In-flight performance of the XRISM/Resolve detector system
F. S. Porter, Caroline A. Kilbourne, Meng P. Chiao, Renata Cumbee, Megan E. Eckart, Ryuichi Fujimoto, Yoshitaka Ishisaki, Yoshiaki Kanemaru, Richard L. Kelley, Maurice A. Leutenegger, Yoshitomo Maeda, Misaki Mizumoto, Kosuke Sato, Makoto Sawada, Gary A. Sneiderman, Yoh Takei, Masahiro Tsujimoto, Yuusuke Uchida, Tomomi Watanabe, Shinya Yamada
Abstract
The Resolve instrument was launched on-board the XRISM observatory in early September 2023. The Resolve spectrometer is based on a high-sensitivity X-ray calorimeter detector system that has been successfully deployed in many ground and sub-orbital spectrometers. However, the Resolve instrument will be the first long-term implementation in space. The instrument will provide essential diagnostics for nearly every class of X-ray emitting objects, from the atmosphere of Jupiter to the outskirts of galaxy clusters, without degradation for spatially extended objects. The Resolve detector system consists of a 36-pixel microcalorimeter array operated at a heat-sink temperature of 50mK. In pre-flight testing, the detector system demonstrated a resolving power of better than 1300 at 6 keV with a simultaneous bandpass from below 0.3 keV to above 12 keV and a timing precision better than 100 μs. An anti-coincidence detector placed directly behind the microcalorimeter array effectively suppresses background. The detector energy-resolution budget included terms for interference from the Resolve cooling system and the spacecraft. Additional terms for energy-scale stability, on-orbit effects, and use of mid-grade events were also included, predicting an end-of-life, on-orbit performance for high and mid-grade events that meets the requirement of 7 eV FWHM at 6 keV. Here we discuss the actual on-orbit performance of the Resolve detector system and compare this to performance in pre-flight testing, on-orbit predictions, and the almost identical Hitomi/SXS instrument. We will also discuss the on-orbit gain stability, any additional on-orbit interference, and measurements of the on-orbit background.