Hints

The algorithm used relies on the input frame being in the following state (the standard for all ECHOMOP processes).

• No pre-processing has been performed which impacts on pixel intensities.
• The Bias has been subtracted.
• The readout-noise is known.
• The ADU-to-electron conversion ratio is known.

If the above conditions can not be satisfied then the algorithm will probably be unable to reliably detect the faintest cosmic ray pixels and the acceptance of final fit probability will have to be set very low, however, the majority of cosmic ray pixels will still be detected and flagged correctly.

If you have many `identical' object frames then these may be processed together to provide a more reliable cosmic-ray rejection. The script

    $ECHOMOP_SOURCE/decos_many

provides this facility and should be the preferred method when multiple frames are available.

The procedure calculates a median image and then rejects pixels which deviate by more than n sigma from the median value (note that this means that all the frames must be of equal exposure time). Bad pixels are flagged by placing values in the quality array of the frame concerned.