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Object selection ideas for NGAO

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Light from TT stars is close to or at same wavelength as science field ... Cheap, reliable at -40C (piezo driven, like Echidna) Need vertical path length compensation ... – PowerPoint PPT presentation

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Title: Object selection ideas for NGAO


1
Object selection ideas for NGAO
  • NGAO Meeting 6
  • Anna Moore
  • April 26, 2007

2
Key drivers
  • Light from TT stars is close to or at same
    wavelength as science field
  • limited use of beamsplitters to pick-off light
  • Shame as unlike TMT the Keck beam size is
    manageable wrt dichroics
  • (6-8 diameter ok, 20k)

3
Beamsplitter-fed TT mode?
  • IF one can do TT sensing close to but out of the
    science band
  • Have a slide with a user selectable range of
    beamsplitters ahead of the science instrument
    (aka optical switchyard of Indian Wells?)
  • Only feeding 3 TT sensors in any case (!),
    positionable over max 240 FoR (180mm)

4
Key drivers
  • Keck Plate scale is 0.75mm/arcsec
  • TMT has larger real estate for fitting in
    mechanical pick-offs (2.25 mm per arcsec)
  • Should keep in mind AAT/VLT etc like pick-off
    devices and maybe get inspiration from those for
    30m

5
TMT IRMOS Caltech/LAM
  • Richard Ellis (PI) et al
  • Prieto/Taylor/Moore based on KMOS2 concept

6
TMT IRMOS Florida/HIA
  • Steve Eikenberry PI et al

7
IRMOS includes TT pick-off
  • Both TMT IRMOS instruments had to provide means
    of picking off TT light at instrument focal
    plane. This has the benefit of sampling TT light
    delivered to the instrument.
  • NGAO could go this way however
  • Requires full TT field relayed to science
    instrument
  • Possibly will have restricted access to central
    FoR due to vignetting of science field
  • Requires at least 2 TT pick-off systems, with 3
    MEMS per system, one for d-IFU and one for the
    on-axis instruments

8
Near-future 8m d-IFU concept KMOS
  • VLT 2010
  • Durham/ATC et al
  • Courtesy of Allington-Smith

NB KMOS is NOT combined with AO Still, quite
possible to have (d-ifu) NGAO requirement of 13
pick-offs though at what cost should be a
simpler solution
To IFU and spectrograph
9
More radical solutions?
  • Kickbot/Starbug concepts for focal plane pick-off
    (Moore/McGrath)
  • In principle low cross sectional area robotic
    positioners
  • Cheap, reliable at -40C (piezo driven, like
    Echidna)
  • Need vertical path length compensation

Drawing by Andrew McGrath, AAO
10
Kickbots for NGAO?
From telescope
  • Maybe

Transparent horizontal glass window (must be
clean!)
To science instrument/s
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