Today on Galileo
Saturday, May 26, and Sunday, May 27, 2001
DOY 2001/146 and 147
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