instrumentation concepts for the 30-meter gsmt

AURA New Initiatives Office

S.C. Barden, M. Liang, K.H. Hinkle, C.F.W. Harmer, R.R. Joyce (NOAO/NIO) September 17, 2001

Instrumentation Concepts for the 30-meter GSMT


GSMT Point Design Instrument Study• Develop telescope, AO and instruments as an

integrated system• Design concepts driven by science objectives

– Multi-Object, Multi-Fiber, Optical Spectrograph MOMFOS (science: tomography of the universe)

– Near IR Deployable Integral Field Spectrograph NIRDIF (science: tomography of pre-galaxy fragments)

– Mid-IR, High Dispersion, AO Spectrograph MIHDAS (science: origins of planetary systems)

– MCAO-fed near-IR imager (science: stellar populations)

• Build on extant concepts where possible• Define major design challenges• Identify needed technologies


Multi-Object Multi-Fiber Optical Spectrograph (MOMFOS)

• 20 arc-minute field at f/1 Prime Focus• 60-meter fiber cable• 700 0.7” fibers

• 3 spectrographs, ~230 fibers each• VPH gratings• Articulated collimator for different resolution regimes

Resolution Example ranges with single grating• R= 1,000 350nm – 650nm• R= 5,000 470nm – 530nm• R= 18,000 491nm – 508nm

• Detects 13% - 23% of photons hitting the 30m


Prime Focus MOMFOS


MOMFOS with Prime

Focus Corrector

Conceptual design fits in a 3m dia by 5m long cylinder


MOMFOS Spectrograph Micro-Lens Relay

500 m diameterfiber fed by two micro-lenses with spherical surfaces.

100% of light couples into fiber.

Field stop limitslight to 0.72” aperture. Comparable lens required at fiber output.


MOMFOS Spectrograph Fiber Positioner

Positioner based on Echidna positioner built by AAO for FMOS on Suburu

Echidna prototype image from www.aao.gov.au/local/www/echidna/


MOMFOS Spectrograph

R=18000mode

R=5000mode

R=1000mode

500mm pupil; all spherical optics

4K by 4K CCD15 m pixels2 pixel binning

3 Spectrographs

230 fibers each

10 VPH gratingsto cover fulloptical rangeand 3 resolutionmodes.

f/4.5 Collimator

f/0.86 Camera

Articulatedcollimator


MOMFOS Spectrograph Predicted Efficiency


Spot Diagrams for MOMFOS Spectrograph

R = 50001126 l/mm794-904 nm28.6°

On-Axis

Half-Field

Full-Field

Fiber Diameter


Tomography of Individual Galaxies out to z ~3

GSMT 3 hour, 3 limit at R=5,000

0.1”x0.1” IFU pixel0.1”x0.1” IFU pixel(sub-kpc scale structures)

J H K 26.5 25.5 24.0


Near Infra-Red Deployable Integral Field Spectrograph (NIRDIF)

• MCAO fed• 1.5 to 2.0 arc-minute FOV

• 1 – 2.5 m wavelength coverage

• Deployable IFU units• 1.5 arc-second FOV per IFU probe• 31 slices per IFU probe (0.048” per slice)• ~26 deployable units



Relay optics contained in deployable arm.

1.5 by 1.5 arc-second field of view.

f/38 to f/128 converter from MCAO field to imageslicer.

Telecentric input and output.

Cold stop located within relay.



f/128 image slicer with 31 slices converted to f/11.5 for the spectrograph.

Spectrographs• 2 IFU’s per spectrograph• ~13 spectrographs• R = 1000 to 10,000• Z, J, H, and K spectral coverage• 2 K detector format assumed



Image Relay

Image Slicer

Spectrograph

Two Image Slicers per Spectrograph



Spot diagrams for NIRDIF spectrograph.

Slice 1

Slice 16

Slice 31


Origins of Planetary Systems• Goals:

– Understand where and when planets form– Infer planetary architectures via observation of ‘gaps’

• Measurements:Spectra of accreting PMS stars (R~105; m)

• Key requirements:On axis, high Strehl AO; low emissivity


Mid-Infrared High Dispersion AO Spectrograph (MIHDAS)

• Adaptive Secondary AO feed• On-Axis, Narrow Field/Point Source• R=120,000

• 3 spectrographs• 2-5 m (small beamed, x-dispersed), 0.2 arc-second slit length• 10-14 m (x-dispersed), 1 arc-second slit• 16-20 m (x-dispersed), 1 arc-second slit

• 10-14 m spectrograph likely to utilize same collimator as 16-20 m instrument. Different Gratings and Camera.

• 2-5 m spectrograph may require additional AO mirrors.



16-20 mm spectrograph will be large. Diffraction limitat 20 microns is about ¼ arc-second, comparable tonative seeing limit.

Echelle grating is 1.5 meters in length! Overall Overall instrument is expected to take up a instrument is expected to take up a volume of volume of about 4 by 2 by 3 meters!about 4 by 2 by 3 meters!

All of which needs to be cryogenically cooled.

Instrument to be located at Cass location and movewith the telescope.



1K by 1K Si:As detector27 m pixels

150 mm by 1500 mmR10 (84°) Echelle7 mm/line (0.143 l/mm)

f/18.75 Collimator

f/2 Camera

4-mirror camera

Off-axis paraboliccollimator

360 mm diametercross-disperser45 l/mm, 26.5° blaze


MCAO Near-IR Imager• f/38 input with 1:1 reimaging optics

• 1.5 to 2 arc-minute field of view

Monolithic imager - 5.5 mm/arc-second plate scale! 0.004 arc-second per pixel sampling 685 mm sized detector array for 2 arc-min field! 28K by 28K detector! 7 by 7 mosaic of 4K arrays

Alternative approach is to have deployable capability for imaging over a subset of the total field.


Instrument Locations on Telescope

MCAO-fedNIRDIForMCAO Imager

Cass-fedMIHDAS

Fiber-fedMOMFOS


Information on AURA NIO activities is available at:

www.aura-nio.noao.edu

instrumentation concepts for the 30-meter gsmt

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