The next generation of the National Oceanic and Atmospheric Administration's (NOAA) Geo-Stationary Operational Environmental Satellite (GOES) spacecraft will include an X-ray telescope that will monitor the Sun for predicting solar energetic events and for providing information about the large-scale solar magnetic field. The Solar X-ray Imager that will be flown on the GOES N spacecraft in late 2004 makes use of a super-polished grazing incidence mirror, a highly efficient back-thinned CCD, and thin metalized filters to observe the million-degree corona with 10-arcsec resolution (5 arcsec pixel size). Full-sun images will be acquired with SXI on a one-minute cadence at wavelengths between approximately 10 and 60 Å. SXI data will be used to forecast 'space weather', i.e., the 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 hazards during space walks, and power blackouts. Data acquired by the SXI will additionally provide invaluable context information for upcoming solar missions such as STEREO and SDO. The Lockheed Martin Solar and Astrophysics Laboratory has prepared two flight model SXIs that are being readied for flight on the GOES N and GOES O or P spacecraft.