Using ACIS on the Chandra X-ray Observatory as a particle radiation monitor

• Main Authors: La Marr, Beverly J. (Contributor), Bautz, Marshall W. (Contributor), O'Dell, S. L. (Author), Grant, Catherine E (Author)
• Other Authors: MIT Kavli Institute for Astrophysics and Space Research (Contributor), Grant, Catherine E. (Contributor)
• Format: Article
• Language: English
• Published: SPIE, 2011-03-09T14:45:03Z.
• Subjects: Article
• Online Access: Get fulltext

 The Advanced CCD Imaging Spectrometer (ACIS) is one of two focal-plane instruments on the Chandra X-ray Observatory. During initial radiation-belt passes, the exposed ACIS suffered significant radiation damage from trapped soft protons scattering off the x-ray telescope's mirrors. The primary effect of this damage was to increase the charge-transfer inefficiency (CTI) of the ACIS 8 front-illuminated CCDs. Subsequently, the Chandra team implemented procedures to remove the ACIS from the telescope's focus during high-radiation events: planned protection during radiation-belt transits; autonomous protection triggered by an on-board radiation monitor; and manual intervention based upon assessment of space-weather conditions. However, as Chandra's multilayer insulation ages, elevated temperatures have reduced the effectiveness of the on-board radiation monitor for autonomous protection. Here we investigate using the ACIS CCDs themselves as a radiation monitor. We explore the 10-year database to evaluate the CCDs' response to particle radiation and to compare this response with other radiation data and environment models.