Galileo Joins Jupiter, Literally
The flight team for NASA's Jupiter-orbiting Galileo spacecraft ended the probe's long, image-rich journey.
In the years since astronauts deployed Galileo from the cargo bay of Space Shuttle Atlantis in 1989, the mission has produced a string of discoveries about asteroids, a fragmented comet, Jupiter's atmosphere, Jupiter's magnetic environment, and especially about the geologic diversity of Jupiter's four largest moons.
The prime mission ended six years ago, after two years of orbiting Jupiter. NASA extended the mission three times to continue taking advantage of Galileo's unique capabilities for accomplishing valuable science.
Now, the onboard supply of propellant is nearly depleted. Without propellant, the spacecraft would not be able to point its antenna toward Earth nor adjust its trajectory, so controlling the spacecraft would no longer be possible. Before that could happen, the flight team last year put Galileo on course for disposal by a dive into the crushing pressure of Jupiter's atmosphere.
This strategy eliminates any possibility of an unwanted impact between the spacecraft and the moon Europa. Galileo's own discovery of a likely subsurface ocean on Europa has raised interest in the possibility of life there and concern about protecting it.
On Nov. 5, 2002, the orbiter passed closer to Jupiter than it had ever ventured before, flying near an inner moon named Amalthea and through part of Jupiter's gossamer ring to begin its 35th and last orbit around the giant planet. That elongated farewell loop took Galileo farther from Jupiter than it had been since before it entered orbit in 1995, to a point more than 26 million kilometers (16 million miles) away on April 14 before heading back in for impact on September 21.
"After this month, we have no further activities planned until the day of impact," Theilig said last February.
The specifications on the Galileo spacecraft and its science milestones are:
On-orbit mass: 2380 Kg
Power System: Radioisotope Thermal Generators (RTGs) of 570 W
Dimensions: The length of the spacecraft is 9 m and, with the high-gain antenna (HGA) deployed, is 4.6 m in diameter.
Gravity Assist: The trajectory which the spacecraft followed was called a VEEGA (Venus-Earth-Earth Gravity Assist), traveling first in toward the Sun for a gravity assist from Venus before encountering the Earth two times (spaced two years apart). These encounters with Venus and the Earth allowed Galileo to gain enough velocity to get it out to Jupiter.
Launch Date: 18 October 1989 at 22:23 UTC
Launch Vehicle: Shuttle/Inertial Upper Stage
The Galileo flight team numbered about 300 people at its peak during the prime mission, but has run much leaner in recent years, with about 30 since the Amalthea flyby. That smaller team is now disbanding, mostly to work on other JPL-managed NASA missions that are in development or already flying.
JPL, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C. Additional information about the mission and its discoveries is available online at http://galileo.jpl.nasa.gov.