Observations affected by temporal aspect drift

Under some circumstances the positions of X-ray sources can appear to drift by 0.1 to 0.4 arcsec during an observation. This occurs due to thermal alignment changes in the fiducial transfer system periscope related to overall spacecraft heating. The list below shows all observations in the archive for which the X-ray image data may have drifts of more than 0.1 arcsec. Please contact the CXC Helpdesk for information on improving the aspect image reconstruction for an observation in this list.

obsid obi expected drift (arcsec) aspect pipeline version last aspect processing