Cassini Significant Events
for 02/11/09 - 02/17/09

The most recent spacecraft telemetry was acquired
on Feb. 17 from the Deep Space Network tracking
complex at Goldstone, California. The Cassini
spacecraft is in an excellent state of health.
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/mission/presentposition/.

Wednesday, Feb. 11 (DOY 042)

A two-day NASA Senior Review of a proposal for a
Cassini Extended Extended Mission (XXM) concluded
today. The review board's comments and questions
indicated that they were quite impressed with the
science, science team, and technical
presentations, and that they understood and
appreciated the XXM plans, rationale, and
concerns. Within a month the final review board
report should be available and some time after
that a final decision is expected from NASA Headquarters.

Eight Instrument Expanded Block files in support
of S48 were uplinked to the spacecraft today.
Proper receipt and registration to the SSR has
been verified. The background sequence will go up
late Thursday night, and S48 will begin execution next Tuesday.

Thursday, Feb. 12 (DOY 043):

Science Planning has analyzed the Navigation
Team's orbit determination solution released last
Monday. Based on the results, the live inertial
Vector Propagator update currently scheduled for
DOY-056 need not be performed. All errors are
significantly less than 2.4 mrad. The necessary
instrument teams have concurred so the update has been cancelled.

Files were delivered for the second of two input
ports as part of the S51 Science Operations Plan
process. A merge of all the files will be released tomorrow for team
review.

The Composite Infrared Spectrometer (CIRS)
observed the rings today for 11 and a half hours
at 45 degrees north latitude at high phase. This
was part of a paired observation designed to look
at both the lit and unlit sides of the rings at
similar geometries to study the vertical thermal
distribution within the rings. Part two of this
observation occurs Saturday where CIRS will
observe the rings for 9 =BD hours at 45 degrees
south latitude at high phase. How much sunlight
is absorbed as it passes through the rings?
Answering this question will help us understand
ring dynamics and ring particle properties.

Friday, Feb. 13 (DOY 044):

A non-targeted flyby of Titan occurred today.

Sunday, Feb. 15 (DOY 046):

Today the Optical Remote Sensing instruments
participated in a Titan cloud monitoring
observation. This campaign contained observations
that are typically requested when Titan is at low
phase and when the Cassini spacecraft is around
one to two million km away from Titan. These
observations provide isolated snapshots and are
intended to improve our understanding of how
often there are clouds on Titan, where they're
appearing as the seasons change, how fast and in
what direction the winds blow, and also how the
haze evolves with the season.

Tuesday, Feb. 17 (DOY 048):

The S47 sequence concluded and S48 began
execution today at 2009-048T12:35 SCET. The
sequence will run for 37 days and conclude on
Mar. 26. During that time there will be no
targeted encounters and only one non-targeted
flyby of Titan on DOY-080. Two maneuvers are
scheduled, numbered 183 and 184. It is fortunate
that S48 is light on flybys. This allowed the
Spacecraft Team time to select a window to
perform the upcoming thruster branch swap.

Work continued this week on planning for the swap
to the thruster B-branch with nominal and
contingency file generation, Flight Software
Development System testing, procedure
preparation, and internal reviews. The actual
swap is scheduled to begin Mar. 12. Two periodic
engineering activities, originally scheduled to
occur in what has become the swap timeframe, have
been rescheduled. Periodic Engineering
Maintenance-A, originally set for Mar. 12, will
now occur on Mar. 23. The back up gyro
calibration, originally set for Mar. 14, will now
occur on Oct. 4 during the execution of S53.

Visit the JPL Cassini home page for more
information about the Cassini Project:
http://saturn.jpl.nasa.gov/>" target="new">http://saturn.jpl.nasa.gov/>http://saturn.jpl.nasa.gov/>
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