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WFPC2 Optical Test Results
SCIENCE
INm1UTE
User's Committee
Chris Burrows
28-May-1993 1
Pickoff Mirror works
W2
•
Phase Retrieval
°
Commanded
•
Positions
•
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WFPC2 Optical Test Results
��-
User's Committee
Chris Burrows
28-May-1993 2
AFMs Work
W4
.
•
0
-.
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•
Phase Retrieval
o
Commanded
•
•
Positions
•
f-
+----+--+---+
+2:1 •
•
•
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0
WFPC2 Optical Test Results
{jj�•
o
•
User's Committee
Chris Burrows
28-May-1993 3
Coma is Correctable
Phase Retrieval
W3
Commanded
Positions
•
•
•
00.
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WFPC2 Optical Test Results
��-
User's Committee
Chris Burrows
28-May-1993 4
PC1
�.
0
•
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Phase Retrieval
o
Commanded
•
Positions
•
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•
Nominal and Cold orbit data overplotted
•
Each tickmark is 0.01 microns rms
•
•
Zero volts is at center of hexagon formed by
44 V settings on single actuators and pairs
"Flight" setting is near origin - zero coma
�
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I2i'SJIr'SITlUTI
WFPC2 Optical Test Results
Comparison of raytrace,
Actuate program, and best fit
gain factors.
POMM % shearlstep
POMM pixels/F/step
POMM pixels/%
AFM % shear/arcsec
AFM pixels/F/arcsec
AFM Pixels/%/F
Ray
Actuate Fit
0.269
0.279
0.232
0.216
0.200
0.213
0.802
0.717
0.918
0.022
0.023
0.018
0.0037
0.0047
0.0037
0.168
0.203
0.207
Image motion follows the prediction
closely.
Phase retrieved coma has a gain factor
about 20% less than expected.
This may be because of pupil function changes in the
misaligned camera.
User's Committee
Chris Burrows
28-May-1 993 5
(Q)�
�1l'Sl1TUTE
WFPC2 Optical Test Results
User's Committee
Chris Burrows
28-May-1993 6
Aberrations are small
WF2
WF3
WF4
PC1
X-Coma standard deviation
0.003
0.005
0.004
0.005
V-Coma standard deviation
0.007
0.004
0.004
0.003
Astigmatism
-0.011
0.008
0.009
0.008
45 degree astigmatism
-0.016
0.022
-0.008
0.010
Spherical aberration
-0.003
-0.008
-0.008
0.001
5th order spherical
0.002
0.001
-0.001
0.001
Focus from 1260 from sharpness
0.003
-0.03
-0.01
0.026
Overall wavefront error microns rms
0.022
0.037
0.017
0.03
1/waves at 6328
29.26
16.92
37.28
21.42
Results do not include subtraction of Stimulus aberrations, and addition of OTA
aberrations (breathing, collimation, mid frequency errors, trefoil)
Wavefront error is dominated by focus offsets between cameras.
UUr5.bPE
M�
WFPC2 Optical Test Results
User's Committee
Chris Burrows
28-May-1993 7
Phase retrieval is
consistent
Orbit
Align-
Lamp
FocusAstig-
45 Deg.
3rd Ord.
5th
Order
(mm)
ment
Flight
Nominal
Flight
Nominal
Flight
Nominal
Cold
-10,-10 L7
Cold
-10,+10L7
Cold
Flight L7
Cold
+10,-10L7
Cold
+10,+10
Mean
L7
L8
L9
-0.12
0.02
0.01
-0.15
L7
matism Astig.
Spher. Spherical
-0.0083 -0.0175 -0.0055 0.0020
0.02
-0.0152 -0.0156 -0.0060 0.0026
0.03
-0.0137 -0.0175 -0.0047 0.0028
-0.01
-0.0179 -0.0312 0.0006 0.0023
-0.0288 -0.0182 -0.0025 0.0025
-0.0098 -0.0147 -0.0051 0.0023
-0.0011 -0.0190 -0.0013 -0.0021
0.01
0.0101 0.0024 -0.0028 -0.0001
-0.011
-0.016
-0.003
0.002
•
Very different (50%) illumination patterns solved for
•
Focus may be most affected by illumination uncertainties
��
WFPC2 Optical Test Results
Sharpness is unexpectedly low
Focus
Camera
Median
0.0537
1324
PC
WF2
0.0599
1286
0.1115
1286
WF3
0.1005
WF4
1286
WF2 Simulations:
Measured aberrations 0.1844
+Pinhole size = 10 microns
0.2601
+Pinhole size = 20 microns
0.2305
+Pinhole size =30 microns
0.2007
+40 mas rms jitter
0.1567
0.1688
+PSF at pixel (0,0)
Min
Max
0.0802
0.2086
0.1946
0.1872
0.0666 0.0666
0.1460 0.1458
0.1494 0.1478
0.1420 0.1415
Mean
0.3314 0.2729 0.2751
0.1829 0.3167 0.2618
0.1765 0.3043 0.2353
0.1656 0.2516 0.2023
0.1434 0.1711 0.1563
0.3447 0.2634 0.2622
User's Committee
Chris Burrows
28-May-1 993 8
�SIN:E
TII..ESCJ::H
�
WFPC2 Optical Test Results
User's Committee
Chris Burrows
28-May-1993 9
POMM was stable
throughout TV
xpom
ypom
pomx
pomy
Pre-Environmental test
10
30
-0.02
-0.04
Post-Env before rezero
Post-Env test
V @14 before adiust
V @14 after adjust
Thermal vac hot orbit
Thermal Vac Cold orbit
10
30
-6.65
-9.35
11
26
-1.11
3.24
11
2
-0.92
3.25
10
2'
-0.21
1.91
10
28
-0.43
1.84
10
28
-0.62
1.96
Note commanded steps do not exactly cancel coma changes.
For example xpom+pomx should be constant.
Post Env before rezero is POMM motion during shake, and
before reestablishing zero position.
Other motions are along V2 direction
I
WFPC2 Optical Test Results
��
User's Committee
Chris Burrows
28-May-1 993 10
Global Image motion
•
Probably caused by stimulus instabilities (M4)
•
All motions excect cost enviroqmental along V2
--mgx targy
I
Pre-Environmental test
0.13
-0.05
Post-Env before rezero
Post-Env test
TV @14 before adjust
TV @14 after adjust
Thermal vac hot orbit
Thermal Vac Cold orbit
3.92
-1.60
1.25
-1.04
-7.78
1.30
-1.45
0.57
1.13
-1.75
-1.59
4.08
l1li
III
l1li
II
..
V2
III
l1li
(QJ�
M,i'SITIUfE
WF2
WF3
WF4
PCl
•
•
•
•
WFPC2 Optical Test Results
User's Committee
Chris Burrows
28-May-1993 11
Camera to camera shifts in WF
pixels between tests.
xtv
xtvc
ypre
ypost
ytv
ytvc
xpre
xpost
0.000
0.295
0.662
-0.799
0.000 0.000 0.000 0.000 0.000 0.000 0.000
0.073 -0.092 -0.495 -0.219 -0.173 -0.371 0.722
0.525 0.300 -0.143 -0.374 -0.179 0.065 -0.486
-0.630 -0.218 0.445 0.589 0.674 0.441 -0.140
Note large shifts between nominal (tv) and cold (tvc)
orbits.
No significant relative motion during shake test
(between pre and post environmental tests)
Global shift means cannot know if it occurs in target
exposure for WF2
Is not associated with significant coma changes (>0.01
microns rms)
WFPC2 Optical Test Results
(Q)�
M,NillfUTE
User's Committee
Chris Burrows
28-May-1 993 12
Camera to camera
pointing variations
•
Seen both in target images and K-spots
•
Differential effect is about 0.5 pixels
•
Occurs in WF2 K-spots - Not j ust the AFM
temperature effect
•
Temperature change on bench of 1-2 degrees
•
Makes astrometry between chips very hard
•
Unlikely to affect single exposures - images
were stable at given orbital condition.
WFPC2 Optical Test Results
��
User's Committee
Chris Burrows
28-May-1993 13
Conclusions
•
Spherical aberration well corrected.
•
Coma is correctable
•
Some small astigmatism
•
•
•
•
Significant focus differences between
cameras
Camera boresights stable at given bench
temperature, but change relatively by about
0.5 pixels with 1-2 C temperature change.
Mechanisms appear to be stable between
exposures at 0.3 pixel level
Short term stability of mechanisms not tested
because of stimulus vibrations.