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Trade Study Report: NGAO versus Keck AO Upgrade

Trade Study Report: NGAO versus Keck AO Upgrade. NGAO Meeting #5 Peter Wizinowich March 7, 2007. Presentation Sequence. Dictionary Definition & Status Performance Budgets versus Requirements Potential Upgrade Plan Summary. WBS Dictionary Definition & Status.

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Trade Study Report: NGAO versus Keck AO Upgrade

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

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

  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 • 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 • 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 • Remaining • More work on performance budgets • Discussion of opto-mechanical constraints & upgradeability of embedded & supervisory control systems • Discussion of impact on science operations

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

  5. Wavefront Error Budget (KAON 461) 2nd 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 3rd step: Evaluate the wavefront error budget using the NGAO tool • 3 cases considered • NGS AO with an 8th mag NGS • LGS AO with a 10th mag NGS • LGS AO with an 18th mag NGS

  6. Wavefront Error Budget LGS (10th 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. Wavefront Error Budget LGS (18th 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. Wavefront Error Budget NGS (8th mag) case: • Upgrade achieves 149 nm • No significant difference between Upgrade & NGAO • Relevant requirements: 155 nm for 1% sky coverage

  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. 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. Potential Upgrade Plan

  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)

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