GOES solar x-ray imager: overview and operational goals

The first solar x-ray imager (SXI) will provide a major advance in real-time, continuous monitoring of solar- terrestrial conditions. This instrument, which will fly on a Geostationary Operational Environmental Satellite (GOES), will provide full-disk images of the Sun once a minute in the 0.6-6 nm range with 5 arcsec pixels. SXI's images will complement x-ray fluxes from the disk-integrating GOES x-ray sensor and optical images from ground-based observatories. THe automated sequence of SXI images will make it easy for forecasters, researchers, and image processing algorithms to interpret the images. SXI is being built to meet five operational goals for real-time prediction of solar- terrestrial disturbances: 1) SXI will provide clear evidence of x-ray coronal holes that are associate with recurrent geomagnetic storms. 2) SXI will provide flare locations that are used to estimate the magnitude and timing of energetic particle events, including flares from regions behind the solar limb that are not visible at other wavelengths. 3) SXI could provide a significant improvement in forecasting geomagnetic disturbances if CME-associated brightenings can be readily observed. 4) SXI images will show the complexity of the active regions, which will be used to estimate each region's flare potential.