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Real Time Space Weather Support for Chandra X-Ray Observatory Operations
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Author and Affiliation:
O'Dell, Stephen L.(NASA Marshall Space Flight Center, Huntsville, AL, United States);
Minow, Joseph I.(NASA Marshall Space Flight Center, Huntsville, AL, United States);
Miller, J. Scott(Qualis Corp., Huntsville, AL, United States);
Wolk, Scott J.(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, United States);
Aldcroft, Thomas L.(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, United States);
Spitzbart, Bradley D.(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, United States);
Swartz. Douglas A.(Universities Space Research Association, Huntsville, AL, United States)
Abstract: NASA launched the Chandra X-ray Observatory in July 1999. Soon after first light in August 1999, however, degradation in the energy resolution and charge transfer efficiency of the Advanced CCD Imaging Spectrometer (ACIS) x-ray detectors was observed. The source of the degradation was quickly identified as radiation damage in the charge-transfer channel of the front-illuminated CCDs, by weakly penetrating ( soft , 100 500 keV) protons as Chandra passed through the Earth s radiation belts and ring currents. As soft protons were not considered a risk to spacecraft health before launch, the only on-board radiation monitoring system is the Electron, Proton, and Helium Instrument (EPHIN) which was included on Chandra with the primary purpose of monitoring energetic solar particle events. Further damage to the ACIS detector has been successfully mitigated through a combination of careful mission planning, autonomous on-board radiation protection, and manual intervention based upon real-time monitoring of the soft-proton environment. The AE-8 and AP-8 trapped radiation models and Chandra Radiation Models are used to schedule science operations in regions of low proton flux. EPHIN has been used as the primary autonomous in-situ radiation trigger; but, it is not sensitive to the soft protons that damage the front-illuminated CCDs. Monitoring of near-real-time space weather data sources provides critical information on the proton environment outside the Earth s magnetosphere due to solar proton events and other phenomena. The operations team uses data from the Geostationary Operational Environmental Satellites (GOES) to provide near-real-time monitoring of the proton environment; however, these data do not give a representative measure of the soft-proton (< 1 MeV) flux in Chandra s high elliptical orbit. The only source of relevant measurements of sub-MeV protons is the Electron, Proton, and Alpha Monitor (EPAM) aboard the Advanced Composition Explorer (ACE) satellite at L1, with real-time data provided by NOAA s Space Weather Prediction Center. This presentation describes the radiation mitigation strategies to minimize the proton damage in the ACIS CCD detectors and the importance of real-time data sources that are used to protect the ACIS detector system from space weather events.
Publication Date: Dec 03, 2012
Document ID:
20130001876
(Acquired Jan 20, 2013)
Subject Category: ASTROPHYSICS
Report/Patent Number: M12-2336
Document Type: Oral/Visual Presentation
Publication Information: (SEE 20130001852)
Meeting Information: 2012 American Geophysical Union (AGU) 45th Annual Fall Meeting; 3-7 Dec. 2012; San Francisco, CA; United States
Financial Sponsor: NASA Marshall Space Flight Center; Huntsville, AL, United States
Organization Source: NASA Marshall Space Flight Center; Huntsville, AL, United States
Description: 1p; In English; Original contains color and black and white illustrations
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution as joint owner in the copyright
NASA Terms: ADVANCED COMPOSITION EXPLORER; CHARGE COUPLED DEVICES; CHARGE TRANSFER; ELLIPTICAL ORBITS; RADIATION DAMAGE; REAL TIME OPERATION; SOLAR CORPUSCULAR RADIATION; SOLAR FLARES; SOLAR PROTONS; SPACE WEATHER; TERRESTRIAL RADIATION; X RAY ASTROPHYSICS FACILITY; X RAY DETECTORS
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