Fourier-Kelvin Stellar Interferometer

1. Fourier-Kelvin Stellar Interferometer Optics Dennis Charles Evans - ISAL Joe Howard & Mark Wilson – FSKI Project 24 May 2002

2. Afocal Telescope (Global Reference) 1 meter diameter f/1.32 primary 20% linear obscuration 4% area obscuration 5 cm diameter exit beam

3. Beam Combiner Telescope

4. Beam Combiner Telescope

5. System to Combiner Focal Surface

6. System to Combiner Focal Surface FOV ±15 arc sec FOV ±1 arc min FOV ±1 arc min

7. System Baseline; to Combiner Focal Plane

8. Summary of Preliminary Tolerance Analysis • Each Collector Path is diffraction limited at 2 for entire path to Detector • Mirror Quality: 1/20th wave HeNe • All powered mirrors treated equally • Kodak ULE Mirror • Displacement Control • few microns (<<10) per element • Tilt Control • (analysis incomplete) • sub second-of-arc control IFOV is required • Diffraction Limited, 20m aperture: 1st dark ring is 0.025 arc sec • system magnification relaxes tilt controls by up to factors of 20 • IFOV/FOV Control • IFOV limited to ±15 arc seconds • 1 arc minute off axis source will not reach focal plane • tilting the Afocal Secondary and the following fold(s) will allow IFOV steering for several arc minutes

9. Open Items • Delay Line location • In front or back of the Afocal Primary Mirrors • Depends on Telescope Tilt Mechanism volume requirements • Need to route two delay lines around the Spacecraft • Orientation and Input of Delay Lines into Beam Combiner • Don’t know location of Instruments yet. • May require additional fold mirrors • Instrument Stacking parallel to Beam Combiner • Not enough area for common plane layout • Need additional fold mirrors

10. Combiner Focal Plane Scale

11. Suggested Optical Layout Instruments: a) Fringe Tracker b) Angle Tracker c) MIR Camera 5 Afocal Telescopes 1 combiner 5 Beam lines with “Delay line” mechanisms

12. Delay Line Folding Procedures

13. MIR Dichroic Beamsplitter 800 mm Combiner Image Pupil Access Angle Tracker 18 mm pixels 50/50 Beamsplitter 550 mm Fringe Tracker Focal Plane F/18 Fringe Tracker: l = 2 micron

14. 600 mm 500 mm Focal Plane: F/5.5 27 mm pixels Dewar Pupil Access MIR Science Instrument: l = 10 micron

15. 1 2 4 ZEMAX Non Sequential Example

16. FKSI ZEMAX Nonsequential Baseline • Prescription: FKSI NS Test - 0.ZMX • Model is true nonsequential, not a cut & paste overlay. • Layout has all components, but paths have not been equalized. • Image has not been focused.

17. FKSI ZEMAX Nonsequential Baseline

18. Interferometer Simulation • Beam Combiner Telescope Only • Combiner_F18.zmx • Image output display is at Combiner Focal Plane • Square Aperture • ZEMAX set-up time constraint • Apertures modeled • Single aperture (near center) • Dual aperture (ends, 20 meter spacing) • Five apertures • Aperture Spacing: 0 3.3 8.6 12.9 20 meters

19. Illumination on Beam Combiner The Collector aperture relative positions are: 0.0, 3.3, 8.6, 12.9, & 20 meters. The apertures above on the Beam combiner show that an off axis telescope of some type will be required.

20. Five Aperture Interferometer Simulation

21. Single Aperture Simulation

22. Dual Aperture Interferometer Simulation

23. Wavelength Distribution

24. Single Aperture

25. Dual Aperture, 10 , monochromatic

26. Dual Aperture, 8-1212 irregularly spaced wavelengths

27. Five Apertures; 10; monochromatic

28. Five Apertures; 8-12; 12 wavelengths, irregular distribution

29. Kodak Lightweight Cryostable Mirror

30. Kodak Lightweight Cryostable Mirror

31. Kodak Lightweight Cryostable Mirror

32. SiC Egg Crate Mirror

33. Monolithic SiC Mirror

34. Composite Optics Mirror .41×.74 = 0.3034 square meters 2.98 kg ÷ 0.3034 m2 = 9.8 kg/m2 Area density of a quarter is about 12 kg/m2 Area of Schmidt Primary = 45.2 m2 4.52 m2x 9.8 kg/m2 = 444.3 kg (SPIE Paper 3785-02 Mark Lake et al (1999) A Deployable Primary Mirror for Space Telescopes)

35. Estimated Primary Mirror Mass MirrorDensityDiameterVolumeMassScaled to 1 meterMass ULE 2.21 .559 m ------ 4.54kg (1÷.559)*3=5.7 25.9kg (1÷.559)*2=3.2 14.5kg SiC 2.91 .360 m 1693cc 4.9kg (1÷.360)*3=21.4 104.86kg EggCrate (1÷.360)*2= 7.7 37.73kg SiC 2.91 .360 m 936cc 2.7kg 57.8kg Monolithic 20.8kg Composite n/a .74x.41m@9.8kg/m2 3.0kg (1÷.74)*3=1.8 7.5kg Optics (1÷.74)*2=2.5 5.4kg HST/ULE 2.91 2.24 m ------ 818kg (1÷2.24)*3=0.089 72.8kg (1÷2.24)*2=0.199 163.0kg

36. Estimated Cost for Optical Components • Based on Kodak Cryostable ULE SBIR Mirror • One meter diameter requires new fabrication facility at Corning • Estimated Cost for 1-meter mirror in lot of 8-10 = $2.5 Million • One-meter Mirrors Needed = 12 Units @ $2.5 M = $30 Million • 5 Flight Afocal Telescopes 1 Flight Spare 2 Engineering Afocal Units 1 Beam Combiner Telescope 1 Flight Spare Combiner 1 Engineering Combiner 1 Contingent • Figuring Primaries and Secondaries = $250 K / Set = $ 3 M • All other optics [Secondarys, Flats, Filters, Dichroics] = $2 M • Unspecified = $2 M • Total for Optical Components = $37 Million

37. Laser Interferometric Metrology • SMX Laser Tracker • Angular resolution: 0.06 arc-sec • Distance Accuracy: 20 + 1 /m • Distance Precision: 0.158 • 0-360 Az; -50 to +80 El • 180 deg/sec, 1000 deg/sec2 • Standard range: 0-35 meters • Interferometer/Time of Flight • System Weight: 25 kg

38. Ball CT602 Star Tracker • 3 arc-sec single star angular accuracy • Autonomous acquisition and tracking • Multiple stars with no apriori inputs • Reports angular positions and intensities • Mass: 5.4 kg • Power: 10 watts