Today on Galileo
Saturday, May 26, and Sunday, May 27, 2001

Galileo's Mission at Jupiter - Days 4 and 5 of the Callisto 30 Encounter

These last two days of the present encounter sequence are relatively quiet. The spacecraft is now receding from the planet and its satellites at a goodly clip, the tape recorder is nearly full of data, and it's nearly time to start playing that recorded data back.

Saturday morning, at 2:30 a.m. PDT [See Note 1], the Solid State Imaging camera (SSI) takes its last look at Callisto. This parting shot is a color image of the fully lit disk of the satellite, and the first full-disk color look at this hemisphere of the body.

At 9 a.m. PDT, the command sequence that will govern the activities of the spacecraft for the next ten weeks is transmitted from the tracking station at Goldstone in the Southern California desert. The antenna from which the commands are transmitted is 70 meters in diameter (230 feet). If this dish were on the surface of Callisto, Galileo, at its closest point during this flyby, could easily see it as an object 14 pixels across!

On Sunday, just before 1 a.m. PDT, SSI begins a short series of observations of Jupiter. These pictures target some of the hot spots in the atmosphere which have been popular objects of study by several of the science instruments during Galileo's tour of the Jovian system. These observations finish loading up the tape recorder, and shortly after SSI concludes its activities, the playback of the taped data begins.

At the end of day Sunday, the Extreme Ultraviolet Spectrometer (EUV) instrument is turned on to prepare for its observing opportunities. This instrument cannot operate effectively close to Jupiter in the more intense radiation environment. It also shares some of the spacecraft data processing resources with the Heavy Ion Counter (HIC) instrument, so only one of the two instruments can be used at a time.

We hope you have enjoyed following Galileo's journey through the Jupiter system this week. Our next close flyby is on August 5, when we will be sailing within 200 kilometers (124 miles) of the volcanic satellite Io.

Note 1. Pacific Daylight Time (PDT) is 7 hours behind Greenwich Mean Time (GMT). The time when an event occurs at the spacecraft is known as Spacecraft Event Time (SCET). The time at which radio signals reach Earth indicating that an event has occurred is known as Earth Received Time (ERT). Currently, it takes Galileo's radio signals 50 minutes to travel between the spacecraft and Earth. All times quoted above are in Earth Received Time.

For more information on the Galileo spacecraft and its mission to Jupiter, please visit the Galileo home page at one of the following URL's: