http://hea-www.harvard.edu/arots/nvometa/STC.html
The Stc class does not have a constructor function of its own, as it is simply a container class for a family of specialised sub-classes including StcCatalogEntryLocationStcCatalogEntryLocation, StcResourceProfileStcResourceProfile, StcSearchLocationStcSearchLocation and StcObsDataLocationStcObsDataLocation.