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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

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22

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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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- 24

- 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

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15

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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.