Canada's MOPITT is seen here in a clear room at the University of Toronto prior to its launch in 1999.ComDev/University of Toronto/Supplied
Atmospheric researchers have bid farewell to what may be the longest running space science experiment in Canadian history.
MOPITT – which stands for Measurement of Pollution in the Troposphere – is a Canadian-built device that was launched as one of five instruments on board NASA’s Terra satellite in December, 1999. It operated successfully until it was switched off Wednesday to conserve power on the ailing spacecraft.
The decision to terminate the experiment was made earlier this year and is unrelated to moves by the Trump administration in the United States to cut funding to climate-related science, said Jim Drummond, a professor emeritus at the University of Toronto and Dalhousie University who is Canada’s principal investigator for MOPITT.
“At the end it was a decision to power down one of the instruments and unfortunately we got the short straw,” Dr. Drummond said.
He spoke to The Globe and Mail from the Canadian Space Agency’s headquarters in Longueuil, Que., where scientists were gathered for a two-day meeting to discuss MOPITT’s results and scientific legacy.
ComDev (now Honeywell Aerospace) of Cambridge, Ont., built MOPITT to measure carbon monoxide, a byproduct of incomplete combustion that plays an important global role as an airborne pollutant.
Intended to last for five years, MOPITT was the first instrument to show the global reach of pollution associated with the burning of carbon-based fuel, including industrial emissions and forest fires.
It far exceeded its planned lifespan and ended up providing an unbroken record of carbon monoxide levels for 25 years, with enough detail to capture regional differences and spot changes on the scale of individual cities.
Prior to its launch, no such database existed except for measurements from NASA’s space shuttle, which could only be made at times when a shuttle happened to be in orbit.
And though parallel measurements can now be obtained by combining observations from other satellites, only MOPITT offered such a comprehensive and continuous series of measurements from a single device over such a long span of time.
MOPITT is one of five instruments launched on Dec. 18, 1999, aboard Terra, a NASA satellite orbiting 705 kilometres above the Earth.Canadian Space Agency
“When you have this consistent record for 25 years, it’s easier to look at trends,” said Helen Worden, MOPITT’s U.S. principal investigator and an atmospheric chemist at the National Center for Atmospheric Research in Boulder, Colo., who was also at this week’s meeting.
A key feature of MOPITT was its ability to measure carbon monoxide in two ways, allowing scientists to understand how its presence was changing at different levels in the atmosphere and get a better handle on sources of the gas near the surface.
Among the trends documented by MOPITT was a gradual decrease in overall carbon monoxide emissions from China and other countries as they shifted from residential coal burning to increased electrification and cleaner vehicles. More recently, MOPITT has also observed what may be a growing trend in emissions from large-scale wildfires, including Canada’s record-breaking 2023 fire season, which burned about 4 per cent of the country’s forests.
Because carbon monoxide is relatively straightforward to detect, it serves as a tracer for other pollutants associated with fire, including small particulates that have an effect on human health. It can also can be used as a separate check on rates of deforestation through burning in the Amazon rainforest and elsewhere.
Separately, carbon monoxide measurements are also crucial for understanding Earth’s climate. Although not a major contributor to climate change on its own, it reacts with the hydroxyl radical (OH). As a side effect, that leaves less OH available to remove methane from the atmosphere, which is a strong greenhouse gas.
The interaction underscores the importance of accurate carbon monoxide measurements for predicting climate, Dr Worden said.
She added that the partnership that put MOPITT on a U.S. satellite 25 years ago exemplifies the benefits of scientific collaboration for both countries and for researchers worldwide who have made use of MOPITT’s data.
“If we weren’t talking to each other, we would not make nearly the amount of progress we made, in my opinion,” she said.