This Month on Galileo
March 15 - April 18, 1999
Notice: Due to solar conjunction this edition covers the next five weeks.
For three of the next five weeks, Galileo's activity level is dramatically reduced as the orbital motion of Earth and Jupiter brings the sun in between the two planets (this is known as solar conjunction), creating radio interference, and making reliable communications impossible. The weeks prior to and after this period of unreliable communication are utilized in the playback of science data stored on the spacecraft's onboard tape recorder. Playback of data is interrupted several times to perform standard engineering and navigation activities. The spacecraft performs a flight path correction on March 19. Standard maintenance on the propulsion systems is performed on March 20 and April 10. Maintenance of the onboard tape recorder is performed on March 21 and April 11. On April 14, the spacecraft executes a standard gyroscope performance test, and on April 16, it executes a small turn to keep its radio antenna pointed toward Earth.
During the next several weeks, Jupiter's motion relative to Earth carries it and the Galileo spacecraft first behind the sun as viewed from Earth, and then back out again. As the spacecraft approaches the sun, its radio signal passes closer and closer to the sun. The sun's activity interferes with the radio signal, corrupting the information contained therein, making communications unreliable. Eventually the sun physically blocks the radio signal from reaching Earth. As the spacecraft emerges from behind the sun, the path of Galileo's radio signal also moves away from the sun, communications get less noisy, and are eventually restored to their normal state.
Playback plans for the first and last of the next five weeks include observations that were described in the previous edition of This Week on Galileo. The schedule delay is the result of data from some observations not being compressed as much as expected, thus taking more time to transmit.
On the schedule we find Near-Infrared Mapping Spectrometer observations designed to differentiate between the different possible crystalline forms of water ice on Europa. Detection of forms other than the expected hexagonal ice could could provide scientists with evidence of geologic activity (cryovolcanism, plumes) on Europa. In addition, the Fields and Particles instruments continue the return of a 50 minute long observation recorded during closest approach to Europa. The data contained in the observation will add to the scientists' understanding of the interaction between Europa and Jupiter's magnetosphere. Finally, the Photopolarimeter Radiometer returns a polarimetry observation of Ganymede. These polarimetric measurements will provide information about the texture and composition of Ganymede's surface material.
For more information on the Galileo spacecraft and its mission to Jupiter, please visit the Galileo home page:
http://www.jpl.nasa.gov/galileo
Return to Project Galileo Homepage