JPL's Galileo spacecraft is scheduled to observe 16 of the 21 possible impacts of the fragments of Comet Shoemaker-Levy-9 with Jupiter this July, according to project scientist Dr. Torrence Johnson.
Speaking at the 1994 spring meeting of the American Geophysical Union in Baltimore last month, Johnson described plans for the only observation platform actually able to photograph the impact sites.
"Galileo's imaging system and its near-infrared mapping spectrometer will divide up most of the opportunities," Johnson said, "while the photopolarimeter observes several other events."
Galileo's ultraviolet spectrometer, plasma-wave sensors and dust detector will also be involved in the effort, as will other distant spacecraft and many observers on Earth. Galileo's camera will be used in several different ways, including time-lapse sequences with and without color filters, slow scans and very long, sweeping scans with an open shutter.
"We're hoping that one or more of our observational schemes will succeed in recording observations of the impact events themselves with their immediate consequences, possibly including large hot fireballs produced by the explosion of comet fragments as they are stopped by Jupiter's atmosphere," Johnson said.
"Theories of what happens in such large atmospheric impacts," he continued, "are important to an understanding of the evolution of the early Earth and other planets, as well as the later Cretaceous-Tertiary extinctions (of dinosaurs and many other species). We hope for the first time to provide actual observations that can test and improve these theories."
Galileo will be about 240 million kilometers (150 million miles) from Jupiter, at an angle from which part of the night side, including the comet impact site, is visible. All the fragments will impact on the far side of Jupiter relative to the Earth and sun.
The spacecraft will tape-record its images and other science
data, Johnson said, and play them back slowly over the next
several months. Playback of selected Shoemaker-Levy data from
Galileo may continue until the end of January 1995, using a
sample-and-select approach like that employed with the pictures
of asteroids Gaspra and Ida.