Cassini Significant Events
for 08/27/08 - 09/02/08
The most recent spacecraft telemetry was acquired on Sept. 2 from the
Deep Space Network tracking complex at Madrid, Spain. The Cassini
spacecraft is in an excellent state of health and all subsystems are
operating normally.
Information on the present position and speed of the Cassini
spacecraft may be found on the “Present Position” page at:
http://saturn.jpl.nasa.gov/operations/present-position.cfm.
Wednesday, Aug. 27 (DOY 240):
An AACS piggyback gyro calibration was completed today. The term
“piggyback” is applied when the calibration is combined with an
activity that already turns the spacecraft. Sometimes a separate
calibration activity is scheduled with independent turns specifically
for that activity.
The kick-off meeting for the S48 Science Operations Plan
implementation process was held today. The process will run for
about twelve more weeks and conclude on Nov. 21. At that time the
final sequence development process will begin. S48 begins execution
on board the spacecraft in February of 2009.
Using the latest Navigation orbit determination solution for the
result of maneuver 164, analysis has been performed on a proposed
live update due to execute on DOY-254. Both the prime instrument for
this time frame, the Ultraviolet Imaging Spectrograph (UVIS), and
Science Planning have recommended a “no go” so the update has been
cancelled.
A combined Optical Remote Sensing (ORS) campaign to look for auroras
in Saturn’s south polar region filled up eleven and a half hours of
observation time today. The day concluded with an Optical Navigation
(OPNAV) image. OPNAVs are images taken by the narrow-angle camera of
one of Saturn’s moons against a star background. Analysis of these
images allows the Navigation team to make more accurate estimates of
the orbital paths of both the moons and the spacecraft.
Thursday, Aug. 28 (DOY 241):
Science today began with a nearly nine-hour Composite Infrared
Spectrometer (CIRS) observation of Saturn’s rings. This was
followed with a five-hour joint ORS observation of Saturn’s moon
Rhea. Rhea appears as a thin crescent, which provides the ORS
instruments views of unique shadows as well as the “night side” of
the moon.
Saturday, Aug. 30 (DOY 243):
The Cassini Plasma Spectrometer (CAPS), which is one of the four
Magnetospheric and Plasma Science (MAPS) instruments, took control of
the spacecraft to point its sensors toward the magnetic field of
Saturn. This was followed by an ISS on-going campaign to further
deduce the orbits of some of the lesser-known satellites of Saturn.
Science activities concluded with a thirteen hour “movie” of Saturn’s
F ring by three instruments: Visual and Infrared Mapping Spectrometer
(VIMS), CIRS, and ISS.
Sunday, Aug. 31 (DOY 244):
A non-targeted flyby of Titan occurred today.
Titan composition observations performed by CIRS began today’s
science activities. This was a seven-hour long series of infrared
images of Titan’s mid-southern latitudes. ISS and CIRS then
continued their long-term temporal monitoring of the F ring.
Monday, Sept. 1 (DOY 245):
Solar conjunction occurs during the week of Sept. 1 as the
Sun-Earth-Probe (SEP) angle drops below 3 degrees. Approximately once
a year the orbital motions of Earth and Saturn create an alignment
where the sun blocks the view of Earth as seen from Saturn and the
Cassini spacecraft. In preparation for this, the command loss timer
was set to 10 days from the normal 90 hours on Aug. 30. It will be
decremented daily during the conjunction period until Sept. 7, when
it will be returned to the normal value. Spacecraft operating rules
during this period fix spacecraft pointing to Earth. With this, the
MAPS and Radio Science instruments will be the only ones performing
science observations during the conjunction period. This particular
orientation is generally not usable by the other instruments.
Tuesday, Sept. 2 (DOY 246):
A non-targeted flyby of Janus occurred today.
On this the second day of solar conjunction, the spacecraft continued
to be Earth-pointed with science activities restricted to
Magetospheric and Plasma Science (MAPS) and Radio Science
observations. Later today, the SEP angle will drop to 2 degrees.
Minimum separation will occur tomorrow at 1.67 degrees.
Visit the JPL Cassini home page for more information about the
Cassini Project: http://saturn.jpl.nasa.gov/