Table of Contents

Space Science Experiments

OGLOW
(Measurement of Optical Emissions (glow) on and from the Shuttle Orbiter)

Since the third Space Shuttle mission, crew members have noticed that the orbiter develops a reddish glow. This phenomenon could interfere with sensitive optical measurements on other payloads in space.

The immediate worry for Canadian scientists was the glow's possible adverse effects on an experiment called WAMDII (Wide Angle Michaelson Doppler Imaging Interferometer) that flew in1988 . WAMDII was a remote sensing optical instrument designed to measure neutral winds and temperatures at altitudes between 80 and 300 kilometres (50 and 185 miles).

OGLOW was also designed to learn enough about the characteristics and causes of the glow to make sure the Canadian WAMDII experiment would not be affected. A secondary objective was to gather data on the southern aurora (aurora australis), air glow at night time and the bioluminescence of oceans.

The experiment took place during Day 2 and Day 7 of the mission during darkness. Because Challenger orbits the Earth every 90 minutes, there are 16 "nights" every 24 hours.

Marc Garneau used a 35-millimetre camera, a special holder containing 12 narrow-band filters and an image intensifier to magnify all visible light. Using one filter at a time, Garneau was able to take pictures at different visible light wavelengths.

By determining the intensity of the light being emitted by the glow at the different wavelengths, it was possible to estimate any interference on WAMDII. This spectral information also provided clues regarding the physical origin of the glow.

The orbiter flew at a different altitude on Day 2 than on Day 7, resulting in glows of different intensities.

SPEAM (Sunphotometer Earth Atmosphere Measurements)

The Canadian-made Sunphotometer is being used by the Atmospheric Environment Service of Canada to measure local atmospheric constituents and to spectrally monitor acidic haze. It is known that sunlight is scattered or absorbed by dust, moisture, pollution and acidic haze, but it is very difficult to estimate the extent with any great precision. The Sunphotometer's absolute accuracy needed to be established from space to obviate the effects of the Earth's atmosphere on the instrument's calibration.

The experiment had two parts. The first was to calibrate the instrument. The other is to investigate the distribution of water vapour and other atmospheric gases - which affect the chemistry of the ozone layer; and to determine the density and distribution of the E1 Chichon volcanic cloud before it had completely disappeared. Mexico's E1 Chichon volcano erupted March 26, 1982.

The calibration part took 15 minutes to set up and another 15 minutes to complete. It was conducted once on Day 4 and once on Day 7 of the mission. Marc Garneau pointed the Sunphotometer directly at the sun from the side hatch window because it was the only one that let in ultraviolet rays.

For the second part, Marc Garneau pointed the Sunphotometer at the sun at sunrise and sunset when the sun is viewed through the Earth's atmosphere. He did this through various windows of the shuttle. These measurements took 15 minutes to set up and three minutes to take. Garneau took them as often as possible.

The data was stored in a portable computer and regularly transferred to a cassette tape.