WASHINGTON — The Magnetospheric Multiscale (MMS) mission will need at least $26 million more than NASA has budgeted for the formation-flying heliophysics observatory, the U.S. Government Accountability Office warned in an April 15 report.

The four-spacecraft observatory — identified by the heliophysics community as a top priority in a 10-year roadmap, or decadal survey, published in 2003 — has been plagued by defective parts in its Fast Plasma Instrument suites, but it was the partial government shutdown of 2013 that ultimately set MMS on a course to exceed the budget NASA established for the mission in 2009 by about 3 percent, GAO said.

MMS was supposed to launch this October aboard a United Launch Alliance Atlas 5, but last October’s partial government shutdown locked workers out of the Goddard Space Flight Center in Greenbelt, Md., where MMS is being built, for about two weeks. The work stoppage forced NASA to reschedule launch for no earlier than March 2015 — the earliest date United Launch Alliance could accommodate the mission once it blew its October launch date, Chris Scolese, director of the Goddard Space Flight Center, said in March.

“However, the project’s committed level of funding is insufficient to cover this slip,” GAO wrote in its annual report on NASA projects expected to cost $250 million or more. As of last July, MMS had spent about $800 million of the roughly $850 million baseline development cost NASA established in 2009.

If MMS limits its cost growth to the $26 million identified in the April 15 GAO report, NASA will be spared from sending a formal report on the breach, and the agency’s planned fix, to Congress. By law, NASA must notify Capitol Hill whenever it appears a major project such as MMS will exceed its baseline development cost estimate by 15 percent or more. 

Meanwhile, the MMS team is still trying to figure out the cause of component failures in the eight-instrument Fast Plasma Instrument suites each MMS spacecraft will carry. The results of that investigation are expected in May, GAO said.

The failed components, discovered during flight-unit tests, are electrical devices known as optocouplers. The four MMS Fast Plasma Instrument suites use a total of 288 optocouplers, GAO said. The April 15 report suggested there might be a broad supply chain issue behind the optocoupler failures. The GAO has previously flagged these components for contributing to problems with other space and missile defense programs.

“The most likely cause of the failures stems from epoxy delamination during the testing process,” NASA spokesman Dwayne Brown wrote in an April 25 email. “The optocoupler failures were thoroughly investigated and have been addressed through a combination of parts replacement, additional parts testing, and additional testing of the instruments.

“Multiple failures of optocouplers have potential to prevent the Fast Plasma Instrument from operating,” Brown wrote in his email. 

The Southwest Research Institute in San Antonio is overseeing construction of the MMS instrument suite under a fixed-price contract awarded in 2004 and worth roughly $225 million. MMS is the fourth in NASA’s Solar Terrestrial Probes program. The observatory will study how the magnetic fields of Earth and the sun interact over a two-year primary mission.

Maria Martinez, a spokeswoman for the Southwest Research Institute, deferred to NASA for comment. 

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Dan Leone is the NASA reporter for SpaceNews, where he also covers other civilian-run U.S. government space programs and a growing number of entrepreneurial space companies. He joined SpaceNews in 2011.Dan earned a bachelor's degree in public communications...