Canada’s SCISAT satellite, which last year marked 10 years of actively observing more than 30 different molecules in our planet’s upper and lower atmosphere, has earned a reputation for providing a unique collection of measurements that sometimes contain surprises. This reputation was reinforced this past November with findings of a recent and unexpected increase of hydrochloric acid (HCl) in the Northern Hemisphere’s lower stratosphere.

The result, which was reported in Nature, dates this increase from 2007 and contrasts with a steady decrease in gases closer to the surface that could generate HCl. In their official statement the researchers studying this trend attribute it to a slowing of atmospheric circulation that has led to some of these source gases migrating upward. They also note that this trend could lead to similar effects for other gases that are being monitored. “Without reliable HCl measurements in the lower stratosphere provided by the Canadian instrument, we could not have reached this conclusion,” says University of Waterloo chemist Peter Bernath, who is principal investigator with the satellite’s ongoing Atmospheric Chemistry Experiment. “No other single instrument has provided such a wide range of data products for such a long time.”    

SCISAT is outfitted with an optical Fourier transform infrared spectrometer and an ultraviolet spectrophotometer that can take advantage of occultation, analyzing sunlight as it passes through the atmosphere. Although tracking the fate of chlorofluorocarbons responsible for ozone depletion was a primary objective when the satellite was designed in the 1990s, the same hardware has since been repurposed to follow such things as climate-altering greenhouse gases.

This long-lived orbital mission has also achieved significant commercial success, recouping its original $20 million price tag many times over with sales of remote sensing data to various industrial clients. This accomplishment, along with the scientific surprises, has highlighted the career of Kaley Walker, a University of Toronto physicist who has served as deputy mission scientist since SCISAT went into orbit. “We’ve developed further data products that have allowed us to contribute in so many other areas,” Walker says.