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The NVTF, managed by HAO, is a unique facility that consists of a class 10,000 clean room and a coronagraph calibration chamber. This chamber has been used to calibrate instruments such as the ATM/Skylab Coronagraph, the Solar Maximum Mission Coronagraph/Polarimeter, the Spartan 201 White Light Coronagraph, and COR-1. The NVTF was brought back into operation in FY2001 for NASA's COR-1 coronagraph design evaluation as part of the STEREO Mission.
The calibration chamber (vacuum tunnel) is used for testing and calibrating both internally and externally occulted coronagraphs. Scattered light, polarization and photometric tests are made. The NVTF consists of five major elements; the staging area, a class 10,000 clean room, instrument tank, extension tube, and the altitude-azimuth solar feed. The instrument to be calibrated is placed on a platform in the instrument tank and aligned to the optical axis of the tunnel. The instrument tank door is then closed and the chamber pumped down to 20 - 50 mTorr of vacuum. Testing is done under vacuum so that the dust and water vapor in the air between the instrument and the solar feed does not influence the scattered light measurements. The solar feed is a two-mirror altitude-azimuth system that is actively controlled.