Cassini Significant Events 12/21/05 - 01/04/06

January 6, 2006

(Source: Cassini Project)

The most recent spacecraft telemetry was acquired Wednesday, January 4, 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 .

Cassini Significant Events 12/21/05 - 01/04/06

Due to the holidays, no Significant Events report was generated last week.
The report this week covers 15 days from December 21, 2005 through January
4, 2006. Hang on, it's gonna be a long report!

Wednesday, December 21 (DOY 355):

Uplink Operations personnel sent commands to the spacecraft today to perform an on-board live Inertial Vector Propagation (IVP) update. The update will execute on DOY 358/359 and will update vectors for Dione, Tethys, Enceladus,
Saturn, and Telesto.

Science activities today included a distant observation of Hyperion involving all Optical Remote Sensing (ORS) instruments, and Imaging Science Subsystem (ISS) tracks of many small moons as part of the Satellite Orbit
Determination Campaign.

Thursday, December 22 (DOY 356):

A preparation meeting was held today for Orbit Trim Maneuver (OTM) 047. The
maneuver is scheduled to execute on December 29.

Friday, December 23 (DOY 357):

The RADAR instrument performed an engineering test that will address radiometer calibration issues using Saturn as a reference target.

Saturday, December 24 (DOY 358):

Today marked the start of the annual sequence development hiatus. The Aftermarket, Science Operations Plan Update (SOPU), and Science and Sequence Update Process will pause activities from today through January 2, 2006.
The processes will begin again on January 3. Early on in the tour, program
management identified the difficulty of trying to conduct this type of
development over the Christmas and New Year's holidays due to varying
vacation schedules and the different holiday schedules of our foreign
partners. As a result, each year a pause is built in to the development
schedules that lasts for about two weeks during this time. Operations work
continues, OTMs, real time commanding, downlink, etc. It's just these three
processes that pause. Well, OK, we do cancel a few meetings(:>)

Non-targeted flybys of Enceladus and Pallene occurred today. The Enceladus
flyby was at an altitude of 93,984 km.

Whoa. It's been a year. Today is the one-year anniversary of the Huygens
Probe release! For those of you who would like to remember where we were
last year at this time, here is an extract from the Significant Events
report for December 24, 2004, Christmas Eve:

Everything looks good and nominal.

JPL provided dinner for those of us who had to work. There was slight
congestion at the dessert table, but everything else was nominal.

All Orbiter instruments reported in. Everyone is in the correct
configuration and is ready for release.

The project set up a conference line so that Cassini flight team members who
are not working the event but who came in anyway to show their support can
listen in on events as they unfold.

The Huygens Probe was successfully deployed from the Cassini Orbiter!
Navigation and Spacecraft Operations Office teams confirmed the nominal
separation of the Probe at 7:24 Pacific time. The Probe is now in free
flight at a spin rate of 7.5 rpm as detected by the Magnetometer Subsystem.
All systems performed as expected, there were no problems reported with the
Cassini spacecraft, no red alarms, no fault protection. Congratulations

After release, the Uplink Operations (ULO) sequence lead called for the
start of planned Probe optical navigation imaging. This is a 4.5 hour
process. Currently we are on schedule.

The head of the Huygens Spacecraft Operations Unit expressed his thanks to
the team for a wonderful adventure in the exploration of Saturn. Huygens
personnel are now waiting with great expectation for the Probe descent on
January 14, 2005.

Sunday, December 25 (DOY 359):

Non-targeted flybys of Helene and Telesto occurred today.

Science activities today included a Composite Infrared Spectrometer (CIRS)
Saturn Tethys F-Ring movie, and the first of three Radio Science Subsystem
(RSS) Gravity Science Enhancement passes on and after Christmas - DOY 359,
361, and 362. These are additional downlink passes at Ka-band to obtain
Titan gravity science.

Monday, December 26 (DOY 360):

On December 26, Cassini flew by Titan at an altitude of 10,409 kilometers.
At this time, the Imaging Science Subsystem (ISS) acquired a mosaic of
Titan's albedo features Aztlan and Quivira, Bazaruto and Elba Faculae, and
Omacatl Macula, at low phase angles of approximately 25 degrees and pixel
resolution scales of approximately 700 to 450 meters. This ISS observation
also overlaps eastern portions of the Titan A and Titan 3 RADAR swaths. The
Composite Infrared Spectrometer (CIRS) obtained information on trace
constituents in Titan's stratosphere. An integration of the limb obtained
information on CO, HCN, and CH4. The Ultraviolet Imaging Spectrograph
(UVIS) used its Hydrogen-Deuterium Absorption Cell (HDAC) to conduct key
measurements of the Titan atmosphere as well. Measurements of the D/H ratio
in the Titan atmosphere will yield clues to the formation and history of
Titan and the Saturnian system. The Visual and Infrared Mapping
Spectrometer (VIMS) also obtained a medium resolution regional map using the
same observing strategy as the previous Titan flyby.

Moreover, this Titan flyby presented an excellent diametric wake crossing at
5.04 Titan radii downstream for all of the Magnetospheric and Plasma Science
(MAPS) instruments, which will be ideal for comparisons to the Voyager-1
Titan flyby data set. Cassini's encounter possessed similar observing
geometry as the encounter of Voyager-1 in November 1980. Especially with
the increased capability of Cassini, the MAPS instruments will finally be
able to compare the Cassini and Voyager data sets to further study Titan's
atmospheric loss and the structure of Titan's plasma wake. But more
importantly, this flyby will represent the only crossing of Titan's
magnetotail at an intermediate distance in the Cassini tour, which will be
highly valuable for the study of the formation of Titan's magnetotail as a
function of distance.

Tuesday, December 27 (DOY 361):

It was reported today at the weekly Operations Status and Coordination
meeting that data from the Titan 9 flyby yesterday has been successfully
downlinked. In particular UVIS reported that they had received the entire
HDAC observation data set. There were several gaps of less than one minute
due to some problems at DSS-14, but nothing that required the implementation
of the contingency plans and procedures that had been developed and reported
on last week.

Wednesday, December 28 (DOY 362):

An article was presented in the December 27 Aerospace Daily & Defense Report
stating that NASA is considering a two-year extension to the Cassini mission
that would extend the exploration of Saturn and its moons through 2010.
"NASA has given us some additional funding to study what the options would
be" for the extra two years, said Bob Mitchell, Cassini program manager at
the Jet Propulsion Laboratory in Pasadena, Calif. The spacecraft's lifetime
ultimately will be determined by what kind of follow-on mission, if any, is
carried out. "If we put together a tour that would look very much like what
we're doing now - a Titan flyby every month or so and an icy satellite flyby
stuck in here and there - then another two years would probably about run us
out of propellant. However, if the spacecraft is placed in a fairly
uneventful orbit and dedicated to studying Saturn's ring system, for
example, it could likely last years longer." he said.

Thursday, December 29 (DOY 363):

OTM-047 was successfully performed today. This was the cleanup maneuver
from the Titan-9 flyby that occurred on December 26. The reaction control
subsystem (RCS) burn began at 7:55 pm Pacific Time. Telemetry obtained
immediately after the maneuver showed the burn duration was 198.9 seconds,
giving a burn delta-V of 0.179 m/s. All subsystems reported nominal
performance after the OTM.

Beginning today and running through January 4, science activities involve
the entire suite of MAPS instruments simultaneously performing low-rate
outer magnetospheric surveys to observe the variability of magnetospheric
boundaries at a variety of radial distances. Optical remote sensing
activities include ISS observations of a mutual event capturing Janus
crossing Dione, many photometric calibrations done with a variety of stars,
and narrow-angle camera lightning searches in Saturn's northern hemisphere.
Finally, UVIS will obtain mosaics of Saturn's inner magnetosphere.

Friday, December 30 (DOY 364):

Today is the fifth anniversary of the Cassini flyby of Jupiter on December
30, 2000.

Saturday, December 31 (DOY 365):

Documenting a year at Saturn, Astronomy Picture of the Day selected for
their picture today an image of Saturn's moon Dione in front of edge-on
rings and the cloud tops of Saturn draped with broad ring shadows. It's
very cool!


Sunday, January 1 (DOY 001):

This feels more like a Christmas present than a report of what to expect in
the New Year! In 2006 Cassini will execute all or part of 10 on-board
sequences from S17 through S26, and all or part of 18 orbits of Saturn from
Rev 19 through Rev 36 will occur. During this time there will be 13
targeted flybys of Titan including T10 through T22, 20 non-targeted flybys
including Helene, Rhea, Polydeuces, Tethys, Telesto, Titan, Atlas, Calypso,
Enceladus, Methone, and Dione, 39 opportunities for maneuvers from OTM-048
through OTM-086, the start of extended mission development will begin in
January, one superior conjunction will occur in August, and finally a
partridge in a pear tree will occur next December. (:>). Should be a busy

Monday, January 2 (DOY 002):

OTM-48, originally scheduled for today, was cancelled back in early November
along with OTM-54 and OTM-60. This was done because there were only three
DSN tracks between the cleanup and apoapsis maneuvers, delivery errors did
not improve after the apoapsis maneuver, and the maneuvers would be
difficult to cancel in real time. The delta-V cost was about 0.8 m/sec.
The capability to execute a maneuver on the planned prime and backup passes
was retained but proved unnecessary for OTM-048. Spacecraft Operations and
Navigation will re-evaluate OTMs 54 and 60 as necessary.

Tuesday, January 3 (DOY 003):

Dark terrain on Iapetus was selected as Astronomy Picture of the Day today.

Flight software (FSW) normalization for CIRS and the Cassini Plasma
Spectrometer (CAPS) was begun today and will continue through January 6.
There are four copies of an instrument's FSW in partitions 0 through 3 on
each SSR. When the instrument team has a new version of FSW, it is uploaded
into 2 of the partitions, in this case partitions 2 and 3, leaving copies of
the old software on 0 and 1. The old version is retained until the
instrument team performs a flight software checkout and confirms the new
version. After the confirmation, "normalization" is performed where the new
version replaces the old version in the remaining partitions on both SSRs,
in this case 0 and 1.

Wednesday, January 4 (DOY 004):

The Science Operations Plan Update process for S20 kicked off today. The
process will run for five weeks and will conclude on February 10.

Wrap up:

Check out the Cassini web site at for the latest
press releases and images.

The Cassini-Huygens mission is a cooperative project of NASA, the European
Space Agency and the Italian Space 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.