Right:  Prof. Gordon Shepherd

The $40-million Canadian-built instrument, sponsored by the Canadian Space Agency and the Centre National d'Etudes Spatiales (CNES) of France, was one of ten instruments on NASA’s Upper Atmosphere Research Satellite (UARS) launched aboard the space shuttle in 1991.

Prior to the NASA satellite (UARS) in 1991, the winds of the upper atmosphere were largely unknown territory.  The WINDII (Wind Imaging Interferometer) instrument on the UARS measured winds high in the earth's upper atmosphere, between the altitudes of 80 and 300 km.

Lead for the WINDII scientific team is York Professor Gordon Shepherd, who served as principal investigator, and is director of York's Centre for Research in Earth & Space Science (CRESS). At the gathering of leading space scientists from around the world involved in the mission, the team described how the scientific community’s understanding of the earth’s upper atmosphere has changed over the years.

“Every day, winds routinely reach speeds of over 200 kilometres per hour on either side of the equator -- at about 20 degrees North and South latitude -- which did surprise us,” says Shepherd. “These intense winds are hurricane speed, however the thin air at high altitudes would make them feel more like a light breeze.”

“We observed and measured the existence of 24-hour tidal waves of winds that originate near the earth’s surface,” said Shepherd. “Unlike the twice-daily ocean tides, these gusty winds are driven by the sun’s heat, not the earth’s gravity.”

WINDII used a technique, conceived by Shepherd and colleagues, called Doppler Michelson Imaging. Due to the complicated process of measuring winds in the upper atmosphere (the satellite was several hundred kilometers above where the winds occur) researchers used light as a kind of remote sensor. They measured “airglow,” a form of light in the visible spectrum which is emitted by oxygen atoms and molecules in the atmosphere during the release of stored chemical energy. In particular, it tracked the movements of the oxygen atoms by measuring shifts in the wavelength of light they emit. Through this technology, scientists were effectively able to “see” the wind.

“It’s difficult for many scientists to accept that events so high up in the atmosphere have an effect on what goes on closer to the earth, but the more we study this, the more we see the links between the regions,” Shepherd says.

Years of effort and engineering went into the creation of the WINDII instrument, the first of its kind to be used in space. The instrument took measurements in two directions, allowing scientist to calculate winds moving north and south as well as east and west.

WINDII provided scientists with a revolutionary, new understanding of the dynamics of the upper atmosphere. It demonstrated that waves play an important role in the circulation of the upper atmosphere and transport the atomic oxygen over large distances.  (Photo: From left to right: Gerard Thuillier, Centre National d'Etudes Spatiales, York space scientists Ian McDade and Gordon Shepherd (centre), Charley Jackman, NASA, and Roger Colley, Canadian Space Agency)

Shepherd concluded, “Over the years, these insights have caused meteorologists to view the atmosphere differently and model weather patterns at higher altitudes than had been thought necessary. Looking to the future, the pioneering work of WINDII is the foundation for new missions that will improve our understanding of climate change, help protect the ozone layer, and perhaps produce better weather forecasts.”

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Nancy White
Director, Media Relations
York University
416-736-5603
whiten@yorku.ca