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46.5 Cosmic Rays

The WF/PC-1 Investigation Definition Team (IDT) (OV/SV Report, 1992) analyzed several different cases, based on specific pixel threshold levels; two of these are summarized in the short table below.

Cosmic Ray Events by Threshold Level


Count Rate of Cosmic Ray Events

Above Threshold

Average Number per Event

9 DN

4.7 pixels/sec/CCD

2.7 pixels

20 DN

3.2 pixels/sec/CCD

1.88 pixels

The event rate is estimated at about 1.7 events per second per CCD. As expected, long observations are most affected by cosmic ray events. Generally any exposure longer than 10 minutes is split into multiple integrations unless it was specified otherwise by the observer. The STSDAS task crrej may be used to correct a series of images for cosmic rays.

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Copyright © 1997, Association of Universities for Research in Astronomy. All rights reserved. Last updated: 01/14/98 16:08:59