It was almost 10 years ago when Andrew Thorpe received a text from the crew flying overhead in a small aircraft: They had spotted a new methane hot spot.
Thorpe drove along winding dirt and mountain roads in an unwieldy rental SUV near the Four Corners region of the southwestern U.S. When he arrived at the spot relayed from the plane, he pulled out a thermal camera to scan for the plume. Sure enough, methane was seeping out of the ground, likely from a pipeline leak.
He found a marker sticking out of the desert with the phone number for a gas company, so he gave them a call. “I had the most confused individual on the other side of the phone,” Thorpe said. “I was trying to explain to them why I was calling, but this was back many years ago when there really weren’t any technologies that could do this.”
Over the years, the work has gotten Thorpe some unwanted attention. “I did some driving surveys in California .… A rent-a-cop was very suspicious of me and tried to scare me off,” said Thorpe. “If you set up a thermal camera on a public road and you’re pointing it at a tank beyond the fence, people are going to get nervous. I’ve been heckled by some oil and gas workers, but that’s par for the course.”
Today, Thorpe is part of a group that is at the forefront of greenhouse gas monitoring at NASA’s Jet Propulsion Laboratory in La Cañada Flintridge. For over 40 years, the Microdevices Laboratory at JPL has developed specialized instruments to measure methane and carbon dioxide with extreme precision.
The instruments, called spectrometers, detect gases based on which colors of sunlight they absorb. Earlier this year, a team of researchers from JPL, Caltech and research nonprofit Carnegie Science was selected as a finalist for a NASA award to put the technology into orbit.
If chosen for the satellite mission, the team’s carbon investigation, called Carbon-I, would launch in the early 2030s. Over the course of three years, Carbon-I would continuously map greenhouse gas emissions around the globe and take daily snapshots of areas of interest, allowing scientists to identify sources of climate pollution, such as power plants, pipeline leaks, farms and landfills.
While there are already multiple satellites monitoring these gases, Carbon-I’s resolution is unprecedented and would eliminate any guesswork in determining where the gas was emitted. “There’s no denying it anymore — once we see a plume, there’s no other potential source,” said Christian Frankenberg, co-principal investigator for Carbon-I and a professor of environmental science and engineering at Caltech.
Carbon-I’s finest, 100-foot resolution “is a very high resolution from space. That’s an incredible resolution to be able to get,” said Debra Wunch, a professor at the University of Toronto who studies Earth’s carbon cycle and is not involved in the Carbon-I proposal. “It would be able to give us much more insight into exactly the source of emissions .… This would be groundbreaking. You would be able to see individual stacks, individual parts of landfills, even.”
Historically, monitoring the release of greenhouse gases from individual emitters has been challenging — both carbon dioxide and methane are colorless and odorless. So scientists have often had to rely on adding up self-reported values from companies and estimates from research. For example, to estimate the amount of methane cows produce, scientists would have to determine how much methane one cow releases and multiply it by the total number of cows on Earth.
“If you look at international policies … currently they’re all based on these bottom-up inventories,” said Anna Michalak, co-principal investigator for Carbon-I and the founding director of the Carnegie Climate and Resilience Hub at Carnegie Science. “We need to get to a point where … we actually have an independent way of tracking what the emissions are.”
Carbon-I’s resolution will also give scientists new access to the atmosphere of the tropics, where clouds currently obscure most forms of satellite surveillance. “It’s their Achilles’ heel,” said Frankenberg.
Since tropical and subtropical forests absorb roughly a quarter of the CO2 humanity produces by burning fossil fuels, accurate data from this region of the globe is badly needed.
Satellites currently orbiting Earth with lower resolution can’t see through small gaps in the cloud coverage. They only see a blurred average of the cloudy and clear spots in the sky for each pixel. Carbon-I, with each pixel’s area almost 50 times smaller than that of most other satellites, can see the clearings and take measurements through them. In an April 2024 paper, Frankenberg, Michalak and their collaborators estimated that Carbon-I would be able to see past the clouds in the tropics anywhere from 10 to 100 times more frequently than its predecessors.
Carbon-I “is going to see things where people don’t know what’s going on,” said Thorpe, who has moved on from his graduate school days pointing thermal cameras at gas leaks and now works as a research technologist with the Microdevices Laboratory. “It’s going to open a whole new realm of science.”
JPL’s airborne greenhouse gas-monitoring program goes back decades, but the field of space monitoring is still fairly new. Near the start of 2016, NASA headquarters contacted the JPL team. There was an ongoing massive blowout at the Aliso Canyon gas storage facility near Porter Ranch, and NASA wanted the team to check it out.
The team flew over the site in a variant of a 1960s-era spy plane on three days over the course of a month while the Southern California Gas Co. fought to contain the blowout. At the same time, NASA’s Goddard Flight Center in Maryland pointed the NASA Earth Observing spacecraft’s Hyperion spectrometer at the leak.
Hyperion was designed to make observations of the Earth’s surface and filter out noise from the atmosphere. Now, they were trying to observe the atmosphere and filter out the surface, and for the first time, scientists observed a human-made point source of methane from orbit.
“The Hyperion result was pretty noisy, but you could still see the plume,” said Thorpe. “This was really a proof of concept that we could do it from space.”
Even if Carbon-I launches, it doesn’t mean the team will stop putting instruments on planes. From aircraft, the team is able to monitor areas of interest in even sharper resolution and for consecutive days at a time. Right now, a leaner, meaner version of the spectrometers that observed the Four Corners leak and Aliso Canyon blowout is flying a series of missions to monitor the emissions of offshore oil rigs in the Gulf of Mexico.
Plane missions also give the team an opportunity to try out new and improve spectrometers. “You can fix them, and you can upgrade them,” said JPL engineer Michael Eastwood, who’s worked with the spectrometers for over three decades and regularly flies with them. “You can take more risks, as opposed to spacecraft that need really mature, really well-known, high reliability — we’re not constrained like that.”
The air team is nimble, too. Typically, two crew members sit in the second row of a King Air twin-propeller aircraft looking at a stack of laptops and instruments with enough buttons to rival the plane’s cockpit. On the screens, they can look at real-time GPS data and spectrometer results and coordinate a flight plan with the pilots. The spectrometer — called AVIRIS, short for Airborne Visible/Infrared Imaging Spectrometer — sits in the third row, looking down through a window cut out in the floor.
The NASA program for which Carbon-I was selected as a finalist aims to fund space-based Earth science that will benefit society. The team was awarded $5 million to sharpen its project proposal before a final NASA review in 2025. There are three other finalists, and two will be selected for the launch.
This two-step process for selecting missions is new for NASA’s Earth science programs and requires JPL to compete with the rest of the scientific community, independent of their association with the space agency.
“If we’re talking about grocery money, [$5 million] seems like a lot of money, but it’s really a bargain,” said Michalak. “If you think about the fact that you’re committing $300 million toward a mission, spending 1.5% of that to really make sure it’s going to be fabulous and successful is extremely smart.”
In the meantime, the Carbon-I team is focused on showing NASA that it has the technical know-how to execute the project on time and under budget.
“I think all four of the missions in the current phase are absolutely worthwhile scientific missions,” said Michalak, “and 50% odds are not bad odds for a satellite mission.”
