With the advent of the 6-way NPOI configuration in which the observer can switch in and out stations, the number of participating stations can change throughout the night. This is equivalent to VLBI, where different sub-arrays are observing. In OYSTER, this is (so far) the only allowed exemption from the required invariability of the system configuration during observations. It is handled using a field in the scan table (scantable.station), which, for every scan, indicates which stations were used. When reading point data, this so called scan configuration is used to flag the data involving unused stations, as CONSTRICTOR has processed all data, good or bad.
Some calibration procedures must consider which configuration was used,
and therefore require input as to which scans are to be combined in the
analysis. In these cases, the scan selection directive has the list of
different scan configurations attached to the standard directives. This
acts as a simple scan selection, but based on a criterion (here: the
scan configuration). There is a command line function, scanconfig(),
which can be used for quick information regarding scan configurations, as
Return list of different scan configurations used.scanconfig(scan)
Return scan configuration used for the specified scan ID.scanconfig(config_char)
Return scan IDs which correspond to the specified scan configuration.