The wide field imager for the NewAthena mission: preliminary design and verification

The Wide Field Imager (WFI) is one of two focal plane instruments for NewAthena, ESA’s next large X-ray observatory, planned for launch in 2037. It will study the growth mechanisms of supermassive black holes, the origin of their violent outflows and their impact on the evolution of their hosting galaxies, and the processes that lead to the assembly of luminous matter into the cosmic web [1]. WFI is a Si-based detector using DEPFET Active Pixel Sensor (APS) technology designed for sensitive wide-field imaging, spectroscopy, and high-count capability. The instrument's focal plane consists of a Large Detector Array (LDA) composed of four sensors with 512x512 pixels each and a smaller Fast Detector (FD) with 64x64 pixels, optimised for high-count rate applications.

The WFI instrument had its System Requirements Review in 2022, after which the Athena mission underwent a design-to-cost exercise to reduce the estimated Cost-at-Completion to restart the mission with a Delta Phase A-B from 2024. In the meantime, the WFI design has continued its development, including the verification of the most critical aspects to improve the maturity of the technologies used. This paper presents WFI's preliminary design based on its structural, thermal, and functional requirements. It includes the results of the numerical and experimental activities aiming at design verification and demonstration of technology readiness.