Interferometer Types PDF
Preview Interferometer Types
Introduction to Optics part II Overview Lecture Space Systems Engineering presented by: Prof. David Miller prepared by: Olivier de Weck Revised and augmented by: Soon-Jo Chung Chart: 1 16.684 Space Systems Product Development MIT Space Systems Laboratory February 13, 2001 Interferometer Types (NASA, AirForce) SIM-2006 Space Technology 3-2005 Air Force UltraLITE Michelson Interferometer Michelson Interferometer Fizeau Interferometer Precision Astrometry Earth Observing Telescope TPF - 2011 NGST - 2007 Michelson Interferometer A Common Secondary Mirror (MMT, Fizeau) Primary Mirror = 8 m diameter Chart: 2 16.684 Space Systems Product Development MIT Space Systems Laboratory February 13, 2001 Interferometer Types (Ground) Keck Interferometer-2006 Michelson Interferometer (Infrared) Twin 10 m Keck Telescopes and four 1.8 m outriggers Baseline 85m Palomar Testbed Interferometer Michelson Interferometer (Infrared) Testbed for Keck and SIM Mark III Interferometer Michelson Interferometer (Visible) Keck Observatory: Multiple Mirror Telescope (MMT) Fizeau Interferometer (Visible, Infrared) 36 hexagonal segments => 10 m overall aperture Chart: 3 16.684 Space Systems Product Development MIT Space Systems Laboratory February 13, 2001 Michelson Interferometer Michelson Interferometer Stellar Imaging with Michelson Interferometer wa vefr y v v v y o nt + x u u u x FT -1 "FT " Beamsplitter Object u-v (Fourier plane) Reconstructed Collector image Baseline orientations: Detector Collector Optical delay Detector line Independent 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 time Chart: 4 16.684 Space Systems Product Development MIT Space Systems Laboratory February 13, 2001 Fizeau Interferometer Fizeau Interferometer Detector Detector Telescopes "Beam combiner" Sparse aperture Telescope Fizeau Interferometer Telescope 1 2 3 Gives 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) Chart: 5 16.684 Space Systems Product Development MIT Space Systems Laboratory February 13, 2001 Comparison (Fizeau, Michelson) Fizea u Miche lson Inte rferomete r Int erferomet er Produce a direct im age o f its Takes a subset of u-v points targ et (Full Instant u-v c overage obtaine d a period o f time. provided) Wide angle(f ield) of view Ast rome try, imaging app lications Nulling Interferom etry Rapidly Cha nging targe ts Targ et unchan ged (Terre strial, Ea rth Objects) (Ast ron omical Objects) Takes the comb ined sci ence Me asure s points in Fourier light from all the apertures and tran sform of ima ges => Inverse focuses it into C CD FFT needed U-V resolution depends on both Angula r re solution de pend s the separa tion and the size of solely on the separa tion of aperture s aperture s Optima l Configuration: The angul ar resolution im proves Golay (m inim um aper ture size) as the separation increases Chart: 6 16.684 Space Systems Product Development MIT Space Systems Laboratory February 13, 2001 Common Secondary vs Sub Telescope Common Secondary Mirror Array Phased Sub- Telescope Arrays Beam CCD Combiner Common Primary Sub Telescope Fizeau Precise Off Axis Configuration Need Combiner + Phase sensing and Off Axis Optical Aberration compensater mechanism (complex) Less Central Obstruction(Off Axis) On Axis Suffers Central Obstruction Hard to change the Configuration Can employ Off-the-shelf telescopes AirForce is studying two options for UltraLITE(Golay 6) Chart: 7 16.684 Space Systems Product Development MIT Space Systems Laboratory February 13, 2001 Optical Arrays Instead of using a single aperture use several and combine their light to form a single image Aperture positions (uv) are critical - look at combined PSF / Transmissivity of the Optical Array Optical Array Configuration 0.25 0.2 0.15 0.1 m] e [ 0.05 c n a 0 st Di -0.05 - Y Transmissivity Function: -0.1 -0.15 -0.2 Derivation see separate -0.25 handout (Mennesson) -0.3 -0.2 -0.1 0 0.1 0.2 0.3 X -Distance [m] Chart: 8 16.684 Space Systems Product Development MIT Space Systems Laboratory February 13, 2001 CDIO: Breaking the Paradigm Optical Array Configuration Optical Array Configuration PPhhyyssiiccaall 0.4 0.3 AAppeerrttuurree 0.3 0.2 LLaayyoouutt 0.2 m] 0.1 m] 0.1 e [ e [ Distanc 0 Distanc 0 Y - -0.1 Y - -0.1 -0.2 Compare -0.2 -0.3 Architectures -0.3 with -0.4 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 X - Distance [m] Quantitative -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 X - Distance [m] GGoollaayy--33 00..66 mm tteelleessccooppee MMoonnoolliitthhiicc 00..66 mm tteelleessccooppee Metrics PPSSFF Chart: 9 16.684 Space Systems Product Development MIT Space Systems Laboratory February 13, 2001 Effective Radius of Optical Array How to find the effective radius(Reff) of the array? R • =the radius of the array eff thought as that of a monolithic aperture. • UV coverage plot x − x y − y u = ± 2 1 v = ± 2 1 λ λ x,y is any point within aperture R • : the maximum radius of uv uv plot without any holes • R = 0.5R eff uv • Fill Factor: the array’s total collecting area over the area of a filled aperture with the same uv coverage(the same Reff) Chart: 10 16.684 Space Systems Product Development MIT Space Systems Laboratory February 13, 2001
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