The instrument called the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) will monitor one of the most basic processes in living plants: the loss of water through the tiny pores in leaves.
It is a high-resolution thermal infrared radiometer, which works like a giant thermometer from space to measure the temperature of plants and the amount of heat radiating from Earth's surface.
"If we find a plant is too hot, that is because it is not getting enough water to cool itself down," said Josh Fisher, research scientist at NASA's Jet Propulsion Laboratory (JPL), Pasadena, California.
When people lose water through their pores, the process is called sweating. The related process in plants is known as transpiration.
Because water that evaporates from soil around plants also affects the amount of water that plants can use, ECOSTRESS will measure combined evaporation and transpiration, known as evapotranspiration, the US space agency said.
"If plants do not get enough water, they show signs of stress. By measuring evapotranspiration, we get an early indicator of that stress, and we can do something about it before the plants collapse," Simon Hook, a research scientist at JPL and the project's principal investigator, explained.
By combining the instrument's measurements with other ecosystem data, scientists would be able to calculate how efficiently plants use water to process carbon dioxide and identify plants likely to be more resilient during droughts.
"That has huge implications for our understanding of global water and carbon cycling, and which plants are going to live or die in a future world of greater droughts," Fisher noted.