NASA is closing in on the root cause of the anomalous results produced by a December 3 vibration test on the James Webb Space Telescope (JWST). Thomas Zurbuchen, the new head of NASA’s Science Mission Directorate (SMD), told SpacePolicyOnline.com that dealing with the problem likely will consume one of the remaining six months of schedule reserve.

NASA is posting information about the anomalous test results and the agency’s subsequent actions on a special JWST webpage: jwst.nasa.gov/vibrationTest Status.html. The Twitter feed for the program, @NASAWebb, has not carried any news about the problem.

During the December 3 vibration test, accelerometers on the telescope “detected anomalous readings during a particular test,” the website posting states. Today’s update adds that the team is making “good progress” in identifying the root cause and two “low level vibrations” have been successfully conducted. Analysis of the tests is ongoing “with the goal of having a review of their findings, conclusions and plans for resuming vibration testing in January.”

Via email, Zurbuchen added that before the December 3 test, the program had approximately six months of schedule reserve and “we are now down to something less, probably closer to around 5 months.” The project is still “trending high in reserves compared to what one would expect for a project at this time of development,” he said, and the October 2018 launch date is unchanged. Some of the reserves could be regained by rephasing of tasks and “I am sure we will try hard to do that early [in] 2017.”

Zurbuchen became Associate Administrator for SMD on October 3, succeeding John Grunsfeld. He is a heliophysicst who previously was a professor of space science and engineering at the University of Michigan in Ann Arbor.

After repeated delays and cost growth, the JWST program was rebaselined in 2011 and has been holding to that new schedule (launch in October 2018) and cost estimate ($8 billion for development) ever since. Thirteen months of schedule reserve were built into the new plan. Reserve is just that — a margin to deal with unexpected problems like this one. Conceptually, a program would utilize all of its schedule reserve by the launch date.

The Government Accountability Office (GAO) is required by Congress to assess JWST’s progress every year. Its most recent report, released two weeks ago, made no recommendations, but noted that the program’s success “hinges on NASA’s ability to anticipate, identify, and respond to” challenges in a “timely and cost-effective manner.”