This Week on Galileo May 22-28, 2000
Jupiter continues to dominate Galileo’s observation schedule on Monday
as
instruments focus on the planet’s aurora and its atmosphere, including
the
Great Red Spot. The spacecraft makes its closest approach to Callisto
at
4:39 p.m. PDT [see Note 1] Monday at a range of 331,000 kilometers
(206,000
miles).
The first three observations of the week are spectral scans of
Jupiter’s
bright limb, performed by the Near-Infrared Mapping Spectrometer
(NIMS).
Like observations performed on Sunday, May 21, these scans will be used
to
provide scientists with data on the bulge created at Jupiter’s equator
as
Jupiter rotates once every 10 hours. NIMS follows these observations
with
a series of 10 spectral scans of Jupiter’s north polar region. The
series
consists of 10-minute samples separated by 60 minutes, and is designed
to
capture auroral activity.
Interspersed with the aurora observations are three global observations
performed by NIMS and three Great Red Spot observations performed by
the
Solid-State Imaging camera (SSI). Taken together, the global
observations
performed by NIMS will map a substantial proportion of the complete
range
of longitudes of the planet. The Great Red Spot observations performed
by
SSI will provide scientists with high spatial and time resolution
images of
this storm, which is over 400 years old. Similar observations were
taken
at the beginning of Galileo’s orbital tour in June 1996, so scientists
will
be able to observe long-term changes in the characteristics of the
Great
Red Spot. The Great Red Spot is so large that the Earth fits two times
across it!
A brief interlude from Jupiter is afforded to SSI to obtain a set of
global
images of Europa through four different color filters. The images will
fill in a gap in existing global color coverage between 120 and 230
degrees
longitude. Five more Jovian equatorial bulge observations are then
performed by NIMS. The first three occur on Monday night, with the
remaining two performed on Tuesday morning. Next, SSI takes a set of
global images through different color filters that capture Europa while
eclipsed from the Sun by Jupiter. The observation should help
scientists
search for auroral glows in Europa’s tenuous atmosphere. These glows
would
be produced by the interaction of atmospheric gases with Jupiter’s
magnetosphere, and may produce current flow between Europa and Jupiter.
The geometry and timing of this observation are superior to those of
similar observations taken earlier in the mission.
SSI’s eclipse observation brings to a close the bulk of this
encounter’s
observing. In previous encounters, playback of recorded data was
initiated
at this point. But Galileo is not yet finished collecting data. The
Fields and Particles instruments will continue observing for nearly one
month. This will allow them to extend their typical survey of the
inner
magnetosphere (performed at each encounter) through the outer
magnetosphere, and through the transition from inside Jupiter’s vast
magnetosphere into the solar wind. Some data will be returned in
realtime
and some will be placed on the tape recorder for return after the
conclusion of the survey.
The survey is interrupted once during the remainder of the week. On
Wednesday, the spacecraft will perform a flight path adjustment, if
needed.
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.
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:
