The Instrument A sketch of the proposed tool is shown in Figure 1 . A shaft, screwed onto the actuator, provides a reference for a jig that slides over the shaft. A step in the shaft permits location of the jig. Four electronic dial indicators mounted to the jig make contact with the reference points on the panel. The indicator is battery powered, with a battery life of 500 hours.
Gravity is a convenient reference to use here.
In the radial direction, the angle of the surface tangent with respect to gravity is know for each actuator position. In the circumferencial direction, horizontal is a convenient reference plane. A series of wedges will be needed to maintain the radial inclinometer within its range for the outer parts of the reflector. This simple option has been chosen over a servo controlled platform which, while more elegant, would be more bulky and complex. A block diagram illustrating the various components is shown in Figure 2 .