Cassini Update - March 10, 2006

Cassini Significant Events
for 03/02/06 - 03/08/06

The most recent spacecraft telemetry was acquired Wednesday, March 8,
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/operation...t-position.cfm .

Thursday, March 2 (DOY 061)

The final sequence and command approval meetings for the S19 background
sequence were held today. The sequence will go active on-board the
spacecraft on Friday, March 10.

Uplink Operations and the Spacecraft Operations Office sent commands to
the
spacecraft today for a Radio Science Ka-band test with the Deep Space
Network, and for a DOY 068 roll halt and reaction wheel assembly bias
that
will execute at the end of S18.

A Colorado Saturn Observation Campaign Member was able to show Saturn
this
past Thursday to a group of elementary school kids. Some of the
students
thought Saturn looked like Mickey Mouse tilted to the side! Everyone
received Cassini handouts.

Friday, March 3 (DOY 062):

The Irish Astronomical Society and the South Dublin Astronomical
Society
showcased Saturn and the moon to 120 children and their parents at St
Brigid's School, Greystones, Ireland, March 3 & 4. The beautiful planet
Saturn showed itself extremely well in the cold Irish air.

Saturday, March 4 (DOY 063):

Last week during the Orbit Trim Maneuver (OTM) 53 pre-burn yaw turn,
while
the spacecraft was off Earth point, the Helium Latch Valve Driver
(HELVD)
Solid State Power Switch (SSPS) tripped unexpectedly. It has been 17
weeks
since the last such trip on November 4, 2005. These SSPS trips have
been
seen before and are most likely caused by Galactic Cosmic Rays. So far
in
the mission there have been 15 such trips. They are predicted to occur
at a
rate of about 2 per year so the spacecraft is right on track! There
was no
impact to spacecraft performance as this driver was actually OFF at the
time. Today the HELVD was powered off redundantly and the SSPS trip
was
cleared. All subsystems reported nominal performance following this
activity.

Monday, March 6 (DOY 065):

Today the sequence leads for S19 began sending up sequence related
files.
Instrument Expanded Block (IEB) files for the Cassini Plasma
Spectrometer
(CAPS), Composite Infrared Spectrometer (CIRS), Imaging Science
Subsystem
(ISS), Magnetospheric Imaging Instrument (MIMI), Ultraviolet Imaging
Spectrograph (UVIS), and Visual and Infrared Mapping Spectrometer
(VIMS)
were sent. Tuesday and Wednesday the Optical Navigation IEBs and the
background sequence will be sent.

Preliminary files for the Science Operations Plan Update process for
S21
were submitted to the Science Planning team today. The final versions
are
due on Friday.

A "Come See Saturn" event in Simi Valley, California, attracted over
200
people, including one 94 year old youngster-at-heart who climbed the
stairs
to view Saturn for his very first time through the Moorpark College
Observatory telescope. Cassini Outreach material was distributed at
the
event. Additional members of the Ventura County Astronomical Society
set up
10 telescopes near the observatory.

Tuesday, March 7 (DOY 066):

The preliminary End-to-End ITL test for the Monopropellant Tank
Assembly
(MTA) Recharge and AACS flight software version A8.7.4 uplink
activities was
performed March 7-9. This activity will be performed on the spacecraft
during the execution of S19, on April 10-13. The recharge brings the
thrusters up to nominal pressure to provide control authority for the
planned lower altitude Titan flybys, starting with Titan-16 on July 22,
at
950 km. ACS will upload a flight software patch to bring the default
thruster magnitudes used in safing in line with the expected values.
The B
branch will be updated before the recharge, and the A - and redundantly
B -
branches will be updated afterwards. This strategy of splitting the
patch
uploads is robust to a leaky thruster after a successful MTA recharge,
and
to a safing event after a failed MTA recharge.

A Science Archive Working Group meeting was held today to discuss
archive
status. At this time all instruments are on schedule to meet the
fourth
archive milestone on April 1.

Aviation Week has released their 49th annual selections for the Laurel
Awards. "The Cassini/Huygens spacecraft team for the successful
landing of
the European Space Agency's Huygens Probe on Saturn's moon Titan, and
for
the science return and poetic images from NASA's Cassini orbiter that
will
continue for many years."

Wednesday, March 8 (DOY 067):

As the distance from Saturn increased following last week's periapse,
the
Magnetospheric and Plasma Science instruments resumed their
magnetospheric
boundary survey. In contrast to the early part of S18, observations
this
week were on the dusk side.

ISS observed transits of Enceladus across Dione, Rhea, and Helene; of
Helene
across Dione; and of Janus across Helene. By shuttering the narrow
angle
camera every minute for the duration of the observation, the exact time
of
alignment can be calculated and incorporated into orbit computations.
Other
images for orbit determination were taken of Atlas, Epimetheus, Janus,
Helene, Pan, Pandora, Prometheus, Calypso, Pallene, Telesto, Methone,
and
Polydeuces.

ISS also targeted Dione and Rhea for spectrophotometry using various
color
and polarizing filters. UVIS participated in these observations to
measure
the ultraviolet albedo for different longitudes and phase angles.

Not all attention was focused on Saturn's satellites. ISS, with VIMS
riding
along, performed polarimetry observations of Saturn itself on three
different days at phase angles between 123 and 128 degrees. With Saturn
nearly 2.6 million kilometers away on Saturday, the UVIS field of view
slit
covered the diameter of Saturn. Taking advantage of this coverage, in a
lengthy observation UVIS made several slow scans across Saturn's
visible
hemisphere to form spectral images in the ultraviolet. These will be
used to
study atmospheric composition and auroral activity.

Upcoming Events:

On March 10, at The Cook Center Planetarium, Navarro College,
Corsicana,
Texas:
Join SOC members who will show Ring World inside the planetarium
followed by
Saturn, Mars, Orion nebula and moon viewing through telescopes.

Wrap up:

Check out the Cassini web site at http://saturn.jpl.nasa.gov 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.