Thermal vacuum chamber testing for mechanical characterizations

Telescope performance depends on stability in the nanometer range, so the stability of the fully instrumented backplanes is critical. They need to be tested in thermal vacuum chambers suitable for testing under cryogenic conditions, and designed to ensure unique thermal stability at temperatures below –250 °C (–420 °F). Testing in the vacuum chamber requires accelerometers and force sensors with ultra-low temperature capabilities.

Backplanes can carry the primary mirror as well as other telescope optics and the entire module of scientific instruments. Testing allows modification of the system so that the backplanes – and ultimately the telescope – can be isolated in the chamber. Some testing environments include a new, layered helium and nitrogen cooling system: this allows the backplanes to reach the low temperatures that simulate operating temperatures in space. They allow for cryogenic optical alignment and testing of multiple primary mirror segments in a process known as "phasing". Testing of this sort calls for accelerometers and force sensors with ultra-low temperature capabilities.

Important technologies for the application

Accelerometers from Kistler detect background vibrations in the micro-vibration range.

Our PiezoStar-based IEPE (voltage mode) accelerometers are the ideal sensors for precision vibration testing because of their low sensitivity to temperature variations.

Charge output sensors or cryogenic, voltage mode IEPE accelerometers from Kistler feature an outstanding temperature range from below the typical -54°C (-65°F) down to -196°C (-320°F), so they can safely survive liquid helium temperatures in the thermal vacuum chamber.

Exposure to the high vacuum level of a space environment induces material outgassing that releases entrapped gas. This can condense on surfaces such as camera lenses, rendering them inoperative for the intended application. Hermetically sealed sensors and low-outgassing cables from Kistler are designed to meet all needs ideally.

NASA's James Webb Space Telescope Structure

NASA's James Webb Space Telescope Structure is prepared for thermal vacuum testing.
(source: NASA/Chris Gunn)

The full-scale James Webb Space Telescope pathfinder (test version of our backplane) entering NASA Johnson's huge Chamber A for cryogenic testing.
(source: NASA/Chris Gunn)

Kistler Instrument Corp.

Sensors can be safely exposed to the high vacuum level in a space environment 

Background micro-vibrations are reliably detected 

Stable measurement results

(max 25 Mb)