Introduction to Optics part IIInterferometer Types (NASA, AirForce)Interferometer Types (Ground)Michelson InterferometerFizeau InterferometerComparison (Fizeau, Michelson)Common Secondary vs Sub TelescopeOptical ArraysCDIO: Breaking the ParadigmEffective Radius of Optical ArrayGolay ConfigurationsTechnological TrendsOptical Performance CriteriaOptical SensitivityPSF,EE (Golay Array –3)Modulation Transfer FunctionOptical Control and Beam CombiningLateral Pupil Geometry ErrorOptical ToleranceBeam Combining LayoutSensor System Optics(Example from AFRL)ReferencesOptical System Design Process16.684 Space Systems Product DevelopmentChart: 1February 13, 2001MIT Space Systems LaboratoryIntroduction to Optics part IIOverview LectureSpace Systems Engineeringpresented by: Prof. David Millerprepared by: Olivier de WeckRevised and augmented by: Soon-Jo Chung16.684 Space Systems Product DevelopmentChart: 2February 13, 2001MIT Space Systems LaboratoryInterferometer Types (NASA, AirForce)Space Technology 3-2005Air Force UltraLITESIM-2006Michelson InterferometerPrecision AstrometryMichelson InterferometerFizeau InterferometerEarth Observing TelescopeTPF - 2011NGST - 2007Michelson InterferometerA Common Secondary Mirror (MMT, Fizeau)Primary Mirror = 8 m diameter16.684 Space Systems Product DevelopmentChart: 3February 13, 2001MIT Space Systems LaboratoryInterferometer Types (Ground)Michelson Interferometer (Visible)Keck Interferometer-2006Michelson Interferometer (Infrared)Twin 10 m Keck Telescopes and four 1.8 m outriggersBaseline 85mPalomar Testbed InterferometerMichelson Interferometer (Infrared)Testbed for Keck and SIMMark III InterferometerKeck Observatory: Multiple Mirror Telescope (MMT)Fizeau Interferometer (Visible, Infrared)36 hexagonal segments => 10 m overall aperture16.684 Space Systems Product DevelopmentChart: 4February 13, 2001MIT Space Systems LaboratoryMichelson InterferometerIndependent Light Collectors feed light to a common beam combiner. Get interfered fringes => Inverse Fourier Transform (CLEAN,MEM)Suitable for Astronomical Objects:Unchanged over a long period of timeBeamsplitterCollectorCollectorMichelson InterferometerStellar wavefrontDetectorDetectorOptical delay lineObjectImaging with Michelson InterferometerFT"FT-1"Baseline orientations:+yxyvvvuuuxu-v (Fourier plane) Reconstructed image16.684 Space Systems Product DevelopmentChart: 5February 13, 2001MIT Space Systems LaboratoryFizeau InterferometerGives a direct image of a target from a large combined primary mirror, and a wide field of view (Imaging applications in space and MMT)Suitable for Wide Angle Astrometry And for rapidly changing targets (Terrestrial, Earth Objects)1 2 3TelescopeTelescopesFizeau InterferometerFizeau InterferometerDetectorDetectorSparse aperture Telescope"Beam combiner"16.684 Space Systems Product DevelopmentChart: 6February 13, 2001MIT Space Systems LaboratoryComparison (Fizeau, Michelson)Fi zea uInt erf er omet erM iche lson Inte rfe rom ete rPro duce a dir ec t im age o f itstarg et ( Ful l Inst an t u- v c over agepr ov id ed)Takes a s ub se t o f u- v po intsobtaine d a peri od o f tim e.Wide angle(field) of viewim agi ng app licationsAst rome try,N ulling Inter ferom etr yRapi dly Cha ngi ng t arge ts(Terre st rial, Ea rth Objects)Targ et u nc han ged(Ast ron omi cal O bjects)Takes t he c omb ine d sci en celigh t from all the ap erture s an dfocuses it i nto C CDMe as ure s po ints in Fouriertran sf orm of ima ges => Inver seFFT ne ededU- V re so lu tion dep end s on b oththe separa tion and the size ofaper ture sAngula r re so lu tion de pend ssolel y on the s epara tion ofaper ture sOptima l Con fig ura tio n:Gol ay (m inim um aper ture size )The angul ar res ol ution im pro vesas t he s ep ara tio n incre as es16.684 Space Systems Product DevelopmentChart: 7February 13, 2001MIT Space Systems LaboratoryCCDBeamCombinerCommon Secondary vs Sub TelescopePhased Sub-Telescope Arrays Common Primary Sub Telescope FizeauPrecise Off Axis ConfigurationOff Axis Optical AberrationNeed Combiner + Phase sensing andcompensater mechanism (complex)Less Central Obstruction(Off Axis) On Axis Suffers Central ObstructionHard to change the Configuration Can employ Off-the-shelf telescopesCommon Secondary Mirror ArrayAirForce is studying two options for UltraLITE(Golay 6)16.684 Space Systems Product DevelopmentChart: 8February 13, 2001MIT Space Systems LaboratoryOptical Arrays-0.3 -0.2 -0.1 0 0.1 0.2 0.3-0.25-0.2-0.15-0.1-0.0500.050.10.150.20.25Optical Array ConfigurationX - Distance [m] Y - Distance [m] Instead of using a single aperture use several and combine their light to form a single imageAperture positions (uv) are critical -look at combined PSF / Transmissivityof the Optical ArrayTransmissivity Function:Derivation see separatehandout (Mennesson)16.684 Space Systems Product DevelopmentChart: 9February 13, 2001MIT Space Systems LaboratoryCDIO: Breaking the Paradigm-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5-0.4-0.3-0.2-0.100.10.20.30.4Optical Array Configuration X - Distance [m] Y - Distance [m] GolayGolay--3 0.6 m telescope3 0.6 m telescope-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4-0.3-0.2-0.100.10.20.3Optical Array Configuration X - Distance [m] Y - Distance [m] Physical Physical ApertureApertureLayoutLayoutMonolithic 0.6 m telescopeMonolithic 0.6 m telescopeCompareArchitectureswithQuantitativeMetricsPSFPSF16.684 Space Systems Product DevelopmentChart: 10February 13, 2001MIT Space Systems LaboratoryEffective Radius of Optical ArrayHow to find the effective radius(Reff) of the array?• =the radius of the arraythought as that of a monolithicaperture.• UV coverage plotx,y is any point within aperture• : the maximum radius ofuv plot without any holes •• Fill Factor: the array’s total collecting area over the area of a filled aperture with the same uvcoverage(the same Reff)u =±x2−x1λv =±y2−y1λRuvReffReff=0.5Ruv16.684 Space Systems Product DevelopmentChart: 11February 13, 2001MIT Space Systems LaboratoryGolay Configurations•Optimum Golayis Deff-dependent• Labor moves Golay benefits to larger Deff• Golay’s sacrifice Encircled EnergyEE=83.5% EE=26.4% EE=9.3%EE=3.6%EE=2.2%16.684 Space Systems Product DevelopmentChart: 12February 13, 2001MIT Space Systems LaboratoryTechnological Trends• Lightweight (Low-Area-Density) Optics - 15kg/m2• Deployable Optics• Adaptive and Active Optics• Membrane Mirrors and Inflatables• Ultra-Large Arrays (CCD