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Improving the Science Observing Efficiency of the Chandra X-Ray Observatory via the Chandra Radiation ModelThe Chandra X-ray Observatory (CXO), NASA's latest "Great Observatory", was launched on July 23, 1999 and reached its final orbit on August 7, 1999. The CXO is in a highly elliptical orbit, approximately 140,000 km x 10,000 km, and has a period of approximately 63.5 hours (N 2.65 days). It transits the Earth's Van Allen belts once per orbit during which no science observations can be performed due to the high radiation environment. The Chandra X-ray Observatory Center currently uses the National Space Science Data Center's "near Earth" AP-8/AE-8 radiation belt model to predict the start and end times of passage through the radiation belts. Our earlier analysis demonstrated that our implementation of the AP-8/AE-8 model (a simple dipole model of the Earth's magnetic field) does not always give sufficiently accurate predictions of the start and end times of transit of the Van Allen belts. This led to a change in our operating procedure whereby we "padded" the start and end times of transit by 10 kiloseconds (ks) so that ACIS, the primary science instrument on-board Chandra, would not be exposed to the "fringes" of the Van Allen belts on ingress and egress for any given transit. This additional 20 ks per orbit during which Chandra is unable to perform science observations sums to approximately 3 Ms of "lost" science time per year and therefore reduces the science observing efficiency of the Observatory. To address the need for a higher fidelity radiation model appropriate for the Chandra orbit, the Chandra Radiation Model (CRM) was developed. The CRM is an ion model for the outer magnetosphere and is based on data from the EPIC/ICS instrument on-board the Geotail satellite as well as data from the CEPPAD/IPS instrument on-board the Polar satellite. With the production and Implementation of the CRM, we present the results of a study designed to investigate the science observing time that may be recovered by using the CRM as a function of the additional low-energy proton exposure to ACIS.
Document ID
20030071105
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Virani, Shanil
(Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Schwartz, Daniel
(Smithsonian Astrophysical Observatory Cambridge, MA, United States)
Cameron, Robert
(Smithsonian Astrophysical Observatory Cambridge, MA, United States)
Plucinsky, Paul
(Smithsonian Astrophysical Observatory Cambridge, MA, United States)
O'Dell, Stephen
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Munow, Joseph
(Sverdrup Technology, Inc. Huntsville, AL, United States)
Blackwell, William
(Sverdrup Technology, Inc. Huntsville, AL, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2003
Subject Category
Astrophysics
Meeting Information
Meeting: X-Ray and Gamma-Ray Instrumentation for Astronomy XIII
Location: San Diego, CA
Country: United States
Start Date: August 3, 2003
End Date: August 8, 2003
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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