During the last 24 hours the on-board load continued to operate as expected with HRC-S/LETG focus plate measurements on Capella and HRC-I observations of the science target CEN A. Preparations continue for the next load scheduled to begin late on 9/11.
Analysis of ACIS calibration source data from the last 5 days has shown an unexplained degredation in the energy resolution of the front-side illuminated CCD chips of ACIS. The degredation is evident in data starting from 5 days ago and shows a change in the FWHM from approx 130 eV to 500 eV. A series of diagnostic measurements were scheduled during the real-time passes yesterday and further diagnostic work will continue over the next 24 hours in order to understand the behavior. The ACIS engineering team is working to develop a fault tree to ensure all possible causes are covered.
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