UCLA Infrared Lab


Multi-Object Spectrometer for Infra-Red Exploration
First Light Obtained: April 4, 2012

The leaders of the MOSFIRE team were Prof. Ian McLean (UCLA) and Prof. Charles Steidel (Caltech), with other leading roles in instrumentation, optics and astronomical software being played by Keith Matthews (Caltech), Prof. Harland Epps (UCSC), and Prof. James Larkin (UCLA) respectively. Nicholas Konidaris (MOSFIRE postdoc) was responsible for the data reduction pipeline and optical integration. The project was managed by Sean Adkins for the W.M. Keck Observatory.


MOSFIRE provides NIR multi-object spectroscopy over a field of view of 6.1' x 6.1', one atmospheric band at a time: Y(0.97-1.12μm), J(1.15-1.35μm), H (1.46-1.81μm), or K(1.93-2.45μm). The spectra cover most or all of the atmospheric band for slits placed anywhere within the field. A multiplex advantage of up to 46 slits is possible using a unique cryogenic robotic slit mask system that is reconfigurable electronically in < 5 minutes without any thermal cycling of the instrument.


The Configurable Slit mask Unit (CSU) is based on a prototype developed for the James Webb Space Telescope by the Swiss Centre for Micro-Electronics (CSEM). Using a single state-of-the-art Teledyne Hawaii 2RG HgCdTe detector with 2K x 2K pixels, MOSFIRE will capture most or all of an atmospheric window in a single exposure for any slit placed within a 6' x 3' field, and the instrument will employ a single, fixed diffraction grating used in multiple orders (3, 4, 5, and 6) for dispersion in the K, H, J and Y (a.k.a. Z) bands, respectively. In addition, MOSFIRE has been designed to be located at the Cassegrain focus of the Keck I telescope where it will provide faint object imaging and spectroscopic capabilities entirely complementary to the dual-beamed optical (0.3-1µm) spectrograph, LRIS.


MOSFIRE 2010 SPIE Paper -- Design and development of MOSFIRE, the Multi-Object Spectrometer For Infra-Red Exploration at the Keck Observatory

MOSFIRE 2012 SPIE Paper -- MOSFIRE, the Multi-Object Spectrometer For Infra-Red Exploration at the Keck Observatory



First Light on April 4th, 2012!

Delivered to Hawaii on February 17th, 2012

PDR - passed April 13, 2006 DDR - passed April 20, 2007 PSR - passed April 11, 2011
MOSFIRE Requirements v1.0 MOSFIRE Requirements v1.4  
MOSFIRE PDR Report v4.0 MOSFIRE DDR Report v2.0 MOSFIRE PSR Report v2.0
Final Report of PDR Committee Final Report of DDR Committee Final Report of PSR Committee


Wavelength coverage 0.9–2.5 μm; fixed grating used in orders 3,4,5,6 (K, H, J, Y)
Spectral Resolution Rθ = 2290 => R = 3270 w/0.7″ slit, 3 pix/resolution element, R= 4770 w/0.48" slit, 2 pix/resolution element
Simultaneous Wavelength Range Coverage is 0.45 μm (21%) in K band; 1.97-2.42 μm for a slit at the center of the field; H band coverage 1.48-1.81 μm for the same slit
Pixel Scale 0.18″ in imaging mode
Field Size 6.14' x 6.14' for imaging
Multiplex Cryogenic Configurable Slit Unit (CSU): ~45 remotely configurable slits each 7.3" long; configurable as a smaller number of longer slits. Each slit width can be adjusted arbitrarily.
Image Quality Design delivers < 0.2″ images over 0.9–2.5 μm with no re-focus.
Stability <0.1 pixel residual image motion at detector over 2 hr observation. Open-loop flexure compensation using tip/tilt mirror, look-up table.
Guiding Optical CCD guider, exterior to the cryostat. Must cover at least 7 arcmin2. Any significant relative motion between guider and detector must be removed by the flexure compensation system.
Throughput: spectroscopy >35% not including telescope, on order blaze
Mask Configuration Time <5 minutes for full re-configuration
Filters Minimum complement is order sorting filters for K, H, J, Y; additional Ks photometric filter for imaging. Goal: up to 5 additional photometric broad or narrow-band filters.
Accessible Pupil Optical design allows for an accessible pupil image so that a suitable cold mask can be used to minimize stray thermal radiation.
Detector 2048 x 2048 Teledyne Technologies Hawaii-2RG and ASIC; 18 μm pixels, long-wavelength cutoff @2.5 μm; low charge persistence; highest QE


MOSFIRE Design Concept


Multi-object spectrographs (MOSs) are required to understand object populations. The Keck community has already used the single object near-IR spectrograph NIRSPEC to study many young stars, galactic center objects, high redshift galaxies, and star formation in obscured galaxies. These observations have revealed much about the properties of small numbers of these objects, including numerous important and unique discoveries. However, detailed knowledge about object populations will elude us until we have hundreds or thousands of near-IR spectra of these objects, spanning a variety of environments, physical conditions, etc.  Many of the most exciting applications of near-IR spectroscopy are the most difficult, and will require extremely long integration times even with a 10m aperture; the ability to observe many objects at once will make such challenging observations feasible for the first time.

There is a compelling science case for a powerful near-IR MOS on Keck, including investigations in the following broad areas:

  • Young stars
  • Galactic center objects
  • Extremely low mass stars in star forming regions
  • Low mass end of the initial mass function (IMF)
  • Stellar populations in nearby galaxies
  • Surveys of star-forming galaxies and AGN at z~1.5-4
  • Surveys of  passively evolving galaxies beyond z~1
  • Star formation and populations of dusty galaxies
  • Searches for extremely high redshift objects (“first light” surveys)

MOSFIRE first light on the telescope was achieved on April 4th, 2012.

MOSFIRE Field of View

MOSFIRE Dewar Rendering

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