The RHESSI Flare Image Archive, located in the flare_images_v2 directory, contains image cube FITS files that can be used with RHESSI image object software, converted to map structures via hsi_fits2map, or read by any standard FITS reader.
The Back Projection technique reconstructs solar flare X-ray and gamma-ray images by projecting modulated detector data back onto the image plane and summing contributions from all detectors and rotation angles. This method provides a quick, approximate image but is inherently blurred and contains artifacts, so it is typically used as an initial step or reference for advanced algorithms such as CLEAN, MEM, or PIXON.
Back Projection FITS files follow the naming convention hsi_imagecube_bproj_image_YYYYMMDD_HHMM_xxxxx.fits, where YYYYMMDD and HHMM represent the observation date and start time (UTC), and xxxxx indicates the bin size identifier.