麻省理工学院：《Satellite Engineering》Lecture 7 Introduction to Optics part II

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 February 13, 2001 MIT Space Systems Laboratory

16.684 Space Systems Product Development Chart: 1 February 13, 2001 MIT Space Systems Laboratory 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

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 February 13, 2001 MIT Space Systems Laboratory

16.684 Space Systems Product Development Chart: 2 February 13, 2001 MIT Space Systems Laboratory Interferometer Types (NASA, AirForce) SIM-2006 Space Technology 3-2005 Air Force UltraLITE Michelson Interferometer Precision Astrometry Michelson Interferometer Fizeau Interferometer Earth Observing Telescope TPF - 2011 NGST - 2007 Michelson Interferometer A Common Secondary Mirror (MMT, Fizeau) Primary Mirror = 8 m diameter

Interferometer Types(Ground) THE KECK INTERFEROMETEP Keck Interferometer -2006 Michelson Interferometer(Infrared) Twin 10 m Keck Telescopes and four 1.8 m outriggers Baseline 85 LASARJPL CAR Palomar testbed Interferometer Michelson Interferometer(Infrared Testbed for Keck and sim Mark lll 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 February 13, 2001 MIT Space Systems Laboratory

16.684 Space Systems Product Development Chart: 3 February 13, 2001 MIT Space Systems Laboratory Interferometer Types (Ground) Michelson Interferometer (Visible) 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 Keck Observatory: Multiple Mirror Telescope (MMT) Fizeau Interferometer (Visible, Infrared) 36 hexagonal segments => 10 m overall aperture

Michelson interferometer Michelson lnterferometer Imaging with Michelson Interferometer Collector Beamsplitter slane Reconstructed Baseline orientations. Detector Collector Optical delay Detecto 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 February 13, 2001 MIT Space Systems Laboratory

16.684 Space Systems Product Development Chart: 4 February 13, 2001 MIT Space Systems Laboratory Michelson Interferometer 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 Beamsplitter Collector Collector Michelson Interferometer Stellar wavefront Detector Detector Optical delay line Object Imaging with Michelson Interferometer FT "FT-1" Baseline orientations: + y x v v v y u u u x u-v (Fourier plane) Reconstructed image

Fizeau interferometer Fizeau Interferometer Detector Detector Telescopes Beam combiner Telescope Sparse aperture Fizeau Interferometer Telescope 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 February 13, 2001 MIT Space Systems Laboratory

16.684 Space Systems Product Development Chart: 5 February 13, 2001 MIT Space Systems Laboratory Fizeau Interferometer 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) 1 2 3 Telescope Telescopes Fizeau Interferometer Fizeau Interferometer Detector Detector Sparse aperture Telescope "Beam combiner

Comparison(fizeau, Michelson) Fizea u Miche son nte rfe rometer Interferomete er Produce a dir ect im age o f its Takes a sub set of u-v po ints targ et( Full Inst ant u-v c over age obtaine d a peri od of time pr ov id ed) Wide ang le(field) of view Ast rome try. im aging app lications Nulling Inter from etry R api dly cha nging t arge ts T arg et unc han ged (Terre strial, Earth objects) (Ast ron omi cal objects) Takes t he comb ine d sci en ce Me as ure s po ints in Fourier light from all the ap ertures and tran sf orm of ima ges = Inverse focuses it into C CD FFT ne eded U-V re so lution dep end s on b oth Angula r re so lution de pend s the separa tion and the size of solely on the separa tion of a per ture s aperture s Optima I Con figuration The angul ar res olution im proves Golay(m inim um aper ture size) as the sep ara tion incre as es Chart: 6 16.684 Space Systems Product Development February 13, 2001 MIT Space Systems Laboratory

16.684 Space Systems Product Development Chart: 6 February 13, 2001 MIT Space Systems Laboratory Comparison (Fizeau, Michelson) Fi zea u Int erferomet er Miche lson Inte rfe romete r Pro duce a dir ec t im age o f its targ et (Ful l Instan t u- v c over age pr ov ided) Takes a sub se t o f u- v po ints obtaine d a peri od o f tim e. Wide ang le(f ield) of view im aging app lications Ast rome try, Nulling Interferom etry Rapidly Cha nging t arge ts (Terre strial, Ea rth Objects) Targ et u nc han ged (Ast ron omi cal Objects) Takes t he comb ine d sci en ce ligh t from all the ap erture s an d focuses it into C CD Me as ure s po ints in Fourier tran sform of ima ges => Inver se FFT ne eded U- V re so lution dep end s on b oth the separa tion and the size of aperture s Angula r re so lution de pend s solel y on the separa tion of aperture s Optima l Con figura tion: Golay (m inim um aper ture size ) The angul ar res olution im pro ves as t he sep ara tion incre as es

Common Secondary vs sub telescope Common Secondary Mirror Array Phased Sub Telescope Array Beam D Combine Common primal Sub Telescope Fizea 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 Air Force is studying two options for UltraLITE(Golay 6) Chart: 7 16.684 Space Systems Product Development February 13, 2001 MIT Space Systems Laboratory

16.684 Space Systems Product Development Chart: 7 February 13, 2001 MIT Space Systems Laboratory CCD Beam Combiner Common Secondary vs Sub Telescope Phased Sub￾Telescope Arrays Common Primary Sub Telescope Fizeau Precise Off Axis Configuration Off Axis Optical Aberration Need Combiner + Phase sensing and compensater mechanism (complex) Less Central Obstruction(Off Axis) On Axis Suffers Central Obstruction Hard to change the Configuration Can employ Off-the-shelf telescopes Common Secondary Mirror Array AirForce is studying two options for UltraLITE(Golay 6)

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 al 0.4 Optical Array Configuration 0.15 0.1 X1000.05 Elevation [rad Azimuth [rad -0.05 Transmissivity function Derivation see separate -02 handout(mennesson) 0 0.1 X- Distance (m Chart: 8 16.684 Space Systems Product Development February 13, 2001 MIT Space Systems Laboratory

16.684 Space Systems Product Development Chart: 8 February 13, 2001 MIT Space Systems Laboratory Optical Arrays -0.3 -0.2 -0.1 0 0.1 0.2 0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 Optical Array Configuration X - Distance [m] Y - Distance [m] 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 Transmissivity Function: Derivation see separate handout (Mennesson)

CDIO: Breaking the paradigm Optical Array Configuraton Optical Array Configuration Physical Aperture ayo Compare Architectures -0.31 -0.40.3-0.20.100.10.20.30.4 with X- Distance [m 0.50.40.3-02-0.100.10.20.30.40.5 Quantitative Monolithic 0.6 m telescope Metrics Golay-3 0.6 m telescope PSF Elevation [rad Azimuth [rad Elevation [rad) Azimuth [rad Chart: 9 16.684 Space Systems Product Development February 13, 2001 MIT Space Systems Laboratory

16.684 Space Systems Product Development Chart: 9 February 13, 2001 MIT Space Systems Laboratory CDIO: 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 -0.1 0 0.1 0.2 0.3 0.4 Optical Array Configuration X - Distance [m] Y - D i s t an c e [m ] Golay-3 0.6 m telescope 3 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 -0.1 0 0.1 0.2 0.3 Optical Array Configuration X - Distance [m] Y - D i s t an c e [m] Physical Physical Aperture Aperture Layout Monolithic 0.6 m telescope Monolithic 0.6 m telescope Compare Architectures with Quantitative Metrics PSF

Effective Radius of Optical Array Array Configuration, 0.58905m, L=1m PSF Plot How to find the effective radius(reff) of the array? 0.5 Neff =the radius of the array thought as that of a monolithic 5 UV coverage plot x10 XImI 2 Elevation(rad]5-5 Azimuth (rad] =±x2-xy=±少 U-y coverage Encircled Energy =0.60006 x,y is any point within aperture R: the maximum radius of uv plot without any holes 0.5 R=0.5R 1 2 Fill Factor: the array's tota 0 x 10 collecting area over the area of a Elevation(rad)-5-5 Azimuth (rad) filled aperture with the same uv coverage( the same Reff) Chart: 10 16.684 Space Systems Product Development February 13, 2001 MIT Space Systems Laboratory

16.684 Space Systems Product Development Chart: 10 February 13, 2001 MIT Space Systems Laboratory Effective Radius of Optical Array How to find the effective radius(Reff) of the array? • =the radius of the array thought as that of a monolithic aperture. • UV coverage plot x,y is any point within aperture • : the maximum radius of uv plot without any holes • • Fill Factor: the array’s total collecting area over the area of a filled aperture with the same uv coverage(the same Reff) u = ± x2 − x1 λ v = ± y2 − y1 λ Ruv Reff Reff = 0.5Ruv