Galileo Status Report
PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
Yesterday the flight team transmitted commands to control the Galileo spacecraft during its Dec. 7 arrival at Jupiter. This computer program contains all the engineering commands necessary for the relay of data from Galileo's atmospheric descent probe and the firing of the spacecraft's main engine to put it in orbit around the giant planet. The commands will provide all essential control of the spacecraft from Nov. 17 through Dec. 8, by which time the spacecraft will be in orbit around Jupiter and the atmospheric probe mission will have been been completed.
The team also sent commands instructing Galileo's onboard central computer to keep this sequence going in the event of any incident that otherwise would interrupt programmed operations. In addition, another command sequence that began operating on Nov. 6 contains instructions for collecting dust and magnetic field measurements and the use of Galileo's extreme ultraviolet instrument to observe Jupiter's plasma torus as the spacecraft closes in on the giant planet. The plasma torus is a ring of ionized oxygen and sulfur surrounding Jupiter that is believed to be spewed out by volcanoes on Jupiter's moon Io.
On Nov. 13, the flight team sent software changes to the spacecraft to allocate enough memory in the onboard computer to store up to 73 minutes of data from the atmospheric descent probe, instead of 40 minutes previously planned. This means that science data from essentially the full duration of the probe's descent into the Jovian atmosphere will be stored both in the computer and on Galileo's onboard tape recorder for later transmission to Earth.
The navigation team concluded this week that the Galileo orbiter's flight path is so close to the desired trajectory that it is not necessary to perform a tweak by firing Galileo's thrusters in a trajectory correction maneuver that had been tentatively planned for Friday, Nov. 17. The current flight path will send Galileo by Jupiter's moon Io, where the spacecraft will receive a gravity-assist boost that will send it on to Jupiter.
The spacecraft is operating normally, spinning at about 3 rpm and transmitting at 10 bits per second. It has traveled almost 3.8 billion kilometers (2.35 billion miles) around the solar system since launch in October 1989, and has only about 9 million kilometers (6 million miles) to go before Jupiter arrival Dec. 7. Radio signals now take more than 51 minutes to reach Earth from Galileo.