EGU2020-10225
https://doi.org/10.5194/egusphere-egu2020-10225
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Detailed Calibration of the Off-Axis Optical Characteristics for the X-Ray Telescope onboard Hinode

Junho Shin1, Takashi Sakurai2, Ryouhei Kano2, Yong-Jae Moon1, and Yeon-Han Kim3
Junho Shin et al.
  • 1School of Space Research, Kyung Hee University, Yongin 17104, Korea, Republic of (junhosn@khu.ac.kr)
  • 2National Astronomical Observatory of Japan, National Institutes of Natural Sciences, Tokyo 181-8588, Japan
  • 3Space Science Division, Korea Astronomy and Space Science Institute, Daejeon 305-348, Korea

The X-Ray Telescope (XRT) onboard the Hinode satellite has a specially designed Wolter type grazing-incidence (GI) optics with a paraboloid-hyperboloid mirror assembly to measure the solar coronal plasma of temperatures up to 10 MK with a resolution of about one arcsec. One of the main purposes of this scientific mission is to investigate the detailed mechanism of energy transfer processes from the photosphere to the upper coronal region leading to its heating and the solar wind acceleration. To theoretically model the three-dimensional coronal structures is sensitive to the values of plasma properties at the base of solar corona and thus requires beforehand accurate empirical description of those properties. Though the telescope has provided unprecedented observations of solar corona for more than a decade, due to a wide field of view of 34 x 34 arcmin covering the full Sun, the optical performance of the instrument gradually deteriorates as it goes away from the optical center. For this reason, the off-axis characteristics of Hinode/XRT should be examined with care in order to precisely interpret the coronal plasma properties near the solar limb area.

This presentation will explain the importance of accurate calibration of the optical characteristics, especially for the data taken in the off-axis region. Our previous study has shown that the scattered light caused by the XRT mirror surface roughness has a power-law distribution and also shows an energy dependence, with which the PSF profile from the core to the scattering wing has been completed. We will introduce in this study how the level of scattering wing can be determined quantitatively for each focal plane filter from in-flight data analysis. We have also evaluated the vignetting effect in Hinode/XRT by analyzing the 2D distribution of effective area in the field of view taken from MSFC/XRCF pre-launch experiment. It is revealed that, unlike the case of Yohkoh/SXT, the degree of offset of an optical center is not serious and thus shows little deviation from rotational symmetry. Also important is that the vignetting pattern in XRT shows an energy dependence, which has never been considered before for the analyses of XRT data. More interesting results on the calibration of Hinode/XRT scattered light and the correction of vignetting effect will be introduced and discussed thoroughly. 

How to cite: Shin, J., Sakurai, T., Kano, R., Moon, Y.-J., and Kim, Y.-H.: Detailed Calibration of the Off-Axis Optical Characteristics for the X-Ray Telescope onboard Hinode, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10225, https://doi.org/10.5194/egusphere-egu2020-10225, 2020