WASHINGTON — More than a year after the National Research Council (NRC) completed a report outlining different approaches to human space exploration, NASA’s advisers are asking the space agency to provide a formal response.

The NASA Advisory Council, meeting July 30 at the Jet Propulsion Laboratory in Pasadena, California, approved a recommendation calling for NASA to provide a response to the “Pathways to Exploration” report released by the NRC’s Committee on Human Spaceflight in June 2014. That recommendation came after a long discussion regarding NASA’s ongoing exploration activities as well as one alternative Mars exploration concept.

The idea behind the recommendation, council members said, was to get NASA to comment on the record about the report’s findings. Those findings included approaches in the report that, to many, appeared to favor a return to the moon versus a human mission to an asteroid, and a need to significantly increase NASA’s human exploration budget to achieve a human Mars landing before mid-century.

“What’s the value of doing all that work if it doesn’t engage a dialogue?” asked council member Miles O’Brien at the meeting. “I’m actually kind of surprised that there hasn’t been a formal response.”

William Gerstenmaier, NASA associate administrator for human exploration and operations, said the agency did respond to the NRC, but primarily to acknowledge receipt of the report. “There is a letter already, but it’s pretty perfunctory and pretty high level,” he said.

Gerstenmaier and other NASA officials who attended the council meeting, including one person who worked on the report before joining the agency, said the agency’s differences of opinion with the report are far less than widely perceived, even by some council members.

“I think it’s wrong to say that we disagree with the report,” Gerstenmaier said. “There are many areas where we’re in 100-percent agreement with the report.” Those areas of agreement, he said, included seeing Mars as the “horizon goal” for human space exploration and the incorporation of modularity and sustainability in those exploration plans.

The perception of a conflict between NASA’s plans and the NRC report, he argued, was created because NASA was still in the process of formulating its own exploration strategy, called Journey to Mars, while the committee was developing the report. He said that committee members, including co-chairman Mitch Daniels, were broadly supportive of NASA’s plans, but heard about them only as they were finalizing their report.

“My discussions with Mitch were that he was very understanding of which way we were heading, and wished that he could have heard that earlier while they were still in the process of writing the report,” he said.

“It’s not helpful to say that NASA doesn’t agree with the NRC report,” said Dava Newman, the current NASA deputy administrator. Prior to becoming deputy administrator, she served on the technical panel that supported the NRC committee, evaluating various exploration architectures. “I think, after another year of work, we’re very aligned.”

NASA, though, did highlight some differences of opinion with the NRC report. At a meeting of the NASA Advisory Council’s human exploration and operations committee July 27, members heard a presentation on an alternative Mars exploration approach developed at JPL and published earlier this year. That approach, its developers argued, could get humans to Mars in the 2030s within NASA’s existing human spaceflight budgets, adjusted for inflation.

“They’ve shown an existence proof of something that could fit notionally within the budget,” said Greg Williams, NASA deputy associate administrator for human exploration and operation, at the committee meeting. “I think it has corrected, frankly, the view that the NRC promulgated in their Pathways report that the journey to Mars is unaffordable unless you’re at three times the NASA budget.”

Williams added that while NASA was studying various aspects of the JPL architecture, it was not formally endorsing that approach. One major difference between the JPL study and NASA’s plans, he said, is that NASA is emphasizing activities in cislunar space as a proving ground and staging area for Mars expeditions, while the JPL concept makes limited use of missions in the vicinity of the moon.

NASA Administrator Charles Bolden said at the July 30 council meeting he would be amenable to providing a response to the NRC report. “I would be more than happy to take the contents of Gerst’s presentation today and make it a NASA response to the report as we interpreted it,” he said, referring to Gerstenmaier.

“If you don’t do this,” said council member Tom Young of a NASA response to the report, “the whole thing has been a waste.”