Cassini Significant Events for 01/23/08 - 01/29/08

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Cassini Significant Events 
for 01/23/08 - 01/29/08

The most recent spacecraft telemetry was acquired on Monday, January 28,
from the Madrid tracking complex. The Cassini spacecraft is in an excellent
state of health and all subsystems are 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.

Wednesday, January 23 (DOY 023):

The official port for the Science Operations Plan Update (SOPU) process for
S40 occurred today. The delivered products were merged, and reports sent to
the science teams and AACS for end-to-end pointing analysis.

The Command Loss Timer (CLT) is part of fault protection onboard every
spacecraft.  Basically, if a spacecraft has not heard from the flight team
by a specified time since it received its last command, the spacecraft calls
safing, and "phones home."  Based on analysis performed before Saturn Orbit
Insertion, the Cassini CLT countdown duration, with a few exceptions, has
been set for 85 hours.  For some of the recent sequences in development, pre
uplink analysis has shown  points where the CLT countdown would exceed the
limit and go negative. Under the current operational strategy for such
occurrences, commands would have to be included in the background sequence
to increase the CLT to some greater value before the event, and then return
it to 85 hours after the event.    Rather than doing all this commanding, it
was determined that if the nominal timer default was increased by just five
hours, there would be a minimum margin of two hours in many of the cases.
With all this in mind, on Jan. 23, the nominal time duration for the CLT was
changed from 85 to 90 hours.

On Wednesday and Thursday the Cassini Plasma Spectrometer (CAPS) and the
Magnetospheric Imaging Instrument (MIMI) supported an on-going campaign to
observe Saturn's magnetospheric boundaries on Saturn's dusk side at a
variety of latitudes.  In addition, the Visible and Infrared Mapping
Spectrometer (VIMS) observed Saturn's F-ring for nearly 14 hours to obtain a
movie of the ring's rotation. VIMS stared at one ansa of the F-ring and
observed continuously for one orbital period to build up a 360-degree
azimuthal map of the ring from a distance of 25-30 Rs.

Thursday, January 24 (DOY 024):

The last Aftermarket Process for the prime mission concluded today with the
delivery of Target Working Team (TWT)/ Orbiter Science Team (OST) products
for S41.  SOPU for S41 will kick off in about two weeks on Monday, February
4.

Uplink Operations sent commands to the spacecraft today for a Radio Science
Live Movable Block, a Cosmic Dust Analyzer (CDA) flight software demo set to
execute on Jan. 27-28, and an increase in telemetry rates for DOY 30 over
DSS-24.

The Imaging Science Subsystem's Wide Angle Camera (ISS WAC) began
observations this week by searching for small satellites in the
Mimas-Enceladus region.  To do this, ISS stared off the ring ansa and took
pairs of WAC images ~ every 5 minutes for 13.5 hours.  After this, VIMS took
data for a latitude-phase mosaic on each ansa on the unlit face by pointing
the spacecraft at six locations for one hour each.

Other activities this week include a number of occultations.  The Ultra
Violet Imaging Spectrograph (UVIS) observed a series of eight stellar
occultation events of Saturn's A and F rings. UVIS pointed at star SAO
205839 as it crossed the Cassini Division and then the F ring, and observed
star Iot Cen and Kap Cen as they crossed the F ring.

Friday, January 25 (DOY 025):

The TWT/OST integrated products for S42, covering orbits 74 through 80, were
delivered today. The integrated products are in their final form. No
re-integration is planned, as there will be no Aftermarket process to
address re-integration issues.  The next step in sequence development, SOP
implementation, will kick off on Feb. 11.  Between now and then, the
instrument teams will be working on designs for the sequence, and requests
will be passed to the DSN regarding when Cassini needs tracking passes to
support uplink and downlink during execution of S42 in July of this year.
S42 is the first of the sequences for the proposed extended mission.  Over
the next two years the TWT/OST teams will be delivering integrated sequence
products for the extended mission about every five weeks.

Sunday, January 27 (DOY 027):

Non-targeted flybys of Titan, Atlas, Epimetheus, Prometheus, and Pandora
occurred today.

A Radio Science (RSS) orbit 57 rings chord occultation was completed
successfully on Sunday, Jan. 27.  For this experiment, Canberra Deep Space
Station (DSS)-43 assisted with S- and X-band support, and DSS-34 provided X-
and Ka-band support.  With the ring opening angle at 7.4 degrees, the
occultation probed all major ring features - A, Cassini Division, B, and C -
on the way in and out.  The data from this observation will provide valuable
profiling of the dependence of detectable ring structure on observation
longitude. This is important for characterization of the rings'
microstructure, or, the spatial distribution of aggregates of ring
particles.  Like its sister occultation on Orbit 56, the Orbit 57
occultation geometry was optimized to allow capturing favorable Doppler
contours alignment over Ring A near the end of the observation period, and
facilitate determination of physical ring properties from the near-forward
scattered signal observations. The experiment completed normally, and high
quality data were acquired. 

Monday, January 28 (DOY 028):

Monday kicked off a weeklong set of science meetings at JPL as part of
Project Science Group (PSG) meeting #44.  Enceladus Plume, Titan Science,
Titan Operations, Saturn, Rings, Magnetospheric and Plasma Science (MAPS),
and Icy Satellite working group meetings will be held this week along with
two Plenary Sessions where general status for Spacecraft, Operations, and
Instruments will be presented along with science results.

Tuesday, January 29 (DOY 029):

An AACS prime reaction wheel (RWA) friction test on wheels 1, 2, and 4 was
performed today.  This test is performed every three months and allows the
Spacecraft team (SCO) to collect statistics on wheel performance and health.
For the test, the RWAs are spun up to 900 rpm in both directions and timed
as they are allowed to spin down to 0 rpm.  SCO is in the process of
analyzing the results.

Today an official dedication was held in Von Karman Auditorium at JPL for a
set of wall murals created by students from the Academia de Arte Yepes in
Los Angeles, California. Using data obtained by Cassini since 2004, the
students have created wonderful works of art representing many Cassini
discoveries. The murals extend through the hallways from floor to ceiling of
the Cassini Instrument Operations area at JPL and provide beautiful
portraits of the Saturnian system.  This week was selected for the
dedication as it coincides with the 44th meeting of the PSG.  Many members
of the instrument teams have traveled to JPL for the meeting and a
dedication this week allowed the scientists to view the murals first hand.

A Cassini-Huygens Analysis and Results of the Mission (CHARM) teleconference
was held today.  A member of the Magnetospheric Imaging Instrument (MIMI)
team gave a presentation on Energetic Particles in Saturn's Rotating
Magnetosphere.

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.


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