Colorado Springs, Colo. — As NASA retools cost and schedule estimates for its over-budget James Webb Space Telescope (JWST), technical progress on the next-generation flagship astronomy mission continues, with nearly three-quarters of JWST hardware currently in production, according to prime contractor Northrop Grumman.

NASA Administrator Charles Bolden, appearing April 11 before the Senate Appropriations commerce, justice, science subcommittee to defend his agency’s 2012 budget request, assured lawmakers that despite Webb’s cost and schedule woes, “the telescope continues to make exceptional technological progress.”

In April, JWST’s first fully manufactured and tested primary mirror segment was delivered to NASA’s Goddard Space Flight Center in Greenbelt, Md., paving the way for completion of all 18 flight mirror segments, according to Scott Willoughby, JWST telescope program manager for Northrop Grumman Aerospace Systems. Willoughby spoke during an April 13 news conference at the National Space Symposium here.

The hexagonal mirror segment, developed by Boulder-based Ball Aerospace and Technologies Corp., is an engineering development unit that will serve as a flight spare for JWST. It was used to pioneer the telescope’s mirror fabrication and polishing processes, which has been under way since 2004.

Willoughby said NASA is ready to begin cryogenic testing of the first six flight primary mirror segments at the agency’s Marshall Space Flight Center in Huntsville, Ala. Willoughby said all 18 segments should complete testing next year.

Meanwhile, Minneapolis-based Alliant Techsystems is manufacturing the structure that supports the mirror segments and has delivered a full-scale engineering model of the flight backplane structure to Redondo Beach, Calif.-based Northrop Grumman to demonstrate integration and test protocols before applying them to the flight telescope.

ITT Corp. completed fabrication of an enormous 63,000-kilogram assembly stand built to support the weight of the entire flight optical telescope, a load of more than 3.7 metric tons. The Rochester, N.Y.-based company also demonstrated mirror installation equipment designed to affix mirror segments to the fight backplane structure.

JWST’s sunshield entered fabrication and testing last year, and work continues to develop a template sunshield currently in production. Engineering models are being built for the spacecraft’s subsystems, with model testing completed and flight production under way for the spacecraft’s solid-state recorder, an electronic memory that stores all science data for transmission to the ground.

“We’re really mature in terms of doing all of the unique things that makes a telescope like this so impressive,” Willoughby said during the news conference.

NASA had been planning to launch JWST in June 2014 but an independent review released last fall called that date into question. The review found that while JWST appears technically sound, poor program management could add at least $1.5 billion to the observatory’s estimated $5 billion price tag and stretch its schedule by at least 15 months.

Since then NASA has been revising cost and schedule estimates for inclusion in the president’s 2013 budget request. NASA Administrator Charles Bolden told lawmakers April 11 that JWST stands to be delayed until 2018.