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Optical Analysis and Stray Light Evaluation Dennis Charles Evans 16 November 2001. ZEMAX Optical Layout ISAL prescription from TMA62 write-up Checked against customer supplied ZEMAX Optical Sensitivities Basic Sensitivity Active Secondary (5-dof) Stray Light Baffle Layout - PowerPoint PPT Presentation
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16 November 2001
Optical Analysis & Stray Light Evaluation Dennis C. Evans p1
SuperNova/Acceleration Probe
Optical Analysisand
Stray Light Evaluation
Dennis Charles Evans
16 November 2001
16 November 2001
Optical Analysis & Stray Light Evaluation Dennis C. Evans p2
SuperNova/Acceleration Probe
• ZEMAX Optical Layout ISAL prescription from TMA62 write-up Checked against customer supplied
ZEMAX
• Optical Sensitivities Basic Sensitivity Active Secondary (5-dof)
• Stray Light Baffle Layout• Spectrograph Enclosure and Insertion• Views from the Detector• Solar Flux• Open Items
16 November 2001
Optical Analysis & Stray Light Evaluation Dennis C. Evans p3
SuperNova/Acceleration Probe
• ZEMAX Optical Layout ISAL prescription from TMA62 write-up Checked against customer supplied
ZEMAX
16 November 2001
Optical Analysis & Stray Light Evaluation Dennis C. Evans p4
SuperNova/Acceleration Probe
16 November 2001
Optical Analysis & Stray Light Evaluation Dennis C. Evans p5
SuperNova/Acceleration Probe
16 November 2001
Optical Analysis & Stray Light Evaluation Dennis C. Evans p6
SuperNova/Acceleration Probe
16 November 2001
Optical Analysis & Stray Light Evaluation Dennis C. Evans p7
SuperNova/Acceleration Probe
Optical Sensitivity•Basic Sensitivity
Individual Element Increments of 0.001 mm or degree to 0.016
MF Limit (RMS Spot Radius)(0.002837÷0.005000)*2 = 0.32194276
•Active Secondary Five degree-of-freedom
—Dx, Dy, Dz, Tx, Ty Limits on Secondary
— ± 1 mm or degree Limits on Elements
— ± 0.256 mm or degree
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p8
SuperNova/Acceleration Probe
Basic Limit Active Secondary Limit
Primary Tilt 0.0003 deg 0.185 deg
Primary-Secondary
Space
0.0008 mm 0.033 mm
Tertiary Tilt 0.016 deg 0.055 deg
Key Tolerance Comparison
16 November 2001
Optical Analysis & Stray Light Evaluation Dennis C. Evans p9
SuperNova/Acceleration Probe
• Basic Sensitivity (limited to 0.005 RMS Radius)TETX TETY Tilt about X & Y 5=Primary 0.000335 deg ×3600 arc-sec/deg = 1.206 arc-secTTHI Thickness 4-6; 0.000802 mm TRAD Radius of Curvature 5 0.001604 mm (= same effect as thickness change)TIRX TIRY Sag (Tilt) Across Lens 5 0.011705 mmTSDX TSDY Surface Decenter 5 0.014518 mmTEDX TEDY Element Decenter 5 0.014518 mm
TETX TETY Tilt about X & Y 8=Secondary 0.001515 deg ×3600 arc-sec/deg = 5.454 arc-secTTHI Thickness 7-9; 0.000602 mm TRAD Radius of Curvature 8 0.001828 mm TIRX TIRY Sag (Tilt) Across Lens 8 0.011261 mmTSDX TSDY Surface Decenter 8 0.014658 mmTEDX TEDY Element Decenter 8 0.014658 mm
TETX Tilt about X & Y 17=Fold Flat 0.008217 deg ×3600 arc-sec/deg = 5.454 arc-secTETY Tilt about X & Y 17 0.011621 deg ×3600 arc-sec/deg = 5.454 arc-secTTHI Thickness 16-18; 0.018010 mm TRAD Radius of Curvature 17 insensitive at 0.256 change TIRX Sag (Tilt) Across Lens 17 0.150454 mm TIRY Sag (Tilt) Across Lens 17 0.106387 mmTSDX TSDY Surface Decenter 17 insensitive at 0.256 change (0.002884)TEDX TEDY Element Decenter 17 insensitive at 0.256 change (0.002884)
TETX TETY Tilt about X & Y 22=Tertiary 0.016927 deg ×3600 arc-sec/deg = 60.9372 arc-secTTHI Thickness 21-23; 0.016919 mm TRAD Radius of Curvature 22 0.031079 mm TIRX TIRY Sag (Tilt) Across Lens 22 0.199252 mmTSDX TSDY Surface Decenter 22 insensitive at 0.256 change (0.003732)TEDX TEDY Element Decenter 22 insensitive at 0.256 change (0.003732)
TETX TETY Tilt about X & Y 32-33=Filter insensitive at 0.256 change (0.002886)TTHI Thickness 21-23; 0.016919 mm TRAD Radius of Curvature 22 0.031079 mm TIRX TIRY Sag (Tilt) Across Lens 22 0.199252 mmTSDX TSDY Surface Decenter 22 insensitive at 0.256 change (0.003732)TEDX TEDY Element Decenter 22 insensitive at 0.256 change (0.003732)
TTHI Filter to Image 36-37 0.136618 mm (Image Plane is compensator for fast analysis)
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p10
SuperNova/Acceleration Probe
|------------ Minimum ------------| |------------ Maximum ------------|Type Value MF Change Value MF Change(Primary Mirror)Thickness tolerance on surface 4 TTHI 4 6 -0.033610 0.005000 0.002163 0.033112 0.005000 0.002163 Thickness 8: 1.00001E+000 -1.00001E+000Radius tolerance on surface 5TRAD 5 -0.066773 0.004566 0.001730 0.066242 0.005000 0.002163 Thickness 8: 1.00001E+000 -1.00001E+000Tilt X tolerance on surfaces 5 through 5 (degrees)TETX 5 5 -0.185670 0.005000 0.002163 0.185670 0.005000 0.002163 Parameter 2 on Surface 7: 9.12416E-002 -9.12419E-002 Parameter 3 on Surface 7: -1.87703E-001 1.87703E-001Tilt Y tolerance on surfaces 5 through 5 (degrees)TETY 5 5 -0.185720 0.005000 0.002163 0.185720 0.005000 0.002163 Parameter 1 on Surface 7: -9.12903E-002 9.12680E-002 Parameter 4 on Surface 7: -1.87754E-001 1.87754E-001
(Fold Flat)Thickness tolerance on surface 16TTHI 16 18 -0.256000 0.004764 0.001927 0.256000 0.004764 0.001927 Thickness 8: 1.74322E-001 -1.87717E-001TIRX 17 -0.256000 0.004388 0.001551 0.256000 0.004388 0.001551 Parameter 1 on Surface 7: -5.13796E-001 5.13786E-001TIR Y tolerance on surface 17TIRY 17 -0.222637 0.005000 0.002163 0.222637 0.005000 0.002163 Parameter 2 on Surface 7: 6.31916E-001 -6.31897E-001Tilt X tolerance on surfaces 17 through 17 (degrees)TETX 17 17 -0.017196 0.005000 0.002163 0.017196 0.005000 0.002163 Parameter 2 on Surface 7: 6.31902E-001 -6.31891E-001Tilt Y tolerance on surfaces 17 through 17 (degrees)TETY 17 17 -0.024319 0.005000 0.002163 0.024319 0.005000 0.002163
(Tertiary Mirror)Tilt X tolerance on surfaces 22 through 22 (degrees)TETX 22 22 -0.055298 0.005000 0.002163 0.055298 0.005000 0.002163 Parameter 2 on Surface 7: -1.00001E+000 1.00001E+000Tilt Y tolerance on surfaces 22 through 22 (degrees)TETY 22 22 -0.055298 0.005000 0.002163 0.055298 0.005000 0.002163 Parameter 1 on Surface 7: 1.00001E+000 -1.00001E+000
Active Secondary Sensitivity
16 November 2001
Optical Analysis & Stray Light Evaluation Dennis C. Evans p11
SuperNova/Acceleration Probe
•Stray Light Baffle Layout
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p12
SuperNova/Acceleration Probe
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p13
SuperNova/Acceleration Probe
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SuperNova/Acceleration Probe
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SuperNova/Acceleration Probe
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p16
SuperNova/Acceleration Probe
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SuperNova/Acceleration Probe
• Spectrograph Enclosure and Insertion
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SuperNova/Acceleration Probe
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p19
SuperNova/Acceleration Probe
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p20
SuperNova/Acceleration Probe
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SuperNova/Acceleration Probe
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p22
SuperNova/Acceleration Probe
• Views from the Detector
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p23
SuperNova/Acceleration Probe
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p24
SuperNova/Acceleration Probe
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p25
SuperNova/Acceleration Probe
• Solar Flux Concentrations inside Instrument Solar Flux = 1 SC = .1367 watt.cm-2 = 1367 watt.m-2
Location Image Radius (mm)
Flux (SC)
Flux(watt.cm-
2)
Flux(watts
)
Entrance Aperture 1000 1 .1367 4295
Secondary Mirror 213 22 3.1 4295
Prime Focus Ring 10.7 4367 597 2147
Focal Plane 1 64 244 33 4295
Shutter Pupil 48 437 60 4295
FP 2 (CCD/Image) 96 109 15 4295
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p26
SuperNova/Acceleration Probe
Open Items&
Concerns
16 November 2001
Optical Analysis & Stray Light Evaluation Dennis C. Evans p27
SuperNova/Acceleration Probe
• Open Items
Shade angle (<30o?) and Barrel Baffle length Baffle edge finish (Forward Ring) Cleanliness, especially of Primary Mirror Aft Optics Baffles (Mostly black paint) MLI outer layer vs. mission length Reverse views
— AutoCAD Photo Ray Trace— reverse ray trace, TMA62
Focal plane — parfocalization (filter thickness)
S/G placement — behind focal plane?— center mounted
ASAP diffuse scatter model — (Friday PM – Next Week)
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p28
SuperNova/Acceleration Probe
• Mission Unique Concerns: No mission unique concerns have been
observed.
Stray light issues are manageable using proven baffling techniques that have been successfully demonstrated on flight missions.
Analysis done too early in the design cycle is likely to give false confidence (analytical design is better than real design).
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p29
SuperNova/Acceleration Probe
• Central Obscuration Minimum possible - about 5% (Shadow of
Secondary)
Current minimum design to keep direct light from Focal Surface 1 - about 15%
Maximum practical limit to keep direct light from inner baffle interior and front lip - slightly less than 25%
16 November 2001
Optical Analysis & Stray Light Evaluation Dennis C. Evans p30
SuperNova/Acceleration Probe
• Stray Light Issues Similarity to flight instruments shows successful design is possible
—HST, FUSE, COBE-DIRBE, IUE, OAO
Similarity to flight instruments shows design flaws are possible that will not be detected by stray light analysis, but by careful design, inspection, and testing.
—HST - Door reflections—DIRBE - Barrel Baffle side wall single bounces.—IUE/OAO - Pinhole leaks into aft optics assemblies; bolt head locations.
Design & Analysis Similarity—SIRTF - IRAC—WIRE (minor changes make orders of magnitude stray light differences)—GOES Earth Limb Sensor (light leaks around filters and side wall reflections)—MODIS - Stray light in calibrator designs, not instrument designs
16 November 2001
Optical Analysis & Stray Light Evaluation Dennis C. Evans p31
SuperNova/Acceleration Probe
• Focus Drive Mechanism Definition of acceptable image size needs to be
reviewed. RMS radius of 0.005 mm may be to conservative for
a pixel limited performance instrument. Range of motions used were +/- 1 mm and degree. The Displacement motions may be effectively
increased to 5 or 10 mm for some corrections. Tolerance analysis so far is only with two elements at
a time and has not included Image Plane tilts.
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Optical Analysis & Stray Light Evaluation Dennis C. Evans p32
SuperNova/Acceleration Probe
• View from the detector inspection is important. Fold Flat throat can be illuminated by sky. Fold flat throat design as in this study may not
allow AFT star tracker
• AFT optics baffles and black surfaces Baffles not designed yet Black paint has been known to cause CTE
changes in GFRP structures.