Some NASA satellites will soon stop sending data to Earth

Sometime over the next few years — no one knows exactly when — three NASA satellites, each as heavy as an elephant, will go off scale.

They are already drifting and losing altitude little by little. They’ve been staring at the planet for more than two decades, much longer than anyone expected, helping us predict the weather, manage wildfires, monitor oil spills, and much more. But age catches up with them, and soon they will serve their last serve and begin their slow and final fall to the ground.

It is a moment that scientists fear.

When the three orbiters — Terra, Aqua and Aura — are shut down, much of the data they were collecting will go with them, and newer satellites won’t make up for all the slowdown. Researchers will either have to rely on alternative sources that may not meet their specific needs or look for alternative solutions to allow their records to continue.

With some of the data these satellites collect, the situation gets even worse: no other instruments will continue to collect it. In a few years, the beautiful features it reveals about our world will become even more mysterious.

“The loss of this irreplaceable data is simply tragic,” said Susan Solomon, an atmospheric chemist at MIT. “At a time when the planet desperately needs a focus on understanding how we are affected by it, and how we affect it, we appear to be catastrophically asleep at the wheel.”

The main area we overlook is the stratosphere, the most important home of the ozone layer.

Through the thin, cold air of the stratosphere, ozone molecules are constantly being created and destroyed, ejected and swept away, as they interact with other gases. Some of these gases have natural origins; Others are there because of us.

One instrument on Aura, a microwave probe, gives us our best view into this intense chemical drama, said Ross J. Salwich, an atmospheric scientist at the University of Maryland. Once the corona disappears, our vision will become considerably dim, he said.

Recently, data from limb microwave probes have proven their importance in unexpected ways, Dr. Salwich said. It showed the extent of damage to ozone by devastating bushfires in Australia in late 2019 and early 2020, and by an undersea volcanic eruption near Tonga in 2022. It helped show how much ozone-depleting pollution is rising into the stratosphere over the east. Asia by Summer monsoon in the region.

If the Internet connection is not cut off so quickly, the audio device may also help unravel a major mystery, Dr. Salwich said. “The thickness of the ozone layer over populated areas in the Northern Hemisphere has remained almost unchanged over the past decade,” he said. “He should be recovering. And he’s not.”

Jack Kay, associate administrator for research at NASA’s Earth Sciences Division, acknowledged researchers’ concerns about the probe’s end. But other sources, including instruments on newer satellites, on the International Space Station and here on Earth, will still provide a “very good window into what the atmosphere is doing,” he said.

Financial realities are forcing NASA to make “difficult decisions,” Dr. Kay said. “Would it be great if everything stayed forever? Yes,” he said. He added that part of NASA’s mission is also to provide new tools for scientists, tools that help them look at our world in new ways. “It’s not the same, but, as “You know, if everything’s not the same, you have to do your best.”

For scientists studying our changing planet, the difference between the same and almost the same data can be significant. They may think they understand how something develops. But only by monitoring it continuously, in an unchanging manner, over a long period of time, can they be confident about what is happening.

Even a short break in the logs can create problems. Suppose the ice shelf collapses in Greenland. William B. said: Gale, former president of the American Meteorological Society, said that unless you were measuring sea level rise before, during and after, you could never be sure that a sudden change was caused by a collapse. “You might imagine it, but you don’t have a quantitative record,” he said.

Last year, NASA surveyed scientists about how the end of Terra, Aqua, and Aura would affect their work. More than 180 of them answered the call.

In their letters, which were obtained by The New York Times through a Freedom of Information Act request, the researchers expressed concerns about a wide range of data from the satellites. Information about particles found in wildfire smoke, desert dust, and volcanic plumes. Cloud thickness measurements. Fine-scale maps of the world’s forests, grasslands, wetlands and crops.

Even if alternative sources of this information exist, they may be less frequent, less accurate, or limited to certain times of day, all of which are factors that determine how useful the data is, the scientists wrote.

Liz Muir takes a close-up approach to studying the Earth’s atmosphere: by flying instruments through it, on planes at much higher altitudes than most planes can reach. “I got into this field because it is exciting and difficult to access,” said Dr. Muir, who teaches at the University of Chicago. “It’s hard to build instruments that work there, it’s hard to make measurements, and it’s hard to get planes to go there.”

She said it will be more difficult once the corona disappears.

Dr Muir said aircraft could sample atmospheric chemistry directly, but to understand the big picture, scientists still needed to combine aircraft measurements with satellite readings. “Without satellites, we are out there taking snapshots without context,” she said.

Much of Dr. Muir’s research focuses on thin ice clouds that form nine to 12 miles above the Earth’s surface, in one of the most mysterious layers of the atmosphere. These clouds help raise the planet’s temperature, and scientists are still trying to figure out how human-caused climate change will affect them.

“It looks like we will stop monitoring this part of the atmosphere, exactly at the time it is changing,” Dr. Muir said.

The end of Terra and Aqua will affect the way we monitor another important driver of our climate: the amount of solar radiation the planet receives, absorbs, and bounces back into space. The balance between these quantities – or actually the imbalance – determines how much the Earth warms or cools. To understand this, scientists rely on NASA’s cloud instruments and the Earth’s Radiant Energy System, or CERES.

Currently, four satellites are flying with CERES instruments: Terra, Aqua, and two newer satellites that are also nearing the end of their lives. However, there is only one alternative in the works. Her life expectancy? five years.

Norman J. said: “Within the next 10 years, we will go from four missions to one, and the remaining missions will be past their peak,” said Loeb, the NASA scientist who leads CERES. “To me, this is really concerning.”

These days, with the rise of the private space industry and the proliferation of satellites around Earth, NASA and other agencies are exploring a different approach to observing our planet. The future may lie in smaller, lighter instruments, ones that can be put into orbit at a lower cost and are more agile than in the days of Terra, Aqua, and Aura.

The National Oceanic and Atmospheric Administration is developing such a fleet to monitor weather and climate. Dr. Loeb and others at NASA are working on a lightweight instrument to continue their measurements of Earth’s energy balance.

But for such technologies to be useful, Dr. Loeb says, they must start flying before current orbiters disappear.

“You need a good, long period of overlap to understand the differences and work out the kinks,” he said. “If not, it will be very difficult to trust these measurements, if we don’t have the opportunity to prove them against existing measurements.”

In a way, scientists said, it’s to NASA’s credit that Terra, Aqua and Aura have lasted as long as they have. “Through a combination of excellent engineering and a tremendous amount of luck, we’ve had these things for 20 years now,” said Walid Abdel Aty, a former NASA chief scientist now at the University of Colorado Boulder.

“We have become addicted to these satellites. We are victims of our own success,” said Dr. Abdel Aty. “In the end, luck runs out.”