Calibration of the plarization property of SOT
K.Ichimoto, Y.Suematsu, T.Shimizu, Y.Katsukawa, M.noguchi, M.Nakagiri,
M.Miyashita, S.Tsuneta, T.Tarbell, D.Shine, C.Hoffumann, D.Elmore, B.Lites
and SOT team
An end-to-end testing of SOT using natural sunlight was conducted
in June 2005 with a heliostat at Mitaka. During the testing, we performed
the calibration of the polarization characteristics of SOT.
Well calibrated sheet polarizers (linear and circular) was placed
on the OTA to controle the incident Stokes vector, and the polarimeter
response matrix, X, was determided for the spectropolarimeter (SP) and
the narrowband filter instrument (NFI), where X is defined by by S_out =
X S_in with S_in is the Stokes vector incident to the OTA and S_out is
the Stokes vector produced by the onboard demodulation.
It is found for SP that the X matrix can be regarded as uniform
over each left and right CCD and for scan positions.
X matrix for NFI shutterless mode can be regarded as uniform in each
left and right half of the CCD, but they have a mutual rotation of
about 2.8deg. which should be corrected in the data reduction.
We suggest to determin the first colums of the X matrix more accurately
after launch using the continuum in data obtained in orbit.
The sensitivity of SOT on polarization (and also on magnetic fields)
for all wavelengths observed by NFI are also discussed.
Correspondence
Kiyoshi Ichimoto (ichimoto@solar.mtk.nao.ac.jp), NAOJ
presentation
poster