The 30 billion tons of carbon dioxide that human activities produce annually is a global problem, but scientists still don’t have a truly global picture of where carbon in the atmosphere comes from and where it goes.
NASA hoped to begin creating that picture with the launch this morning of its $270 million Orbital Carbon Observatory (OCO), but the satellite never made it to orbit. A piece of equipment that protects the satellite as it shoots through the atmosphere failed to separate from the rocket, NASA officials said. The OCO satellite crashed down in the ocean near Antarctica.
Michael Freilich, NASA’s Earth Sciences Division director, said the agency would be working in the next weeks and months to find ways to continue to advance the OCO mission, including assessing other available satellites. The OCO took about eight years to develop, and the loss of the satellite was a disappointing setback but not the end of the mission, he said.
We will take a good, solid and thoughtful look at how best to advance Earth science, given all the assets we have available now and into the near future, and decide how it is best for science and for the nation to move forward.
The OCO satellite would have provided data complementary to Japan’s newly launched climate satellite GOSAT (Greenhouse Gases Observing Satellite), also known as Ibuki (Japanese for breath). Together, they could have provided the most complete picture of carbon sources and sinks – places such as oceans or forests that absorb carbon – ever seen.
GOSAT measures global concentrations of both CO2 and methane, an even more potent greenhouse gas, but has a lower resolution, meaning a fuzzier picture. OCO would have only measured carbon dioxide, but it would have taken many more measurements, and at a higher resolution. Its smaller measurement footprint would have decreased interference from clouds, and in general, created a more detailed picture.
As David Crisp, a senior research scientist at NASA’s Jet Propulsion Laboratory and the principal investigator of the mission, explained:
Even though [both satellites] are measuring carbon dioxide, the primary missions differ and the measurement approach differs. The GOSAT system was primarily designed to measure human sources of CO2 for treaty compliance such as Kyoto.
The OCO, on the other hand, was to search for carbon sinks that, so far, have absorbed half of the CO2 that humans have emitted since the beginning of the Industrial Age.
The satellite was designed to measure carbon dioxide levels by analyzing sunlight that has bounced off Earth and been reflected back to space. Three times a second, three spectrometers on board would take a snapshot of the sunlight bouncing back from the approximately 2.5 kilometer spot of Earth being observed at that moment. Carbon dioxide absorbs some wavelengths of light, particularly in the infrared region. When seen through spectrometers, the wavelengths that interact with CO2 will be less bright. Measuring their dimness indicates the level of carbon dioxide.
Scientists were counting on those measurements to better understand the carbon cycle by showing how sinks works and locating the most absorbent sinks on the planet:
Will those sinks still be there 50 years from now? I can’t tell you that, because I don’t know where the sink is. I don’t know where in the oceans, what processes are needed to make it work, whether it’s North Atlantic, North Pacific, South Atlantic, South Pacific.
The NASA orbiter would have provided an immensely greater amount of data about the global distribution of carbon dioxide than researchers have ever had, said Anna Michalak, a University of Michigan professor who specializes in the carbon cycle.
Scientists’ current measurements of CO2 are sparse in two ways, Michalak explained. First, the data come from fewer than 300 sites worldwide, with data from the tropics – which are believed to be substantial carbon sinks – being particularly meager.
If I actually showed you a map [of carbon measurement sites], you would see quite a few places in North America and quite a few in Europe but almost no locations anywhere else around the world.
The current data is also sparse in time. The way we measure carbon in the atmosphere is, someone literally goes out with a flask or bottle, fills it with air, closes it back up, ships it to the NOAA lab in Boulder, Colorado, where they’ll measure the concentration of CO2 in that one bottle. So you’ll maybe get one measurement a week.
The satellite could send data all day long, information climatologists need to improve climate models. Policy writers and regulators also benefit from stronger scientific data for writing climate policies, monitoring progress on greenhouse gas reductions and gauging the true effectiveness of carbon offsets.
NASA already has another climate satellite in the works, one expected to overcome some of OCO’s drawbacks, such as the need for sunlight to measure atmospheric carbon.
In the next four to seven years, the space agency plans to launch a system called ASCENDS – Active Sensing of CO2 Emissions over Nights, Days, and Seasons – which will use laser light to measure carbon dioxide, making it capable of capturing data at night.
As Freilich indicated, the agency also plans to look at other satellites and measuring equipment that could make up for some of the loss of the OCO satellite. He stressed that NASA is "committed to advancing Earth system science."
Regular, global measurements that satellites can provide are important for predicting how the climate will change, as Michalak explained:
The rate at which carbon dioxide accumulates in the atmosphere is directly related to how much we put in, minus how much oceans and plants take out. So unless we can predict how much plants and the oceans will take out in the future, we have no way of predicting how the climate will evolve.
