Sign on

SAO/NASA ADS Astronomy Abstract Service

· Find Similar Abstracts (with default settings below)
· Electronic On-line Article (HTML)
· Table of Contents
· Also-Read Articles (Reads History)
·
· Translate This Page
Title:
Improving the science observing efficiency of the Chandra X-ray Observatory via the Chandra radiation model
Authors:
Virani, Shanil N.; DePasquale, Joseph M.; Schwartz, Daniel A.; Cameron, Robert A.; Plucinsky, Paul P.; O'Dell, Stephen L.; Minow, Joseph I.; Blackwell, William C., Jr.
Affiliation:
AA(Harvard-Smithsonian Ctr. for Astrophysics (USA)), AB(Harvard-Smithsonian Ctr. for Astrophysics (USA)), AC(Harvard-Smithsonian Ctr. for Astrophysics (USA)), AD(Harvard-Smithsonian Ctr. for Astrophysics (USA)), AE(Harvard-Smithsonian Ctr. for Astrophysics (USA)), AF(NASA Marshall Space Flight Ctr. (USA)), AG(Jacobs Sverdrup (USA)), AH(Jacobs Sverdrup (USA))
Publication:
X-Ray and Gamma-Ray Instrumentation for Astronomy XIII. Edited by Flanagan, Kathryn A.; Siegmund, Oswald H. W. Proceedings of the SPIE, Volume 5165, pp. 530-541 (2004). (SPIE Homepage)
Publication Date:
02/2004
Origin:
SPIE
DOI:
10.1117/12.505878
Bibliographic Code:
2004SPIE.5165..530V

Abstract

The 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, with an apogee altitude of 120,000 km and a perigee altitude 20,000 km, and has a period of approximately 63.5 hours (≍ 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 (Virani et al, 2000) 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 as determined by the AE-8 model by 10 ks so that ACIS, the Advanced CCD Imaging Spectrometer and 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 integrates 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 Version 2.3, we present the results of a study designed to investigate the science observing time that may be recovered by using the CRM for science mission planning purposes. In this paper, we present a scheme using the CRM such that for a modest increase in ACIS CTI, approximately 500 ks can be recovered each year for new science observations.
Bibtex entry for this abstract   Preferred format for this abstract (see Preferences)
   

Find Similar Abstracts:

Use: Authors
Title
Abstract Text
Return: Query Results Return    items starting with number
Query Form
Database: Astronomy
Physics
arXiv e-prints