18 July 2000 Observed on-orbit background of the ACIS instrument on the Chandra X-ray Observatory
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We have analyzed data acquired during the Orbital Activation and Checkout (OAC) and Guest Observer (GO) phases of the Chandra X-ray Observatory mission in order to characterize the background of the Advanced CCD Imaging Spectrometer (ACIS) instrument produced by energetic particles. The ACIS instrument contains 8 Front-Illuminated (FI) CCDs and 2 Back-Illuminated (BI) CCDs. The FI and BI CCDs exhibit dramatically different responses to enhancements in the particle flux. The FI CCDs show relatively little increase in the overall count rate, typical increases are 1 - 5 cts s-1 above the quiescent level; the BI CCDs can show large excursions to a s high as 100 cts s-1 above the quiescent level. The durations of these intervals of enhanced background are also highly variable ranging from 500 s to 104 s. These periods of enhanced background are sometimes but not always associated with increased particle flux when Chandra is near the radiation belts. We see evidence for a weak correlation with the low-energy electron channel of the Electron, Proton, Helium Instrument particle detector instrument on-board Chandra. We present some of the most extreme examples of these background enhancements identified to this point in the mission.
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Paul P. Plucinsky, Paul P. Plucinsky, Shanil N. Virani, Shanil N. Virani, } "Observed on-orbit background of the ACIS instrument on the Chandra X-ray Observatory", Proc. SPIE 4012, X-Ray Optics, Instruments, and Missions III, (18 July 2000); doi: 10.1117/12.391607; https://doi.org/10.1117/12.391607

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