Design and performance predictions for the GOES SXI telescope

The Solar X-ray Imager (SXI) is a grazing incidence Welter Type I X-ray Telescope to be fabricated and down on the National Oceanic and Atmospheric Administration's (NOAA) Gee-Stationary Operational Environmental Satellite (GOES). The SXI will image the full sun at wavelengths between approximately 6 and 60 angstroms with a detector having 5 arc sec pixels. The goal for SXI is to forecast "space weather", i.e., effects of charged particles that are produced at the Sun as they interact at the earth. Major contributors to space weather include: variations in the Sun's solar wind, solar flares, and solar mass ejections. Effects of space weather include: radiation damage and particle events in high-inclination orbit spacecraft, disruption of various kinds of communications equipment, degradation of navigational tools such as GPS, potential health hazard during space walks, and power blackouts and damage to power company generators. This paper reviews the optical performance requirements of the SXI and the resulting optical design for the grazing incidence telescope. Parametric performance predictions of image quality as degraded by diffraction, geometrical aberrations, and surface scattering effects due to residual optical fabrication errors are presented that establish realistic optical fabrication tolerances necessary to satisfy top-level image quality requirements.