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,
Hinode workshop, 2007.12.8-10, Beijing
Sun’s diameter ～1,400,000 km
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.
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.
Image stability is perfect!
3 times better than the requirement.
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.
SP takes excellent data!
DQUV/Ic ~ 10-3 (5s integ.)
DI/Ic ~ 10-2
dominated by the compression noise
Q=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 absoluteline shift
I-profile after flat correction
Reimaging lens to FPP
BFI has a chromatic aberration (caused by improper installation of a lens).
Science impact is small but not zero.
Reimaging lens 9step = 1.36mm
4step WFE~21nm rms (< l/20 @430nm)
No evidence of chromatic aberration in NFI
- 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.
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.
FG CCD baking
The cause of the loss of throughput is not identified.
No science impact at this point.
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.
Telescope temperature is now stable.
No evidence of significant progress of contamination in OTA.
Tunable elements which carries the bubbles are identified.
TF Bubble in the FOV
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.
The separation can not be free to prevent the motion of particular elements.
Possible tuning w/o moving bubble elements
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 e=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.
I’: line profiles convoluted by TF transmission curve
2nd moments of s and p-components
Maybe better than intensity for seismology…
Good for sunspot Dopplergram
This is possible; maybe useful for prominence /spicule Dopplergram.
TF5,6 and 7 blocked
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
Old OBS_ID 2: takes 3.9 sec
V noise = 7.7 DN, S/N ~350
-20 +24 DN display
New OBS_ID 61: takes 5.9 sec
V noise = 6.5 DN, S/N > 400
-20 +24 DN display
Good seasons for NFI