The OT main GUI contains three major components: the Menu at the top,the Toolbar below this that contains the most frequently used functionsin the Menu and below this, a number of different panes that showinformation about the project and which allow various parameters of aproposal/observing program to be defined. These panes take up most ofthe OT's screen space. An example of the OT's appearance is shown inFigure 2.1 . These components are now briefly described.