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Object selection ideas for NGAO

Object selection ideas for NGAO. NGAO Meeting #6 Anna Moore April 26, 2007. 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

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Object selection ideas for NGAO

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  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. 1 of n beamsplitters Science H/K band Have to be VERY careful about max. simultaneous band coverage for science arm Plus likely larger non-common path errors than picking off TT at science focal plane? (not for super high contrast) TT sensors J 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. Steering mirrors lines DMs Parabolas Field mirrors arrays 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. 24 IFUs, 3 spectrographs 24 Arms field 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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