Between July 16 and 22, 1994, some 20 pieces of comet Shoemaker-Levy 9 plunged into the atmosphere of Jupiter. This event provided scientists with an unprecedented opportunity to study the composition and construction of comets as well as aspects of the Jovian atmosphere itself. Naturally, telescopes around the world and in space were trained on this extraordinary event. Even a new telescope and near infrared camera at the South Pole were on hand to join in these observations.
The South Pole Infrared Explorer, SPIREX for short, is a combination of telescope and near infrared instrument designed to use the outstanding properties of the South Pole for astrophysical research. For these measurements it was the unique location on our spinning globe that gave SPIREX it's special advantage. Located at the bottom of the world, SPIREX's view of Jupiter was completely unobstructed by the bulk of the Earth for the entire week. Jupiter simply traced a circle around the sky, floating above the horizon at all times. From other sites around the world, the planet would rise and set just as the Sun does, making it impossible to see for large portions of the day.
In preparation for this week, over 14,000 pounds of equipment were shipped to the Pole so that the SPIREX Team could install and test it during the summer months. Travel to the South Pole can only be attempted during the summer when the sun is up and the temperature soars to -10 C. By mid-February, when the station is closed to all traffic until the following November, the telescope and instrument package were operating and ready for the long, cold, dark winter to come.
Of the 20 comet fragment impacts that SPIREX attempted to observe only 4 occurred while the view was obscured by heavy clouds. Just 6 turned out to be too faint to be easily detected. The remaining 10 events were seen as bright flashes in the near infrared, a region of the light spectrum sensitive to heat radiation. Some of the impacts left hot spots that were easily visible for days. During the entire exciting week we snapped over 2500 electronic images with the near infrared camera and transmitted them all to our laboratory in Chicago via the Internet over a special satellite link.
We designed the SPIREX poster to give you an idea of what we saw. Each of the 10 most extraordinary events (labeled from top to bottom A, C, E, G, H, K, L, Q1, R, and W) are shown as small sequences of three pictures. The first image in the triplet shows Jupiter a few minutes before the impact became visible to us. The middle, or second, image is the brightest picture in our collection. In it the hot spot has just rotated around Jupiter's limb and into our view. It is visible at the lower left edge of the circular disc of the planet. The third and final frame shows the planet several minutes later as the hot spot has begun to dim. Also in some of the frames, as many as two of Jupiter's moons are visible. They are the bright spots which are a distance from the planetary disc.