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