Дата: 21 июля 1998 (1998-07-21)
От: Alexander Bondugin
Тема: Today On Galileo - July 19, 1998
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TODAY ON GALILEO
July 19, 1998
The fifth encounter of the Galileo Europa Mission starts late today,
seven months after the start of the spacecraft's mission extension.
The encounter features the sixth consecutive flyby of Jupiter's moon
Europa. The first in the series was the last encounter of Galileo's
primary mission. During the next 3-1/2 days, Galileo will concentrate
on Europa, but will also make observations of a white oval and hot
spots in Jupiter's atmosphere. The encounter will also include
selected observations of Io and Ganymede. During the encounter, the
spacecraft finds itself at distance of 656 million kilometers (408
million miles) from Earth. At that distance, it will take radio
signals approximately 36-1/2 minutes to travel to and from the
spacecraft.
The main computer on board Galileo will start executing the encounter
command sequence at 9:55 pm PDT [See Note 1 below]. By coincidence, at
that same time, the spacecraft will be passing Jupiter's volcanic moon
Io at a distance of just under 701,000 kilometers (436,000 miles).
This is the spacecraft's closest approach to Io for this orbit.
The start of the encounter is also the start of the fields and
particles instruments' survey of Jupiter's dust, plasma, magnetic and
electric field environment. The survey has been repeated during every
encounter of the Galileo's mission at Jupiter. The survey collects
information at a very low rate (a few bits of data per second), but is
important as it provides background or context information for higher
rate observations recorded later in the encounter. The survey also
allows scientists to track global changes in Jupiter's fields and
particles from orbit to orbit.
The sole remote sensing observation performed today is done by the
near-infrared spectrometer. The observation is designed to look for
changes in Io's surface due to recent volcanic activity. The geometry
of the observation provides good nightside coverage of a region
including the Prometheus volcano. Half of Io is in darkness and the
other half is in sunlight at the time the observation is taken.
Note 1. All times listed correspond to the Pacific Time zone
(currently daylight saving) and spacecraft event time. Radio signals
indicating that an event has occurred on the spacecraft reach the Earth
35 to 50 minutes later, depending on the time of year (currently 36.5
minutes).
For more information on the Galileo spacecraft and its mission to Jupiter,
please visit the Galileo home page:
http://www.jpl.nasa.gov/galileo
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