Application of graphical interaction to the analysis of radio astronomy data

A highly interactive computer graphics system has been implemented for the display and analysis of high-resolution radio images which are produced by the Very Large Array radio telescope being built by the National Radio Astronomy Observatory. Some of the users of this system are in-house scientists who use the system routinely. However, many of the users are occasional visitors from other institutions who are not necessarily computer programming experts and who have little time or inclination to learn a complex data processing control language. In order to accommodate this mix of users, the system is controlled primarily through the use of a data tablet. Appropriate feedback to the user is provided by both a refreshed line drawing display and a color raster scan image display. Keyboard input is used only for specifying output file names and for specifying a few of the numerical parameters for processing operations. After the digital images are received from another computer system, the entire display and analysis system runs in a stand-alone PDP-11/40. The use of a line drawing display for user interaction and for displaying system status information has proven to be a very useful technique. Although the system is powerful and flexible, the user interface is friendly and can be quickly and easily learned.