NASA Administrator Charles Bolden warned a Senate panel March 12 that commercial crew contractors Boeing [BA] and Space Exploration Technologies Corp. (SpaceX) could miss their 2017 launch readiness deadlines if the civil space agency doesn’t receive all of the $1.2 billion it requested for the program in fiscal year 2016.

“Any amount short of the $1.2 billion we requested will mean we will have to reduce the milestones that the two manufacturers accomplish,” Bolden told the Senate Commerce, Science and Transportation space, science and competitiveness subcommittee during a hearing on NASA’s FY ’16 budget request.

Much of the hearing revolved around the appropriate level of funding for NASA’s earth science programs and split along partisan lines. Subcommittee Chairman Ted Cruz (R-Texas) and Sen. Cory Gardner (R-Colo.) said they want the civil space agency to focus more on exploration as opposed to its earth science programs. Cruz said NASA’s “core function” is to explore space and that he’s concerned it has lost its “full focus” on exploration. Cruz took chairmanship of the subcommittee when the Republicans took over the Senate earlier this year. Gardner is a freshman senator.

Cruz claimed NASA disproportionately increased its earth sciences budgets since 2009 compared to its exploration and space operations budgets. Cruz presented a chart that showed a roughly 40 percent increase in earth science budgets over the last six years, which Bolden later dismissed as “chartsmanship.”

Bolden called the decrease in exploration “somewhat intentional” as the agency reached further into the solar system. It used to cost NASA $2 billion per year to maintain the Space Shuttle whether it was flown or not, Bolden said. NASA in September awarded Boeing and SpaceX $6.8 billion total in contracts for what Bolden said was 16 total commercial crew flights to the International Space Station (ISS) over “three or four” years. NASA, overall, requested $18.5 billion for FY ’16.

“The fact that earth science (budges have) increased, I’m proud to say has enabled us to understand our planet far better than we ever did before,” Bolden said. “It’s absolutely critical.”

Sen. Bill Nelson (D-Fla.) and freshman Sen. Gary Peters (D-Mich.) defended NASA’s budget request. Nelson cited increases from enacted FY ’15 levels in commercial crew, exploration ground systems, exploration research and development (R&D), cross agency support and space technology, which he said is part of exploration, just a different line item. Peters cited the astronautics portion of NASA as a core mission and said it was important to view NASA’s portfolio as “very broad.”

“Those numbers, just looking at the specific isolated SLS (Space Launch System) and Orion, don’t tell us the whole story,” Nelson said.

Boeing and SpaceX did not respond to requests for comment by press time.