The Solar Optical Telescope (SOT) onboard Hinode aims to obtain vector magnetic fields on the Sun through precise spectropolarimetry of solar spectral lines with a spatial resolution of 0.2 -0.3 arcsec. A photometric accuracy of 10 −3 is achieved and, after the polarization calibration, any artificial polarization from crosstalk among Stokes parameters is required to be suppressed below the level of the statistical noise over the SOT's field of view. This goal was achieved by the highly optimized design of the SOT as a polarimeter, extensive analyses and testing of optical elements, and an end-to-end calibration test of the entire system. In this paper we review both the approach adopted to realize the high-precision polarimeter of the SOT and its final polarization characteristics.

A new imaging system of the coronal green line (Fe XIV 5303 Å) was constructed at the Norikura Solar Observatory. The system consists of a 10-cm coronagraph, a tunable Lyot filter, and a cooled CCD camera. The transmission curve of the Lyot filter can be modulated by two liquid-crystal variable retarders. This scheme provides quick wavelength tuning and efficient subtraction of sky background. Two-dimensional distributions of the intensity and Doppler shift of the coronal green line can be obtained within 30 seconds with accuracies of better than 10−6I⊙ and 1 km s−1. Regular operation was started in 1997 September. The aim of the new system is to investigate plasma motions associated with the magnetic field reconnection and waves in the solar corona.

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An infrared spectro-polarimeter installed on the Solar Flare Telescope at the Mitaka headquarters of the National Astronomical Observatory of Japan is described. The new spectro-polarimeter observes the full Sun via slit scans performed at two wavelength bands, one near 1565 nm for a Zeeman-sensitive spectral line of Fe i and the other near 1083 nm for He i and Si i lines. The full Stokes profiles are recorded; the Fe i and Si i lines give information on photospheric vector magnetic fields, and the helium line is suitable for deriving chromospheric magnetic fields. The infrared detector we are using is an InGaAs camera with 640 × 512 pixels and a read-out speed of 90 frames s−1. The solar disk is covered by two swaths (the northern and southern hemispheres) of 640 pixels each. The final magnetic maps are made of 1200 × 1200 pixels with a pixel size of $1{^{\prime\prime}_{.}}8$. We have been carrying out regular observations since 2010 April, and have provided full-disk, full-Stokes maps, at the rate of a few maps per day, on the internet.

The Sunrise chromospheric infrared spectropolarimeter (SCIP) installed in the international balloon experiment sunrise iii will perform spectropolarimetric observations in the near-infrared band to measure solar photospheric and chromospheric magnetic fields simultaneously. The main components of SCIP for polarization measurements are a rotating wave plate, polarization beam splitters, and CMOS imaging sensors. In each of the sensors, SCIP records the orthogonal linearly polarized components of light. The polarization is later demodulated on-board. Each sensor covers one of the two distinct wavelength regions centered at 770 and 850 nm. To retrieve the proper circular polarization, the new parameter R , defined as the 45° phase shifted component of Stokes V in the modulation curve, is introduced. SCIP is aimed at achieving high polarization precision ( 1 σ < Privacy Policy and Terms of Service apply.