NASA plans to launch two new satellites by the end of 2018 in order to explore Earth's ice sheets, sea ice, glaciers, snow cover and permafrost, collectively known as the "cryosphere."

The Gravity Recovery and Climate Experiment Follow-on(GRACE-FO) mission and the Ice, Cloud, and land Elevation Satellite-2(ICESat-2) will both detect changes in Earth's ice, which impacts people all around the world, according to a statement from NASA. Changes in the cryosphere impact sea level rise, which affects global coastlines. It also changes the amount of water that comes from snowpack, which more than a billion people rely on, and melting sea ice in the Arctic Ocean plays a large role in Earth’s climate and weather, according to the statement.

GRACE-FO, which consists of twin satellites, will launch in spring and track fluctuations in Earth’s gravity field. Tracking changes in the gravity field will allow scientists to calculate changes in overall mass on Earth, which includes the mass of ice sheets and underground basins filled with watercalled aquifers. [Pew Pew Pew! Why Scientists Are Fired Up About Futuristic Space Lasers]

ICESat-2 will launch in the fall and use lasers to measure the changing elevation of ice around the world. The mission will provide measurements of the height of Earth's ice in greater detail than ever before, to within two-tenths of an inch (0.4 centimeters),according to NASA. In addition, GRACE-FO will measure groundwater reserves and deep ocean currents, and ICESat-2 will measure sea ice thickness and vegetation height.

These two new missions combined with existing airborne missions such as Operation IceBridge and Oceans Melting Greenland will help NASA track how much the melting of ice sheets in Greenland and Antarctica are contributing to sea level rise, and other impacts of the changing cryosphere, NASA officials said in the statement.

Ice sheets in both Greenland and Antarctica have rapidly lost mass in recent decades, they added, and summertime ice in the Arctic Ocean covers about 40 percent less area than it did in the 1970s, when satellites first began monitoring the ice. "This kind of significant change could increase the rate of warming already in progress, affect further sea ice loss in the Arctic, and alter shipping access to the Arctic Ocean," NASA officials said in the statement.

Permafrost — frozen ground in the Arctic that contains heat-trapping gases such as methane and carbon dioxide — is also thawing at faster rates than before, and its condition could have a global impact. NASA's two new satellites as well as existing missions will work together to increase the agency's understanding of how the cryosphere is changing and how those changes affect Earth, according to NASA.

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