The active surface system is responsible for properly positioning and protecting its electronics. The main components of the active surface are described below.
The active surface system contains 2209 electro-mechanical actuators. The actuators are nothing more than automated jacks. The actuators are configured to support up to 4 adjacent panel corners. For initial mechanical settings, the actuators are mounted on a "stool" which is situated on a flat plate. The stool is adjusted to within 3.2mm of the design paraboloid and, the vertical adjustment is pinned and the horizontal adjustment is welded. The adjustment screws on the hat bracket provide a relative adjustment of the panel corners.
Once the laser metrology system is operational it will provides commands for the ideal position coordinates. The active surface system will modify these coordinates taking into account temperature and pertinent faults to the system.
The 2,000 panels that make up the GBT's surface are mounted at their corners on actuators. The panels make up the surface of the main dish and are adjusted by the actuators. Such adjustment will be crucial to the high-frequency performance of the GBT in which an accurate surface figure must be maintained.
The MCB is provided to give monitor and control capabilities. It is used to monitor the master oscillator, shut down power supplies, and various sundry tasks. The MCB hardware will give the active surface system the ability to shutdown all critical hardware in its subsystem.
A single board computer, with the responsibility to validate data from the Precision Pointing system. The master computer translates between ideal positions to actual commanded positions and vice-versa. All position commands must pass through the master computer before a slave computer can process them. It also monitors the slave computers and the Intelligent Input/Output Port's (IIOP) Dual Port Ram.
A single board computer, each of the two VME based slave computers will control two IIOPs, thus actively controlling each actuator, at least 10 times per second. The slave computers position their actuators to within 0.001 inches of their commanded position. They also detect and properly respond to actuator over-currents, seizures, runaways, etc.