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Intra-pixel Sensitivity Testing Preliminary Design Review 3 August 2001 Stella Jang

SPACE TELESCOPE SCIENCE INSTITUTE. Intra-pixel Sensitivity Testing Preliminary Design Review 3 August 2001 Stella Jang. Goals. Present the calibrated target/ 3-axis stage design Present requirements for blackbody radiation contrast and pixel saturation

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Intra-pixel Sensitivity Testing Preliminary Design Review 3 August 2001 Stella Jang

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  1. SPACE TELESCOPE SCIENCE INSTITUTE Intra-pixel Sensitivity Testing Preliminary Design Review 3 August 2001 Stella Jang

  2. Goals • Present the calibrated target/ 3-axis stage design • Present requirements for blackbody radiation contrast and pixel saturation • Show that the proposed design meets the necessary requirements • Show that required tolerances can be met • Approve a plan for moving from PDR to CDR 2

  3. Definition of Intra-pixel Sensitivity Ni,j =number of electrons/second detected in pixel i,j ei,j(x,y) =intra-pixel sensitivity at x,y in pixel i,j I =number of photons/second arriving at x,y in pixel i,j j+2 j+1 j i+3 i i+1 i+2 3

  4. Figure 8. DRM-quality photometry (1%) cannot be achieved according to our measurements of intra-pixel sensitivity. (Left) Intra-pixel sensitivity of HgCdTe to a point source measured by Co-I Finger. (Right) NICMOS magnitude errors as a function of intra-pixel source location (Stiavelli, private communication). Definition of Intra-pixel Sensitivity 4

  5. IPS Experiment Requirements(from TFST0900, Table 1) 5

  6. NGST RequirementsNDC0200 (from NGST Doc. #641) 6

  7. Modules 3-axis stage pinhole Offner light source light guide focal reducer filters window 7

  8. Layout with f/1.5 focal reducer 45° flat 45° flat Offner secondary f/10 point source detector focal reducer filter window Offner primary 8

  9. Shaded model -- with focal reducer 9

  10. Close-up of f/1.5 focal reducer 10

  11. Modules Requirements 11

  12. 12

  13. 13

  14. PSF 14

  15. 10 x 10 pixel field (l = 5 mm) 15

  16. Flux Equation T =temperature of source QE =absolute quantum efficiency of detector Toptics =transmission of window, mirrors, and central obscuration of the focal reducer Tvar =variable transmission at light guide exit port TPK50 =transmission of PK50 blocking filter Tfilter =transmission of bandpass filter W =solid angle subtended by entrance pupil at source A =area of emitting surface ti =integration time 16

  17. T=300K 17

  18. T=3250K 18

  19. 19

  20. PK50 light guide 20

  21. Johnson-R 21

  22. Johnson-R 22

  23. Johnson-I 23

  24. Johnson-I 24

  25. J 25

  26. J 26

  27. H 27

  28. H 28

  29. K 29

  30. K 30

  31. L’ 31

  32. L’ 32

  33. M’ 33

  34. M’ 34

  35. Software Requirements • Integrated control software • exposure (multi-plane FITS) • filter wheels • 3D stage • light source (on/off and intensity)? • Analysis software • data reduction pipeline • IDL 35

  36. Designs • Light source - Coherent quartz tungsten halogen -150W/3250K - Variable intensity • Light guide - Coherent 24” multi-fiber gooseneck - 5.54mm exit port diameter • Pinhole - 5 mm diameter in a 1” retaining ring mount • 3-axis stage - 3 Newport compact motorized translation stages - Newport motion controller • Window - 110mm - 10mm thickness - Mounted in end plate of dewar. • Filters - Johnson-R, Johnson-I, J, H, K, L’, M’, PK50 36

  37. Designs (cont’d) • Offner relay - Re-images source 1:1 onto detector • Allows decent imaging at f/10 over full 2K2 field • Provides excellent imaging over a smaller central region • Compact, folded design fits available space • All reflective optical design is free from chromatic aberration • Focal reducer - Produces f/1.5 beam for sub-pixel imaging • At f/10, diffraction-limited FWHM = 22.6 mm (l = 2.2 mm) • At f/1.5, diffraction-limited FWHM is = 3.4 mm (l = 2.2 mm) • Single-element optic with 4 different surface radii (2 elliptical, 2 spherical) • Reflective coatings on the two elliptical surfaces • Parfocal with f/10 beam, designed to reside in a filter wheel • Provides subpixel imaging over a 10 pixel diameter region 37

  38. Designs 38

  39. Hardware Set-up • 3-axis motion stages are assembled and attached to the motion driver • Pinhole and light source needs to be attached to 3-axis stage • Flux from light guide exit port must be variable 39

  40. Notes on Schedule • Some hardware not ordered yet • Anticipate that the hardware will be complete no earlier than December 40

  41. Open Issues • Controlling efficiency at the light guide exit port • This has implications for the pinhole/stage design • M’ filter bandwidth • How to suppress flux for wavelength < 4 mm ? • Monochromator vs. Filters • Cost • Time 41

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