TripleSpec Project

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TripleSpec Project

• 3 nearly-identical NIR spectrographs for 5-10
  meter telescopes

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• John Wilson
• Mike Skrutskie

• Keith Matthews
• Dae-Sik Moon

Chuck Henderson Terry Herter Joe Adams
Nick Gautier Mike Ressler
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CorMASS (R300)
Triplespec (R2700)
256 pix
256 pix
35 dia FOV (Palomar 60-inch)
slit
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Talk Outline

• Scientific Logistical Rationale
• Optical Design
• Mechanical Design
• Expected Performance
• Current Areas of Study
• Timeline

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Copy 3 Visitor Instrument Magellan ?, MMT ?,
Gemini ?, LBT ?, APO ? UVA Cornell
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Scientific Rationale

• Triage instrument for efficient NIR spectral
  follow-up of survey objects (e.g. Spitzer)
• Sufficient resolution to avoid airglow effects
• 0.8 2.4 µm all-at-once
• 100 km/sec per resolution element (2.7 pix)
• Sufficient slit length for nodding point sources
• Separate NIR slit viewing channel

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What science will it address?
Any project that requires moderate resolution NIR
spectroscopy, but it will excel at

• Identifying objects discovered in surveys (e.g.
  Spitzer, CHANDRA, 2MASS)
• Especially Red objects with no visual counterpart
  such as

Brown Dwarfs
McLean et al. 2003
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What science will it address?
Any project that requires moderate resolution NIR
spectroscopy, but it will excel at

• Identifying objects discovered in surveys (e.g.
  Spitzer, CHANDRA, 2MASS)
• Especially Red objects with no visual counterpart
  such as

High z objects
Balcells, 2003, RevMexAA Conf Series
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What science will it address?
Any project that requires moderate resolution NIR
spectroscopy, but it will excel at

• Identifying objects discovered in surveys (e.g.
  Spitzer, CHANDRA, 2MASS)
• Especially Red objects with no visual counterpart
  such as

Active Galaxies
NOAO/E.J. Schreier(STSci)/NASA
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But arent there already NIR spectrographs for
this science?
Shared between sites
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Why partner-up and make multiple copies?

• Instruments are cheaper by the dozen, but
  usually we just build one
• Share knowledge / expertise
• Efficient use of collaboration labor
• Maximize chance of success
• Share lessons learned during commissioning

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A third copy built at UVA?

• Economies of Scale
• Likelihood of Success Take advantage of lessons
  learned on first two
• Establish Lab reputation
• Trade instrument (funded locally) for telescope
  time on 6-10 meter
• Create collaborative opportunities

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Same instruments used at such different
telescopes?

• Tailor re-imager to transfer telescope f/ to
  common f/11
• Larger telescopes are generally at sites w/
  better seeing
• Dewar tolerant of various telescope mountings

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Instrument Optical Design
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Re-imaging Section
Dewar Window
Telescope Focus
Off Axis Paraboloid 1
Reflective Slit
Off Axis Paraboloid 2
Lyot Stop
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Collimation Folds
Dewar Window
Telescope Focus
Reflective Slit
Fold Mirror 1
Collimator (Off Axis Paraboloid)
Fold Mirror 2
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Re-imaging Section
Dewar Window
Off Axis Paraboloid 1
Off Axis Paraboloid 2
Fold Mirror 1
Collimator (Off Axis Paraboloid)
Fold Mirror 2
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Cross-Dispersing Prisms (2) ZnSe (1) Infrasil
Fold Mirror 2
Spectrograph
Reflection Grating (110.5 l/mm, 22 deg blaze)
7-element Refractive Camera
Detector (2 quadrant HAWAII-II)
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Telic Optics Designed f/1.6 Spectrograph Camera
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Imager Overview
Clearance Relief
Bulkhead Interface Mounting Holes
Lens Athermalization Pins
Spring loaded Lens Retainer
Auxiliary Bolt Circle (Rear Face)
Low Reflection Surfaces
Vent ports
Auxiliary Bolt Circle
Insulated Mounting Ring
Telic Optics
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Slit Viewer
Detector (HAWAII-I)
Reflective Slit
Fold Mirror
Lyot Stop Ks Filter
Lens 1 (ZnSe, aspheric)
Lens 2 (ZnSe, aspheric)
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Mechanical Design
2 Folds for packaging
SV Camera
Collimator
Dewar Window
Clam Shell LN2 Tank 60 liter half-load
2 day hold time
Fits inside 30 dia, 46.5 long dewar. 700 lbs
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Mechanical Design
Prism Stack
Spectrograph Camera
Tight Packaging to minimize Grating Turn Angle
(30?)
Grating
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Mechanical Design
Auxiliary LN2 Tank for Detector Temp Stability
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Mechanical Design
Bulkheads to resist closing of clam shell horns
Optics Mount to inner 3 bulkheads
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Mechanical Design
Second Radiation Shield Cooled by Neck
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Mechanical Design
4 G-10 straps at each end roll restraint.
Stabilizes 450 lbs (full cryogens) to 1 mil
radially
Flexure Control current slit movement lt 65
µm (1/4 slit width)
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Mechanical Design
30 ¼
46 1/2
Weight 800 lb w/ cryogens
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Spectral Resolution
Spectral resolution for 1.0 arcsec slit at
Palomar with 2.78 pixels/arcsecond.
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Grating Efficiency
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Spectrograph Continuum Sensitivity

• Assumptions
• At Palomar
• S/N 5 per resolution element
• System throughput 0.17, 0.19, 0.22 in J, H, K
• Between OH-lines (J,H,K bkgnd 70, 200, 70
  mJy/arcsec2)
• RN 5 e-, i(dark) 0.01 e-/sec

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Slit Viewer

• Design Specs at Palomar
• Operates at Ks
• Plate Scale 0.24 arcsec/pix
• 4 arcmin FOV gt 16 sq. arcmin

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In work

• AR Coatings
• High Performance (T99) Coatings imperative
• 22 refractive surfaces, 6 refl surfaces, and
  detector substrate
• Caltech has received very promising test coatings
  from Spectrum Thin Films

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In work (cont)

• Stray Light Analysis
• We are concerned with stray light potential due
  to thermal background (2.4 microns) that is
  passed by grating
• Careful placement of baffles / grooved camera
  interior / painted camera interior
• Baffles around grating / prisms / fold mirrors
• Use of blocking filter ?
• 8-week study contract w/ Breault Research
  Organization (BRO)

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Selected Milestones