Transcript Optical Analysis and Stray Light Evaluation SuperNova/Acceleration Probe

SuperNova/Acceleration Probe
Optical Analysis
and
Stray Light Evaluation
Dennis Charles Evans
16 November 2001
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SuperNova/Acceleration Probe
• ZEMAX Optical Layout
 ISAL prescription from TMA62 write-up
 Checked against customer supplied ZEMAX
• Optical Sensitivities
 Basic Sensitivity
 Active Secondary (5-dof)
•
•
•
•
•
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Stray Light Baffle Layout
Spectrograph Enclosure and Insertion
Views from the Detector
Solar Flux
Open Items
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SuperNova/Acceleration Probe
• ZEMAX Optical Layout
ISAL prescription from TMA62 write-up
Checked against customer supplied ZEMAX
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SuperNova/Acceleration Probe
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Optical Sensitivity
•Basic Sensitivity
 Individual Element Increments of 0.001 mm
or degree to 0.016
 MF Limit (RMS Spot Radius)
(0.002837÷0.005000)*2 = 0.32194276
•Active Secondary
 Five degree-of-freedom
—Dx, Dy, Dz, Tx, Ty
 Limits on Secondary
— ± 1 mm or degree
 Limits on Elements
— ± 0.256 mm or degree
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Key Tolerance Comparison
Basic Limit
Active Secondary
Limit
Primary Tilt
0.0003 deg
0.185 deg
PrimarySecondary Space
Tertiary Tilt
0.0008 mm
0.033 mm
0.016 deg
0.055 deg
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• Basic Sensitivity (limited to 0.005 RMS Radius)
TETX
TTHI
TRAD
TIRX
TSDX
TEDX
Tilt about X & Y
Thickness
Radius of Curvature
Sag (Tilt) Across Lens
Surface Decenter
Element Decenter
5=Primary
4-6;
5
5
5
5
0.000335
0.000802
0.001604
0.011705
0.014518
0.014518
deg ×3600 arc-sec/deg = 1.206 arc-sec
mm
mm (= same effect as thickness change)
mm
mm
mm
8=Secondary
7-9;
8
8
8
8
0.001515
0.000602
0.001828
0.011261
0.014658
0.014658
deg ×3600 arc-sec/deg = 5.454
mm
mm
mm
mm
mm
arc-sec
TIRY
TSDY
TEDY
Tilt about X & Y
Thickness
Radius of Curvature
Sag (Tilt) Across Lens
Surface Decenter
Element Decenter
TETX
TETY
TTHI
TRAD
TIRX
TIRY
TSDX TSDY
TEDX TEDY
Tilt about X & Y
Tilt about X & Y
Thickness
Radius of Curvature
Sag (Tilt) Across Lens
Sag (Tilt) Across Lens
Surface Decenter
Element Decenter
17=Fold Flat
17
16-18;
17
17
17
17
17
0.008217 deg ×3600 arc-sec/deg = 5.454
0.011621 deg ×3600 arc-sec/deg = 5.454
0.018010 mm
insensitive at 0.256 change
0.150454 mm
0.106387 mm
insensitive at 0.256 change (0.002884)
insensitive at 0.256 change (0.002884)
arc-sec
arc-sec
TETX
TTHI
TRAD
TIRX
TSDX
TEDX
TETY
Tilt about X & Y
Thickness
Radius of Curvature
Sag (Tilt) Across Lens
Surface Decenter
Element Decenter
22=Tertiary
21-23;
22
22
22
22
0.016927 deg ×3600 arc-sec/deg = 60.9372
0.016919 mm
0.031079 mm
0.199252 mm
insensitive at 0.256 change (0.003732)
insensitive at 0.256 change (0.003732)
TETX
TTHI
TRAD
TIRX
TSDX
TEDX
TETY
Tilt about X & Y
Thickness
Radius of Curvature
Sag (Tilt) Across Lens
Surface Decenter
Element Decenter
32-33=Filter
21-23;
22
22
22
22
insensitive at 0.256 change (0.002886)
0.016919 mm
0.031079 mm
0.199252 mm
insensitive at 0.256 change (0.003732)
insensitive at 0.256 change (0.003732)
Filter to Image
36-37
0.136618 mm
TETX
TTHI
TRAD
TIRX
TSDX
TEDX
TTHI
TETY
TIRY
TSDY
TEDY
TETY
TIRY
TSDY
TEDY
TIRY
TSDY
TEDY
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arc-sec
(Image Plane is compensator for fast analysis)
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Active Secondary Sensitivity
|-----------Type
Value
(Primary Mirror)
Thickness tolerance on surface
TTHI
4
6
-0.033610
Thickness
8:
Radius tolerance on surface 5
TRAD
5
-0.066773
Thickness
8:
Tilt X tolerance on surfaces 5
TETX
5
5
-0.185670
Parameter 2 on Surface
7:
Parameter 3 on Surface
7:
Tilt Y tolerance on surfaces 5
TETY
5
5
-0.185720
Parameter 1 on Surface
7:
Parameter 4 on Surface
7:
Minimum ------------| |------------ Maximum ------------|
MF
Change
Value
MF
Change
4
0.005000
0.002163
1.00001E+000
0.004566
0.001730
1.00001E+000
through 5 (degrees)
0.005000
0.002163
9.12416E-002
-1.87703E-001
through 5 (degrees)
0.005000
0.002163
-9.12903E-002
-1.87754E-001
(Fold Flat)
Thickness tolerance on surface 16
TTHI 16 18
-0.256000
0.004764
0.001927
Thickness
8:
1.74322E-001
TIRX 17
-0.256000
0.004388
0.001551
Parameter 1 on Surface
7:
-5.13796E-001
TIR Y tolerance on surface 17
TIRY 17
-0.222637
0.005000
0.002163
Parameter 2 on Surface
7:
6.31916E-001
Tilt X tolerance on surfaces 17 through 17 (degrees)
TETX 17 17
-0.017196
0.005000
0.002163
Parameter 2 on Surface
7:
6.31902E-001
Tilt Y tolerance on surfaces 17 through 17 (degrees)
TETY 17 17
-0.024319
0.005000
0.002163
(Tertiary Mirror)
Tilt X tolerance on surfaces 22 through 22 (degrees)
TETX 22 22
-0.055298
0.005000
0.002163
Parameter 2 on Surface
7:
-1.00001E+000
Tilt Y tolerance on surfaces 22 through 22 (degrees)
TETY 22 22
-0.055298
0.005000
0.002163
Parameter 1 on Surface
7:
1.00001E+000
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0.033112
0.005000
0.002163
-1.00001E+000
0.066242
0.005000
0.002163
-1.00001E+000
0.185670
0.005000
0.002163
-9.12419E-002
1.87703E-001
0.185720
0.005000
0.002163
9.12680E-002
1.87754E-001
0.256000
0.004764
0.001927
-1.87717E-001
0.004388
0.001551
5.13786E-001
0.256000
0.222637
0.005000
0.002163
-6.31897E-001
0.017196
0.005000
0.002163
-6.31891E-001
0.024319
0.005000
0.055298
0.005000
0.002163
1.00001E+000
0.055298
0.005000
0.002163
-1.00001E+000
Optical Analysis & Stray Light Evaluation
0.002163
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SuperNova/Acceleration Probe
• Stray Light Baffle Layout
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SuperNova/Acceleration Probe
• Spectrograph Enclosure and Insertion
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• Views from the Detector
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SuperNova/Acceleration Probe
1
3
2
4
5
1
6
7
8
1 Cosmic Ray Shield (green)
2 Fold Mirror Back (cyan)
3 Secondary Mirror Baffle (yellow)
4 Reference Surface (red)
5 Strut, 1 of 3 (brown)
6 Inner Baffle in reflection off Secondary (white)
7 Fold Mirror Edge in reflection off Tertiary (cyan)
8 Black central X is reflection of detector focal plane
in Secondary.
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• Solar Flux Concentrations inside Instrument
 Solar Flux = 1 SC = .1367 watt.cm-2 = 1367 watt.m-2
Location
Image Radius
(mm)
Flux
(SC)
Entrance Aperture
Secondary Mirror
Prime Focus Ring
1000
213
10.7
1
22
4367
.1367
3.1
597
4295
4295
2147
Focal Plane 1
Shutter Pupil
FP 2 (CCD/Image)
64
48
96
244
437
109
33
60
15
4295
4295
4295
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Flux
Flux
(watt.cm-2) (watts)
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Open Items
&
Concerns
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• Open Items






Shade angle (<30o?) and Barrel Baffle length
Baffle edge finish (Forward Ring)
Cleanliness, especially of Primary Mirror
Aft Optics Baffles (Mostly black paint)
MLI outer layer vs. mission length
Reverse views
— AutoCAD Photo Ray Trace
— reverse ray trace, TMA62
 Focal plane
— parfocalization (filter thickness)
 S/G placement
— behind focal plane?
— center mounted
 ASAP diffuse scatter model
— (Friday PM – Next Week)
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• Mission Unique Concerns:
No mission unique concerns have been observed.
Stray light issues are manageable using proven
baffling techniques that have been successfully
demonstrated on flight missions.
Analysis done too early in the design cycle is
likely to give false confidence (analytical design
is better than real design).
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• Central Obscuration
Minimum possible - about 5% (Shadow of
Secondary)
Current minimum design to keep direct light
from Focal Surface 1 - about 15%
Maximum practical limit to keep direct light from
inner baffle interior and front lip - slightly less
than 25%
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• Stray Light Issues
 Similarity to flight instruments shows successful design is possible
— HST, FUSE, COBE-DIRBE, IUE, OAO
 Similarity to flight instruments shows design flaws are possible that will
not be detected by stray light analysis, but by careful design,
inspection, and testing.
— HST - Door reflections
— DIRBE - Barrel Baffle side wall single bounces.
— IUE/OAO - Pinhole leaks into aft optics assemblies; bolt head locations.
 Design & Analysis Similarity
— SIRTF - IRAC
— WIRE (minor changes make orders of magnitude stray light differences)
— GOES Earth Limb Sensor (light leaks around filters and side wall reflections)
— MODIS - Stray light in calibrator designs, not instrument designs
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• Focus Drive Mechanism
Definition of acceptable image size needs to be reviewed.
RMS radius of 0.005 mm may be to conservative for a pixel
limited performance instrument.
Range of motions used were +/- 1 mm and degree.
The Displacement motions may be effectively increased to
5 or 10 mm for some corrections.
Tolerance analysis so far is only with two elements at a
time and has not included Image Plane tilts.
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• View from the detector inspection is important.
Fold Flat throat can be illuminated by sky.
Fold flat throat design as in this study may not allow
AFT star tracker
• AFT optics baffles and black surfaces
Baffles not designed yet
Black paint has been known to cause CTE changes in
GFRP structures.
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Addendum
(Added after final presentation.)
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ASAP Models
(in progress)
See ReadMe.txt
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(Semi) Final Thoughts
Based on the many concerns about baffle
vane width, barrel baffle diameter and length,
a central tower secondary support might be
effectively reconsidered.
This would at least minimize the stray
light initial questions. It would work towards a
longer outer baffle with a minimum (still
around 15%) obscuration.
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