WASHINGTON — While some members of Congress would like to see NASA launch the Solar Probe Plus mission by 2015, agency officials say they lack the funding needed to finish and fly the solar spacecraft before 2018.
“This is a $1.2 billion program,” said Richard Fisher, heliophysics division chief for NASA’s Science Mission Directorate here. “We don’t get enough budget between now and 2015 to launch it. That was an idea, but it’s a concept; it isn’t a real possibility.”
NASA’s current heliophysics budget of nearly $630 million pays for more than a dozen ongoing missions, including the $850 million Solar Dynamics Observatory that launched in February, and funds development of four more missions slated to launch between 2012 and 2014.
Under the spending plan NASA sent to Congress in February, the heliophysics division’s budget is forecast to steadily rise to $750 million by 2015. A big part of that planned increase is expected to go to the Living with a Star program, under which NASA is funding preliminary work on Solar Probe Plus.
Mission development would kick into higher gear in 2014, putting Solar Probe Plus on track to launch in August 2018 to begin a seven-year journey to the sun’s corona, a blistering hot region 6 million kilometers above the surface of the massive star.
Solar scientists for decades have wanted to send a probe plunging into the sun’s atmosphere, but technical and funding challenges have long stood in the way. In 2003, the National Research Council called on NASA to build and launch a flagship-class solar probe within 10 years, estimating the cost of the mission at $650 million.
As the mission concept has evolved over the past several years, the price tag has risen considerably as NASA and the Johns Hopkins Applied Physics Laboratory in Laurel, Md., came to terms over what it will take to build a 600-kilogram flagship solar observatory designed to survive the brutal temperature swings it will encounter as it approaches the sun.
During a two-day public meeting of the NASA Advisory Council heliophysics subcommittee Sept. 20-21, Fisher said he expects building, launching and operating such a technically challenging mission to cost between $1.1 billion and $1.3 billion.
“We have to not undertake more than we can complete in that cost envelope, and we have to launch it on time because the planetary windows are 19 months apart,” Fisher told the panel.
NASA planned to spend just $4 million on Solar Probe Plus in 2010 but Congress required the agency to spend $40 million. Fisher said the additional $36 million, which NASA had to take out of other heliophysics programs, is being used to fund various Solar Probe Plus design and mission requirement studies.
Congress has yet to pass any spending bills for 2011, but draft legislation approved by the Senate Appropriations Committee in July approved NASA’s plan to spend just $14 million on Solar Probe Plus next year even as it included a provision requiring NASA to keep the mission on track for a 2015 launch.
NASA has budgeted a total of $420 million for Solar Probe Plus over the next five years, well under half what it would need to spend to make a 2015 launch.
While NASA’s annual spending on Solar Probe Plus will not exceed $100 until 2013 under current plans, Fisher said the agency is taking important steps now to ensure the mission’s success.
In September, NASA picked the five science investigations that will comprise the Solar Probe Plus mission. The agency said it plans to invest $180 million in the selected proposals for preliminary analysis, design, development and tests.
Fisher said the Solar Probe Plus suite of instruments must not exceed 40 kilograms and require no more than 40 watts of power.