HI Instrument Optical Design

HI Instrument Optical DesignJ.M. Defise, J.Ph. Halain, E. Mazy, P.RochusCentre Spatial de Liège – Belgium021104-06SECCHI CDR HI Optical.1

Optical Requirements HI-1 HI-2– FOV: 20 From 13.7 to 88.7 Rs– FOV: 70 From 68.9 to 331.4 Rs– Image Area 28 mm x 28 mm(13.5 µm pixels)– Image Area 28 mm x 28 mm(13.5 µm pixels)– Spectral Range: 630 - 730 nm– Spectral Range: 400 - 900 nm– Aperture: 16 mm– Aperture: 7 mm– Max Background Noise: 5 10-13– Max Background Noise: 10-14021104-06SECCHI CDR HI Optical.2

Optics Design Main Challenges:– Faint Detection Capability High Stray-Light Rejection Requirements(Ghosts)– Large FOV Specific Optics HI-1 and HI-2– Large Spectral Range for HI-2HI 2Solar lightHI 1Forward BaffleInternal Baffle021104-06SECCHI CDR HI Optical.3

Optics Design: HI-1 Design Drivers:– Minimize Size of Lens #1 (Entrance Pupil on Lens #1)– 20 FOVLAK9LAK9BK7– Radiation Tolerant Glasses– Ghost Rejections– Margins on MechanicalMount Design Performance:– Minimized RMS Spot DiameterLF588 mmf 78 mmAperture 16 mmFOV 20 – Designed for Extended Thermal Range [-20 C , 30 C]021104-06SECCHI CDR HI Optical.4

B/B0Optics Design: HI-11 .1071 .1081 .1091 .10101 .10111 .10121 .10131 .10141 .10151 .10161 .10171 .10181 .1019 RMS Spot Diameter:– Φ 20.7 µm Ghost Images:– Φ 3.5 mm Coatings:– SiO2 on Surface #1– High Pass Coating 630 nm432GhostBubble (B1)Micro-roughness (2 nm)021104-06SECCHI CDR HI Optical.510[mm]1234– Low Pass Coating 730 nm– AR Coatings on OtherSurfaces

Optics Design: HI-2 Design Drivers:SF6SF6– Ghost ImagesSF4BK7SF6SK16– Large Spectral Range (400-900 nm)– 70 FOV– Radiation Tolerant Glasses Design Performance:46 mmHI-2– Minimized RMS Spot Diameterf 20 mmAperture 7 mmFOV 70 – Maximized Ghost Diameters– Designed for Extended Thermal Range [-20 C , 30 C]– Minimized Incidence Angle on Optical Surfaces for Coating Efficiency021104-06SECCHI CDR HI Optical.6

B/B0Optics Design: HI-21 .1081 .1091 .10101 .10111 .10121 .10131 .10141 .10151 .10161 .10171 .10181 .10191 .1020 RMS Spot Diameter:– Φ 47.2 µm Ghost Images:– Φ 3 mm Coatings– SiO2 On Surface #1– AR Coatings on OtherSurfaces (MgF2)1510Ghost (mv -5)µroughness (1 nm)Bubble (B1)021104-06SECCHI CDR HI Optical.750[mm]51015– No Bandpass Filter

Optics Design: BudgetsHI-1HI-2 Error Budget Including: Error Budget Including:– Lens Figuring– Lens Figuring– Lens Positioning– Lens Positioning– Glass Properties Uncertainties– Glass Properties Uncertainties– Thermal Changes WithTitanium Lens Mounts Within[-20 C, 30 C]– Thermal Changes WithTitanium Lens Mounts Within[-20 C, 30 C]– Detector Positioning– Detector Positioning– RMS Spot Diam. Between45 µm and 69 µm– RMS Spot Diam. Between105 µm and 145 µm021104-06SECCHI CDR HI Optical.8

Changes Since PDR HI-1 Spectral Range Slightly Shifted From 650-750 to 630-730 nm(to Allow Interferometric Tests at 633 nm) HI-2 Effective Focal Length Adjusted to Cope With Distortion Effects Glass Selection With Supplier Availability (HI-1 & HI-2) Tolerance Budget Updated With Lens Barrel Design and Thermal Behavior021104-06SECCHI CDR HI Optical.9

HI Baffle Design Stray-Light Rejection Requirements:– HI-1: Instrumental Background 5 10-13 B0– HI-2: Instrumental Background 10-14 B0 Major Stray-Light Contributors and Dedicated Baffles:– Direct Solar Light (B0): Front Baffle– Bright Sources in and Out FOV (Planets, Stars): Inner Baffle– Payload Elements Near UFOV: Perimeter Baffle021104-06SECCHI CDR HI Optical.10

HI Baffle Design: Front Baffle HI Front Baffle Is Key Element in Background Light Reduction It Has to Provide a 10-9 Rejection Factor for HI-1 (Assuming 10-4 InternalRejection) [a Single Vane System Would Only Provide a 10-4 Rejection]1.E 001.E-01vane #11.E-02HI-1forward baffleRejection level1.E-03vane #21.E-041.E-05vane #31.E-06vane #41.E-071.E-08vane #51.E-09HI-2X1.E-101.E-111.E-1200.020.04HI-1 opticsCascade Fresnel Edge-Diffraction System021104-06SECCHI CDR HI Optical.110.060.080.1X [mm]HI-2 optics

HI Baffle Design: Inner Baffle HI Inner Baffle Is Based on Multi-Reflections on Absorbing Surfaces It Has to Protect HI-1 and HI-2 From Planets and Bright Stars LightReflection on HI Structure Ray Trace Analyses Were Used to Define and Optimize BaffleGeometry, Taking Into Account Manufacturing Constrains021104-06SECCHI CDR HI Optical.12

HI Optical Analysis-80-70-60-50Zodiacal light and stars-40-30HI-2 FOVHI-1CCD-20Planet 1Earth-10Planet 30 Contributors toInstrument Background:Sun10Planet 220HI-1 FOV30HI-2 CCD4060SWAVES Boom7080-80 -70 -60 -50 -40 -30 -20 -1001020304050607080xy angle0 0 - xy zxy021104-06SECCHI CDR HI Optical.13 xy - zx zx zx angle50

HI Optical Analysis Overall Stray-Light Background in HI-1Total HI-1 stray-light at FPA level (B/B0)HI-1 stray-light sky map1.E-121.E-13maximum HI-1 acceptable background 4-06SECCHI CDR HI g]1.E-201.E-21EarthStarsZodiacal Swaves PlanetsSunTotal

HI Optical Analysis Overall Stray-Light Background in HI-2Total HI-2 stray-light at FPA level (B/B0)HI-2 stray-light sky map1.E-121.E-13maximum HI-2 acceptable background 800-60-40-20[deg]021104-06SECCHI CDR HI vesSunEarthZodiacal PlanetsTotal

HI Optical Analysis – Conclusions Front Baffle Has Been Designed to Provide Required Rejection of SunLight (Better Than 10-9 for HI-1 and 10-11 for HI-2) Internal Baffle Has Been Designed to Provide a 2.10-14 and 9. 10-15Rejection Level for HI-1 and for All Other Stray-Light Sources Optics Have Been Optimized to Avoid Ghost Problems Raytrace Studies Have Shown an Additional Margin Due to Lens Barreland Focal Plane Out-of-Field Attenuation (10-6 Rejection) Overall Theoretical Straylight Background Meets Science Requirement021104-06SECCHI CDR HI Optical.16

HI Optical Testing HI Success Directly Relies on Rejection Performance of Front Baffle( 10-9 at HI-1 Level)– Design Is Based on Theoretical Analyses (Fresnel Diffraction)– Preliminary Verifications Indicated Rejection Better Than 10-6 Inner Baffle Performance Is Directly Related to Absorbing Propertiesof Black Coatings Used on CFRP Vanes Verification Program Has Been Set up to Demonstrate ExperimentallyFront Baffle Performance and Black Coating Scattering Properties inFacilities of Centre Spatial De Liège (B)021104-06SECCHI CDR HI Optical.17

Optical Testing: Test Set-Up Goal: Measure Diffracted Light by Cascade Knife Edge System at Level ofHI-1 and HI-2 (10-9 and 10-11 Rejection Factors)– Front Baffle Mock-Up– Powerful Collimated Beam: 20 W Continuous Laser Diode OpticalFiber Collimator– High Sensitivity Detector: Photomultiplier Used in Photon CountingMode– Protection Against External Light and Internal Reflection: Set-Up IsInstalled in a Black Enclosure– “Super Light Trap” to Absorb All Unshaded Direct Flux (108 Efficiency)– Possibility to Run Test Under Vacuum to Avoid Air Perturbations: TestSet Up Is Implemented in a Vacuum Chamber021104-06SECCHI CDR HI Optical.18

HI Optical Testing: Test Set-UpBlack EnclosureFront Baffle Test Mock-UpAttenuatorCollimatorOptical FiberLaser DiodeOptical Bench021104-06SECCHI CDR HI Optical.19Light TrapDetector

HI Optical Testing: Test Mock ibution:Log (I / I0)-2-4-6-8-10Rotation around last vane edge [arcdeg]021104-06SECCHI CDR HI .31.10.90.70.50.30.1-0.1-12

HI Optical Testing: Test Set-UpLight TrapCollimatorVanesDetectorCollimated LightVanes021104-06SECCHI CDR HI Optical.21

Front Baffle Mockup Tests in Air1.E 02Intensity Profile [B/B0]1.E 001.E-02Theoretical values1.E-041 vane (measured)1.E-062 vanes (measured)1.E-083 vanes (measured)4 vanes (measured)1.E-105 vanes (measured)1.E-1210-1-2-3-4Angular offset [arcdeg]021104-06SECCHI CDR HI Optical.22-5-6-7

Front Baffle Mockup: Air/VacuumComparison021104-06SECCHI CDR HI Optical.23

Front Baffle QM: PreliminaryMeasurementsSTEREO - SECCHI- HI Front Baffle : Diffraction Measurements on EQM1.E 011.E 00EQM (air)Relative Intensity Profile -061.E-071.E-081.E-091.E-101.E-11HI-1 front lens location1.E-120.50-0.5-1-1.5-2-2.5-3-3.5Angular offset [arcdeg] Good Indications That the Front BaffleWill Meet the Specification for RejectionRequirements Test to Be Pursued With Alignment andDimensional Checks021104-06SECCHI CDR HI Optical.24-4

Front Baffle Tests - Conclusions Concept of Front Baffle Has Been Demonstrated by Analyses and Tests New Test Set-Up Has Been Developed and We Have MeasuredUnprecedented Experimental Data With Rejection Levels Down to 10-11 Measurements Are Consistent With Theoretical Data (Mock-Up Tests)Therefore We Can Rely on Our Theoretical Data for:– Design Optimization– Misalignment Sensitivity Evaluations Tests on HI Hardware Still Need to Be Pursued, and Are Going on at CSL021104-06SECCHI CDR HI Optical.25

Inner Baffle Verification: BRDFMeasurements BRDF Major Input for RaytraceAnalysis of Inner BaffleDetectorS Z307 Data Not Yet Publishedα Raytrace Analyses Conducted WithZ306 Dataobs-D αinc Laser sourceSample Measurements Shows Similar BRDF,Which Confirms Our PreviousAnalyses 110 deg15 deg30 deg45 deg60 degZ306 Paint0.1Z307 Paint0.10.010.010.0010.001-80-60021104-06SECCHI CDR HI Optical.26-40-20 [deg]020406080-80-60-40-20020[deg]0 deg15 deg30 deg45 deg60 deg406080

HI Instrument Optical Design J.M. Defise, J.Ph. Halain, E. Mazy, P.Rochus Centre Spatial de Liège - Belgium 021104-06SECCHI_CDR_HI Optical.1. Optical Requirements . - Minimized Incidence Angle on Optical Surfaces for Coating Efficiency SF6 SF 6 SF4 BK7 SK16 SF 46 mm f 20 mm