UCSC, Mar 18

1
UCSC, Mar 18

• IWG Members

2
IWG Meetings

• Telecons every 1-2 weeks since Nov
• Tucson meeting Dec 16, 2003
• Santa Cruz meeting Mar 17, 2004

3
IWG Meetings

• Decided other instruments may be just as
  problematic as WFOS
• Believes that should have some simple instruments
  for first light
• Need to consider detector procurement issues
  early

4
IWG to SAC Questions (Dec)

• WFOS
• Precise wavelength range(s) (310-700,500-1300)
• How desirable is simultaneous
• Delivered telescope IQ?, nominal slit width?
• Resolution (slit width) desired?
• Is it important to retain central field for AO
  (for rapid changes)?
• Vertical mounting preferred
• Is an imaging mode required?
• MCAO Imager/dIFU/IFU
• Two instruments best
• dIFU with 50mas sampling
• single IFU with diffraction limited sampling (and
  lt 2.5mu)
• How important is 2-5-5mu for latter?

5
IWG to SAC Questions (Dec)

• MIR
• Biggest impact on telescope
• Baffles, under-sized or exchangeable secondaries
• Gaps, spiders, coatings
• Diffraction limited imaging capability is most
  unique (even if telescope not MIR optimized)
• Interchangeable secondaries envisaged?
  Tertiaries?
• What is emissivity floor (due to spiders, gaps,
  etc)?
• MTHR
• Good candidate for first light instrument
  (natural seeing, no unknown tech)
• Requires tennis court Nasymth
• Fibre mode? (If yes, then MTHR should be close)
• Could build one arm first with minimal impact on
  science capability
• Others
• Quick telescope nods required for both MIR and
  NS
• OIWFS before nodder advantageous

6
WFOS

• 3 independent studies
• HIA (Bev Oke, Denis Laurin, Ian Powell)
• Caltech (Keith Taylor, Damien Jones)
• UCSC (Harland Epps, Joe Miller)
• 3 completely different solutions
• Caltech HIA use a focal reducer to diminish
  scale

7
WFOS

• 3 independent studies
• HIA (Bev Oke, Denis Laurin, Ian Powell)
• Caltech (Keith Taylor, Damien Jones)
• UCSC (Harlan Epps, Joe Miller)
• 3 completely different solutions
• Caltech HIA use a focal reducer to diminish
  scale

8
Introducing B. Okes WFOS Concept

• A Thirty metre telescope imager and low
  resolution spectrograph

9
Oke WFOS Concept

• Principal Components
• Collimator
• Off-axis paraboloid 2300 mm focal length.
• From a 3 m diameter parabolic mirror, section
  1250 x 850 mm.
• Folding Mirror
• Flat, rectangular (477 x 656 mm).
• First Transfer Lens
• 900 mm focal length, must cover 3100 to 12000 Å
• Second Focal Surface
• Scale is 0.39 telescope field.
• Tilted 5.3 deg., R curvature 4223 mm.
• Ideal location for slit mask (smaller field) with
  ADC above this surface.

10
WFOS Concept

• Principal Components (continued)
• Dichroic splitter
• 3100-6000 and 6000-12000 Å.
• 400 x 600 mm, tilted 67.5 deg.
• Second Transfer Lenses
• Two lenses (for the blue and red cameras).
• Symmetrical to First Transfer Lens, optimized for
  small spectral ranges.
• Gratings
• Standard gratings 165 x 220 mm.
• Cameras
• Can use existing design by Epps (for DEIMOS or
  IMACS), scaled.
• Scale at the CCD is 0.316 mm/arcsec.
• Use 3x3 CCD mosaic (2048x2048 pixels).

11
WFOS Concept Zemax Model

• First approximation all paraxial to determine
  verify placement of elements scale.
• CELT telescope included.
• Parabolic collimator.
• Re-imaging lenses are paraxial lenses for now
  (challenging design to come!)
• About 600 to 700 mm diameter.
• Wide spectral range.
• Compensate for telescope curved focal plane,
  aberrations?
• Not shown are possible ADC and slit-mask.

12
Oke Concept
Standard 165 220mm gratings
13
Oke WFOS Concept

• Telescope Focal Surface Field
  Partitions(units are arcmin)

14
Taylor CFOS concept for CELT
15
CFOS 4-shooter(only 2 arms shown)

• FoV 20-by-14 on a side
• 350 lt ? lt 1000nm
• Beam ? 400mm
• Camera f-ratio f/1.1
• Detector 6k2
• 0.75 slit-width (8-pixels)
• ROctave 850
• RMax 7,600 (?? 60nm)
• M lt 1,000 (NS)
• ?Peak-R gt 35 (total)
• NB Vertical optical axis

Satisfies SAC requirements
Except for
16
Epps ELVIS

• (Efficient Large Versatile Imaging Spectrograph)

17
ELVIS fig 2
18
ELVIS fig 3

• Could go at Cass

19
ELVIS fig 4
9.2234mm

• Detectors

5.6
20
WFOS concepts

• Many similar problems
• Size of CaF2 refractive elements?
• need large beam to get resolution requested
• Size of beamsplitters?
• Size of filters?
• Efficiency of AR and reflective coatings?
• 0.31-1.1microns
• Efficiency and size of VPH gratings?
• may need VPH gratings to get spectra resolution
• Very different sizes
• is size and/or mass a real issue?
• HIA design is dual beam, simultaneous blue and
  red spectra
• UCSC offers selection of UV, broad-band or NIR
  spectra
• Caltech design offers biggest contiguous field

21
VPH gratings

• High peak efficiency
• Low bandwidth
• UV efficiency?
• Operational eff?
• Calibration?

22
Ca F2

• From Denis Laurin list of CaF2 suppliers from
  readily available info (websites)
• Schott Lithotec (New-York, USA or Germany) up to
  350 mm dia, 100 mm thick http//www.us.schott.com/
  lithotec        
• Corning (New-York, USA) produces up to 368 mm
  (14.5) dia. http//www.corning.com/semiconductoro
  ptics/products__services/semiconductor_optics/fluo
  ride_crystals.asp  
• Crystran up to 250 dia http//www.crystran.co.uk/c
  af2data.htm
• O'hara (Japan) http//www.ohara-inc.co.jp/b/b.htm
  CaF2 not found  
• Optovac (MA) was acquired by Corning Inc, NY.
  (Jan 2000)
• Harland says Canon Japan is contracted to deliver
  400mm (16) CaF2 lenses for Binospec, thinks 20
  possible

23
WFOS comparison
24
WFOS comparison
25
HROS

• HROS

26
HROS

• HROS

27
HROS Issues

• HROS

28
Mast Questions

• WFOS
• range, or a scaling) of the following as a
  function of the telescope final f-ratio?
•         image quality
•         spectral resolution
•         field of view
•         instrument mass
•         instrument size
•         science achievable
•         instrument cost

29
TMT Point designs

• HROS

30
IWG to AOWG Questions

• Knowledge of PSF available?
• Delivered IQ?
• WFE budget for MCAO, XAO?