Scattered Light Characterization of FORTIS

摘要

We describe our efforts to build a Wide-Field Lyman α Geocoronal simulator (WFLαGs) for characterizing the end-to-end sensitivity of FORTIS (Far-UV Off Rowland-circle Telescope for Imaging and Spectroscopy) to scattered Lyα emission from outside of the nominal (1/2 degree) field-of-view. WFLαGs is a 50 mm diameter F/1 aluminum parabolic collimator fed by a hollow cathode discharge lamp with a 80 mm clear MgF_2 window housed in a vacuum skin. It creates emission over a 10 degree FOV. WFLαGs will allow us to validate and refine a recently developed scattered light model and verify our scatter light mitigation strategies, which will incorporate low scatter baffle materials, and possibly 3-d printed light traps, covering exposed scatter centers. We present measurements of scattering intensity of Lyman alpha as a function of angle with respect to the specular reflectance direction for several candidate baffle materials. Initial testing of WFLαGs will be described.