WASHINGTON — NASA intends to spare human spaceflight, aeronautics research and Earth observation programs during its scramble to find extra cash for the overbudget James Webb Space Telescope (JWST) in 2012, but the project’s massive cost overruns will likely require agency-wide sacrifice in the subsequent four years, JWST’s program director said.

The telescope, which NASA now says will cost $8.7 billion to build, launch and operate for five years, needs $156 million on top of the $375 million already included in U.S. President Barack Obama’s 2012 budget request, JWST Program Director Rick Howard said Sept. 21. He spoke during an online presentation hosted by the Space Telescope Science Institute, the Baltimore-based institute that will serve as the JWST science and operations center.

Half of the additional money JWST needs in 2012 will come from within NASA’s Science Mission Directorate, and every NASA science division except Earth Science will chip in. Howard said the other half will come from NASA’s Cross-Agency Support account, a $3 billion-plus budget largely used to cover overhead expenses at the agency’s nine government-run field centers.

The Senate Appropriations Committee on Sept. 15 — breaking with its House counterpart, which voted in July to cancel the telescope — included $530 million for JWST in the NASA spending bill for 2012. That appropriation, which did not identify specific offsets for the increase, would about cover what Howard says the telescope needs in 2012. For 2013 through 2016, however, JWST will need about $1.1 billion more than the $1.5 billion — or $375 million a year — that the agency laid out in its five-year spending plan in February, Howard said.

He said the details on where those additional funds will come from are still being worked out. He said JWST is being treated as “an agency priority, not just a science priority.”

The information Howard presented during the online event comes from a long-awaited NASA “replan” detailing the agency’s strategy for getting the budget-busting flagship telescope on track for launch in 2018. The full replan will not be released publicly until February, when the Obama administration is expected to release its 2013 budget request.

NASA first acknowledged in late August that JWST would cost $8.7 billion, or nearly $3.7 billion more than the agency was projecting at the start of 2010.

By the end of last year, an independent panel concluded that JWST would miss its mid-2014 launch date by at least 15 months and cost a total of $6.5 billion. That assessment, however, assumed a series of near-term cash infusions considerably larger than NASA intends to make under a stretched-out schedule that culminates with a 2018 launch aboard a European Space Agency-provided Ariane 5 rocket.

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.