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Staggered Frames

Staggered Frames mode is a unique data mode for ACIS-2C. This mode is a mixture of Continuous Clocking and Full Frame modes. Similar to continuous clocking, pixels are continuously transferred to the frame store array; however, instead of going 1 row at a time, groups of rows are transferred. The result is a kind of moving window across the CCD. The integration time is then the amount of time to read out the group of rows.

This mode trades off the advantages and disadvantages of Full Frame and Continuous clocking. You have spatial resolution on a scale as big as the window you are using; however, the bigger the window the longer the integration time. There were several window sizes to choose from so the planners chose which parameter is the most important and designed tests accordingly.

In the raw FITS images of the Staggered Frames mode data, there is 2 pixel wide spacer row between each window. These are ignored by the event finding routine.

Mark Bautz