Webb Telescope’s NIRSpec Instrument Ready for Testing

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OTTOBRUNN, Germany — European contractors on Oct. 14 completed work on a full-scale test model of one of the four observing instruments for the James Webb Space Telescope (JWST) and told NASA the hardware was ready for shipment.

An engineering test model of the 200-kilogram Near Infrared Spectrograph, NIRSpec, is the first of JWST’s principal instruments to be declared ready for a battery of tests to be performed in 2010 at NASA’s Goddard Space Flight Center in Greenbelt, Md.

JWST features major contributions by the European Space Agency including two of the four JWST telescopes. The European Space Agency (ESA) is also handling the launch of JWST, now scheduled for June 2014 on a European Ariane 5 rocket.

NASA officials agreed this summer to delay the satellite’s launch by one year following an overall judgment by program officials that the mid-2013 launch did not leave sufficient room for hardware delivery or testing hiccups.

The yearlong delay is adding about $300 million to NASA’s JWST budget, which now stands at slightly less than $5 billion, including five years of in-orbit operations, according to Phil Sabelhaus, JWST program manager at NASA. That figure does not include ESA’s contribution to JWST, which he said is expected to total around 500 million euros ($737 million), including the launch and Europe’s contributions to the satellite’s in-orbit operations.

Torsten Boeker, ESA’s deputy JWST project scientist, said Europe will send about 15 people to Baltimore to work at the Space Telescope Science Institute during JWST’s operating life.

In an interview here at Astrium GmbH, which is prime contractor for the NIRSpec, Sabelhous said JWST’s mission critical design review remains scheduled for around April 2010 despite the launch date slip. That will be the next big program milestone.

Sabelhaus said the difficulties encountered with development of the Near-Infrared camera provided by the University of Arizona have been resolved, and that development of the JWST’s individual components appears on track.

The big worry, he said, is testing of the satellite in a large space-environment test chamber being readied for JWST at NASA’s Johnson Space Center in Houston. Because of its size, JWST cannot fit into even what will be the world’s largest thermal-vacuum chamber, which is expected to be completed in mid-2011.

That being the case, the satellite’s skeletal support, or bus, and its distinctive multilayered heat shield will not be included in the series of thermal-vacuum tests scheduled to start in September 2012 following preliminary tests of components to begin in September 2011.

“It’s fair to say that a list of worries is how the testing will go,” Sabelhaus said. “Testing optical instruments at cryogenic temperatures has never been done before and this presents challenges. We need to maintain temperatures [in the thermal-vacuum chamber] of 30 degrees Kelvin for a considerable period of time — we need about 8 kilowatts of cooling capacity — and you have around 4,000 kilograms of hardware that is being tested.”

NIRSpec prime contractor Astrium Satellites GmbH employs about 70 people at its production facilities here and in Friedrichshafen, Germany, to work on the project. A separate Astrium team in Britain is working on the Mid-Infrared Instrument, also under contract to ESA.

Evert Dudok, chief executive of Astrium Satellites, said during an Oct. 14 press briefing here that the NIRSpec contract has enabled Astrium to hone its ability to develop silicon carbide structures. The NIRSpec mirrors, mounts and its optical base plate are all constructed from this material.