Triana epic stray light evaluation
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Triana EPIC Stray Light Evaluation. Preliminary Analysis and Results Dennis Charles Evans Optics Branch, Code 551 Instrument Synthesis & Analysis Laboratory 301-286-6237 / 301-262-2230 / [email protected] February 27, 2002. EPIC Optical & Mechanical Models. Optical Models GTRIANA.SEQ

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Triana EPIC Stray Light Evaluation

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Triana epic stray light evaluation

Triana EPIC Stray Light Evaluation

Preliminary Analysis and Results

Dennis Charles Evans

Optics Branch, Code 551

Instrument Synthesis & Analysis Laboratory

301-286-6237 / 301-262-2230 / [email protected]

February 27, 2002

EPIC ASAP RESULTS.ppt


Epic optical mechanical models

EPIC Optical & Mechanical Models

  • Optical Models

    • GTRIANA.SEQ

      • Failed to load successfully in Code-V

      • Converted to ZEMAX OK using SEQ2ZMX.exe

    • GTRIANA-00.ZMX

      • Good optical performance

        • Strehl Ratio 0.66-0.60 for all wavelengths over FOV

  • Mechanical Model

    • Epic.igs (provided)

    • Epic-IGS-02.dwg (converted, edited AutoCAD)

EPIC ASAP RESULTS.ppt


Epic optical mechanical models1

EPIC Optical & Mechanical Models

  • Reasonable Agreement Mechanical & Optical Models

    • Telescope Optics and Focal Plane within 0.01 inch

      • As good as fabrication and assembly tolerances

    • Filter position different by up to 1.74 inch (ZMX=aft of IGES)

      • Not expected to have any significant effect

    • No IGES Lenses, but ZMX lenses centered in “Lens Holder”

  • No printed copy ICD drawings of optical system

    • There have been obvious design changes from concept to build

    • No really good optics illustration available, especially baffle system

EPIC ASAP RESULTS.ppt


Zemax model

ZEMAX Model

EPIC ASAP RESULTS.ppt


Asap 3d model telescope detector

ASAP 3D Model (Telescope & Detector)

View from behind Telescope

View looking into telescope.

Note Green Detector.

EPIC ASAP RESULTS.ppt


Full asap model

Full ASAP Model

View from behind Telescope

View looking into telescope.

Note: Lenses & Filter covers Detector.

EPIC ASAP RESULTS.ppt


Asap 3d model as traced

ASAP 3D Model as Traced

EPIC ASAP RESULTS.ppt


View from detector

View from Detector

Smooth Cylinder Wall

that can be illuminated

EPIC ASAP RESULTS.ppt


Asap optical model

ASAP Optical Model

  • IGES Conversion Problems

    • Did not trim extended flat surfaces correctly

    • Typical problem with IGES flavors

    • Not likely to be a problem in model construction

  • ASAP Model constructed by selective modeling

    • Typical procedure, usually better than blind IGES insertion in both speed and quality

EPIC ASAP RESULTS.ppt


Baffling observations

Baffling Observations

  • Does not meet definition of well baffled system

    • Detector can see space [through lenses & filter]

    • No significant space sources likely (Moon occasionally)

    • Missing Primary central baffle tube an academic concern

  • Limited Vane implementation

    • None detected on Barrel Baffle

    • None on Spider arms or inner ring (cylinder)

      • Spider arms not modeled, but inner ring cylinder was modeled

    • None inside Secondary Housing

    • Limited to none on cylinder near Detector

  • Dominate Stray Light

    • From optical surface ghosts [at 1/600 level]

    • Missing vanes unlikely to be significant for EPIC

    • Would not be good low light level instrument, but doesn’t need to be.

EPIC ASAP RESULTS.ppt


Asap surface models

ASAP Surface Models

  • Mirrors

    • Reflectivity, 0.98

    • BRDF, none applied, unlikely to be a problem

  • Three Lenses & Single Filter

    • Coating Per Surface: (ARF05)

      • 0.95 Transmission, 0.05 Reflection

  • Detector Cover

    • 0.80 Transmission, 0.20 Reflection

  • All other surface

    • 0.00 Transmission, 0.05 Reflection (Lambertian)

  • EPIC ASAP RESULTS.ppt


    Triana epic stray light evaluation

    Floor at 1E-3

    Near ghost < 1/1000

    EPIC ASAP RESULTS.ppt


    Triana epic stray light evaluation

    Floor at 1E-4

    Near ghost between 1/1000 and

    1/10,000

    EPIC ASAP RESULTS.ppt


    Triana epic stray light evaluation

    Floor at 1E-5

    Near ghost between 1/1000 and

    1/10,000.

    General ghosting obvious.

    EPIC ASAP RESULTS.ppt


    Triana epic stray light evaluation

    Floor at 1E-6

    Near ghost between 1/1000 and

    1/10,000.

    General ghosting obvious.

    EPIC ASAP RESULTS.ppt


    Triana epic stray light evaluation

    Floor at 1E-3

    Near ghost is about 1/600

    EPIC ASAP RESULTS.ppt


    Triana epic stray light evaluation

    Floor at 1E-4

    Near ghost is about 1/600.

    General ghosts between

    1/600 to 1/1000.

    All look like surface ghosts.

    EPIC ASAP RESULTS.ppt


    Triana epic stray light evaluation

    Floor at 1E-5

    Near ghost is about 1/600.

    General ghosts between

    1/600 to 1/1000.

    All look like surface ghosts.

    No new ghosts.

    EPIC ASAP RESULTS.ppt


    Triana epic stray light evaluation

    Floor at 1E-6

    Near ghost is about 1/600.

    General ghosts between

    1/600 to 1/1000.

    All look like surface ghosts.

    EPIC ASAP RESULTS.ppt


    Asap spot plot displays

    ASAP Spot Plot Displays

    • Point Sources:

      • At combinations of 6371 and 3186 km referenced to Earth

        • Each, 5 rings of 36 rays for 180 rays,

    • Extended Source:

      • 102 mm radius, shifted 300 mm up (+Y)

      • 150 meters from Secondary Vertex

      • (1/2916)-(1/150000)=(1/2861); 55 mm image shift

      • f/9 implies ± 2.5 mm edge blurring (unlikely to mask any problems)

      • ASAP low flux limit.

        • Intended source; 2000 km diameter at 1.5E6 km distance, 3000 km offset.

    • Result

      • Stray light (ghosting) begins at the 1/600 to 1/1000 level.

    EPIC ASAP RESULTS.ppt


    Asap spot plot displays1

    ASAP Spot Plot Displays

    • Displays

      • Adjusted for peak flux (logarithmic) density [Flux/sq-mm]

      • Lower level truncation at 3, 4, 5, and 6 decades below peak

      • Pixilation is 256 x 256 over 36 mm square. [0.140 mm pixels]

    • Point Source Ray Statistics

      • 5 rings of 36 rays each; 180 rays

      • 1620 rays starting from 9 field points

      • 554,937 rays traced (ray splits at transmission surfaces)

      • 120,659 rays absorbed by detector

    • Extend Source Ray Statistics

      • 200,000 rays left source aimed for oversized entrance edge

      • 3,193,734 rays traced (ray splits at transmission surfaces)

      • 1,053,293 rays absorbed by detector

    EPIC ASAP RESULTS.ppt


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