NASA is one of the largest and most well-known agencies in the US government. But while many Americans associate the famous agency with moon walkers, space shuttles, and dramatic countdowns from 10, the agency actually has two clearly defined missions: Simply put, it is NASA's job to both study space from Earth and to study Earth from space.

And it was these two core missions that Sen. Ted Cruz wanted to discuss with NASA Administrator Charles Bolden in a Senate subcommittee hearing yesterday. More specifically, how the two missions should be funded next year.

Senator Cruz, (R) of Texas, became the new chair of the Senate's subcommittee on Space, Science, and Competitiveness when the Republican Party took control of the chamber in January. Since that time, he has been pushing the agency to adopt a "more space, less Earth" strategy.

His position ran into some opposition on Capitol Hill yesterday during the hearing on President Obama's $18.5 billion budget request for NASA for fiscal 2016, when he told Mr. Bolden he'd like to start "by asking a general question."

"In your judgment, what is the core mission of NASA?" Cruz asked Bolden, according to the National Journal.

Bolden replied that he'd been contemplating that mission over the past few days, including reading over the National Aeronautics and Space Act of 1958, which created the agency.

"Our core mission from the very beginning has been to investigate, explore space and the Earth environment, and to help us make this place a better place," Bolden said.

The answer did not seem to satisfy Cruz, according to the National Journal, who replied that "almost any American would agree that the core function of NASA is to explore space."

"That's what inspires little boys and little girls across this country," Cruz added. "I am concerned that NASA in the current environment has lost its full focus on that core mission."

Cruz then pointed to a chart behind him illustrating that, since 2009, NASA funding for Earth sciences has seen a 41 percent increase, while funding for exploration and space operations has seen a 7.6 percent decrease.

"In my judgment, this does not represent a fair or appropriate allocation of resources, that it is shifting resources away from the core functions of NASA to other functions," Cruz said. "Do you share that assessment?"

Bolden, who decides how to allocate NASA's annual budget, replied, chuckling, that "there's a lot of chartsmanship" regarding NASA's funding. The decrease in space exploration funding, for example, was "somewhat intentional" because the agency was trying to get the cost of exploration down as it reaches farther out into the solar system. NASA's now-defunct space shuttles cost the agency $2 billion a year to maintain whether they flew or not, Bolden said. Today, NASA has a $6.6 billion contract with private companies Boeing and SpaceX that will provide for 16 human spaceflights over a span of three to four years.

"So, by my statement, I was not acknowledging that I agree with the numbers on the chart," Bolden said. "I don't want everyone to say I accept the numbers on the chart."

Bolden added that more money for Earth-science research is a good thing, and that the increases have "enabled us to understand our planet far better than we ever did before."

Cruz drew headlines in January when he was made chair of the Senate space and science subcommittee despite a long history of climate change skepticism, including telling CNN in a February 2014 interview that there was no data to support the existence of climate change.

"The last 15 years, there has been no recorded warming," Cruz said in the CNN interview. "Contrary to all the theories that they are expounding, there should have been warming over the last 15 years. It hasn’t happened."

NASA's research on Earth science is extensive, with the agency spending more than $1 billion annually on Earth science, according to The Washington Post. NASA facilities themselves are also under imminent threat from climate change, in particular the Kennedy Space Center in Cape Canaveral, Fla., the launching site for the agency's famous Apollo Program missions to the moon.

Since 2003, nearly 100 feet of beach next to the launch pads have been lost to sea level rise, according to CBS News. NASA is now spending $2.8 million on a new mile-long dune to protect the site's launch pads. Three more dunes are also planned.

"We can't go anywhere if the Kennedy Space Center goes underwater and we don't know it—and that's understanding our environment," Bolden said at yesterday's hearing. "It is absolutely critical that we understand Earth environment because this is the only place that we have to live."

NASA also has made tough decisions recently prioritizing some space exploration missions over Earth science research. In its 2015 budget proposal the agency dropped a bombshell proposal to cut funding for the Stratospheric Observatory for Infrared Astronomy (SOFIA), a 747 jetliner equipped with a 8.2-foot telescope that can make observations about infrared-absorbing water vapor in the Earth's atmosphere.

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At the time, Bolden said the cut to SOFIA funding was a result of the agency having to prioritize other programs, such as the James Webb Space Telescope (JWST) – successor to the Hubble Space Telescope – and a 2020 Mars rover mission.

"It turned out that we had to make very difficult choices about where we go with astrophysics and planetary science and Earth science, and SOFIA happened to be what fell off the plate this time," he said shortly after the budget proposal came out.