The wide field monitor onboard the eXTP mission

The eXTP (enhanced X-ray Timing and Polarimetry) mission is a major project\nof the Chinese Academy of Sciences (CAS) and China National Space\nAdministration (CNSA) currently performing an extended phase A study and\nproposed for a launch by 2025 in a low-earth orbit. The eXTP scientific payload\nenvisages a suite of instruments (Spectroscopy Focusing Array, Polarimetry\nFocusing Array, Large Area Detector and Wide Field Monitor) offering\nunprecedented simultaneous wide-band X-ray timing and polarimetry sensitivity.\nA large European consortium is contributing to the eXTP study and it is\nexpected to provide key hardware elements, including a Wide Field Monitor\n(WFM). The WFM instrument for eXTP is based on the design originally proposed\nfor the LOFT mission within the ESA context. The eXTP/WFM envisages a wide\nfield X-ray monitor system in the 2-50 keV energy range, achieved through the\ntechnology of the large-area Silicon Drift Detectors. The WFM will consist of 3\npairs of coded mask cameras with a total combined Field of View (FoV) of 90x180\ndegrees at zero response and a source localization accuracy of ~1 arcmin. In\nthis paper we provide an overview of the WFM instrument design, including new\nelements with respect to the earlier LOFT configuration, and anticipated\nperformance.\n