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GHOST Gemini High Resolution Optical SpecTrograph

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March 2018

Arriving at Gemini South is the first part of our new instrument '' GHOST ”.  The instrument consists of a unit mounted in the Instrument Support Structure in charge of 'capturing' the light of the telescope.  The spectrograph will be installed in the pierlab connected by over 80 feet of cable.

The Australian Astronomical Observatory designed and built the Cassegrain unit, with software design coming from the Australian National University.  Members of each organization traveled from Australia to Pachón to unpack, assemble, and test the unit with critical support from the Gemini South day crew, and from Gabriel Perez, Eduardo Toro, Cristian Urrutia, Steve Margheim, John Bassett, and David Henderson. The unit was the prepared and installed on the telescope to make the first checks on sky in early February.

The team had a very successful first night of testing.  The instrument performed very well. A few of the accomplishments of the evening were confirming the coordinate systems and field center of GHOST are aligned within our measurements, and the probe map of the positioners is well behaved.  The team were also able to map the coordinate systems to the sky and acquire targets repeated over the entire 7 arcmin FOV, and verify that target acquisition, both direct and via spiral search were working as expected in both the single target and two target modes.  The team was enthusiastic about the performance of the GHOST unit and now await the arrival of the spectrograph from National Research Council Canada later in the year.

December 2017

The build of the GHOST Cassegrain unit is nearly complete. In November, Gemini staff participated in weighing and inspecting the fully assembled unit at the Australian Astronomical Observatory (AAO) lab in North Ryde, New South Wales. The unit is currently on its way to Chile. In December, Gemini representatives spent a week at the AAO testing the Integral Filed Unit (IFU) positioner and verifying the assembly and operation of the electronics and software of the Cassegrain Unit. Following 4 and a half days of inspections, tests, and demonstrations the positioner, electronics, and software were accepted for shipment to Gemini South. The electronics unit is expected to be shipped to Chile by year's end where the team will begin preliminary testing and debugging on the telescope in late January.

What is GHOST

GHOST, the Gemini High-resolution Optical SpecTrograph is the next Gemini facility instrument and will provide world-class, high-resolution spectroscopic capabilities to the Gemini community.  GHOST will provide a wide simultaneous wavelength coverage at high observational efficiency, enabling astronomers to investigate a broad range of science from the composition of the first stars to the characterization of exoplanetary systems.  A data reduction pipeline will be delivered with the instrument. The Australian Astronomical Observatory leads the GHOST team which includes the National Research Council Herzberg (NRC-H) for the construction of the spectrograph and the Australian National University (ANU) for instrument control system and data reduction software.

GHOST Science Cases

Designed to be a workhorse instrument, GHOST’s world-class efficiency, resolution, wavelength coverage, and stability will enable a broad range of science by the Gemini community. Scientific expertise and guidance for the development of GHOST is provided by the Combined Science Team, joint led by Michael Ireland (ANU) and Verne Smith (NOAO).

Examples include:

  • Characterization of exoplanet systems

  • Extremely metal-poor stars in the Milky Way and nearby dwarf satellites

  • Follow-up of GAIA targets

  • Radial velocity confirmation of transiting planet candidates, particularly from TESS

  • Abundance studies of extra-galactic globular clusters

GHOST Instrument Design

GHOST provides simultaneous wavelength coverage from 363 nm to 950 nm. It has two selectable spectral resolution modes: standard-resolution mode with R>50,000 and high-resolution mode with R>75,000. The instrument will obtain a limiting magnitude of 17.5 at 450 nm (30 sigma per resolution element). GHOST will spatially sample each target object over a field size of 1.2 arcsec, well matched to the wide range of seeing conditions at the observatory.

In standard-resolution mode, GHOST will have the capability to observe 2 targets simultaneously over a 7.5 arcmin diameter field of and provide a radial velocity precision of 600 m/s over the full wavelength. GHOST will have the capability to provide a radial velocity precision of 10 m/s over the wavelength range from 430nm to 750nm in the high-resolution mode, which can utilitze a simultaneous ThXe calibration source.

GHOST consists of three primary components; the cassegrain unit mounted on the telescope, the spectrograph bench located in the pier lab, and a fiber cable connecting the two. The cassegrain unit contains the positioning arm system, the object and sky fiber IFUs, and mini-ADCs.  The bench spectrograph is isolated in the telescope pier lab for image and wavelength stability.

The GHOST spectrograph is an echelle white-pupil design, using VPH grating for cross-dispersion.  A slit unit camera provides for object acquisition and active monitoring of the slit illumination.  The bench uses active thermal stabilization to help provide the image and wavelength stability necessary for operation efficiency and radial velocity precision.

IFUs

The Detectors

The Cameras

 

The GHOST Team 

Gemini

  • David Henderson, Project Manager
  • Cathy Blough, Project Support
  • Natalia Gonzalez, Project Support
  • Manuel Lazo, Project Engineer
  • John Basset, Systems Engineer
  • Steve Margheim, Project Scientist
  • Gabriel Perez, Mechanical Engineer
  • Cristian Urrutia, Software Engineer
  • Luc Boucher, Detector Engineer
  • Kathleen Labrie, Data Reduction Software Engineer
  • Manuel Gomez, Science Operations Specialist

AAO

  • Gabriella Baker, Project Manager
  • Richard McDermid, Project Scientist
  • Gordon Robertson, Instrument Scientist
  • Vladimir Churilov, Mechanical Engineer
  • Tony Farrell, Software Engineer
  • Ross Zhelem, Optical Engineer
  • Yuriy Kondrat, Mechanical Engineer
  • Lew Waller, Electronics Engineer
  • Michael Edgar, Project Engineer

NRC Hertzberg

  • John Pazder, Project and Optical Engineer
  • Andre Anthony, Mechanical Engineer
  • Greg Burley, Project Manager and Detector Engineer
  • Jennifer Dunn, Software Engineer
  • Scott MacDonald, Electronics
  • Mark Halman, Electronics
  • Joeleff Fitzsimmons, Mechanical

ANU

  • Michael Ireland, Project Scientist
  • Peter Young, Project Manager
  • Jon Nielson, Software Engineering Technical Lead
  • Lance Luvaul, Software Engineer
  • Marc White, Data Reduction Programmer
  • Rob Sharp, Instrument Scientist

 


Gemini Observatory Participants