Event List

The integration mode event list is very similar to the photon counting event list as far as the FITS format goes; however the criteria of what an event list is has changed. In integration mode, any pixel in the bias subtracted image that is above some user set threshold is output to the event list. This is simply a way to encode the images as an event list. The differences in the event list are

• Long integer. The pulse height column is a single long integer, instead of multiple short integers. This is to accommodate the ACIS-2C electronics that read data out in the range from 0-65535. Any pixel that has a value of 65535 was pinned at the A/D converter limit and should be rejected.
• Extra ``Grade'' column. To make this data format compatible with ASCDS (ASC Data Systems) software, an extra column was added to the event list. This is simply a column of 0's ...as in integration mode, the event list is treated as events with flight grades assigned.

  The advantage of this format is that every frame is recorded individually, resulting in a much finer time scale. The disadvantage is that this is a difficult format to understand ... basically we are simply changing an image into an event list.