Dennis C. Evans p1 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation Optical Analysis and Stray Light Evaluation Dennis Charles Evans 16 November 2001

Dennis C. Evans p2 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation 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

Dennis C. Evans p3 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation ZEMAX Optical Layout  ISAL prescription from TMA62 write-up  Checked against customer supplied ZEMAX

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 16 November 2001 Optical Analysis & Stray Light Evaluation Optical Sensitivity Basic Sensitivity  Individual Element Increments of mm or degree to  MF Limit (RMS Spot Radius) ( ÷ )*2 = Active Secondary  Five degree-of-freedom —Dx, Dy, Dz, Tx, Ty  Limits on Secondary — ± 1 mm or degree  Limits on Elements — ± mm or degree

Dennis C. Evans p8 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation Basic LimitActive Secondary Limit Primary Tilt deg0.185 deg Primary- Secondary Space mm0.033 mm Tertiary Tilt0.016 deg0.055 deg Key Tolerance Comparison

Dennis C. Evans p9 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation Basic Sensitivity (limited to RMS Radius) TETX TETY Tilt about X & Y 5=Primary deg ×3600 arc-sec/deg = arc-sec TTHI Thickness 4-6; mm TRAD Radius of Curvature mm (= same effect as thickness change) TIRX TIRY Sag (Tilt) Across Lens mm TSDX TSDY Surface Decenter mm TEDX TEDY Element Decenter mm TETX TETY Tilt about X & Y 8=Secondary deg ×3600 arc-sec/deg = arc-sec TTHI Thickness 7-9; mm TRAD Radius of Curvature mm TIRX TIRY Sag (Tilt) Across Lens mm TSDX TSDY Surface Decenter mm TEDX TEDY Element Decenter mm TETX Tilt about X & Y 17=Fold Flat deg ×3600 arc-sec/deg = arc-sec TETY Tilt about X & Y deg ×3600 arc-sec/deg = arc-sec TTHI Thickness 16-18; mm TRAD Radius of Curvature 17 insensitive at change TIRX Sag (Tilt) Across Lens mm TIRY Sag (Tilt) Across Lens mm TSDX TSDY Surface Decenter 17 insensitive at change ( ) TEDX TEDY Element Decenter 17 insensitive at change ( ) TETX TETY Tilt about X & Y 22=Tertiary deg ×3600 arc-sec/deg = arc-sec TTHI Thickness 21-23; mm TRAD Radius of Curvature mm TIRX TIRY Sag (Tilt) Across Lens mm TSDX TSDY Surface Decenter 22 insensitive at change ( ) TEDX TEDY Element Decenter 22 insensitive at change ( ) TETX TETY Tilt about X & Y 32-33=Filter insensitive at change ( ) TTHI Thickness 21-23; mm TRAD Radius of Curvature mm TIRX TIRY Sag (Tilt) Across Lens mm TSDX TSDY Surface Decenter 22 insensitive at change ( ) TEDX TEDY Element Decenter 22 insensitive at change ( ) TTHI Filter to Image mm (Image Plane is compensator for fast analysis)

Dennis C. Evans p10 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation | Minimum | | Maximum | Type Value MF Change Value MF Change (Primary Mirror) Thickness tolerance on surface 4 TTHI Thickness 8: E E+000 Radius tolerance on surface 5 TRAD Thickness 8: E E+000 Tilt X tolerance on surfaces 5 through 5 (degrees) TETX Parameter 2 on Surface 7: E E-002 Parameter 3 on Surface 7: E E-001 Tilt Y tolerance on surfaces 5 through 5 (degrees) TETY Parameter 1 on Surface 7: E E-002 Parameter 4 on Surface 7: E E-001 (Fold Flat) Thickness tolerance on surface 16 TTHI Thickness 8: E E-001 TIRX Parameter 1 on Surface 7: E E-001 TIR Y tolerance on surface 17 TIRY Parameter 2 on Surface 7: E E-001 Tilt X tolerance on surfaces 17 through 17 (degrees) TETX Parameter 2 on Surface 7: E E-001 Tilt Y tolerance on surfaces 17 through 17 (degrees) TETY (Tertiary Mirror) Tilt X tolerance on surfaces 22 through 22 (degrees) TETX Parameter 2 on Surface 7: E E+000 Tilt Y tolerance on surfaces 22 through 22 (degrees) TETY Parameter 1 on Surface 7: E E+000 Active Secondary Sensitivity

Dennis C. Evans p11 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation Stray Light Baffle Layout

Dennis C. Evans p12 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation

Dennis C. Evans p13 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation

Dennis C. Evans p14 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation

Dennis C. Evans p15 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation

Dennis C. Evans p16 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation

Dennis C. Evans p17 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation Spectrograph Enclosure and Insertion

Dennis C. Evans p18 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation

Dennis C. Evans p19 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation

Dennis C. Evans p20 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation

Dennis C. Evans p21 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation

Dennis C. Evans p22 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation Views from the Detector

Dennis C. Evans p23 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation

Dennis C. Evans p24 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation

Dennis C. Evans p25 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation Solar Flux Concentrations inside Instrument  Solar Flux = 1 SC =.1367 watt.cm -2 = 1367 watt.m -2 LocationImage Radius (mm) Flux (SC) Flux (watt.cm -2 ) Flux (watts) Entrance Aperture Secondary Mirror Prime Focus Ring Focal Plane Shutter Pupil FP 2 (CCD/Image)

Dennis C. Evans p26 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation Open Items & Concerns

Dennis C. Evans p27 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation Open Items  Shade angle (<30 o ?) 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)

Dennis C. Evans p28 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation 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).

Dennis C. Evans p29 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation 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%

Dennis C. Evans p30 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation 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

Dennis C. Evans p31 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation Focus Drive Mechanism  Definition of acceptable image size needs to be reviewed.  RMS radius of 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.

Dennis C. Evans p32 SuperNova/Acceleration Probe 16 November 2001 Optical Analysis & Stray Light Evaluation 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.