NGAO System Performance Summary Matthew Britton July 9
NGAO System Performance Summary Matthew Britton July 9, 2007
Performance Budget Reports Performance Budget Personnel KAON Date WFE and Ensq. Energy Dekany, Flicker, Gavel, Max, Wizinowich 471 July 8, 2007 Photometric precision Britton, Dekany, Flicker, Olsen 474 April 10, 2007 Astrometric precision Cameron, Britton, Dekany, Ghez, Lu 480 May 3, 2007 High Contrast Flicker, Dekany, Liu, Macintosh, Neyman 497 June 27, 2007 Polarimetric precision Ireland, Dekany - - 463 Feb 16, 2007 - - Transmission and background Bouchez, Dekany Observing efficiency Le Mignant System uptime Johansson, Chin
Wavefront Error and Ensquared Energy
WFE and Ensq. Energy Status • Report considered five different observing scenarios – Io, Kuiper belt, Exo Jupiter, Extended Groth, Galactic Center • Assumed two different AO architectures: – NGSAO architecture with 64 x 64 subaps – LGSAO architecture with 64 x 64 subaps, 6 LGS asterism, tilt guiding on single NGS • Uses wavefront error budget spreadsheet v 1. 22 • Spreadsheets for each observing scenario are posted under the systems architecture collection and linked to the performance budget page.
WFE Results Scenario Io Exp. Time (sec) TT GS HO GS LGS Ast. Diam. TT Error (mas) Sky Cvge HO Error (nm) H band Strehl 10 Sci target Sci. target - 1. 7 N/A 96 87% Kuiper belt 300 Field star 6 x. LGS 41” 6. 2 10% 150 61% Exo Jupiter 300 Sci. target 6 x. LGS 12” 3. 3 N/A 124 76% Ext. Groth 1800 Field star 6 x. LGS 90” 18. 5 30% 159 25% 30 IRS 7 6 x. LGS 11” 2. 0 N/A 170 64% Gal. Ctr
Ensquared Energy Results for the Extended Groth Strip Spaxial Size (asec) Ensq. Energy Fraction . 05 37% . 07 57% . 08 65% . 12 81% . 24 88% . 48 93% 1. 00 95%
Photometric Precision
Photometric Precision Status • Report considered a variety of effects that impact photometric precision • Anisoplanatism, variability in Cn 2 profile, scintillation, variable atmospheric attenuation, detector effects, crowding • Case study of crowded stellar pops in nearby galaxies • Included discussion of PSF variability and deconvolution. • Presented four recommendations on how to improve photometric precision
Recommendations • Require turbulence monitoring capabilities that deliver Cn 2 measurements on minute timescales • Consider an auxiliary imaging camera for PSF monitoring • Consider performing PSF estimation experiment with existing Keck AO system • Consider providing facility deconvolution pipelines for NGAO
Astrometric Precision
Astrometric Precision Status • Report considered four effects that impact photometric precision • Differential atmospheric tilt jitter, distortion, atmospheric refraction, and crowding • Two case studies presented • Galactic Center • Faint targets in sparsely populated fields • Presented six recommendations on how to improve astrometric precision
Recommendations • Require turbulence monitoring capabilities that deliver Cn 2 measurements on minute timescales • Consider an auxiliary imaging camera for PSF monitoring • Require capability to monitor distortion in the AO system and instrument • Consider providing an ADC • Ensure plate scale stability of 1 e-4 • A WFE < 140 nm may be required to meet 100 uas astrometric goal
High Contrast
High Contrast Status • Report evaluates contrast ratio as a function of angular offset from the primary • Uses spatial frequency code, full Monte Carlo numerical simulation • Considers two architectures: – Clear aperture – Apodized Lyot coronagraph
High Contrast Results • d. J = 10 at 0. 2” – Achieved at 8 s by 6 l/D or 10 l/D coronagraph • d. J = 8. 5 at 0. 1” – Achieved at 8 s by 6 l/D coronagraph • d. J = 11 at 0. 2” – Achieved at 5 s by 6 l/D or 10 l/D coronagraph • d. J = 11 at 0. 1” – Not achieved • d. J = 9 at 0. 07” – Possibly achieved at 5 s by 6 l/D coronagraph
Polarimetric Precision
Polarimetric Precision Status • One power point slide has been generated for this performance budget • There are no requirements in the Science requirements document.
Transmission and Background
Transmission and Background Status • There are 4 powerpoint slides from an team meeting 5. • Model of current K 2 AO system and an AM 2 system for NGAO
Observing Efficiency and System Uptime
Observing Efficiency and System Uptime Status • Report summarizes lessons learned from the Keck LGS AO system • Keck LGS efficiency – 37% of time lost due to operational overhead – 25% of time lost due to weather – 16% of time lost due to system faults
Summary • 5 of 8 performance budgets have generated KAONs • Reports: – Discuss performance of current generation AO systems and how this performance may be improved. – Make architectural assumptions to generate performance predictions. • Future steps: – Evaluate requirements against performance predictions. (KAON 456, v 1. 11)
- Slides: 22