Cassini Significant Events 03/11/09

As part of the RCS thruster swap activities, the background sequence was
deactivated today. The last science observations to be performed before the
instruments were either put to sleep or switched off were an Imaging Science
13.5 hour movie of the F-Ring with the Composite Infrared Spectrometer and

On Mar. 12, the B branch RCS thrusters on board Cassini were made prime.
>From Mar. 13 through Mar. 15, on board activities centered on exercising and
verifying the newly activated hardware. Reaction wheel momentum biases were
performed, and the spacecraft was commanded to hold fixed pointing attitudes
within various deadbands for about an hour each. After the deadbanding
tests, the spacecraft performed fast and slow turns about each of the X, Y,
and Z-axes. Cleanup commands were issued, and preparation for the
reactivation of the S48 background sequence occurred Mar. 15. All
activities completed normally. For more on the thruster swap link to:

A meeting was held today to discuss the thruster swap outcome. With
Spacecraft Office and Project Management's concurrence, the swap to the
backup thrusters was deemed complete and successful. A go-ahead was given to
uplink and re-activate the S48 background sequence and awaken the science
instruments. The necessary files were radiated to the spacecraft after the

An update on dust hazard periods during the extended or Equinox mission and
beyond was presented today at the Mission Planning Forum.

Orbit Trim Maneuver (OTM) #183x was performed today. This is a cleanup
maneuver from OTM-183 on Mar. 9. The Reaction Control Subsystem burn began
at 6:14PM PDT. Telemetry immediately after the maneuver showed the burn
duration was 12.75 seconds, giving a delta-V of 21.64 mm/s. This was an
extra unplanned maneuver inserted into the timeline one week prior to
OTM184, the last maneuver prior to the T51 Titan flyby. Since OTM184 would
otherwise have been the first RCS maneuver to be performed after the
thruster swap, this extra maneuver was added to provide time margin in the
event of any surprises associated with the first maneuver on the new
thrusters. In fact the maneuver was performed flawlessly and OTM184 will
very likely not be required.

A command approval meeting was held today for the nine instrument expanded
block files to be uplinked in support of S49. Uplink will begin on Mar. 19,
the background sequence will go up on Mar. 22, and sequence execution will
begin on Thursday, Mar. 26.

Commands to re-activate the S48 background sequence executed last night.
While observing telemetry, and just before the pass ended, the sequence
leads were able to observe the completion of the first two commands issued
from the background sequence.

Saturn Related:

The March 2009 What's Up podcast is all about Saturn. It spans from
Galileo's first views of Saturn 400 years ago to Cassini at Saturn right now!
http://www.jpl.nasa.gov/video/index.cfm?id=821.

The Hubble Telescope released gorgeous images of Saturn taken
just a few weeks ago while four of Saturn's moons crossed in front of the
planet. Here is the Hubble news release:
http://www.jpl.nasa.gov/news/news.cfm?release=2009-051.

Finally, if you haven't seen Saturn yet, here is the Viewing Saturn in 2009
viewing guide:
http://saturn.jpl.nasa.gov/Education/saturnobservation/viewing2009/ .

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Cassini Significant Events 03/11/09 - 03/17/09