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Abstract

The Wide Field Imager (WFI) instrument for ESA’s next large X-ray mission Athena is designed for imaging and spectroscopy over a large field of view, and high count rate observations up to and beyond 1 Crab source intensity. The other focal plane instrument, the cryogenic X-IFU camera, is designed for high-spectral resolution imaging. Both cameras share alternately a mirror system based on silicon pore optics with a focal length of 12 m and unprecedented large effective area of about 1.4 m² at 1 keV. The WFI instrument employs DEPFET active pixel sensors, which are fully depleted, back-illuminated silicon devices of 450 μm thickness. These provide high quantum efficiency over the 0.2 keV to 15 keV range with state-of-the art spectral resolution and extremely fast readout speeds compared to previous generations of Si detectors for X-ray astronomy. The sensors are controlled and read out by customized ASICs developed for this project. The focal plane comprises a Large Detector Array (LDA) with over 1 million pixels of 130 μm × 130 μm size, providing oversampling of the PSF by a factor <2 over the large (40’ × 40’) field of view, complemented by a smaller Fast Detector (FD) optimized for high count rate applications. The WFI development has entered phase B of the project at the end of 2018 after a successful Preliminary Requirements Review of the instrument conducted jointly by ESA and DLR. A further important milestone was the endorsement of the both instrument consortia by ESA, also end of 2018. The results of breadboard model development and testing will be presented as well as the preliminary design of WFI and an outlook to the next steps of the development.