Cassini Update - November 17, 2006

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Cassini Significant Events 
for 11/09/06 - 11/15/06

The most recent spacecraft telemetry was acquired Wednesday, November 15,
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 located at
http://saturn.jpl.nasa.gov/operations/present-position.cfm .

Thursday, November 9 (DOY 313):

Cassini passed by Enceladus today at an altitude of 91,500 km. Additional
non-targeted flybys included Tethys and Calypso.

Orbit Trim Maneuver (OTM) #80 was performed today. This is the first of
three maneuvers setting up for the Titan 21 encounter on December 12. The
main engine burn began at 7:45 AM PDT. Telemetry obtained after the maneuver
showed a burn duration of 22.7 seconds, giving a delta-V of approximately
3.6 m/s, as designed. All subsystems reported nominal performance after the
maneuver.

The Spacecraft Operations Office (SCO) held a tabletop walkthrough today.
The team went through the Deep Under-voltage System Fault Protection
response. The purpose was to provide training for the team in understanding
how the spacecraft responds in a deep UV scenario, and the final spacecraft
states after safing completes. This activity is part of SCO ongoing
refresher training, and operational readiness tests to exercise and train
new and "old" members of the spacecraft team.

The DSN/Goldstone Cassini track over station DSS-14 was cut short today in
order to support an MGS request for additional 70m coverage. However, the
DSN schedulers were able to obtain additional time for Cassini over DSS-15
from 09:45 to 18:45. Due to the differences in antenna capabilities, a real
time command was uplinked to change the telemetry mode compatible with the
change from DSS-14 to DSS-15. Additional time was also obtained for Cassini
on DOY 315, this time for additional DSS-14 coverage from 09:30 to 13:05. A
command will be sent on that day to implement the telemetry mode change from
DSS-15 to DSS-14.

Last week it was reported that Cassini gave up DSN coverage over DOY 311 as
a result of the MGS anomaly. The result was loss of science and engineering
data from DOY 311 for about 4 hours and 35 minutes, plus an additional loss
over DSS-65 on DOY 312 due to rain in Spain. The impact to science is a loss
of a portion of a Composite Infrared Spectrometer ring observation, a loss
of an Imaging Science Subsystem Ring observation, loss of some real time
Magnetospheric and Plasma Science data, and loss of the Radio and Plasma
Wave Science (RPWS) whistler observation. This particular RPWS observation
included intentional transitions to and from reaction control subsystem
control instead of being on reaction wheels. A whistler is caused by a
lightning stroke. It emits a low frequency emission that allows RPWS to
remotely sense plasma density. Normally, plasma density can only be sensed
by RPWS in the vicinity of the instrument on board the spacecraft.

Friday, November 10 (DOY 314):

The Caltech Pre-College Science Initiative completed its yearlong evaluation
of the Cassini language arts unit "Reading, Writing & Rings" (RWR). The
evaluation noted that teachers find the materials to be of high quality and
that RWR improved attitudes toward science and reading. However, the current
high stakes testing atmosphere in classrooms makes implementation difficult.
The team that produced RWR will work to address teachers' needs and the
realities of schooling to improve implementation and explore RWR uses
outside formal educational settings such as after school settings, museums,
and amateur astronomy groups.

Monday, November 13 (DOY 317):

An image of a hurricane-like storm over Saturn's south pole is Astronomy
Picture of the Day today. 

The final approval meeting was held today for S26. The sequence will be
uplinked on November 21, and will begin execution on Friday, November 24.

Tuesday, November 14 (DOY 318):

The topic at the Mission Planning Forum this week was Titan minimum
altitudes during extended mission. Existing models and tumble densities have
been extrapolated for the extended mission to get a feel for what altitudes
will be acceptable, versus the 1000 km baseline that was delivered to the
tour designers for study purposes. This is likely to be an ongoing topic of
discussion in future meetings.

The patch to Cosmic Dust Analyzer instrument flight software version 10.4
will run onboard the spacecraft today and tomorrow. Results will be reported
over the next several weeks.

A delivery coordination meeting was held today for an upgrade to the Cassini
Archive Tracking System (CATS). This version of CATS contains a number of
changes and new capabilities. The driver for this delivery stems from the
need to gather more information about what is being archived and how much.
This delivery also includes some changes requested by the users. 

Wednesday, November 15 (DOY 319):

The S29 Science Operations Plan Update process kickoff meeting was held
today. The process will run for approximately eight weeks and will conclude
on January 12 of 2007.

An AACS friction test on the prime reaction wheels, numbers one, two, and
four, was run onboard the spacecraft today. In this test, performed every
three months, the wheels are spun up to 900 rpm in both directions and timed
as they are allowed to run down to zero. The longer the rundown time, the
better. For this exercise, AACS updated the custom telemetry schedule to
obtain data at a 1 Hz frequency to support characterization in the frequency
domain.

Wrap up:

Check out the Cassini web site at http://saturn.jpl.nasa.gov for the latest
press releases and images.

The Cassini-Huygens mission is a cooperative project of NASA, the European
Space Agency and the Italian Spsce Agency. The Jet Propulsion Laboratory, a
division of the California Institute of Technology in Pasadena, manages the
Cassini-Huygens mission for NASA's Science Mission Directorate, Washington,
D.C.  JPL designed, developed and assembled the Cassini orbiter.

 
 




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