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Instrumentation Concepts Ground-based Optical Telescopes

Instrumentation Concepts Ground-based Optical Telescopes. Keith Taylor (IAG/USP) Aug-Nov, 2008. IAG-USP (Keith Taylor). Aug-Sep, 2008. Ground Layer Adaptive Optics (GLAO). Thanks to: Andrei Tokovinin (SOAR) Norbert Hubin (ESO). Laser beams. Reference Stars. High Altitude Layer.

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Instrumentation Concepts Ground-based Optical Telescopes

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  1. IAG/USP (Keith Taylor)‏ Instrumentation ConceptsGround-based Optical Telescopes Keith Taylor (IAG/USP) Aug-Nov, 2008 IAG-USP (Keith Taylor) Aug-Sep, 2008

  2. IAG/USP (Keith Taylor)‏ Ground Layer Adaptive Optics(GLAO) Thanks to: Andrei Tokovinin (SOAR) Norbert Hubin (ESO)

  3. IAG/USP (Keith Taylor)‏ Laser beams Reference Stars High Altitude Layer Altitude Layers Ground Layer Telescope Real Time Computer Averaged WF.. DM conjugated Telescope pupil Ground Layer WFSs WHAT IS GROUND LAYER AO?

  4. IAG/USP (Keith Taylor)‏ Does a ground layer exist? PARANAL OBSERVATORY Courtesy: M. Sarazin Ex: 50% of the time there is 55% OR LESS turbulence in the 1st 500m More measurements are being carried out (M. Sarazin)

  5. IAG/USP (Keith Taylor)‏ Seeing-limited(>90% of Ground-based Astronomy!) Ground Layer Adaptive Optics Better seeing in wider field • Turbulence profile • Guide star(s) • Gain? = Diffraction limit (full AO or MCAO)

  6. IAG/USP (Keith Taylor)‏ FoV No Correction: Seeing limit GLAO: reduced apparent seeing « Ground Layer » Adaptive Optics [GLAO] GLAO: • multi-GS WFS • single ground DM correcting average perturbation ~ near ground turbulence Expected performance: single Ground DM seeing improved and stabilized in very large FoV gain ~2 in 10 arcmin for NIR VLT obs.

  7. IAG/USP (Keith Taylor)‏ Turbulence Profile and ground layer Mauna Kea, October 22/23, 2002: G-scidar 15km 10km 5km 0km Data: J.Vernin, A.Ziad

  8. IAG/USP (Keith Taylor)‏ Turbulence Profile and ground layer CERRO TOLOLO OBSERVATORY Courtesy: M. Sarazin R. Wilson

  9. IAG/USP (Keith Taylor)‏ Turbulence Profile and ground layer CERRO TOLOLO OBSERVATORY Courtesy: M. Sarazin

  10. IAG/USP (Keith Taylor)‏ Investigation of Ground layer at Paranal • Multi Aperture Scintillation Sensor MASS + DIMM: Cn2 profile • SLODAR: Slope Detection and ranging: Higher resolution of ground layer Courtesy: R. Wilson

  11. IAG/USP (Keith Taylor)‏ Seeing PSF on-axis PSF off-axis 8’ FOV Improved seeing, Sr(K) ~ 4% Reduced confusion in Stellar populations & Cluster fields Seeing reducer Better light concentration Reduced exposure & Telescope time GLAO as seeing reducer?

  12. IAG/USP (Keith Taylor)‏ Science with GLAO • Dynamics of galaxies, AGNs (+IFU) • Stellar populations, clusters (confusion!) • Supernovae, cepheids • Weak lensing • ISM (PNe, jets) • and more… GLAO benefits most “classical” astronomical programs

  13. IAG/USP (Keith Taylor)‏ GLAO as seeing reducer? Seeing K Band, gain: 100% FWHM Y Band, Gain: 30% With AO

  14. IAG/USP (Keith Taylor)‏ GLAO improves Ensquared Energy? Pixel: 0.1” With AO K Band, EE doubled Y Band, gain: 50% Seeing

  15. IAG/USP (Keith Taylor)‏ GLAO reduces confusion? Yes but more difficult! Seeing K Band, gain: 40% Y Band, Gain: 30% With AO

  16. IAG/USP (Keith Taylor)‏ Tip-tilt limiting magnitude (R-Band) Probability for (top to bottom) 1,2,3 TT NGS In 1arcmin annular FOV Tip-tilt limiting magnitude (R-Band) Probability for (top to bottom) 1,2,3 TT NGS In 2 arcmin annular FOV GLAO and full sky coverage? • Need Laser artificial stars for WFS tomography because of: • Median to bad seeing conditions assumptions • Science performed down to short λ • Require Natural Guide Star for Tip-tilt correction 1 VIS NGS

  17. GLAO Gain + in the visible!!! Sky coverage ~100% IAG/USP (Keith Taylor)‏

  18. IAG/USP (Keith Taylor)‏ @750nm; FOV=1’ GLAO Seeing GLAO in the visible?

  19. IAG/USP (Keith Taylor)‏ Two GLAO systems R-GLAO Rayleigh LGS S-GLAO 5 sodium LGSs

  20. IAG/USP (Keith Taylor)‏ MASS/DIMM measures

  21. IAG/USP (Keith Taylor)‏ Compare S-GLAO with R-GLAO R-GLAO S-GLAO 17% at 8km, 83% at 0.5km

  22. IAG/USP (Keith Taylor)‏ Further comparison

  23. IAG/USP (Keith Taylor)‏ Typical night: Jan 11/12, 2003 Seeing • ~0.5m • ~0.7m

  24. IAG/USP (Keith Taylor)‏ Typical night: Jan 15/16, 2003 Seeing • ~0.5m • ~0.7m

  25. IAG/USP (Keith Taylor)‏ Statistics: FWHM

  26. IAG/USP (Keith Taylor)‏ SAM = SOAR Adaptive Module • Rayleigh LGS • 355 nm, 8W, 10km • S-H WFS, 9x9 • Bimorph DM • CCD imager • FoV = 3’x3’ • Visitor instrument • Collimated space PDR: 2004 First light: 2006 (now 9/09) LGS: 2007 (now 9/10)

  27. IAG/USP (Keith Taylor)‏ Optical design: OAP • All-reflective • Excellent quality • Collimated space

  28. IAG/USP (Keith Taylor)‏ SAM as adaptor

  29. IAG/USP (Keith Taylor)‏ GLAO: useful for most astronomical programs • Ground Layer Adaptive Optics = Seeing reducer • Reduced Seeing => reduced exposure & telescope times • Reduced seeing => Reduced confusion in Stellar populations & Cluster fields • Ground Layer Adaptive Optics = Seeing “stabilizer” • Seeing stabilizer => better percentile seeing for your site! • Seeing reducer is “easily” achievable at all λs (down to vis.) • High Sky coverage GLAO systems will benefit most astronomical programs • Seeing reducer = light concentration: Sufficient for distant (“small”) galaxies with low surface brightness (0.2-0.1” pixel enough)

  30. IAG/USP (Keith Taylor)‏ Conclusions • GLAO is complementary to AO, MCAO • Opens “visible” window, all-sky • Rayleigh LGS is quite good • SAM _ first implementation, test-bench • Need data on turbulence in the first km!

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