 arcmin 

IFS mode: 35 x 35 arcsec

Filters

Available Filters

Gratings

Available Gratings

Date of first light 

GMOS-N: 2002

GMOS-S: 2003

Science goals

Multi-purpose instrument for scientific observations in the visible range.

Images taken with the instruments

Link

Images of the instrument

Link

Press releases with the instrument

Link