NASA has successfully launched a space probe to measure the amount of carbon dioxide in the Earth’s atmosphere. Launched today by a Falcon 9 rocket from Cape Canaveral in Florida at 02:48 local time, the Orbiting Carbon Observatory 3 (OCO-3) will now be installed on the International Space Station (ISS) over the coming days. Costing around $100m, OCO-3’s will map the Earth’s carbon dioxide, search for areas that produce and absorb large quantities of the gas and examine how levels change during the day.
The first OCO mission, costing $270m, failed just 14 minutes after lift-off in February 2009. NASA then rebuilt the craft — renamed as OCO-2 — at a cost of $465m. That probe was successfully launched in July 2014 and put into polar orbit, where it became NASA’s first spacecraft dedicated to making space-based observations of atmospheric carbon dioxide. Although originally meant to operate for only two years, OCO-2 is still running and has already helped scientists to get a better understanding of the 2015-2016 El Niño weather pattern on the carbon cycle.
OCO-3 will paint the most detailed picture ever of human and plant influences on the carbon cycle and in turn, the Earth as a system and how it is changing
Ralph Basilio
As OCO-2 is in a polar orbit, it goes over any given location at the same time of day. OCO-3, however, will instead be installed on the Japanese Experiment Module-Exposed Facility aboard the ISS The ISS orbits Earth with an inclination around 52 north to 52 south — or around London to Patagonia. This means that OCO-3’s location over Earth changes a little on each orbit allowing it to scan a given location across its sunlit hours. This will let OCO-3 measure local changes in carbon dioxide at different times in the day as well as solar-induced chlorophyll fluorescence levels — the light re-emitted by chlorophyll molecules in plants during photosynthesis.
OCO-3 will pick out “sources and sinks” of carbon dioxide with the ability to measure concentration of the gas in the atmosphere to an accuracy of around 0.4%. “Dozens of areas of interest, for example, large urban centres, will be mapped each day,” OCO-3 project manager Ralph Basilio from NASA’s Jet Propulsion Laboratory in California told Physics World. “This will help to determine if carbon dioxide emissions are due to human activity or part of the natural cycle. In addition, this will provide for more detailed assessment of plant health over time.”
Painting a picture
OCO-3 will contain three spectrometers that were built as spare parts for the OCO-2 mission. Rather than directly measuring the amount of gases in the atmosphere, these spectrometers detect the change in intensity of sunlight that has been reflected from the Earth’s surface and then absorbed by carbon dioxide and oxygen. One spectrometer on OCO-3 is dedicated to studying oxygen, while the other two measure carbon dioxide at two different sets of wavelengths. Reborn carbon mission launches after five-year wait
OCO-3 is expected to last for three years, but like its predecessor, OCO-2, the mission could go on for much longer. “When combined with the five-year dataset of OCO-2, OCO-3 will paint the most detailed picture ever of human and plant influences on the carbon cycle and in turn, the Earth as a system and how it is changing,” adds Basilio.
