1. NGAO System Design Phase Update Peter Wizinowich, Rich Dekany, Don Gavel, Claire Max for NGAO Team SSC Meeting April 3, 2007

2. 2 Presentation Sequence Project Report #2 Science Requirements Performance Budgets Trade Studies Summary

3. 3 Project Report #2 2 nd report submitted to Directors on Mar. 31 http://www.oir.caltech.edu/twiki_oir/bin/view.cgi/Keck/NGAO/SystemDesignPhasePlanning Emphasis to date continues to be understanding the major design drivers through a process of iteratively developing the science case requirements & the performance budgets Work also continues on a number of trade studies in support of the performance budgets & the future design choices

4. 4 Project Report #2 #MILESTONEDATEDESCRIPTIONSTATUS 1 SD SEMP Approved 10/9/06Approval of this plan by the Directors. SEMP released to Directors on 9/29/06. Verbal approval received. Written approval requested 2 SD phase contracts in place 10/27/06Contracts issued to Caltech & UCSC for the system design phase. $50k initial contracts issued on 12/20 3 Science Case Requirements Summary v1.0 Release 10/27/06Initial Release as input to trade studies & performance budgeting Complete 4 System Requirements Document v1.0 Release 12/8/06Initial release of System Requirements with emphasis on science requirements Complete 5 Performance Budgets Summary v1.0 Release 2/27/071 st round of all performance budgets complete & documented Good progress 6 System Requirements Doc v2.0 Release 3/22/072 nd release of System Requirements Document Recently started 7 Trade Studies Complete 5/25/07All trade studies complete (Keck Adaptive Optics Notes) Good progress

5. 5 Project Report #2

6. 6 Schedule Still behind schedule, but catching up some (need to catch up more) 21% of System Design Phase activities complete through Mar. Budget $772k initially budgeted for FY07. $46k recently added to achieve SEMP request. $234k spent through Feb. –29% of the FY07 budget (versus plan of ~ 40%) –20% of the System Design Phase budget Replan Scheduled mid-year replan in process Will use this to help address schedule slip Still intend to hold to overall schedule & budget

7. 7 Project Report #2 Products since last report include the following KAONs: –456 Science Case Requirements Document – Release1 –457 System Requirements Document – Release1 –461 Wavefront error budget predictions & measured performance for current & upgraded Keck AO –462 Keck AO upgrade trade study –463 Lessons learned on LGS operations: weather impact, efficiency & science operations model –465 NGAO LGS wavefront sensor: Type & number of subapertures –466 Computer simulations of AO PSFs for NGAO –468 An algorithm for reconstruction of Keck telescope segment figures –469 Effect of segment figure errors on Keck AO performance –470 NGAO sky coverage modeling –472 GLAO for non-NGAO instruments –473 NGAO System Design Phase Report #2

8. Science Case Requirements & Science Instruments

9. 9 Science Case Requirements Document Release 1 contains the following: –JWST and ALMA capabilities –Future AO capabilities of other observatories –Key science cases that stress various aspects of AO: Multiplicity, size, and shape of minor planets Planetary & brown dwarf companions to low mass stars General relativistic effects in the Galactic Center Assembly and star formation history of high z galaxies Release 2 (in progress) will also include –Solar System: Titan, Io, Jovian planet icy moons –Galactic astronomy: Protostellar objects, Debris disks –Extragalactic astronomy: Strong lensing, AGNs, QSO host gals Still to come: resolved stellar populations

10. 10 Developments since Release 1: Complementarity of JWST and NGAO C. Max trip to GSFC to meet with JWST folks Broad-band imaging: limiting mag of JWST ~ 4-5 mags fainter than NGAO JWST not diffraction limited below K band –PSF FWHM same for 0.6  m < < 2  m as it is at 2  m: FWHM ~ 0.07 arc sec –Spectroscopy: NIRSpec px scale 0.1” Enclosed energy at 1  m = 60-64% within 0.15” Areas where Keck NGAO would nicely complement JWST 1.Spectra @ spatial resolution better than 0.1”, = 0.6 - 2 μm 2.Imaging @ spatial resolution better than 0.07”, = 0.6 - 2 μm 3.Spectral resolution R > 2700 4.Multi-IFU spectroscopy

11. 11 JWST: Implications for high-z galaxy science case One of our key science cases: IFU spectroscopy of high-z galaxies H  is redshifted into K band for z = 2 - 2.6 Yet for  > 2.1  m, NGAO sky background starts to hurt a lot Cooling the AO system can help –Much more feasible if we use MEMS (small volume to be cooled) /  = 2000 T AO = 277.5 K OAP relay

12. 12 How cool is cool enough? Target goal: AO to contribute at most 30% of background This opens “typical” z~2.6 galaxies within reasonable observing times ~ 3 hours How to achieve this? – 65% thruput, cool to -18C – 75% thruput, cool to -12 C – We have to assess how much it’s worth investing to cool NGAO at K band, in view of JWST’s great advantage in sensitivity

13. 13 Astrometry: goal 0.1 mas for Galactic Center Ghez et al. are studying what is limiting astrometric accuracy for current LGS AO system Can achieve average positional uncertainty close to 0.1 mas for bright stars (K < 14). But what is causing the broad spread? Under active investigation: PSF changes due to –Anisoplanatism –Differential atmospheric refraction –Wind shake –.....

14. 14 NGAO Instruments Working Group Focused on interactions with Science team Developing more complete instrument requirements –Requirements for deployable IFU are converging –Further work needed to refine imager requirements –Further work needed to refine visible wavelength instrumentation Membership: Sean Adkins (chair), Steve Eikenberry, Claire Max, David Le Mignant, Anna Moore (and later, James Larkin) Regular telecons & planning future in person workshop sessions

15. 15 Current Instrumentation Thoughts Visible and near-IR –Natural configuration breakpoints based on wavelength coverage –Trying to balance performance, features, cost and risk Imagers –Simple, Nyquist or Nyquist/2 spatial sampling –Coronagraph –Deployable imagers? Spectrographs –Single object IFU –Deployable IFU Specialized instruments? –R ~100 IFU –High contrast imaging

16. NGAO Performance Budget Development

17. 17 Developing Science-based Performance Budgets Systems engineering considers all of the following: –Model assumptions –Model/tool validation –Wavefront error vs. sky coverage for 5-7 science cases –Photometric precision in crowded and sparse stellar fields –Astrometric accuracy at the GC and in sparse fields –High-contrast for diffuse debris disks and compact companions –Polarimetric precisionfor high-contrast observations –Transmission/background/SNRfor several science cases –Observing efficiency –Observing uptime

18. 18 Photometric Precision with NGAO Technical report completed (see Britton, et al., at http://eraserhead.caltech.edu/keck/ngao/photometry/drafts/)http://eraserhead.caltech.edu/keck/ngao/photometry/drafts/ –Considered r 0 variations, stellar crowding (K. Olsen), scintillation, & techniques of PSF estimation Conclusions –Photometric precision intimately tied to knowledge of the PSF On-axis PSF can sometimes be estimated from direct imaging In principle, on-axis PSF can be estimated from AO telemetry (but this has not been tackled for Shack-Hartmann WFS) Off-axis PSF can be estimated using C n 2 (h) information –Single conjugate AO & MOAO relative photometric precision better than 1% should be achievable with NGAO over 30” FoV, assuming appropriate auxiliary systems This meets all of the NGAO science case goals developed so far –The photometric precision performance of MCAO cannot be easily estimated (due to both space & time variability) No obvious precision advantage over MOAO We will have to await ESO’s MAD & Gemini S MCAO to evaluate the performance w.r.t. single conjugate AO & MOAO

19. 19 Photometric Precision IPT Recommendations Active, concurrent C n 2 (h) measurements on minute time scales are essential to precision photometry with NGAO –Provides significant benefit for estimation of off-axis PSF’s –Allows additional optimization of NGAO performance (e.g. tomography algorithms) NGAO should provide an auxiliary PSF imaging capability for all instruments & observing modes –This camera should be Nyquist sampled and deployable over sufficient field of regard to ensure acquisition of an appropriate PSF stars (for narrow field science instruments.) Details of wavelength coverage & other requirements will depend on NGAO architecture As a step toward understand the requirements of the PSF imager, near-term experiments with OSIRIS &/or NIRC2 & the T6 MASS/DIMM should be undertaken –Open issues of access to Keck engineering time & funding for this investigation NGAO should consider incorporating a facility deconvolution pipeline as a program deliverable –This would likely improve consistency & uniformity of photometric & astrometric results

20. 20 Companion Sensitivity NGAO high-contrast science goals and drivers: Direct imaging & spectroscopy of 1) Planets around low-mass stars & brown dwarfs, 2) Resolved debris disks and proto-stellar envelopes LGS tomography –Fainter host stars: larger sky coverage & relaxed contrast requirements –Multi-band studies: optical & near-IR Status (1 st draft of report posted) Contrast budget spreadsheet tool (1 st order approximation) –No coronagraph model; no dynamic telescope aberrations Numerical AO simulations partly done (more accurate modeling) –Band-limited Lyot coronagraph; static & dynamic telescope errors

21. NGAO Trade Studies

22. 22 Trade Studies The following studies have been completed since the last meeting: –Keck AO upgrade –GLAO for non-NGAO instruments –Low order wavefront sensor type & number Additional design studies nearing completion include: –MOAO vs MCAO –Keck Interferometer support –Science instrument re-use –Telescope wavefront errors –Observing model –Rayleigh rejection –LGS wavefront sensor number and type

23. 23 Keck AO Upgrade Wavefront error budget Anchored NGAO tool to measured Keck AO performance Upgrades part 1 (NGWFC, K1 LGS, CCID-56, 2x DM, new science instrument, simplified tomography, vibration reduction, 50W laser) Upgrades 2 would need multiple LGS & multiple IR tip/tilt sensors Companion Sensitivity Performance improvement with Strehl

24. 24 Keck AO Upgrade Pros & cons –Potentially lower cost, but likely lower performance –Interferometer needs addressed Would allow for an incremental approach Conclusion: –Keck AO upgrade worth further consideration, especially as a reduced funding/scope option.

25. 25 GLAO for non-NGAO Instruments GLAO = ground-layer adaptive optics NGAO provides multiple LGS; adaptive secondary mirror assumed GLAO then “only” requires additional WFS, RTC & software to be employed with non-NGAO Keck instruments GLAO produces a modest, but dependable improvement in FWHM & EE over wide fields of view (several arc minutes) –Increase angular resolution, sensitivity & observing efficiency –Recover bad seeing nights to science grade observing –Large sky coverage (>50% at b=30°) From GLAO TS report (KAON 472 - see document for explanation of figures)

26. 26 Low Order Wavefront Sensor IR WFS (J+H bands) preferable to visible WFS Multiple NGS WFS significantly improve tip/tilt estimate over science field Measuring focus with one tilt sensors also helps tip/tilt estimate J=16.4 J=17.1 J=19.0 J=17.4 J=18.7 J=16.6 Field Galaxies science case: Latitude=30 deg

27. 27 Keck Interferometer Trade Study Consider the relative performance, cost, risk, & schedule of feeding KI with NGAO or a repackaged version of the current AO system Decoupling of NGAO from interferometer support may simplify & improve performance of NGAO The feasibility of maintaining a version of the two current AO systems for KI use should be evaluated

28. 28 Keck Interferometer Preliminary Options Swapping Keck I/II AO with NGAO Matching NGAO to Keck I/II AO Two AO systems + NGAO –AO secondary on each telescope GLAO trade study –MEMs AO for each IF arm Challenging with current IF LAO/UCSC Move Large Instruments

29. 29 Telescope Dynamic & Static Wavefront Errors Goal: Improve/document understanding of telescope wavefront errors Telescope tip/tilt errors could dominate tip/tilt error budget –“Encircled Energy Science” might be impacted less –Consider correction or mitigation on current system Segment motion –Acceptable error, comparable to NGAO proposal Segment figures –Acceptable error, already included in NGAO proposal Segment phasing –Small, interaction with figure errors needs testing Correcting for segment figure errors

30. 30 Summary Management: –System design phase efforts continue to be behind schedule –Now at reasonable staffing levels versus plan –Scheduled mid-year replan in process –Intention continues to be to deliver the system design within budget & schedule Technical: –Good progress being made on requirements, performance budgets & trade studies