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

2. 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. 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) Science H/K band TT sensors J 1 of n beamsplitters 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)

4. 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. 5 TMT IRMOS Caltech/LAM Richard Ellis (PI) et al Prieto/Taylor/Moore based on KMOS2 concept Field mirrors arrays Steering mirrors lines Parabolas DMs

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

7. 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. 8 Near-future 8m d-IFU concept: KMOS VLT 2010 Durham/ATC et al Courtesy of Allington-Smith To IFU and spectrograph field 24Arms 24 IFUs, 3 spectrographs 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

9. 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. 10 Kickbots for NGAO? Maybe… Transparent horizontal glass window (must be clean!) From telescope To science instrument/s