Page 1 AO in AO A daptive O ptics in A stronomical O bservations Diana R. Constantin ASTRONOMICAL INSTITUTE OF THE ROMANIAN ACADEMY

Page 2 Why is adaptive optics needed? Even the largest ground-based astronomical telescopes have no better resolution than an 8" telescope! Even the largest ground-based astronomical telescopes have no better resolution than an 8" telescope! Turbulence in earth’s atmosphere makes stars twinkle –which we don’t correct!! More importantly, turbulence spreads out light; makes it a blob rather than a point

Page 3 Turbulence arises in many places stratosphere tropopause Heat sources w/in dome boundary layer ~ 1 km km wind flow over dome

Page 4 The solution: Schematic of adaptive optics system

Page 5 Characterize turbulence strength by quantity r 0 “Coherence Length” r 0 : distance over which optical phase distortion has mean square value of 1 rad 2 (r 0 ~ cm at good observing sites) “Coherence Length” r 0 : distance over which optical phase distortion has mean square value of 1 rad 2 (r 0 ~ cm at good observing sites) PSF is  FWHM λ/D → λ/r 0PSF is  FWHM λ/D → λ/r 0 Easy to remember: r 0 = 10 cm  FWHM = 1 arc sec at = 0.5  mEasy to remember: r 0 = 10 cm  FWHM = 1 arc sec at = 0.5  m Primary mirror of telescope r0r0 “Fried’s parameter” Wavefront of light

Page 6 Adaptive optics increases peak intensity of a point source Lick Observatory No AO With AO No AO With AO Intensity

Page 7 AO produces point spread functions with a “core” and “halo” The GOOD: When AO system performs well (good seeing), more energy in coreThe GOOD: When AO system performs well (good seeing), more energy in core ––space quality imaging!! The BAD: When AO system is stressed (poor seeing), halo contains larger fraction of energy (diameter ~ r 0 )The BAD: When AO system is stressed (poor seeing), halo contains larger fraction of energy (diameter ~ r 0 ) The UGLY: Ratio between core and halo varies during night and in particular during the dayThe UGLY: Ratio between core and halo varies during night and in particular during the day Intensity x Definition of “Strehl”: Ratio of peak intensity to that of “perfect” optical system

Simulation: courtesy Stein, Nordlund&Keller Input data4m in space (perfect optics) ATST good seeing ATST median seeing S>=0.3 S>=0.6S=1 (Hinode: S~0.7) S=0.2 ATST is able to resolve 30 km structures Stokes-V Visible(630.2nm) SRD requirements: NO-AO

Page 9 Summit of Mauna Kea, Hawaii Subaru 2 Kecks Gemini North AO Applications - Astronomy

Page 10 European Southern Observatory: four 8-m Telescopes in Chile

Page 11 Adaptive optics makes it possible to find faint companions around bright stars Two images from Palomar of a brown dwarf companion to GL 105 Credit: David Golimowski 200” telescope No AO With AO Another companion?

Page 12 Uranus with Hubble Space Telescope and Keck AO HST, Visible Keck AO, IR L. Sromovsky Lesson: Keck in near IR has ~ same resolution as Hubble in visible

Page 13 AO Applied to Free-Space Laser Communications 10’s to 100’s of gigabits/sec10’s to 100’s of gigabits/sec Example: AOptixExample: AOptix Applications: flexibility, mobilityApplications: flexibility, mobility –HDTV broadcasting of sports events –Military tactical communications Between ships, on land, land to air Between ships, on land, land to air

Page 14 Defense Systems

Page 15 Keck Observatory Laser guide stars are operating at Lick, Keck, Gemini North, VLT Observatories Lick Observatory

June 10-12, 2007DFG/NSF Conference DLSP Speckle Imager 2kw2k, 25 fps Frame selection Speckle bursts Virtual camera Prototype

June 10-12, 2007DFG/NSF Conference Books "Adaptive Optics for Astronomy", Francois Roddier (ed.), Cambridge University Press, 1999 "Adaptive Optics for Astronomical Telescopes", John W. Hardy, Oxford Books, 1998 "A Field Guide to Adaptive Optics" Robert K. Tyson and Benjamin W. Frazier, SPIE Press "Introduction to Adaptive Optics" Robert K. Tyson and Benjamin W. Frazier, SPIE Press "Principles of Adaptive Optics", Robert K. Tyson, Academic Press, 1997 "Imaging Through Turbulence", Michael C. Roggemann & Byron Welsh, CRC Press, 1996 SPIE Proceedings – tons of it (literally) CFAO web site and list of tutorials there “(Solar) Observations with Adaptive Optics“, “(Solar) Observations with Adaptive Optics“, Thomas Rimmele