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The ACIS door mechanism is a subassembly of the Detector Housing. The Detector Housing Door is remotely activated to open and close during ground operations and open one time on-orbit, once contamination levels inside the AXAF have reached an acceptable level. The motor for the mechanism is a redundant paraffin actuator and has built-in limit switches and latches.
The door mechanism is comprised of a door, actuated through a folding linkage attached to a driveshaft. This driveshaft is rotated by two paraffin actuators with redundant heaters requiring 10 watts each over the operating range of 22 Vdc to 35 Vdc. Actuator limit switches will be monitored to report door position and terminate operation of the mechanism control circuitry. Actuator temperature will also be monitored to terminate operation to prevent rupturing of the paraffin cavity. Temperature measurements will be continuously reported as analog telemetry during operation of the Detector Housing Door. The operating temperature range for the actuator will be -65 C to +130 C. The non-operating survival temperature range will be -76 to +70 C.
The actuator causes rotation of the door, locks it in either open or closed position and indicates the end position of the door. Additionally, the actuator will indicate that it is in a mechanically acceptable state for the next door opening cycle. For the door to fully function, it must press against the door seal retainer containing a sealing o-ring. The entire mechanism is an integral part of the collimator and camera body assembly.