Cassini Status Update
10 Mar 2009
(Source: Jet Propulsion Laboratory)
Cassini Significant Events for 03/04/09 - 03/10/09
The most recent spacecraft telemetry was acquired on Mar. 10 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/operations/present-position.cfm.
Wednesday, March 4 (DOY 063):
Attitude and Articulation Control Subsystem (AACS) engineers
performed annual calibration tests on the Cassini Inertial Reference
Unit today. Results of the test showed continuing normal performance.
Once this activity was complete, the Imaging Science Subsystem (ISS),
Composite Infrared Spectrometer (CIRS), and Visual and Infrared
Mapping Spectrometer (VIMS) observed the F-Ring, then the Ultraviolet
Imaging Spectrograph (UVIS) mapped the volatiles in the immediate
neighborhood of Enceladus in order to test the connection of volatile
changes to plume eruptions.
Although not an image acquired by Cassini, the Astronomy Picture of
the Day for Mar. 4 gave a good depiction of what Saturn currently
looks like through a telescope. At opposition on Mar. 8, Saturn
rises at sunset and sets at sunrise, offering many hours of viewing
enjoyment! If you don't have access to a telescope, contact one of
the 400 members of the Cassini Saturn Observation Campaign to find
out where a viewing event will take place near you. See http://saturn.jpl.nasa.gov/Education/saturnobservation/volunteermembers/ and http://antwrp.gsfc.nasa.gov/apod/ap090304.html.
Thursday, March 5 (DOY 064):
How is it that at one moment Cassini can be found nearly at apoapsis,
the farthest point from Saturn in an orbit, and within a day, be at
periapsis, the closest point to Saturn in an orbit, when its orbital
period is around 16 days? Well, it is happening at the end of March
this year. On DOY-86, Mar. 27, the Titan 51 targeted flyby will
occur. Just a few hours later, apoapsis and the start of orbit #107
would have occurred. However, because of the gravitational influence
of Titan during the flyby, Cassini's orbit is modified such that
apoapsis on the new Saturn centered orbit occurs prior to the Titan
encounter, on an orbit different from the one Cassini actually flew.
For orbit 107, on DOY-87, Mar. 28, Cassini is now at the closest
point to Saturn in that orbit. The above scenario is unique in the
history of the project and will not occur again before the end of the
extended mission. The fact that Cassini's orbit about Saturn is very
nearly circular at this time is what enables this rather curious
sequence of events.
Friday, March 6 (DOY 065):
An Uplink Readiness Review was held today which led to final approval
for the RCS thruster swap to the B branch.
Along with Orbit Trim Maneuver (OTM) #183, commands for the opening
of Latch Valve 41 (LV41) were sent to the spacecraft today. The LV41
commands will execute on Mar. 10 and will enable the flow of
hydrazine to the B-branch thrusters.
Monday, March 9 (DOY 068):
A kick-off meeting was held today as part of the Science Operations
Plan (SOP) process for S53. In addition, all participating teams
delivered files and products for the Port 1 delivery as part of the
SOP process for S52.
Orbit Trim Maneuver (OTM) #183 was performed today. This is the
maneuver setting up for the Titan 51 encounter on Mar. 27. The main
engine burn began at 2:30 AM PDT. Telemetry immediately after the
maneuver showed the burn duration was 29.88 seconds, giving a delta-V
of 5.02 m/s. All subsystems reported nominal performance after the
Following the execution of OTM-183, a red alarm was detected in
association with one of the temperature sensors on the main engine
combustion chamber, and it appears that one of the two redundant
sensors has failed. This will have no effect on the planned RCS swap
to the B side, nor to any future operation of the main engine. It
does mean that there is now one less level of redundancy in
monitoring the performance of the prime main engine.
Science observations today included a 3-hour observation by ISS,
CIRS, and UVIS to attempt to observe the illusive Rhea ring. An
additional six hours focused on Rhea will occur tomorrow. In
addition, The Cosmic Dust Analyzer (CDA) took data as Cassini passed
through the ring plane.
Tuesday, March 10 (DOY 069):
After LV-41 was verified open today via telemetry, several files were
sent to the spacecraft to set the catalyst bed heaters for the
B-branch to "Auto" or "ON" except for when the thruster fires,
deactivate the S48 background sequence, and load the mini-background
sequence that will execute from DOY 70-76. The last two files will
take effect Mar. 12, just prior to AACS branch swap commanding when
the B-branch will be made prime.
The next and final live update in S48 was for Enceladus on DOY-080.
After analyzing the orbit determination solution from DOY-067,
Science Planning has determined that an update to pointing is not
necessary and has recommended that the live update be cancelled.
Visit the JPL Cassini home page for more information about the
Cassini Project: http://saturn.jpl.nasa.gov/