X-Ray Calibration Facility (XRCF)

Cryogenic Optical Test Configuration

Typically, the mirror to be tested is mounted in the cryogenic shroud with the optical axis horizontal and with an Optical Testing System (OTS) located at the mirror's center of curvature. This optical instrumentation remains in an ambient pressure environment outside the chamber during testing.

Both the optical instrumentation and the mirror under test are vibration isolated from external inputs to facilitate wave front measurement. The mirror and support structure are supported by pillars that rest on a massive, isolated, concrete mass located below the chamber.

The OTS sits on a large, isolated concrete pier located immediately to the west of the chamber. The mirror systems are mounted to a remotely controlled support structure that can be precisely adjusted in five degrees of freedom (5 DOF Mirror Support Structure) to provide alignment corrections during thermal vacuum operations.

Pitch and yaw can be adjusted over a range of +/- 30 arc minutes with an accuracy of better than +/- 5 arc seconds. This 5 DOF Mirror Support will soon be modified to add rotational capability in an additional axis. In the present configuration, mirrors up to 2-meters in diameter with base radii of curvatures from 10 to 20 meters can be tested from ambient to temperatures below 30 K.

An array of state-of-the-art optical instrumentation including interferometers and radius of curvature measuring instruments are available. Figure 1 is a schematic cutaway diagram of the facility as configured for the NGST Mirror System Demonstrator (NMSD) program.