Cassini Significant Events -- 05/04/06 - 05/10/06

May 12, 2006

(Source: Cassini Project)


The most recent spacecraft telemetry was acquired Wednesday, May 10, 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, May 4 (DOY 124):

On Wednesday, May 3, the Titan Orbiter Science Team (TOST) held a Titan
flexibility workshop to discuss possible changes to future Titan flyby
sequences based on the current data. No changes were made to the existing
plans.

We all know Earth rotates once every 24 hours, but scientists have long had
difficulty pinpointing how long a day is on Saturn. The Magnetometer
Subsystem (MAG) has, for the first time ever, measured a periodic signal in
Saturn's magnetic field, key information to finally understanding the length
of a Saturn day and the evolution of this gaseous planet. The latest
research suggests a Saturn day is 10 hours, 47 minutes, 6 seconds, plus or
minus 40 seconds. That's 8 minutes slower than NASA Voyager results from the
early 1980s, and slower than previous estimates from another Cassini
instrument. The magnetometer results provide the best estimate of the Saturn
day to date, because it can see deep inside Saturn. These Cassini results
can be found in the May 4 issue of the journal Nature. For more information
link to:
http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=656

Science Planning provided updated numbers for the data recovered from the
Titan 13 flyby last week. Without the playback recovery plan in place, the
science teams would have lost ~2500Mbits out of 3500, or approximately 70%
of the TOST segment, almost all of the closest approach data including
almost all of the Synthetic Aperture RADAR (SAR), and all of the Ultraviolet
Imaging Spectrograph (UVIS) stellar occultation. With the playback recovery
plan in place, this was reduced to ~600Mbits of TOST data lost, or
approximately 17%, and ~2100Mbits of Cross Discipline (XD) data including
Icy Satellite and Rings data. Only the Visual and Infrared Mapping
Spectrometer (VIMS) data was saved of the XD set. Of the 600Mbits lost,
almost 500Mbits of that was the earliest inbound data of the flyby and only
about 100 Mbits were lost from -27 minutes to -12 minutes affecting the
start of the SAR swath.

NASA, the European Space Agency, and the University of Arizona have released
a joint image advisory with two phenomenal movies. The movies show the
dramatic descent of the Huygens probe to the surface of Saturn's moon Titan
on Jan. 14, 2005. To view the movies and for more information link to:
http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=655

Friday, May 5 (DOY 125):

Cassini Outreach participated in two National Space Day events on May 4-5.
On May 4, over 3,000 students from Washington DC area schools as well as
1,000 NASA Explorer school students and teacher teams attended a Space Day
event at Goddard Space Flight Center. On May 5, over 15,000 students and
families from the Washington DC and Northern Virginia area attended a Space
Day event at the Smithsonian Institution's Udvar-Hazy Aerospace Museum in
Washington DC. The Cassini Reading, Writing, and Rings DVD was highlighted
at both events.

Uplink Operations sent commands to the spacecraft today for a Cosmic Dust
Analyzer (CDA) decontamination exercise, and for a real time Reaction Wheel
Assembly (RWA) bias to compensate for the cancelled Orbit Trim Maneuver
(OTM) #60. Both files are registered on-board the spacecraft and will
execute on DOY 128.

Sunday, May 7 (DOY 127):

OTM-60, originally planned for May 7, was deleted last November along with
OTMs 48 and 54. 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.

Monday, May 8 (DOY 128):

The CDS Command Loss Timer (CLT) software patch will be uplinked beginning
today and concluding Wednesday.

The Science Operations Plan Update kickoff meeting for S23 was held today.
The process runs for five weeks and will conclude on June 9.

A very cool panorama of Huygens descending onto the surface of Titan is
Astronomy Picture of the Day today.

Tuesday, May 9 (DOY 129):

On Tuesday, May 9, an Enceladus Plume Debris working group held its first
meeting. The primary goal of this group is to characterize the Enceladus
plumes so that the Rev 61 flyby can be designed so as to not present a
hazard to the spacecraft. The work of this group is also important for
creation and analysis of possible extended mission tours. The group needs to
develop a dust and gas engineering model that can be incorporated into
Mission Planning and Navigation software for planning flyby scenarios.

Wednesday, May 10 (DOY 130):

The Navigation Team has converged the orbit solution after OTM-059 to the
point where it is clear that OTM-061 is a required maneuver with no option
for cancellation. About a 20 km correction is needed to achieve the desired
flyby for Titan 14. The current orbit determination solution uncertainty is
less than 2 km and stable. Further, canceling OTM-061 would increase the
total delta-V by about 9 m/s. OTM-061 will be targeted to the reference
trajectory flyby point.

Since this maneuver will bring us back to the reference trajectory, no
update to the Radio Science Subsystem Inertial Vector Definition file, built
before the S20 uplink, will be required.

The CDS CLT software patch uplink activity was successfully completed today.
This patch corrects a code error found last September that was discovered
when the timer was set back for OTM-31, resulting in data loss for the Titan
7 flyby. A temporary patch to restore normal operations was issued at that
time; this patch fixes the code.

Since the Titan 15 to Titan 16 segment is very similar to the segments where
Navigation recommended deletion of OTMs 48, 54 and 60, Navigation has now
recommended the deletion of OTM-066. Program Management has concurred. In
addition to reducing the number of maneuvers by one, the deletion eliminates
work on the preceding weekend and saves about 0.15 m/s in the mean. The
option to execute the maneuver and its backup on July 10 and 11 will be
maintained.