For more than half a century, NASA has been revealing new wonders about one of the most complex planets in the solar system—Earth. Using its formidable capabilities in building rockets and launching satellites, the space agency has kept a steady eye on our home planet and advanced our understanding of its oceans, weather, and climate systems.

However, that critical service took a serious blow on Thursday, when U.S. President Donald Trump announced his proposed federal budget for 2018.

The $19-billion request for NASA—which still requires approval by Congress—would largely preserve plans for space exploration in the form of continued funding for a 2020 Mars rover, a flyby of Jupiter’s moon Europa, and the passenger-ferrying vehicles known as the Space Launch System and Orion capsule.

At the same time, the budget proposes deep cuts to NASA’s Earth sciences mission, including dismantling three upcoming satellites and discontinuing funding for the Earth-viewing instruments aboard a satellite that launched in 2015.

“That’s a surgical removal, a surgical targeting,” says climate scientist Peter Pilewskie, a professor at the University of Colorado at Boulder. He questions cost-cutting as a rationale, given that $102 million—the money the Trump Administration estimates will be saved from the cuts—is a minuscule fraction of the U.S. federal budget, which is more than $3 trillion.

Here are the four missions that the proposed budget eliminates, and why they matter.

Deep Space Climate Observatory (DSCOVR)

Of the missions potentially on the chopping block, DSCOVR is the only one currently in space. The satellite is parked between Earth and the sun, a unique vantage point roughly a million miles away that allows it to take stunning images of the planet and track changes with unprecedented detail.

One of the images from DSCOVR made widespread headlines in 2016, when a marauding moon photobombed Earth. The pictures were snapped by the EPIC camera aboard the satellite, which stares at the planet and monitors characteristics such as ozone, vegetation, atmospheric aerosols, and cloud heights. (Watch a year on Earth as seen from DSCOVR.)

View Images The DSCOVR satellite took this picture of Earth on July 6, 2015. Photograph by NASA

In addition to taking pretty—and scientifically useful—pictures of our home planet, DSCOVR monitors the solar wind, the charged particles flung outward by activity on the sun.

When these particles collide with Earth’s magnetic field, they can trigger beautiful auroras and—if strong enough—can produce roiling geomagnetic storms capable of taking down power grids. Presumably, this portion of the satellite’s mission will remain functional, although its homeward eyes would be shut.

Kevin Trenberth, a distinguished senior scientist with the National Center for Atmospheric Research’s Climate Analysis Section, is perplexed by the decision to cut funding to part of a functioning satellite: “You’ve got the thing up there, it’s functioning already, [and] it’s producing these spectacular pictures and information that has never been seen before.”

The Plankton, Aerosol, Cloud, and ocean Environment mission (PACE)

Set to launch some time in the next five or six years, PACE is slated to keep a keen eye on the deep blue seas that blanket more than 70 percent of our planet.

Monitoring the state of Earth’s oceans is crucial for understanding how the planet responds to climate change. Carbon released into the atmosphere from, for example, burning fossil fuels is largely returned to the sea, where organisms such as plankton convert it into energy and oxygen.

Orbiting Carbon Observatory 3 (OCO-3)

While the original Orbiting Carbon Observatory was lost in a launch accident, its successor OCO-2 has been monitoring global carbon dioxide levels since 2014 from a perch high above Earth.

The satellite works by tracking the brightness of sunlight reflected off Earth’s surface, looking specifically at infrared wavelengths that oxygen and carbon dioxide absorb. By seeing how much light gets absorbed, scientists can tell how many gas molecules must have been present over a given area. This lets them reconstruct atmospheric concentration from space, as well as better understand how Earth’s atmosphere, land, and ocean exchange CO2 with one another. (Find out more about OCO-2.)

ANIMATION: SEE A NEW 3-D VIEW OF CO2 IN EARTH'S ATMOSPHERE Courtesy NASA Goddard Space Flight Center

Built from spare parts left over from the OCO-2 instrument, the Orbiting Carbon Observatory 3 (OCO-3) is meant to be installed on the Japanese module of the International Space Station after a 2018 launch. From aboard the ISS, it would investigate “important questions about the distribution of carbon dioxide on Earth as it relates to growing urban populations and changing patterns of fossil fuel combustion,” according to NASA.

Climate Absolute Radiance and Refractivity Observatory (CLARREO) Pathfinder

Complementing all of these missions would be the CLARREO Pathfinder, an instrument designed to take detailed measurements of some of the finicky variables essential for accurate predictions of climate change, such as the amount of infrared radiation emitted from Earth to space.

Set to launch sometime in the 2020s and also pegged for installation on the space station, CLARREO would offer scientists the data they need to produce highly accurate climate records, as well as refine and test climate projections—the kinds of projections that might inform decisions about how to respond to rising sea levels, rising global temperatures, and declining air quality.

Delayed Dangers

In a letter accompanying the budget, President Trump justifies the cuts by saying the government “must make the safety of our people its number one priority— because without safety, there can be no prosperity.”

But critics counter that the dangers posed by a changing climate put countless lives at risk.

“The Secretary for Defense [James Mattis] recently stated that changing climate is a large security risk for the United States,” Pilewskie says. “That’s refreshing. It is a security risk.” (Also see “Who's Still Fighting Climate Change? The U.S. Military.”)

In addition to these cuts at NASA, the 2018 budget proposes even steeper cuts to the U.S. Environmental Protection Agency (EPA). The budget would eliminate the agency’s international climate work, climate research programs, and funding for the Clean Power Plan, the Obama Administration’s key effort to regulate the carbon emissions of U.S. power plants.

What’s more, cuts to the U.S. National Oceanographic and Atmospheric Administration (NOAA) would zero out more than $250-million worth of “lower priority” grants and programs dedicated to coastal and marine management and research, including the successful Sea Grant program—funding that would help U.S. coastal communities prepare themselves for rising sea levels. (Find out more about the budget cuts facing EPA and NOAA.)

Current climate research initiatives now “are providing data that our legislators and policymakers are really going to have to have,” Pilewskie says. If the U.S. government cuts them, he warns, “we’ll just be putting off these issues to future generations. It’ll be a pity.”

Trenberth concurs, citing the proverb “an ounce of prevention is worth a pound of cure.”