Data & Observations

The NCAR Vacuum Tunnel Facility (NVTF)

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.

Milestones in NVTF development

  • Calibration chamber built in 1967 for the ATM/Skylab Coronagraph project and installed at HAO on the University of Colorado's Boulder campus.
  • Class 10,000 clean room built at NCAR's Mesa Lab facility in 1980 and the vacuum tunnel was moved from the University of Colorado's Boulder campus to NCAR.
  • NVTF renovation 2001.

Highlights from NVTF calibrated instruments

ATM/Skylab Coronagraph, Skylab
The white light coronagraph was one of the principal ATM (Apollo Telescope Mount) instruments for studying the sun's outer atmosphere.

Skylab info
Solar Maximum Mission Coronagraph/Polarimeter
HAO provided a white-light coronagraph/polarimeter to the mission to aid in the study of the relationship of the corona to the flare process.

SMM info

Spartan 201 White Light Coronagraph
The white-light coronagraph was one of two instruments on the SPARTAN satellite, whose mission was to study the origins of the solar wind.

SPARTAN home page
COR-1 (aboard STEREO)
The STEREO mission consists of two heliocentric orbiting probes, each containing the same suite of instruments, including Cor-1, coronagraphs to study the inner corona.

NASA | John Hopkins

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