“Twinkle, Twinkle Little Star”: An Introduction to Adaptive OpticsTurbulence in the atmosphere limits the performance of astronomical telescopesImages of a bright star, ArcturusTurbulence changes rapidly with timeMeasure details of blurring from “guide star” near the object you want to observeBasic idea of AOAdaptive optics in actionSlide 8Slide 9Deformable mirrors come in many shapes and sizesAdaptive optics system is usually behind main telescope mirrorWhat does a “real” adaptive optics system look like?If there is no nearby star, make your own “star” using a laserSlide 14Slide 15AO at the Keck 10 m TelescopeAdaptive optics on 10-m Keck II Telescope: Factor of 10 increase in spatial resolutionSlide 18Slide 19Neptune in Infrared LightNeptune: Ground-based AO vs. Voyager SpacecraftSaturn’s moon Titan: Shrouded by haze as seen by Hubble Space TelescopeTitan at Keck: with and without adaptive opticsUranus as seen by Hubble Space Telescope and Keck AOKeck AO Can See the Faintest Rings Discovered by VoyagerSlide 26Slide 27Other Uses for AOSlide 29Slide 30Slide 31Slide 32Adaptive optics provides highest resolution images of living human retinaSlide 34Slide 35Retinal Imaging – Basic ScienceSlide 37Primary Mirrors: CELT vs. KeckCELT and StonehengeCELT in PacBell ParkSlide 41Slide 42Slide 43Slide 44“Twinkle, Twinkle Little Star”:An Introduction to Adaptive OpticsMt. Hamilton Visitor’s NightJuly 28, 2001Turbulence in the atmosphere limits the performance of astronomical telescopesEven the largest ground-based astronomical telescopes have no better resolution than an 8" backyard telescope!Even the largest ground-based astronomical telescopes have no better resolution than an 8" backyard telescope!•Turbulence is the reason why stars twinkle•More important for astronomy, turbulence spreads out the light from a star; makes it a blob rather than a pointDistant stars should resemble “points,” if it weren’t for turbulence in Earth’s atmosphere Images of a bright star, ArcturusLick Observatory, 1 m telescopeLong exposureimageShort exposureimage“Perfect” image: diffraction limit of telescopeTurbulence changes rapidly with time Sequence of very short snapshots of a star.Movie is much slower than "real time."Sequence of very short snapshots of a star.Movie is much slower than "real time."Measure details of blurring from “guide star” near the object you want to observeCalculate (on a computer) the shape to apply to deformable mirror to correct blurringLight from both guide star and astronomical object is reflected from deformable mirror; distortions are removedHow to correct for atmospheric blurringBasic idea of AOAberratedwavefrontWavefrontsensorWavefront controlcomputerCorrectedwavefrontWavefrontcorrectorAdaptive optics in actionStar with adaptive opticsStar without adaptive opticsLick Observatory adaptive optics systemThe Deformable MirrorThe Deformable MirrorDeformable mirrors come in many shapes and sizes•Today: mirrors from Xinetics. From 13 to 900 actuators (degrees of freedom); 3 - 15 inches in diameter.• Future: very small mirrors (MEMS, LCDs); very large mirrors (replace secondary mirror of the telescope)Xinetics Inc.Devens, MAAdaptive optics system is usually behind main telescope mirror•Example: AO system at Lick Observatory’s 3 m telescopeSupport for maintelescope mirrorAdaptive optics package under main mirrorWhat does a “real” adaptive optics system look like?Wavefront sensorInfra-red cameraDeformable mirrorLight from telescopeIf there is no nearby star, make your own “star” using a laserConceptImplementationLick Obs.Laser in 120-inch domeLaser guide star adaptive optics at Lick ObservatoryLaser Guide Star correction of a star: Strehl = 0.6Uncorrected image of a starIrcal1129.fits RX J0258.3+1947 10/20/00 2:04 Ks V=15 K=~13.32 20s S=0.6 LGSAO at the Keck 10 m TelescopeAdaptive optics lives hereAdaptive optics on 10-m Keck II Telescope: Factor of 10 increase in spatial resolutionWithout AOwidth = 0.34 arc secWithout AOWith AOwidth = 0.039 arc sec9th magnitude star imaged in infrared light (1.6 m)Neptune in Infrared LightWithout adaptive opticsWith Keck adaptive opticsJune 27, 19992.3 arc secMay 24, 1999 = 1.65 micronsNeptune:Ground-based AO vs. Voyager SpacecraftInfrared: Keck adaptive optics, 2000Visible: Voyager 2 fly-by, 1989Circumferential bandsCompact southern featuresSaturn’s moon Titan: Shrouded by hazeas seen by Hubble Space TelescopeLimb Brightening due to hazeHints of surface detailImage at 0.85 micronsTitan at Keck: with and without adaptive optics Titan with adaptive optics Titan without adaptive optics Typical @ wavelength 1.65 mFebruary 26-27, 1999Uranus as seen by Hubble Space Telescope and Keck AO Hubble Space Telescopefalse-color image (1.1, 1.6, 1.9 m)Keck adaptive optics image (2.1 m)Keck AO Can See the Faintest RingsDiscovered by Voyager Voyager: 4 groups of rings 4 5 6Keck AO: outer  ring plus 3 inner groups (individual rings unresolved)Infrared image (2 microns)1 arc secA volcano erupting on Io: Jupiter's largest moonVolcano erupting on limbIo with adaptive optics sees most of the volcanic features seen by GalileoKeck AO: three IR "colors"Galileo: visible CCD cameraSame volcanoesSame volcanoesOther Uses for AO•High-speed communications with laser beams•Cheaper and lighter telescopes in space•High-powered lasers for fusion power•Vision science researchPerfect EyeAberrated EyeWhy Correct the Eye’s Why Correct the Eye’s Optics?Optics?pupil imagesfollowed by psfs for changing pupil sizeVisual Acuity Is Worse at Night When Pupils DilateVisual Acuity Is Worse at Night When Pupils Dilate1 mm 2 mm 3 mm 4 mm5 mm 6 mm 7 mmThe Rochester Adaptive Optics OphthalmoscopeThe Rochester Adaptive Optics OphthalmoscopeAdaptive optics provides a clear improvement in retinal image qualityWave AberrationPoint Spread FunctionRetinal Image at 550nmRetinal Image inWhite Light6.8 mm pupilBefore adaptive optics:After adaptive optics:1 degYYAdaptive optics provides highest resolution images of living human retinaWithout AOWith AO:Resolve individual conesWilliams, Roorda et al. (U Rochester)JW right eye1 deg field 1 deg eccentricityPhotoreceptorsPhotoreceptorsCapillariesCapillaries10arcmin(48.6 m)Looking Inside the Eye with AOView of Lunar EclipseView of Lunar EclipseRetinal Imaging – Basic ScienceFirst images of the trichromatic photoreceptor