Illustration: NASA / JPL
Some 15 miles northeast of downtown Los Angeles, where urban sprawl finally gives way to the San Gabriel Mountains, lies a place of insatiable curiosity. On the outside, there’s not much to see: A campus of plain, concrete buildings tucked into the rugged foothills below Angeles National Forest. But on the inside, behind locked doors and down maze-like corridors, this is an institute of wonder.
It is here, at NASA’s Jet Propulsion Laboratory (JPL), that brilliant scientists and engineers come to work every day to reach for the stars. Literally. The federally funded facility, which is managed by the California Institute of Technology (Caltech), is famous for pioneering solar-system and deep-space research. You’ll probably recognize some of their most acclaimed missions: The Mars rovers; the Kepler Space Telescope; and various planetary explorers, like Voyagers 1 & 2, Cassini and Juno.
But the department with the biggest budget (at least in recent years) isn’t Mars Exploration, Solar System Exploration or the Interplanetary Network — it’s Earth Science and Technology.
While JPL has been building and launching robotic spacecraft since the 1960s, it wasn’t until the 1970s that scientists began turning their attention back toward Earth. All those instruments and sensors developed to explore the solar system, they realized, would also prove mighty useful for studying our home planet. An experimental satellite called Seasat was subsequently launched in 1978, kicking off an era of Earth observation.
In the decades since, JPL has launched and managed more than a dozen Earth-monitoring missions dedicated to capturing vital climate data. There is a plaque marking “the center of the universe” inside the Mission Control Center at JPL, but you could also argue that the institution is ground zero for climate science. And perhaps no mission is more important to our understanding of global warming and how to combat it than the Orbiting Carbon Observatory-2 (OCO-2).
The Orbiting Carbon Observatory
“OCO-2 is one of the coolest satellites up there!” Dr. Annmarie Eldering, the Deputy Project Scientist working on the mission, tells me as I walk into her office. She’s cheerful, charismatic and clearly loves her job.
“I like talking to people. I like technical work,” she says. “I get to balance those two things.”
Having come to Los Angeles in 1988 to study air pollution at Caltech — where she went on to earn a Ph.D. in Environmental Engineering Science — she says she needed a bigger challenge after LA cleaned up its smoggy act. So in 1999, she headed to JPL, where she worked on a number of projects prior to joining the OCO-2 team in 2010 while the satellite was still being built. In her current role, she manages different teams responsible for various aspects of the mission, like navigation and data operations.
Launched in July 2014, the Orbiting Carbon Observatory is just that — a satellite that measures atmospheric carbon-dioxide (CO2) levels to help scientists better understand how the greenhouse gas enters and leaves the atmosphere.
“Ours is much easier than some of the other missions,” Dr. Eldering says. “We’ve got one instrument and one mission. We just fly around and make our data.”
That one instrument is pretty simple, too: A group of three high-resolution spectrometers (instruments that split light into different colors or spectra) attached to a telescope.
But what does that have to do with CO2 and climate change?
Carbon dioxide absorbs specific colors of near-infrared sunlight as it’s reflected skyward from Earth. By simultaneously measuring the amount of that absorbed light in CO2 and molecular oxygen using OCO-2’s spectrometers, scientists can determine the ratio of the two gases, which they use to calculate the concentration of atmospheric CO2 to a precision of .3 to .5 percent — or 1 to 2 parts per million.
“Looking at resolved spectra from sunlight, you can learn a lot,” Dr. Eldering says. She isn’t kidding.
A New World View
Scientists have been measuring CO2 levels since the 1950s using ground stations and even flasks of air collected by airplanes, an ongoing mission of the National Oceanic & Atmospheric Administration’s (NOAA) cooperative air sampling network. But OCO-2 brings something to the table that a scattered network of collection sites can’t, and that’s truly global coverage.
Orbiting more than 400 miles above the Earth’s surface, OCO-2 typically makes 2 million measurements every month, according to Dr. Eldering. Compared to ground stations, the satellite is not as precise, but having a trove of data from around the world more than makes up for it.
Remarkably, OCO-2 can observe most of the Earth’s surface in just 16 days, allowing for continuous modeling to identify patterns and trends by studying how CO2 moves throughout the atmosphere.
And though it may sound counterintuitive, using a satellite is much cheaper than relying on ground measurement stations, which Dr. Eldering says can cost hundreds of thousands of dollars to build and install. Instead, for a cool $11 million a year, JPL operates OCO-2, collects global data and distributes it to the public. There are still 19 sites around the world where ground instruments are used to validate the satellite data.
Painting a Picture of Carbon Dioxide
Even if you’ve never heard of OCO-2, you’ve likely seen the colorful, swirling models of carbon dioxide created from its measurements.
“Most of the scientific use of the data comes in these big, global, atmospheric models,” Dr. Eldering says.
This, however, is outside the bounds of JPL’s mission. Dr. Eldering and her team focus on avoiding space junk, making sure the satellite and the instrument it carries are operating properly and ensuring that data is flowing and readily available to the public — not modeling the information they collect. That job falls to other scientists, like those working at the NOAA or other parts of NASA.
“We give them the data and talk to them a lot,” Dr. Eldering says, “but it’s their own enterprise.”
For example, here’s what some relatively raw OCO-2 data looks like from JPL. You can even see lines indicating the spacecraft’s orbit:
But when you combine that data with ground measurements of CO2 and weather models that account for factors like wind and ocean currents, a stunning visualization of atmospheric carbon dioxide emerges:
“The question we’re trying to answer is: Over some subcontinental region, how much of the CO2 is staying in the air, going into the trees, going into the ocean?” Dr. Eldering says.
The above model — which uses two years of data from OCO-2 — illustrates how scientists can begin to answer these questions. You’ll notice that in the fall and winter, there is more CO2 in the atmosphere because many plants and trees have lost their leaves. But once spring rolls around, and throughout summer, the amount of CO2 in the atmosphere decreases because greening vegetation in the northern hemisphere absorbs the gas, helping scientists identify and study these areas known as carbon sinks.
After explaining this to me, Dr. Eldering mentions one of her favorite details about OCO-2.
“Another cool thing we have is sensitivity to light that comes from photosynthesis,” she says. “You can see the plants sending light out.”
Once again, she’s not kidding. When plants absorb sunlight to create energy (photosynthesis), some of the radiation is re-emitted in a process called solar-induced chlorophyll fluorescence. We humans can’t see the light these plants emit, but OCO-2 can:
This capability gives OCO-2 another important data set, which scientists can use to study photosynthesis on a global scale — an important advancement for our planet as well as its growing population.
Into the Future
What lies ahead for OCO-2? For now, much of the same.
The mission has already surpassed its expected lifespan of two years, which Dr. Eldering says isn’t unusual.
“You have to design something that’s going to work long enough, so we use two years as a design thing,” she says. “But the parts are often of such good quality that they last longer.”
That being said, she noted that OCO-2 has a higher risk of failure than other satellites because it’s a single-string system, meaning any number of malfunctions or failures could kill the satellite for good. That risk doesn’t dent her optimism, though. “I certainly think we’re going to make it to five,” she says.
Standing in her way, however, could be President Trump, who denies climate change and has filled his administration with like minds. As a candidate, Trump campaigned against climate science — which he called “politically correct environmental monitoring” — and has vowed to pivot NASA’s mission away from Earth and back toward the Moon, Mars and deep space. As president, he seems to have followed through, recently releasing a budget seeking massive reductions in funding for climate research, including a proposed 20 percent cut to the NOAA that specifically targets its satellite program. NASA could very well be next.
Dr. Eldering admits Trump could kill OCO-2. “It’s a statement that makes you worry,” she says, offering her personal opinion, rather than speaking on behalf of NASA or JPL. “If they want to make a statement, they might cut us off.”
But for the most part, she questions whether anyone would stop a mission that’s already in progress, especially since it would only save $11 million per year. It still seems far-fetched enough, she says, that her focus remains on her work, not what’s going on in Washington.
That focus includes OCO-3, an instrument made with spare parts from OCO-2 that will take similar measurements. It will be launched into orbit on a SpaceX Falcon 9 rocket at a yet-to-be-determined date.
“It’s no more costly to build two at a time,” Dr. Eldering says. “We figured out we could package it and put it on the space station. It’s a very affordable place to do experiments.”
If you’re wondering what came of the original Orbiting Carbon Observatory, or OCO-1, it “failed to shed its protective covering during launch, did not make it into orbit, and came back to Earth” during launch in 2009, Dr. Eldering says, hence the OCO-2 designation for the current instrument, even though it’s the first to make it into orbit.
Looking at the long road ahead, especially the fight to combat climate change and mitigate its effects, she admits the data is frightening, but retains some confidence that we’ll figure it all out.
“The one thing that keeps me from being completely depressed about it is that there is activity at state and local levels,” she says. “The people being impacted in many instances are making smart decisions on how they react to it.”
In the meantime, she’ll continue to focus on her mission, driven by its growing importance in a warming world.
“I love this stuff because I feel like it’s making a positive difference,” she says.