Sometime in the next few years, no one knows exactly when, three NASA satellites, each as heavy as an elephant, will go dark.
They are already drifting, losing altitude little by little. They've been looking down on the Earth for more than 20 years, far longer than anyone expected, helping predict the weather, manage wildfires, monitor oil spills, and more. But time will catch up with them and soon they will send their last transmission and slowly begin their final fall to Earth.
It's the moment scientists fear.
When the three orbiting satellites, Terra, Aqua, and Aura, are powered down, much of the data they've been collecting ends with them, and new satellites won't receive all of their extra power. Researchers must either rely on alternative sources that may not meet their exact needs or seek workarounds to allow recording to continue.
The situation is even worse for some of the data these satellites collect. Other devices do not continue to collect data. Within a few years, the finer features they reveal about our world will be much more vague.
“Losing this irreplaceable data is absolutely tragic,” said Susan Solomon, an atmospheric chemist at the Massachusetts Institute of Technology. “At a time when the Earth needs us most to focus on understanding how we impact the Earth and how we are impacting the Earth, we It's like he's asleep at the wheel.”
The main area we are losing sight of is the stratosphere, the most important home of the ozone layer.
In the cold, thin air of the stratosphere, ozone molecules are constantly formed, destroyed, thrown and swept up while interacting with other gases. Some of these gases are of natural origin. Others are there for us.
Ross J. Sarawich, an atmospheric scientist at the University of Maryland, said the Aura microwave limb sounder's instruments offer the best view of this boiling chemical drama. He said that when the aura is gone, our vision becomes much darker.
Recently, data from microwave limb sounders has proven its value in unexpected ways, Dr. Sarawich said. The study showed the extent to which ozone was damaged by the devastating bushfires in Australia in late 2019 and early 2020, and the 2022 submarine volcanic eruption near Tonga. This helped show how much ozone-depleting pollutants are drifting into the eastern stratosphere. Asia is affected by the summer monsoon.
If it doesn't go offline soon, the sounder could also help solve some big mysteries, Dr Sarawich said. “The thickness of the ozone layer in densely populated areas of the Northern Hemisphere has remained largely unchanged over the past decade,” he said. “You should be recovering. And you're not.”
Jack Kaye, associate director of research in NASA's Earth Sciences Division, acknowledged researchers' concerns about Sounder's demise. But other sources, including instruments on the International Space Station and new satellites on Earth, will still provide “a pretty good window into the state of the atmosphere,” he argued.
Economic realities will force NASA to make “difficult decisions,” Dr. Kaye said. “Wouldn't it be great if everything lasted forever? Yes,” he said. But part of NASA's mission is also to give scientists new tools, tools that help them see the world in new ways, he said. “It’s not the same, but we do the best we can, even if everything is not the same,” he said.
For scientists studying a changing Earth, the difference between identical and nearly identical data can be huge. They may think they understand how something is evolving. But only by continuously monitoring it in an unchanging manner over a long period of time can we be sure of what is going on.
Even the slightest interruption in recording can cause problems. Suppose an ice shelf collapses in Greenland. William B. Gale, former president of the American Meteorological Society, said that unless we measure the before, after, and after of sea level rise, we would never be sure that the sudden change was caused by a collapse. “As you might imagine, there is no quantitative record,” he says.
Last year, NASA asked scientists for their thoughts on how the demise of Terra, Aqua, and Aura would affect their research. Of those, he had more than 180 people answer the call.
In a letter obtained by The New York Times through a Freedom of Information Act request, the researchers expressed concerns about the extensive data from the satellite. Information about particles in wildfire smoke, desert dust, and plumes. Measuring cloud thickness. Detailed scale maps of the world's forests, grasslands, wetlands, and crops.
Scientists say that even if there are alternative sources of this information, they may be less frequent, have lower resolution, or be limited to certain times of the day, and that all of these factors affect the data. It says that it determines the usefulness of.
Liz Moyer studies Earth's atmosphere by flying instruments in jet planes that travel at much higher altitudes than most airplanes can reach. “I'm interested in this world because it's exciting and it's hard to get there,” said Dr. Moyer, who teaches at the University of Chicago. “It's hard to build equipment that works there, it's hard to take measurements, it's hard to get aircraft to go there.”
She said it would be even more difficult without Aura.
Although planes can directly sample the chemistry of the atmosphere, scientists still need to combine aircraft measurements with satellite measurements to understand the full picture, Dr. Moyer said. “Without satellites, we're out there taking snapshots without context,” she says.
Much of Dr. Moyer's research focuses on one of the most mysterious layers of the atmosphere: thin, icy clouds that form nine to 12 miles above the ground. These clouds are contributing to global warming, and scientists are trying to understand how human-induced climate change is affecting them.
“It looks like we're going to stop observing that part of the atmosphere at exactly that point,” Dr. Moyer said.
The demise of Terra and Aqua will affect how Earth monitors another important factor in climate: how much solar radiation it receives, absorbs, and bounces back into space. The balance, or actually the imbalance, of these quantities determines the degree to which the planet warms or cools. And to understand that, scientists rely on instruments from NASA's Cloud and Earth Radiant Energy System (CERES).
Currently, four satellites, Terra and Aqua, are flying with CERES equipment on board. Additionally, two new satellites are coming to an end. However, he is the only one for which a replacement is being developed. What is its lifespan? 5 years.
“Within the next 10 years, we'll go from four missions to one, and that one will be past its prime,” said NASA scientist Norman G. Loeb, who heads CERES. “For me, that’s really humbling.”
Recently, with the rise of the private space industry and the proliferation of satellites around Earth, NASA and other agencies are exploring alternative approaches to monitoring the planet. The future may feature smaller, lighter equipment that can be brought into orbit cheaper and more agilely than Terra, Aqua, and Aura were able to do back then.
The National Oceanic and Atmospheric Administration is developing such a fleet to monitor weather and climate. NASA's Dr. Loeb and his colleagues are working to develop lightweight instruments to continue measuring Earth's energy balance.
But for such technology to be useful, Dr. Loeb said, today's orbiters would need to begin flying before dark.
“We need a long enough period of overlap to understand the differences and resolve the issues,” he said. “If not, it would be very difficult to trust these measurements without the opportunity to prove them against current measurements.”
In some ways, scientists say it's a credit to NASA that Terra, Aqua and Aura lasted so long. “Through a combination of great engineering and tremendous luck, we've been able to do this for 20 years,” said Waleed Abdalati, a former NASA chief scientist now at the University of Colorado Boulder. Told.
“We have become completely obsessed with this satellite. We are victims of our own success,” Dr. Abdalati said. “Eventually, luck runs out,” he added.