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Satellite data could refine models that predict carbon flows, seen here peaking in northern spring.

NASA GODDARD SPACE FLIGHT CENTER

Space budget boost puts Europe in lead to monitor carbon from space

Even optimists at the European Space Agency (ESA) were startled last week when its member governments awarded it a €12.5 billion, 3-year budget, its largest ever and more than 20% above its previous 3 years of funding. With the unexpected windfall, ESA will develop a reusable space cargo capsule, support the International Space Station until 2030, and join NASA in retrieving rocks from Mars.

But one of the biggest winners, up 29% to €1.8 billion, is Copernicus, a program supporting a fleet of satellites that continuously tracks features of Earth's atmosphere and surface, including the contours of the sea surface and shifts in vegetation. The money will help Europe expand the fleet to observe humanmade sources of carbon dioxide (CO2) on a daily basis—making ESA the only space agency capable of monitoring pledges made under the Paris accord to cut greenhouse gases. Europe's CO2 monitoring plans are "unparalleled," says Christopher O'Dell, an atmospheric scientist at Colorado State University in Fort Collins. "The Europeans are just running with this."

Just why ministers from ESA's 22 member states were feeling so generous at a meeting last week in Seville, Spain, is unclear. It could be because Europe's economy is better than 3 years ago, or because ESA officials did a good job talking up plans with ministers and stakeholders, says Athena Coustenis, a planetary scientist at the Paris Observatory and chair of the European Space Sciences Committee, an advisory body. Regardless, the only mission not to receive full funding was Lagrange, a set of space weather satellites. "There's no need to kill anything," Coustenis says. "I'm in shock."

ESA's science budget, stagnant for decades, got a 10% hike to €2.8 billion. That should allow the agency to study black holes with two concurrent missions, a gravitational wave detector and an x-ray observatory. The exploration budget was boosted by one-third, which means ESA can launch the ExoMars rover next year—if it can fix problems with its parachutes in time. The money will help ESA join NASA's Artemis program to build a Moonorbiting space station called the Gateway and work toward a human presence on the surface. It will also pay for initial work on a complex mission to bring back samples from Mars. NASA hopes to follow suit next year.

The Copernicus system of Earth-observing Sentinel satellites also got a lot of love. This joint venture with the European Union provides long-lived, unbroken data sets to government, industry, and academic users. Existing Sentinel satellites monitor, for instance, land use and sea surface height. The first three Sentinels are now operational, along with duplicate satellites that serve as backups. Three more Sentinels are in the works. When it comes to Earth observation, "Europe has the most capable fleet in orbit," says Martin Visbeck of the GEOMAR-Helmholtz Centre for Ocean Research in Kiel, Germany, and chair of ESA's Advisory Committee for Earth Observation.

The funding boost ensures ESA can proceed with ambitious plans for a further set of six candidate Sentinels, among them the CO2 monitoring mission. Around the time of the Paris climate pact of 2016, the European Union decided that national carbon budgets, based on disclosures from known emitters such as power plants and cement works, needed checking from the sky. In response, ESA resurrected plans for CarbonSat, which failed to win a launch slot in 2015, and beefed it up into a Sentinel, which would look for the spectral absorption signals of CO2 in infrared sunlight reflected off Earth's surface.

With the new funding, a CO2 Sentinel could launch as soon as 2025, putting Europe in position to contribute to a census of emissions that the Paris accord says should take place every 5 years beginning in 2023. Carbon dioxide is "a quantity we need to watch for years to come," Visbeck says.

The ministers gathered in Seville apparently shared that sense of urgency. "Governments are really putting words into action," says Josef Aschbacher, ESA's director of Earth observation in Frascati, Italy. But their motivations may not be entirely selfless, because the contracts for Copernicus are spread among member states in line with their contributions. "It's a unique opportunity to position your national industry for decades to come," Aschbacher says.

NASA pioneered efforts to track CO2 from space with its Orbiting Carbon Observatory-2 (OCO-2), launched in 2014. But OCO-2 samples a narrow swath, returning to each point on Earth at intervals of weeks, and was only designed to last 2 years. China's current CO2-tracking satellite TanSat, which closely follows OCO-2's design, has struggled with its calibration. And OCO-3, launched this year and attached to the space station, is another short-lived research mission; the United States has no plans to follow up with an operational carbon-monitoring system. "It's a little frustrating watching from the U.S.," O'Dell says. "We've lost the leadership role in this."

ESA's CO2 mission would operate for 20 years, with as many as three identical satellites scanning the entire globe with swaths 300 kilometers wide. The mission would scan each point on Earth every few days, capturing the changing plumes of individual power plants. "We're moving from 1D to 2D," says Michael Buchwitz, an adviser to the project at the University of Bremen in Germany. In a step up from the original CarbonSat proposal, the CO2 Sentinels will also help identify emitters by detecting nitrogen oxides from fossil fuel combustion, and will have sensors for clouds and aerosols to improve accuracy.

The European Union's next 7-year budget, now being negotiated, could determine whether the mission reaches its full potential. ESA is only responsible for the first Sentinel of each type, with the EU paying for the backups. And as the user of the data, the EU will also finance a network of ground sensors to calibrate the satellite carbon measurements as well as data-processing and modeling efforts. "The satellites are a core component," Buchwitz says. But there is also "much, much more."

If Europe sustains its carbon-monitoring efforts, they will be a boon to scientists as well as policymakers, O'Dell says. The high-resolution Sentinel readings will help scientists tune their models of how CO2 flows around the atmosphere. And the missions could also attract more scientists to what remains a small field, he adds. "It will bring more brain power."

With additional reporting by Paul Voosen.