NASA launched an instrument into space that will transform the International Space Station (ISS) into a carbon mapper during the early morning hours on May 4. The Orbiting Carbon Observatory 3 (OCO-3), which is being installed on the ISS, is able to measure the concentration of carbon over land and sea from sunrise to sunset each day. The new tool will help scientists keep tabs on emissions and how carbon cycles through the atmosphere on a daily and annual basis.
OCO-3 is not the only carbon mapper in orbit. OCO-2, a stand-alone satellite, has been on the job since 2014. In fact, Jonathan Amos at the BBC reports OCO-3 is built from parts leftover from the OCO-2 mission. But according to a NASA press release, OCO-2 is in a sun-synchronous polar orbit, which means that when it peers down at Earth, it sees the same spots at the same time each day.
OCO-3, however, will ride along with the ISS, circling the planet every 90 minutes, meaning it will orbit Earth 16 times daily. That’s important because the planet’s ability to absorb carbon varies depending on the time of day, a process we don’t completely understand.
“Getting this different time of day information from the orbit of the space station is going to be really valuable," environmental engineer Annmarie Eldering, a NASA OCO-3 project scientist, tells Amos. “We have a lot of good arguments about diurnal variability: plants' performance over different times of day; what possibly could we learn? So, I think that's going to be exciting scientifically.”
OCO-3 is a little different than its free-floating kin, OCO-2. When OCO-2 needs to look at something, it rotates. But OCO-3 will be installed in the Japanese Experiment Module-Exposed Facility, so it’s essentially just a passenger. So engineers installed an agile pointing mirror to the mapper, allowing it to look at any area within its field of view to create snapshot maps over smaller areas of the planet. This will allow it to get carbon readings for urban areas up to 1,000 square miles. According to the press release, OCO-3 will be able to map the entire Los Angeles Basin in about two minutes. The same task would take OCO-2 several days to complete.
“These targeted measurements will help us disentangle which sources of carbon dioxide are in nature and which are anthropogenic, or human-caused,” Matt Bennett, project systems engineer for OCO-3, says in the release.
Deborah Netburn at the Los Angeles Times reports that OCO-3 is sensitive enough to detect a 1 part per million change in carbon dioxide levels from one day to the next. Currently, carbon dioxide levels are at 414 parts per million. In the previous 400,000 years, they fluctuated between 200 and 280 ppm. Keeping tabs on those levels is critical to modeling how climate change will change the planet.
“Our goal is to get really good data so we can make informed decisions about how to manage carbon and carbon emissions in the future,” Elderling says.
The mapper is also able to measure photosynthesis happening on the surface of the planet by measuring how much chlorophyll fluoresces when the sun is shining on it. This can help researchers understand how much carbon dioxide vegetation is absorbing and how it impacts the nearby atmosphere. That will help researchers understand better how carbon “sinks” that sequester carbon, like oceans and forests, work.
Paul Voosen at Science reports that the launch of OCO-3 is a minor scientific victory. The Trump administration tried to cancel the project several times, but Congress kept it on pace. The original OCO satellite launched in 2009 but crashed into the Indian Ocean. In 2014, OCO-2 was an expensive bird to launch, with a price tag of $465 million.
By attaching OCO-3 to the ISS, which has ten locations fitted for data-collecting instruments, NASA reduced the cost to just $110 million. That means there are compromises—the instrument can’t see Earth’s poles, for instance. But it’s hoped data from the two OCO missions together can be combined to give a good view of the entire planet.
Last year, NASA also attached an instrument to the ISS called Ecostress that monitors heat waves and drought as well as one called Global Ecosystem Dynamics Investigation, which measures the height of tree canopies and understories. Japan is also planning on installing an instrument that monitors land use and forest types on Earth.
OCO-3’s data collection isn’t scheduled to last too long. Voosen reports it’s likely that after a 3-year tour around the planet the instrument will be jettisoned and allowed to burn up before another scientific instrument takes its place.