The detector for the far ultraviolet channel of the imaging instrument (FCU) on board the Spectrum-UV (WSO-UV) space telescope

Abstract

Spectr-UV/WSO-UV is the third and last of the Spektr missions (Spektr-Radio, Spektr-RG, Spektr-UF), spacebased observatories, of the Russian Scientific Space Program. Spektr-UF/WSO-UV is a 2-m class ultraviolet (UV) observatory to be set in geosynchronous orbit in 2025 from the Vostochny launching pad. The observatory is equipped with instrumentation for UV spectroscopy and imaging. The Universidad Complutense de Madrid together with Institute of Astronomy of the Russian Academy of Sciences are developing jointly the imaging instrument for the mission. The instrument has a UV-optical channel designed for wide field imaging from 174 to 600 nm and a far UV (FUV) channel for high resolution imaging in the 115-175 nm range. Also, some low dispersion spectroscopic capabilities are available in the FUV channel. In this contribution, the characteristics and architecture of the MCP detector being developed by Spain for the FUV channel are described. The detector is a three steps detection system that transforms incoming UV photons into optical photons that are detected by a fast and configurable CMOS device. In a first step UV photons strike the photosensitive CsI substrate deposited on the MCP generating ∼ 1 × 10 5 e − per incoming photon. In a second step, the electrons pulse is transformed into a photon pulse at a phosphor (P46) interface; the output photons shower is captured by a bundle of optical fibers that transport the signal to the CMOS detector. In the final step, the optical photons are detected by the CMOS. Different algorithms are implemented to optimize photon counting for various purposes