The Trump administration has reportedly asked the National Aeronautics and Space Administration (NASA) to prepare to shut down two major satellites that monitor atmospheric carbon dioxide (CO2) and crop health.
It was unclear why the missions were being ended prematurely, NPR, which first reported on the plan last week, said.
NASA told The Associated Press (AP) in an emailed statement that the missions were “beyond their prime mission”, and were being terminated “to align with the President’s agenda and budget priorities”.
Experts have argued that the satellites are still more sensitive and accurate than any other mission, operating or planned, in the world.
What are Orbiting Carbon Observatories?
OCOs are a series of dedicated Earth remote sensing satellites that were designed specifically to observe atmospheric CO2 from space in order to better understand the characteristics of climate change.
The first mission, called OCO, of the series failed soon after launch in February 2009, as the launch vehicle’s ‘fairing’, the nose cone that protects the payload, did not separate during the ascent. The extra weight of the fairing prevented the satellite from reaching its orbit.
A replacement satellite, OCO-2, was launched in July 2014. It was built based on the original OCO mission to minimise cost, schedule, and performance impacts.
The satellite not only measures atmospheric CO2, it can also locate its sources and sinks. In addition, the mission tracks crops and crop-growing seasons by measuring the “glow” that plants emit when they photosynthesise.
In 2019, a third mission, OCO-3, was sent to the International Space Station (ISS) to further enhance the observation of atmospheric CO2. OCO-3 was built from the spare components left over after the assembly of OCO-2.
While OCO-3 and OCO-2 do the same job, they provide different perspectives to scientists. This is because OCO-2 flies around Earth in a sun-synchronous polar orbit, which allows it to see any given location at the same time of day. OCO-3, on the other hand, flies aboard the ISS, which orbits Earth every 90 minutes – it can, therefore, observe a location at many different times of day, and add to the dataset of its predecessor mission.
The US government now plans to shut down both OCO-2 and OCO-3 satellites, according to reports.
Why are the OCO missions important?
The data collected by the satellites have revolutionised scientists’ understanding of how quickly CO2 is accumulating in the atmosphere. Before the launch of the OCOs, scientists measured atmospheric CO2 mainly through instruments placed at various locations on the Earth’s surface. This did not provide them information about the whole planet. The OCOs changed that.
CO2 is a potent greenhouse gas, and the primary driver of global warming. The data from the OCO missions help scientists and policymakers assess emission reduction efforts, and to develop effective strategies to tackle climate change.
The OCOs also advanced scientific knowledge by paving the way for some surprising discoveries.
For instance, it had been believed for decades that tropical rainforests functioned as the lungs of the planet by clearing out vast quantities of CO2 from the atmosphere. However, data from OCO-2 revealed the significant role that boreal forests – also known as taiga, the coniferous forests in the higher latitudes of the northern hemisphere – play in the absorption of CO2.
The data also showed how natural carbon sinks such as forests could become carbon emitters due to drought or deforestation.
The ability of OCOs to monitor crop health has several benefits. NASA and other agencies have used the data to create high-resolution maps of plant growth around the world.
“That’s useful to farmers, useful to rangeland and grazing and drought monitoring and forest mapping and all kinds of things, in addition to the CO2 measurements,” Scott Denning, a climate scientist at Colorado State University, told NPR.
The data have been used by the US Department of Agriculture and many private agricultural consulting companies to forecast and track crop yields and drought conditions.
How expensive is it to maintain the OCOs?
Experts have said that the cost of maintaining OCOs in space is a small fraction of the money that was spent to design and launch the satellites.
It took around $750 million to design, build, and launch OCO-2 and OCO-3, David Crisp, a retired NASA scientist who helped put together the original idea for the OCO mission and led the team that designed, developed, and delivered the mission to the launch pad, told NPR.
Maintaining the satellites in orbit, on the other hand, costs about $15 million per year. This includes the cost of downloading the data, maintaining a network of calibration sensors on the ground, etc.
“Just from an economic standpoint, it makes no economic sense to terminate NASA missions that are returning incredibly valuable data,” Crisp told NPR.
However, Congress might yet vote to preserve the satellites, which are funded through the fiscal year that ends on September 30.
The OCO-2 satellite before launch. (Image source: NASA) 
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