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    Earth System Science Pathfinder (ESSP)


OCO2Orbiting Carbon Observatory (OCO2/OCO3)


OCO-2 and OCO-3 NASA’s twin carbon chasing satellites show us CO2 sources and sinks.


OCO-2 was launched on July 2, 2014 and was the first US satellite dedicated to measuring  atmospheric carbon dioxide (CO2) from space, and it is still making measurements today! CO2 is a greenhouse gas, and it has been shown to be increasing due to human activities. OCO-2 has been measuring this change. The more CO2 that is in the air, the warmer the earth is becoming. This causes things like rising sea levels, melting glaciers and ice sheets, thawing permafrost, and droughts. Data from OCO-2 has already shown that tropical forests absorb CO2 in response to drought and warm temperatures, which would mean that CO2 will increase much faster in the future, speeding up the damaging effects of climate change. OCO-2 is critical to help us understand where the CO2 is coming from, how fast the emissions are increasing, and what we can do to reduce CO2 emissions to protect our planet.

“I definitely feel like there is an urgency to addressing Greenhouse Gasses and climate change. We’ve seen clearer information coming out about all the impacts in the world – sea ice and sea level, storms, etc. There is going to be so many impacts to people like food availability and water availability, that I think that it is important that we address this sooner rather than later. Making changes now to avoid emissions is going to more effective than adjusting to all the potential impacts. ” – Annmarie Eldering , Project Scientist, OCO-2

OCO-2 orbits around the earth from pole to pole. This lets it sample  what CO2 looks like over the entire planet and where emissions are the strongest. OCO-2 looks at reflected sunlight from the Earth’s surface and uses three spectrometers to measure gases in the atmosphere. Its data is used by scientists all over the world. Today, fossil fuel combustion and other human activities are currently contributing about 39 billion tons or 39 Gigatons of CO2 into the atmosphere each year. During the pandemic, many industries were closed, and cities and countries issued stay at home orders, keeping people off the road.

Scientists are using OCO-2 data to determine if there was an impact on CO2 emissions due to the COVID-19 pandemic. The data from OCO-2 remains very valuable and the OCO-2 mission will continue to contribute to scientific investigations that are related to the global carbon cycle.

How are NASA’s OCO-3 and OCO-2 different? The OCO-3 spectrometer (instrument) is a duplicate of OCO-2, and in fact was made from spare parts from OCO-2. They both measure CO2 over the earth using reflected sunlight, and they both provide a significant amount of information about climate change. What is different is where they are in space. While the older sibling OCO-2 orbits the earth from pole to pole, the younger sibling OCO-3 is hitching a ride on the International Space Station (ISS)! The path that the ISS takes around the Earth is very different from the path of the OCO-2 satellite, and this means that OCO-3 sees the earth in a different way. OCO-3 will be able to measure different regions of the Earth at all different times of day, so we can see how CO2 is changing throughout the day over forests. OCO-3 is also able to swivel and point to a compact, city-sized area to get more details on CO2 behavior.

Along with OCO-2, OCO-3 will show us what the emissions of CO2 are around the Earth, and how it is absorbed by forests and impacting their health. We can use data from the instruments to find some plumes from power plants and cities. The two OCO siblings are helping us understand climate change and how we can prepare for the future climate.


The Orbiting Carbon Observatory-2 (OCO-2) model intercomparison project (MIP) is a collaboration among atmospheric CO2 modelers to study the impact of assimilating OCO-2 retrieval data into atmospheric inversion models. The results from the set of simulations performed by this project have been released as a level-4 flux product.


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