Before any data, the system configuration (consisting of the general configuration and the earth and geometric parameters) and the background and scan tables must be loaded. You do not have to load all these by individually selecting each one, just use the ACCESSLOADINTERFEROMETRY button, which will load all items listed above it. (This button is also used to read .cha files, as it automatically detects the format to read the relevant data.) Please note, that in addition to this the INTERFEROMETRY button will load the startable for the observed stars and will compute (for scan data) the derived geometric quantities (uv-coverage, hour and zenith angles, etc.).