TORONTO, July 28, 1997 -- York University could be the first university in Canada to lead a microsatellite space mission.

The Canadian Space Agency (CSA) has chosen a team of York University scientists to be one of five competing for a chance to launch either a microsatellite or a rocket into space. The York team, led by Dr. Ian McDade, a professor of Earth and Atmospheric Science, is proposing that it launch a microsatellite so it can study the "permanent aurora"-- the glowing shell of gas around the earth's atmosphere that displays some of the same fascinating colours as the Northern Lights.

The CSA has narrowed the field from 16 to five proposals: one for a rocket, and four for microsatellites. If York's team of scientists wins the competition, York will be one of the few universities in North America to have its own spacecraft in orbit.

McDade's team includes Dr. Brian Solheim and York graduate student Craig Haley. Since making it through the first round of the competition, they received $150,000 from the CSA to study the proposal's engineering and scientific feasibility. The research will be conducted at York University and in Winnipeg, at the headquarters of the project's industrial partner, Bristol Aerospace Ltd. The Institute for Space and Terrestrial Science (ISTS), located at York University, is also a partner in the project.

"I'm quite confident that York's MESO project (Microsat Experiment for Sounding Oxygen atom densities) has a very good chance of gaining the CSA's approval because it's a simple, inexpensive microsatellite that can shed light on a very intriguing subject -- the shell of light that circles the atmosphere," said McDade.

McDade said the shell of light around the earth is fascinating because it gives scientists clues about how air circulates in the atmosphere. The light is caused when regular oxygen molecules are split by daytime sunlight into two oxygen atoms. These oxygen atoms slowly come back together at night, forming "energy-rich" oxygen molecules -- exotic forms of oxygen that radiate light in different colour bands. The many different shades of colour found in this shell (also called the airglow layer) change constantly and increase and decrease in brightness. These changes occur because the air in the atmosphere is moving up and down and across the surface of the earth. This circulation is caused in part by atmospheric tides.

By measuring the brightness of the glowing gas, the MESO satellite will be able to track the movement of the oxygen molecules. Special light meters will be attached to the underside of the microsatellite, which, once built by Bristol in Winnipeg, will measure approximately 30 cm by 30 cm by 60 cm. As it circles the earth -- about once every 90 minutes at a height of about 600 km above the surface -- it will map the changes in brightness and colour in the airglow layer.

The MESO satellite will be equipped with solar panels and a special boom to ensure the light meters always point towards the earth and are always capable of observing the airglow layer. About once a day, the satellite will send its data to a ground station on earth, possibly on the York University campus. As the data comes in, McDade and his colleagues will be able to create a global map of the variations in brightness in the airglow.

"These maps will go a long way in helping us understand the atmosphere and atmospheric motions," said McDade. "There are complex wind patterns in the upper atmosphere and even tides that redistribute atmospheric gases. This study should expand our knowledge in these areas, and may even help us understand how ozone (a molecule made up of three oxygen atoms) is transported in the atmosphere." McDade's team has until December to develop a report on MESO's viability. McDade said he expects the CSA to approve at least one, and perhaps two, microsatellites out of the four in contention. "Our project has a big advantage in that we use a fairly simple, and therefore fairly inexpensive, method of ensuring that the satellite is always pointing towards the earth," said McDade.

Microsatellites are not launched into space on their own -- they hitch a ride with a larger satellite that is able to drop them off at an appropriate point in space. Part of the challenge now facing McDade is to find a regular satellite that is going into space at an appropriate time. The York microsatellite would "piggy-back" on it, thus reducing costs.

McDade expects the CSA to make a final decision by next spring. If York's microsatellite is given the green light, its design and construction will take approximately two years.

"This is a tremendous step -- for York University, for its students who look to York faculty for excellence in research and teaching, and for science in general," said Dr. Brock Fenton, York University's Associate Vice-President (Research and Faculties). "Congratulations to my colleagues Ian McDade, Brian Solheim and the MESO team. This project reinforces York's excellent reputation in the field of space and atmospheric science, and I am looking forward to more successful results in the next round of the Canadian Space Agency competition."

For more information, please contact:

Dr. Ian McDade
Department of Earth and Atmospheric Science
York University
(416) 736-2100, ext. 40124 or 736-5245

Sine MacKinnon
Senior Advisor for Media Relations
York University
(416) 736-2100, ext. 22087

Alison Masemann
Media Relations Officer
York University
(416) 736-2100, ext. 22086
YU/063/97

The shell of glowing gas in the earth's upper atmosphere is called the airglow layer. It is also known as the permanent aurora or nightglow layer. Approximately 10 km thick, it forms a thin luminous shell around the earth, at about 100 km above the earth's surface.

The airglow layer was first identified around the turn of the century when astronomers recognized that much of the faint light in the night sky must originate from very close to the earth, rather than from stars in the heavens above. In 1909, the astronomer Yntema named it `Earthlight.' It is barely discernible to the naked eye on earth, but astronauts in space can see it and its rich green/gray/orange colouration clearly when looking sideways at the earth's horizon.

What causes the airglow layer to exist?

At about 100 km above the earth's surface, oxygen molecules, which are normally made up of two joined oxygen atoms, are split into two separate atoms by ultraviolet (UV) daytime sunlight. These atoms move around like any other atmospheric gas, but eventually they collide and in a chemical process called `atomic recombination,' they reform oxygen. The oxygen created in this way is an energy-rich or `excited' form of normal oxygen. This `excited' oxygen reverts to regular oxygen after getting rid of its extra energy by emitting light of various colours.

This process can only occur under the very low-pressure conditions that exist at 100 km above the earth's surface (about one-millionth of that at ground level.) York University can create these conditions through laboratory simulations, using an experimental apparatus to generate artificial airglow with an intensity visible to the naked eye.

What can we learn from the airglow layer?

The brightness of the airglow layer is directly proportional to the concentration of oxygen atoms in the atmosphere. This means that measurements of the brightness of the airglow, such as those to be made by the MESO satellite, can be used to deduce the amount of atomic oxygen in the atmosphere. It was only in the late 1950s, with the advent of rocket experiments, that a connection between the airglow brightness and atomic oxygen was established. More recent rocket experiments performed during the last few years (many of which involved McDade and Solheim) have considerably refined our understanding of the quantitative relationship between the airglow brightness and the oxygen atom densities.

When viewed with instruments that can resolve the many colours in the airglow light into their individual colour components, the airglow is seen to consist of narrow colour bands. This colour distribution, or `spectrum' of bands, is similar to that of the Northern Lights or polar aurora, but the chemical processes involved in the production of these two types of light are quite different.

Scientists' previous discovery that the brightness of the airglow is related to the density of oxygen atoms makes the MESO project possible, because it means that McDade and Solheim can use measurements of the airglow layer's brightness to develop detailed maps of the distribution of oxygen atoms in that part of the atmosphere at various times. These maps will allow them to document how the air in the atmosphere circulates.