on-orbit sot performance
DESCRIPTION
On-orbit SOT performance. Kiyoshi Ichimoto and SOT-team. Hinode workshop , 2007.12.8-10, Beijing. On-orbit performance of SOT reported in this presentation Image quality (BFI preliminary), Image stability, SP performance, Chromatic aberration, Focus stability, Throughput trend, - PowerPoint PPT PresentationTRANSCRIPT
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On-orbit SOT performance
Kiyoshi Ichimoto
and
SOT-team
Hinode workshop, 2007.12.8-10, Beijing
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On-orbit performance of SOT reported in this presentation
- Image quality (BFI preliminary),- Image stability,- SP performance,- Chromatic aberration,- Focus stability,- Throughput trend,- Tunable filter status,
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Hinode SOT First Light image, 2006.10.25
Above: The sun in white light (420 nm). Above-right and right:: From SOT showing in detail solar granulation (convection cells), and bright points between granules that are locations of concentrations of magnetic field.
Sun’s diameter ~ 1,400,000 km
10,000 km
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Granules and bright points corresponding to tiny magnetic features are clearly seen in the movie.
SOT achieves the diffraction limit resolution of 50cm-aperture telescope, 0.2 arcsec in the wavelength of 430 nm.
16000km
0.2 arcsec
4000km
Close-up of granules in G-band (430nm)
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2006.10.31 CT servo-On, error signal/TM angle time profiles
Servo-off~0.01arcsec rms
Image stability is perfect!3 times better than the requirement.
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FW1 FW2 VLS-close
0.031”rms0.028”rms
0.032”rms 0.036”rms
RSS=0.142”(3)0.5sRSS=0.128”(3)
VLS-open
The XRT VLS produces a significant disturbance of SOT image, but, since the duration of its movement is very small fractions of time, there is no impact on SOT data.
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Spectropolarimeter performance
SP takes excellent data!
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Accuracy:
QUV/Ic ~ 10-3 (5s integ.)
I/Ic ~ 10-2
dominated by the compression noiseQ=75 is a compromise..
No crosstalk. The best calibrated polarization instrument!
Orbital drift of spectral image:
Caused by deformation of FPP box.
Minimized by careful heater setting,Corrected by sp_prep using slit pattern,
no info. of absolute line shift
Q=75
I-profile after flat correction
Two remarks on the SP feature
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18
20
22
24
26
28
30
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3500 4000 4500 5000 5500 6000 6500 7000wavelength (A)
focu
s po
sBFI (2006.11.10)BFI (2006.11.17)NFISP
Reimaging lens 9step = 1.36mm 4step WFE~21nm rms (< /20 @430nm)
Rei
mag
ing
lens
to
FP
P
Chromatic aberration
BFI has a chromatic aberration (caused by improper installation of a lens).Science impact is small but not zero.
No evidence of chromatic aberration in NFI
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G-band focus position history
- Gradual drift of the focus is caused by shrinkage of the CFRP structure of OTA due to dehydration. --- expected behavior.
- Focus offset between disk and limb pointing by ~5 steps. Cause is not well understood, but the response is fast enough to adjust
the focus each time by OP.
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- 20
- 15
- 10
- 5
0
5
10
15
20
25
30
35
40
45
10/ 25 12/ 14 2/ 2 3/ 24 5/ 13 7/ 2 8/ 21 10/ 10 11/ 29
eclipse
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- 22
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- 14
- 12
- 10
- 8
- 6
13:00 13:10 13:20 13:30 13:40 13:50 14:00 14:10 14:20 14:30 14:40 14:50 15:00 15:10
focu
s (s
tep)
5
7
9
11
13
15
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19
21
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T_H
DM
(C
)
Gb focusRC focusT_HDM
NGT DAY+10min NGT-3min NGT
Focus drift in eclipse season
The large focus drift is caused by excursion of the temperature of HDM in OTA in day/night cycle (expected).
Eclipse season is certainly a ‘degraded performance period’ of SOT.
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BFI throughput history
FG CCD baking
eclipseThe cause of the loss of throughput is not identified.No science impact at this point.
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NFI throughput history
NFI 6302A lost ~ 60% of throughput due to a degradation of the blocking filter after a long exposure to the UV of sunlight.Since the blocking filter for 589nm (NaI D1) is durable against the UV, this filter is inserted in the beam always during the idle time of the NFI, thus the degradation of filters is suppressed in the current operation.
There is no evidence of significant loss of throughput in other wavelengths of NFI and SP.
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Trend of the telescope temperature
Telescope temperature is now stable.No evidence of significant progress of contamination in OTA.
eclipse
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TF Bubble in the FOV
TF6
TF5~1A
Tunable elements which carries the bubbles are identified.
Tunable filter bubble
big bubble
TF7Small bubbles
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Appearance of tunable filter bubbles
Current situation
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Tunable filter status;
Images of the NFI contain blemishes which degrade or obscure the image over part of the field of view. The artifacts are caused by air bubbles in the index matching fluid inside the tunable filter. They distort and move when the filter is tuned.
The locations of bubbles in the tunable filter were identified. To suppress the disturbance of bubbles, we are required to block 4 tuning elements out of 8. New software to enable such operation was successfully uploaded in Apr. 2007.
This situation limits our capability of tuning the filter, but some useful schemes with a minimum usage of the 4 elements are still available and have been tested.
NFI observing is usually done in one spectral line at one or a small number of wavelengths for extended periods of time. Rapid switching between lines is not allowed.
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Possible tuning w/o moving bubble elements
The separation can not be free to prevent the motion of particular elements.
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Wavelength
(nm) geff
G
Pol. Sensitivity(diag.elem. of X)
Detection limit of B( = 0.001, Gauss)
blocking
TF5-8(mA)V QU Optimized TF specified
Bl Bt Bl Bt
MgI 517.2 1.75 2.88 0.577 0.452 37 970 46 1040 +114
FeI 525.0 3.00 9.00 0.266 0.609 15 210 80 278 +118
FeI 557.6 0.00 0.00 - - - - - - +140
NaI 589.6 1.33 1.33 0.633 0.297 21 1240 27 1290 +156
FeI 630.2 2.50 6.25 0.526 0.503 10 240 48 442 +188
HI 656.3 1.33 1.33 0.402 0.073 78 >5000
360 >5000
+208
Detection limit of NFI for weak magnetic fields
)2(0
)2(1 GGG
2nd moments of and-components
max
222211
2
max2
33//
/'
11~
/'
11~
dIdGxB
ddIgxB
eff
I’: line profiles convoluted by TF transmission curve
Theoretical limit of NFI for detecting weak magnetic fields are evaluated using atlas solar spectrum. Symmetric wavelength observation in blue- and red-side of spectral lines with =0.001 is considered. Zeeman sensitivities of the line, efficiency of the SOT’s polarization modulation, limitation of TF tuning step are taken into account, but no line shift.
2007/11/22 K.I.
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+0.136A
Maybe better than intensity for seismology…Good for sunspot Dopplergram
nfi_dopp_cal.pro
0.04/1(km/s)
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FeI 5576 Dopplergram, 2007.07.14, 5576 + 0.136A
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NaI D1 Dopp./Mag. 2007.6.12, 5896 + 0.156A
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FeI 5250A IQUV 2007.6.21, -0.100/+0.136A
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TF5,6 and 7 blocked
This is possible; maybe useful for prominence /spicule Dopplergram.
Possible tuning w/o moving bubble elements
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Ha Doppler 2007.8.5, H + 0.41AI Dopp.
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6302 Test of New Shuttered IV
New OBS_ID 61: takes 5.9 sec
V noise = 6.5 DN, S/N > 400
-20 +24 DN display
Old OBS_ID 2: takes 3.9 sec
V noise = 7.7 DN, S/N ~350
-20 +24 DN display
Original magnetogram is suffered from significant dI/dt noise (granule evolution)
New scheme by T.Tarbell takes I+V in symmetric manner with time to reduce the dI/dt noise
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Seasonal variation of the orbital Doppler shift
Good seasons for NFI
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Summary:
- On-orbit SOT performance was reviewed. In general, SOT is excellent and sending outstanding data.
- Some unexpected features exist; most of them are recovered by operation, i.e., frequent focus adjustment, frequent heater setting, corrections by calibration software…
- The tunable filter contains air bubbles which degrade the NFI capability.
- Schemes for tuning the filter without disturbing the bubbles have been developed and tested, and some useful procedures to obtain Dopplergram and magnetogram are now available.
- October and March when the orbit of satellite becomes nearly perpendicular to the direction towards the sun provide a favorable condition for continuous runs of the NFI.