Recalibration of the Soft X-Ray Telescope Onboard Yohkoh

We present a new derivation of the X-ray spectral sensitivity of the Soft X-ray Telescope (SXT) experiment onboard Yohkoh . The recalibration is based upon the hypothesis that, during the first 15 months of the mission, an absorbing material gradually built up on the entrance filters of the telescope. We have also re-evaluated the times and sizes of ruptures of the SXT entrance filters. The impact of this recalibration on derived filter-ratio temperature, emission measure, and calculated spectral irradiance is substantial, especially for SXT data prior to November 1992.