1. “Phase C” Design of the JWST/FGS Tunable Filter Imager TIPS/JIM June 15, 2006 Alex Fullerton STScI / UVic

2. TIPS/JIM June 15, 2006 Optical Design at PDR Wavelength Coverage SW: 1.2 to 2.1 microns LW: 2.0 to 4.8 microns

3. TIPS/JIM June 15, 2006 SAT Recommendation Wavelength Coverage SW: 1.2 to 2.1 microns LW: 2.0 to 4.8 microns

4. TIPS/JIM June 15, 2006 SAT Recommendation Wavelength Coverage SW: 1.2 to 2.1 microns LW: 2.0 to 4.8 microns No cost savings to NASA.

5. TIPS/JIM June 15, 2006 SAT Recommendation Wavelength Coverage SW: 1.2 to 2.1 microns LW: 2.0 to 4.8 microns No cost savings to NASA. Removes: 1 dichroic beamsplitter 1 pupil/filter wheel assembly 1 Fabry-Perot etalon 1 camera TMA 1 SCA Half an optical bench 80 kg

6. TIPS/JIM June 15, 2006 SAT Recommendation Wavelength Coverage SW: 1.2 to 2.1 microns LW: 2.0 to 4.8 microns No cost savings to NASA. Removes: 1 dichroic beamsplitter 1 pupil/filter wheel assembly 1 Fabry-Perot etalon 1 camera TMA 1 SCA Half an optical bench 80 kg Hard to achieve science goals with this wavelength coverage!

7. TIPS/JIM June 15, 2006 FGS-TFI Optical Layout at RDR / Phase C 100.00 MM Pick-off Mirror Collimator TMA Camera TMA Fabry Perot Filters Fold Detector

8. TIPS/JIM June 15, 2006 FGS-TFI Optical Layout at RDR / Phase C 100.00 MM Pick-off Mirror Collimator TMA Camera TMA Fabry Perot Filters Fold Detector

9. TIPS/JIM June 15, 2006 Fabry-Perot Etalons Optical path difference = 2µl cos  Phase difference = (2  / ) 2µl cos  +  r µ=index of refraction m = 2µl cos  +  r /2  Tuning: For fixed m, on-axis (  =0)  l Detuning: For fixed m, l, off-axis (  )  cos   1   2 /2

10. TIPS/JIM June 15, 2006 The SAT Challenge: Do More With Less  Improvements with respect to the PDR LW channel: Significantly extended spectral waveband (1.5 to 5 μm) Requirements: 1.6 to 4.9 μm [PDR LW: 2.0 to 4.8 μm] Simplified – just 17 layers ! [PDR LW: 21 layers] Minimal detuning of the etalon with angle-of-incidence An order of magnitude better than earlier versions of this coating!  Non-functional interval between 2.6 and 3 μm Requirements: 2.5 to 3.2 μm System operates at 2.4 μm, where NIRCam is non-functional

11. TIPS/JIM June 15, 2006 Reflectance and Phase 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1500 2000 2500 3000 3500 4000 4500 5000 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Reflectance Phase (radian) Wavelength (nm) Reflectance Phase Non-Functional Waveband

12. TIPS/JIM June 15, 2006 Etalon Gap and Spectral Resolution 0 20 40 60 80 100 120 140 160 1500 2000 2500 3000 3500 4000 4500 5000 2000 3000 4000 5000 6000 7000 8000 9000 10000 Resolution Gap (nm) Wavelength (nm) Resolution Gap Non-Functional Waveband

13. TIPS/JIM June 15, 2006 Etalon Detuning - I  max for TFI

14. TIPS/JIM June 15, 2006 Etalon Detuning - II  max for TFI

15. TIPS/JIM June 15, 2006 Dual Wheel Configuration at PDR FFCal WCal ND Apo1Apo3 Apo4 Lyot Pupil Wheel Apo2 B1 B2 B3 B4 B5 B6 Open Filter Wheel Spare 8 position Filter Wheel allows for 6 blocking filters, an open for calibrations and one spare 8 position Pupil Wheel allows for a Lyot mask, up to 4 apodization masks, 2 calibration source positions and a neutral density position for target acquisition. Note: Calibration source positions on Pupil Wheel also serve as closed positions for dark calibrations

16. TIPS/JIM June 15, 2006 Current Dual Wheel Mechanism Nine Position Wheels Motors Resolvers Bracket

17. TIPS/JIM June 15, 2006 “Phase C” Dual Wheel Design  At least 9 positions are required to cover the full wavelength range (8 blocking filters + 1 “open” position) Otherwise: there is a risk that the wavelength range will be restricted by the blocking filters (not the etalon!)  A larger wheel was not considered (mass).  Spare positions are available in the Pupil / Calibration Wheel Open

18. TIPS/JIM June 15, 2006 Key Performance Requirements Parent*TFI Requirement DescriptionRequirement ValueDesign Current Value FGS-308TFI Channel FOV> 4.7 sq. arcmin4.88 sq. arcmin FGS-638TFI Pixel Size65 mas64.3 to 65.5 mas FGS-306TFI Wavelength Range 1.6 – 2.5  m 3.2 – 4.9  m 1.5 – 2.7  m 3.1 – 5.0  m FGS-311TFI Spectral Resolution> 70 & < 15075 to 105 FGS-315Wavelength Shift in FOV< 1.0% (50% of FOV)< 0.3% (complete FOV) FGS-317 TFI Sensitivity at 3.5  m 126 nJy105 nJy FGS-355Coronagraphic Capability2 Pupil masks 2 Lyot masks 4 Pupil masks 4 Lyot masks NIRCam bandpass TFI bandpass * CSA-JWST-RD-0002 Rev B (JWST-RQMT-002069) - Wavelength Selection Flexibility - Good Sensitivity for Emission Line Objects - Emission Line Diagnostic Imaging- Coronagraphy for AGN studies & Extrasolar Planet Spectra

19. TIPS/JIM June 15, 2006 Etalon Stability / Repeatability  Stability depends on temperature control of etalon electronics Etalon gap changes by 0.12 nm/K with prototype ECE Issue: will flight electronics exhibit a temperature drift? Assume: 1.2 nm/K (  10 worse) Implement: temperature control in ECE; stable to ~1 K Expect: Over the course of a typical observation, etalon gap may vary by ~1.2 nm, or ~7% of a resolution element at 1.5  m. This is consistent with scientific requirements for photometric stability. Can use onboard calibration lamp to check gap spacing during particularly long/critical observations.  Repeatability will depend upon the interval in question. Over ~month, expected to be the same as the stability Over longer intervals, will depend on aging of components Mitigate by checking/updating TFI wavelength calibration