1. N A S A G O D D A R D S P A C E F L I G H T C E N T E R I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Super Star Tracker Optical Design & Analysis Dennis Charles Evans 8 February 2002

2. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp28 February 2002Super Star Tracker Design Baseline 125 mm diameter aperture (small size) Long focal length (4848mm = f/38 beam) Modified Schmidt Cassegrain –Spherical primary –Rigid secondary & beam quadrature –No spider diffraction (not certain if advantage or disadvantage) Optical block base for alignment reference and mounting Optically contacted or fused optics for structural stability Approximately 5 x 10 9 photons into aperture (25% obscuration) –Approximately equivalent to mv=0 magnitude star Input flux of 10 9 photo electrons/sec per “quadrant” 10mm cathode diameter PMTs –Self contained, flight quality pulse counting units available –Present count rate is 500 MHz

3. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp38 February 2002Super Star Tracker Y-Fan Layout

4. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp48 February 2002Super Star Tracker Solid Model Y-Fan, 10-degree Rotation

5. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp58 February 2002Super Star Tracker Prescription SC-02.ZMX #TypeCommentCurvatureRadiusThicknessGlass Semi- DiameterConic2nd Order4th Order6th Order8th Order 0STANDARD 1.00E+10 1STANDARD 1.00E+01 6.25E+01 2STANDARDOBSCURATION 9.00E+01 5.56E+01 3EVENASPH CORRECTOR FRONT1.01E-069.94E+057.41E+00F_SILICA6.25E+010.00E+006.31E-06-7.09E-11-2.44E-143.12E-18 4STANDARD CORRECTOR BACK 5.79E+02 6.25E+01 5STANDARDPRIMARY-6.60E-04-1.51E+03-5.66E+02MIRROR6.23E+01 6STANDARDSECONDARY-2.25E-03-4.45E+025.66E+02MIRROR1.55E+01-6.00E-01 7COORDBRK 0.00E+00 8STANDARD TERTIARY FLAT -6.36E+02MIRROR8.23E+00 9COORDBRK 10COORDBRK 11COORDBRK 12STANDARDIMAGE-3.42E-03-2.92E+02 6.90E-02

6. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp68 February 2002Super Star Tracker Dimensions

7. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp78 February 2002Super Star Tracker GPB Telescope

8. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp88 February 2002Super Star Tracker 50:50 Beam Splitter B A D (IN)(OUT) C Rotated 90 deg WRT AB Path 1 Path 2 Sharp Corner Roof Prism (2 places) Error Signal Generation

9. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp98 February 2002Super Star Tracker Error Signal Generation AB C D Yaw = (A-B)/(A+B) Pitch = (C-D)/(C+D) Optical Path 1Optical Path 2

10. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp108 February 2002Super Star Tracker Photo Real Rendering

11. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp118 February 2002Super Star Tracker Photo Real Rendering

12. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp128 February 2002Super Star Tracker Mass of Optical Components F_Silica=2.2 g/cm*3 Vol(cm*3) Mass(grams) VCor: 169.3868219 × F_Silica = 372.65100818 VPri: 348.0089929 × F_Silica = 765.61978438 VSec: 14.5525599 × F_Silica = 32.015631780000008 VTer: 12.2558027 × F_Silica = 26.962765940000004 VCyl: 3036.2764147000004 × F_Silica = 6679.8081123400008 VBas: 2000 × F_Silica = 4400 Total Mass 12277.05730262 grams

13. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp138 February 2002Super Star Tracker Spot Diagram

14. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp148 February 2002Super Star Tracker Huygens Point Spread Function 5.34 arc-sec square; Strehl Ratio = 0.999

15. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp158 February 2002Super Star Tracker Huygens Point Spread Function 5.34 arc-sec square; Strehl Ratio = 0.999

16. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp168 February 2002Super Star Tracker Huygens Point Spread Function 5.34 arc-sec square; Strehl Ratio = 0.999

17. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp178 February 2002Super Star Tracker Huygens Point Spread Function 5.34 arc-sec square; Strehl Ratio = 0.999

18. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp188 February 2002Super Star Tracker Huygens Point Spread Function 5.34 arc-sec square; Strehl Ratio = 0.999

19. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp198 February 2002Super Star Tracker Huygens Point Spread Function 16.04 arc-sec square; Strehl Ratio = 0.999

20. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp208 February 2002Super Star Tracker Huygens Point Spread Function 16.04 arc-sec square; Strehl Ratio = 0.999

21. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp218 February 2002Super Star Tracker Huygens Point Spread Function 16.04 arc-sec square; Strehl Ratio = 0.999

22. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp228 February 2002Super Star Tracker Huygens Point Spread Function 16.04 arc-sec square; Strehl Ratio = 0.999

23. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp238 February 2002Super Star Tracker Monochromatic Diffraction Profile

24. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp248 February 2002Super Star Tracker Broad Band Diffraction Smoothing

25. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp258 February 2002Super Star Tracker “A” Knife-edge Profile

26. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp268 February 2002Super Star Tracker Tracking Error

27. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp278 February 2002Super Star Tracker Error Analysis Error: s 2 A±B = s 2 A + s 2 B ± 2AB s 2 AB etc. Integration Time – Increasing integration time from seconds to hours would result in nanoarcsecond error signals.

28. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp288 February 2002Super Star Tracker Concerns At micro arc-second resolution everything effects everything else. Cryo environment for structural stability Zerodur may be more stable than Fused Silica There may be some cost and performance advantages of using diamond roof prisms. Error signal analysis is not easily understood without detailed model One second integration period used for present modeling – Time integration can improve error signal by many orders of magnitude Smoother/Broader Point-Spread-Function might improve error signal range and accuracy – Broadband beacon (Incandescent) – “Spider Masks”

29. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp298 February 2002Super Star Tracker History Slides Various considerations in developing the design

30. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp308 February 2002Super Star Tracker Alternate Quadrature Detection Schemes Interferometry offers 5 -10 x signal processing advantage – Need 100 to 10,000 x increase Koesters Prisms – a la HST Fine Guidance – Scale makes exit pupil on order of 0.2 mm – Small size fabrication and sensitivity are problematic Four Tracker “long” baseline Interferometry – Baseline deployment, alignment, and stability concerns – 4 to 10x mass increases (equivalent cost increases)

31. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp318 February 2002Super Star Tracker Polarizing Beamsplitters

32. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp328 February 2002Super Star Tracker Koesters Prism Interferometer Tracker

33. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp338 February 2002Super Star Tracker GPB Design Reference C. W. F. Everitt, D. E. Davidson, and R. A. Van Patten (1986) “Cryogenic star-tracking telescope for Gravity Probe B”, SPIE Proceedings, Vol. 619, Cryogenic Optical Systems and Instruments II, Ramsey K. Melugin, Chairman/Editor.

34. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp348 February 2002Super Star Tracker GP-B Telescope

35. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp358 February 2002Super Star Tracker GP-B Tracking Error

36. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp368 February 2002Super Star Tracker Quadrant Detector Geometry

37. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp378 February 2002Super Star Tracker Microscope Magnifier

38. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp388 February 2002Super Star Tracker Hamamatsu Pulse Counting Photomultiplier

39. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp398 February 2002Super Star Tracker Hamamatsu Pulse Counting Photomultiplier

40. Optical Design I n s t r u m e n t S y n t h e s i s a n d A n a l y s i s L a b o r a t o r y Dennis Evansp408 February 2002Super Star Tracker Pulse Counting Photomultiplier