The Resolve soft X-ray spectrometer is the high spectral resolution microcalorimeter spectrometer for the XRISM mission. In the beam of Resolve there is a filter wheel containing \xray{} filters. In the beam also is an active calibration source (the modulated X-ray source (MXS) that can provide pulsed \xray s to facilitate gain calibration. The filter wheel consists of six filter positions. Two open positions, one 55Fe source to aid in spectrometer characterization during the commissioning phase, and three transmission filters: a neutral density filter, an optical blocking filter, and a beryllium filter. The X-ray intensity, pulse period, and pulse separation of a MXS are highly configurable. Furthermore, the switch--on time is synchronized with the spacecraft's internal clock to give accurate start and end times of the pulses. One of the issues raised during ground testing was the susceptibility of a MXS at high voltage to ambient light. Although measures were taken to mitigate the light leak, the efficacy of those measures must be verified in orbit. Along with an overview of issues raised during ground testing, this article will discuss the calibration source and the filter performance in--flight and compare with the transmission curves present in the Resolve calibration database.
@article{arxiv.2508.13600,
title = {In orbit operation of Resolve Filter Wheel and MXS},
author = {Russell F. Shipman and Shunji Kitamoto and Rob Wolfs and Elisa Costantini and Megan E. Eckart and Carlo Ferrigno and Ludovic Genolet and Nathalie Gorter and Martin Grim and Jan Willem den Herder and Caroline A. Kilbourne and Maurice A. Leutenegger and Erik van der Meer and Misaki Mizumoto and F. Scott Porter and Stéphane Paltani and Makoto Sawada and Simon Strotmann and Masahiro Tsujimoto and Cor P. de Vries},
journal= {arXiv preprint arXiv:2508.13600},
year = {2025}
}