On-Orbit Performance and Calibration of the Soft X-Ray Telescope on Yohkoh

Abstract

This paper documents details of the on-orbit performance, data problem solving, and calibration of the Soft X-ray Telescope (SXT) experiment on Yohkoh. This information is important to a full understanding of the strengths and weaknesses of the SXT data set. The paper begins with summaries of SXT calibration issues and how they have been addressed, operational anomalies experienced during the mission, and a brief discussion of the SXT optical train. The following section on the accuracy of Yohkoh pointing determination provides information important for alignment of SXT images with each other and with other solar data. The remainder of the paper gives details of work by the experiment team to understand and ameliorate the many instrument anomalies and changes which impacted the scientific data.

Recalibration of the Soft X-Ray Telescope Onboard Yohkoh

“…SXT Calibration Notes 5 (Lemen and Hudson, 1990), 29 (Acton, 1992), and 30 (Lemen, 1992), which are available in the YLA, detail aspects of pre-launch calibration and testing. On-orbit issues affecting SXT calibration have been discussed by Acton (2016).…”

“…The SXT instrument has been described by Tsuneta et al (1991). On-orbit data issues and calibration are exhaustively treated by Acton (2016). There it is explained that the entrance apertures of the SXT were covered by duplex entrance filters.…”

“…Thus, derivation of, e.g., temperature and emission measure from filter ratios must take these changes into account. The changes in SXT sensitivity were only approximately accounted for in previous calibrations (Acton, 2016). They are fully treated in the results presented in this article and in the updated SXT data analysis software archived in SolarSoft (sohowww.nascom.nasa.gov/solarsoft/).…”

Chasing White-Light Flares

“…The triple jet (Figure 7) did not make this list, although it struck me as one of the most remarkable of the SXT observations. To conclude the discussion of Yohkoh, it is a pleasure to point out the recent monumental instrument overview of SXT by its Principal Investigator (Acton, 2016).…”