This Week on Galileo - January 12-18, 1998
Flight team members will spend the upcoming week collecting and analyzing engineering data to better understand and correct anomalous behavior from the spacecraft's attitude control subsystem. A second anomalous behavior occurred while the spacecraft was performing an orbit trim maneuver in late December, a few days after the first occurrence during the Europa-Orbit 12 encounter. The behavior of the attitude control subsystem, the system responsible for controlling where the spacecraft is pointing, has left Galileo's radio antenna pointing in a direction that is about 10 degrees from the Earth. This has reduced the amount of science information that was scheduled for transmission to Earth. Typically, Galileo's antenna is maintained within 4 degrees of Earth to maximize the amount of information that can be transmitted to Earth.
Leading theories now place one of the spacecraft's two gyroscopes near the top of the list of possible causes for the anomalous behavior. The gyroscopes are part of the attitude control subsystem that is used to control where the spacecraft is pointing. The primary control mechanism is provided by another part of the subsystem (the star scanner) that scans the sky surrounding the spacecraft for visible stars. The gyroscopes are used when the stars that are visible are not good enough to be used for this purpose, or when the star scanner view must be covered to avoid over-exposure and damage due to the presence of bright light.
As recovery operations have allowed, the spacecraft has processed and transmitted to Earth pictures and other science information stored on its tape recorder during the close flyby of the moon Europa during mid-December. The next few days are expected to include high time resolution fields and particles information of the interaction between Europa and Jupiter's magnetic and electric field environment and images of Europa's Conamara Chaos region. Other images may include regions of mottled or "blotchy" terrain.
By the end of the week, flight team members expect to have performed a spacecraft turn known as a sun acquisition to reduce the angle between Earth and the spacecraft's radio antenna. As its name suggests, a sun acquisition turns the spacecraft toward the sun by using the sun's intense light as a guide. If successful, the sun acquisition will allow flight team members to increase the amount of science and engineering information that can be transmitted to Earth.
Stay tuned to this URL for developments!
http://www.jpl.nasa.gov/galileo/