Cassini Significant Events 08/31/06 - 09/06/06

September 8, 2006

(Source: Cassini Project)


The most recent spacecraft telemetry was acquired Wednesday, Sept. 6,
from the Goldstone tracking stations. The Cassini spacecraft is in an
excellent state of health and is operating normally. Information on the
present position and speed of the Cassini spacecraft may be found on the
"Present Position" web page at
http://saturn.jpl.nasa.gov/operations/present-position.cfm .

Thursday, Aug. 31 (DOY 243):

The Titan 17 flyby, scheduled for Sept. 7, is set for an altitude of
1,000 km. This flyby is at the relatively low latitude of 23 degrees, in the
region where the Titan atmosphere model predicts a greater atmospheric
density. If the results from this flyby indicate that is true, as measured
by the ACS thruster duty cycle and INMS instrument data, trajectory changes
will be considered for Titan 20, which is at 1030 km altitude, but almost
equatorial at 7.5 degrees. A new candidate reference trajectory has been
developed with an increase in the altitude of the Titan 20 flyby from 1030
to 1055 km. The final decision to raise the T20 altitude, or not, will occur
at the Titan Atmosphere Model Working Group meeting on Sept. 11. If the
decision is to raise the altitude, the new trajectory will go into effect on
Sept. 12.

Spacecraft Operations Office personnel held an Exciter RF Loss tabletop
exercise today. This is the first in a periodic sequence of such exercises
for SCO training.

The Radio Science Subsystem (RSS) performed the first of three Operational
Readiness Tests (ORT) today using the Deep Space Network antennas at
Goldstone. Tests two and three will be performed Saturday and Sunday. These
ORTs are used to prepare for the RSS Saturn gravity observation on Sept.
9.

Friday, Sept. 1 (DOY 244):

The S23 sequence leads made the decision to give up the last hour of the
Cassini DSN track over Goldstone today to accommodate station maintenance
work. A glitch with the transmitter was preventing successful uplink of
command files. Maintenance will go toward ensuring the station is available
for the maneuver uplink on Monday. According to Science Planning, only
real-time data was lost. The recorded data will be played back from the SSRs
with no loss.

Monday, Sept. 4 (DOY 247):

Orbit Trim Maneuver (OTM) #70 was performed today. This is the minus 3-day
maneuver setting up for the Titan 17 encounter on Sept. 7. The reaction
control subsystem burn began at 12:45 PM. Telemetry immediately after the
maneuver showed the burn duration was 164.1 seconds, giving a delta-V of
approximately 227.6 mm/s. All subsystems reported nominal performance after
the maneuver.

The Imaging Science Subsystem (ISS) began a 12.5 hour observation of
Saturn's Ring System today. Images of the unlit face of the Cassini Division
at high phase were taken once every 8 minutes. This observation will be used
to search for dust, clumps and variations in the structure of the outer B
Ring.

Tuesday, Sept. 5 (DOY 248):

The kickoff meeting was held today for the S23 Enceladus/Tethys Live
Inertial Vector Propagator (IVP) update for DOY 252-253. The final orbit
determination solution became available last Thursday, and analysis is
scheduled to begin later today. Navigation has recommended that teams look
at the size of the uncertainties as part of the decision process to perform
or not perform the update.

A beautiful image of the white cliffs of Dione was Astronomy Picture of the
Day today.

Wednesday, Sept. 6 (DOY 249):

The Spacecraft Operations Office has requested the S25 sequence lead to
schedule a test of the Titan 20 flyby in the Integrated Test Laboratory.

The Project Briefing, the final meeting held as part of the Science
Operations Plan Update process, was held today for S26. Input products for
the sequence will be handed off to the sequence leads at the end of this
week, and the final development process will kick-off on Sept. 12.

Today concluded with the spacecraft on approach to Titan for the T17
encounter, an inbound flyby. The Composite Infrared Spectrometer (CIRS)
began a 7+ hour activity to obtain information on the thermal structure of
Titan's stratosphere, with ISS and the Visual and Infrared Mapping
Spectrometer (VIMS) taking advantage of the spacecraft pointing to gather
data on Titan.