The Elixir postrun system consists of a series of processing stages, illustrated by the command elixir.postrun state :

imstats	process the unprocessed entries in the imstats database
mkdetrend	run the mkdetrend system to generate the detrend data
mkfringe	run the mkfringe system to generate the fringe data
ptolemy	run the science images through the ptolemy system
standards	process the standard stars and generate zero-point information
validate	perform the image validation stages

These stages must be performed in sequence, and the postrun system automatically enforces the sequencing. At the beginning of a run, each of these stages are in the state 'init'. At any stage, the command elixir.postrun update will attempt to identify the state of each of the processing stages, and run the first which is ready in the init state. While stages are running, elixir.postrun will set their state to 'running', and as the stages finish, they are set to the value 'done'.

In fact, the description above is an ideal, but in practice, the elixir.postrun script does not quite follow these rules. For example, elixir.postrun will not run the mkdetrend or mkfringe systems; these must be run manually with the mkdetrend and mkfringe commands. In addition, the mkfringe and ptolemy systems are required to be run in sequence by elixir.postrun, but these do not really require this sequencing: ptolemy can be run independently of mkfringe since ptolemy does not require the fringe frames.

Furthermore, the error checking in the elixir.postrun system is not very well refined, and manual intervention is occasionally needed. It is possible, therefore, to set the state to appropriate values as needed with the elixir.postrun set (entry) (value) command. Also, the elixir.postrun (entry) command can be used to run the specific stage manually.