1. Trade Study Report: NGAO versus Keck AO Upgrade NGAO Meeting #5 Peter Wizinowich March 7, 2007

2. 2 Presentation Sequence Dictionary Definition & Status Performance Budgets versus Requirements Potential Upgrade Plan Summary

3. 3 WBS Dictionary Definition & Status Definition: Consider the feasibility of upgrading one of the existing Keck AO systems incrementally to meet the NGAO science requirements. Consider opto-mechanical constraints & upgradeability of embedded & supervisory control systems. Consider impact on science operations during NGAO commissioning. Complete when option assessment documented. Status: –Work scope planning sheet approved http://www.oir.caltech.edu/twiki_oir/pub/Keck/NGAO/WorkProducts/3.1.2.1.2_NGAOvsKeckAOUpgrades.doc http://www.oir.caltech.edu/twiki_oir/pub/Keck/NGAO/WorkProducts/3.1.2.1.2_NGAOvsKeckAOUpgrades.doc –KAON 461 Wavefront error budget predictions complete (need to check NGAO results) http://www.oir.caltech.edu/twiki_oir/pub/Keck/NGAO/WorkProducts/KAON461_Keck_AO_Error_Budget.doc http://www.oir.caltech.edu/twiki_oir/pub/Keck/NGAO/WorkProducts/KAON461_Keck_AO_Error_Budget.doc –KAON 462 Trade study report contains comparison of upgrade to performance budgets (needs more work) & a potential upgrade plan http://www.oir.caltech.edu/twiki_oir/pub/Keck/NGAO/WorkProducts/KAON462_Keck_AO_Upgrade.doc http://www.oir.caltech.edu/twiki_oir/pub/Keck/NGAO/WorkProducts/KAON462_Keck_AO_Upgrade.doc Remaining –More work on performance budgets –Discussion of opto-mechanical constraints & upgradeability of embedded & supervisory control systems –Discussion of impact on science operations

4. 4 Wavefront Error Budget (KAON 461) 1 st step: anchor the NGAO excel tool to measured Keck AO performance

5. 5 Wavefront Error Budget (KAON 461) 2 nd step: Define a series of upgrades: NGWFC K1 LGS CCID56 2x DM Science Instrument Simplified Tomography Vibration Reduction 50W Laser For reference the NGAO case was also evaluated 3 rd step: Evaluate the wavefront error budget using the NGAO tool 3 cases considered –NGS AO with an 8 th mag NGS –LGS AO with a 10 th mag NGS –LGS AO with an 18 th mag NGS

6. 6 Wavefront Error Budget LGS (10 th mag) case: Upgrade achieves 229 nm vs 155 nm for NGAO Next upgrade step would be multiple LGS (need to look at feasibility) Relevant requirements: 155 nm for 1% sky coverage 205 nm for 20% sky coverage

7. 7 Wavefront Error Budget LGS (18 th mag) case: Upgrade achieves 419 nm vs 158 nm for NGAO NGAO estimate likely incorrect Next upgrade step would be multiple NIR tilt sensors Relevant requirements: 205 nm for 20% sky coverage 240 nm for 80% sky coverage

8. 8 Wavefront Error Budget NGS (8 th mag) case: Upgrade achieves 149 nm No significant difference between Upgrade & NGAO Relevant requirements: 155 nm for 1% sky coverage

9. 9 Companion Sensitivity Galactic Center Requirement ≥ 4 mags at 0.055” at 1-2.5µm General Requirement ≥ 10 mags at 0.5” at 0.7-3.5µm for 30% sky coverage & ≤ 20” object diameter Conclusions –GC requirement can be met with Upgrade –General requirement can be met at H & K with Upgrade –NGAO only ~ 0.4 mag better at H & K than Upgrade, increasing to 1.5 mag at 1 µm Question –Are these the right requirements?

10. 10 Other Performance Budgets Upgrade likely to meet –Throughput requirements –Galactic Center astrometry requirement (barely) –Other astrometric requirements (may already be met) –Observing efficiency –Observing uptime –Compatibility with new science instruments (designed for Keck AO) –Interferometer support Upgrade not likely to meet –Emissivity requirement Uncertain –Photometric requirements –Polarimetric requirements

11. 11 Potential Upgrade Plan

12. 12 Summary A Keck AO upgrade path is worth further consideration –This could be an incremental or a few-shot approach Pros: –Lower cost –If an incremental approach is taken: Performance improved as funds available Performance improvements sooner –Don’t take all or nothing risk (this can be mitigated some for NGAO) –Interferometer addressed Cons: –Lower performance than NGAO –If an incremental approach is taken Periodic shutdowns for upgrades Risk to operations of a system always under development Risk to development team schedule from supporting operational system –Only two science instruments (possibly 3) at any one time (unless also upgrade other telescope)