WINDII – 12 years in orbit measuring the winds of the upper atmosphere

A Canadian instrument ended its long career in June 2004, 12 years after the beginning of its mission. WINDII, one of ten instruments aboard the American UARS satellite, carried out a valuable scientific research mission on the winds of the upper atmosphere. WINDII was built in cooperation with France's Centre national d'études spatiales. Its performance exceeded all expectations, and what was planned as an 18-month mission actually lasted more than a decade. Under the direction of Gordon G. Shepherd of York University's Centre for Research in Earth and Space Science, WINDII scored a first by enabling the scientific team to study the winds of the upper atmosphere.

Typhoon over the Sea of Japan  (Photo: ESA)

WINDII (Wind Imaging Interferometer)

WINDII's 585-km-high orbit allowed it to study winds occurring at altitudes of 80 to 300 km above the Earth. The objective was to improve our knowledge of wind circulation in this part of the atmosphere. Remote sensing techniques were used to give WINDII the ability to discern the natural luminescence of the atmosphere.

It became possible to make a number of observations thanks to this instrument, such as that winds in this part of the atmosphere can reach speeds higher than expected—sometimes over 200 km an hour. Though fast, they are not very powerful because of the atmosphere's low density at this altitude. Scientists were also surprised to observe that the winds have a seasonally variable cycle: stronger in the spring and fall, growing lighter during the summer and winter. WINDII was also able to gather information on the source of the winds, their magnitude, temperature, chemical composition, structure, and cycles.

Animation showing WINDII aboard UARS. (Animation: NASA Goddard Space Flight Center) - 1 MB

A better understanding of wind circulation in the upper atmosphere will help scientists evaluate future climate change and the effects of global warming on the atmosphere. From its satellite platform, WINDII has given a more comprehensive picture of the upper atmosphere wind forces. The data quality and quantity far exceed all previous measurements: Gordon G. Shepherd's team gathered more than 22 million images, which will sustain research for decades to come.

In recognition of his exceptional contribution to the Canadian Space Program, Gordon G. Shepherd received the prestigious John H. Chapman Award of Excellence in 2003. This award, presented each year by the CSA President, is named after the father of the Canadian Space Program, John Herbert Chapman.