A series of reports authored by Steve O'Dell (Project Science), computing the external fluence of trapped protons as the Chandra orbit evolves, covering the time period August 1999 - December 2026. Each report consists of a text PDF and then a series of attachments, both PDF plots and txt data files. The contents of the attachments are discussed in the text PDF. The report summaries are reproduced here for convenience.

The results from this study informed the ACIS team report on "Consequences of a future unprotected radiation belt transit by ACIS", available here.

Summary: Pursuant to a request from the ACIS team, Project Science computed the long-term external fluence of trapped protons in the evolving orbit of the Chandra X-ray Observatory. These data help characterize the vulnerability of the ACIS front-illuminated CCDs to damage (CTI increase) during unprotected radiation-belt passes, as the orbit evolves. Of course, the Chandra team will not intentionally leave the ACIS exposed during perigee passes.

• Report
• Data Products
  1. orb-eph_27y.txt
  2. orb-dif_27y.txt
  3. orb-int_27y.txt (filename in memo is a typo)
  4. orb-rad_27y.pdf

Summary: In a memorandum dated 2006.01.31, Project Science presented computations of the long-term external fluence of trapped protons in the evolving orbit of the Chandra X-ray Observatory through the AP8 environment. Here we respond to two questions posed by the ACIS team, regarding that memorandum:

1. What is the difference between AP8-Max and AP8-Min estimates?
2. How large are temporal variations about the AP8 environment?

• Report
• Data Products
  1. orb-rad_models.pdf (filename in memo is a typo)
  2. polar_100keV.pdf
  3. ebihara_2002.pdf
  4. walt_2003.pdf
  5. orb-p-fluence_1999.pdf, orb-p-fluence_2006.pdf, orb-p-fluence_2009.pdf, orb-p-fluence_2012.pdf

Summary: In a memorandum dated 2006.01.31, Project Science presented computations of the long-term external fluence of trapped protons in the evolving orbit of the Chandra X-ray Observatory through the AP8 environment. Subsequently, in a memorandum dated 2006.10.31, Project Science address uncertainties in the calculated external fluence due to temporal variations and to rotation of the Earth's slightly asymmetric magnetic field, concluding the following:

1. Temporal variations in the orbit 100-200-keV proton fluence are about a factor of 2 (geomagnetic quiet) up to 4 (geomagnetic active).
2. Rotation of the Earth's magnetic field effects changes in the orbital 100-200-keV proton fluence that are typically less than a factor of 2 orbit-to-orbit, much less for the average of 3 consecutive orbits (~8 days).

• Report
• Data Products
  1. Ip-t_100keV.pdf
  2. orbs_1-20.pdf

Last updated: 7 Apr 2025 by C. Grant