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
, 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 follows.
scanconfig()
Return list of different scan configurations used.scanconfig(scan)
Return scan configuration used for the specified scan ID.scanconfig(config
Return scan IDs which correspond to the specified scan configuration.