Cassini Update - February 2, 2007

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Cassini Significant Events
for 01/25/07 - 01/30/07

The most recent spacecraft telemetry was acquired Tuesday, January 30, from
the Goldstone tracking complexes. 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 .

The schedule for Significant Events production has been adjusted by one day
due to the implementation of the 9/80 Work Week at JPL.  This week the
report covers a 6-day period from Thursday to Tuesday. Beginning next week
the new reporting period will cover a 7-day period from Wednesday to
Tuesday.  This will then be the standard reporting period.  Variations will
occasionally occur.

Thursday, January 25 (DOY 025):

Both the S28 and S29 final sequence development processes continued this
week.  For S28, a Sequence Change Request (SCR) approval meeting was held
with all five submitted changes approved.  S29 also held an SCR approval
meeting where 11 requests were approved and two placed on hold pending
further analysis.  During this process, there are three opportunities for
SCRs to be approved. As the process continues and the time for uplink
approaches, SCRs will not be accepted for "make better" changes, but will
only be considered if they deal with health and safety issues for either the
spacecraft or instruments. As a result, the number of SCRs submitted towards
the end of the process tends to drop.

Friday, January 26 (DOY 026):

Orbit Trim Maneuver (OTM) #91 was performed today. This is the approach
maneuver setting up for the Titan 24 encounter on January 29.  The reaction
control subsystem (RCS) burn began at 2:30 AM PST. Telemetry immediately
after the maneuver showed a burn duration of 7.9 seconds, giving a delta-V
of 0.015 m/s.   The 7.9 second burn makes this the smallest RCS burn to
date.  The previous record holder was OTM-09 in December of 2004 with a
duration of 18.75 seconds and a delta-V of 0.016 m/sec.  All subsystems
reported nominal performance after the maneuver.

As Cassini began to close in on Titan for the T24 flyby, the Composite
Infrared Spectrometer (CIRS) devoted nine hours to a composition map of the
satellite studying its rich atmosphere of organics and other molecules.

On Saturday, the Ultraviolet Imaging Spectrograph (UVIS) will observe an
occultation of the star Eps PsA by Saturn's rings to provide detailed
information on ring structure, dynamics, ring-moon interactions, and ring
particle sizes, and RADAR will seek to determine global ring properties with
low spatial resolution images from medium inclination.

Just prior to closest approach, the Visible and Infrared Mapping
Spectrometer (VIMS) and Imaging Science Subsystem (ISS) will observe the
stellar occultation of Gamma Cru to help understand the structure of Titan's
atmosphere.

Monday, January 29 (DOY 029):

Closest approach for Titan 24 occurred today at 2007-029T07:15:55 GMT.
Cassini, inbound toward Saturn, reached an altitude of 2631 km above Titan's
surface.  For this flyby, the Magnetosphere And Plasma Science (MAPS)
instruments observed the interaction of Titan with Saturn's magnetosphere in
the upstream, inner flank, and wing regions.

Inbound to Titan, ISS searched for lightning and aurorae using night side
imaging with the wide-angle camera, and UVIS made several slow scans across
Titan's visible hemisphere to form spectral images in the ultraviolet.

During closest approach, the Visible and Infrared Mapping Spectrometer
(VIMS) took high spatial resolution images of the development and decay of
mid-latitude clouds. In the north polar region, VIMS mapped volatiles and
other materials.

Today began a weeklong series of meetings and presentations that comprise
the 41st Cassini Project Science Group (PSG) meeting.  One item on the
agenda for this week is for the science teams and working groups to come to
a consensus on a tour extension trajectory to be used in a proposal to NASA
for a continuation of the Cassini mission beyond its current nominal plan of
four years.  Ten tours and a number variations to those tours have been
offered up for consideration by the scientists.

The Spacecraft Operations Office (SCO) hosted a meeting today to discuss
with project management a new flight software build for the Command Data
System (CDS).  Version 10 of the software is desired in order to add the
capability to remove a "bad" SSR memory submodule from use.  This capability
has been on the implementation list for several years but has not been
included due to workforce and time limitations.  CDS proposed that
implementation of Version 10 would be a good opportunity to add this and
other capabilities.  The project has concurred, and SCO will now begin
addressing the issues related to this development effort.

Because the best things deserve to be repeated, Cassini's image of Hyperion
-originally Astronomy Picture of the Day in October 2005 - was Astronomy
Picture of the Day again yesterday.

The preliminary product input port for the S30 Science Operations Plan
Update process occurred today.  The official port is scheduled next week on
Feb. 6.

The Aftermarket Process for the S32 sequence began today. This 5-week
process will address proposed changes that require re-integration of the
segments contained in the S32 sequence.

Tuesday, January 30 (DOY 030):

The spacecraft team began the procedure to uplink AACS flight software
version A8.7.5 to the spacecraft today.  Uplinks will continue through Feb.
5 with normalization scheduled for March 4. This software update changes
parameters and vectors only.  There are no logic changes.

The Navigation team has reported that since the Titan 24 encounter was a
high altitude flyby on reaction wheel control, the orbit determination
solution is already well converged.  The current estimate for Orbit Trim
Maneuver (OTM) #92 is only 9 mm/s, and there is a slight delta V saving for
canceling and accomplishing all of the correction at OTM-093.  Based on
these factors, there is no driving reason to execute OTM-092, so it has been
cancelled.

The Cassini-Huygens Analysis and Results of the Mission (CHARM)
teleconference for January was held today. The topic, Basics of
Interplanetary Flight, was presented by the Cassini Real Time Mission
Control lead from the Mission Support and Services Office.  The presentation
offered an introduction to the online tutorial 

http://www.jpl.nasa.gov/basics.

The presentation can be found here:  

http://saturn.jpl.nasa.gov/multimedia/products/CHARM.cfm.

Cassini Outreach has released an interactive flash - Saturn Moons Explorer:
Titan.  To view this feature link to: 

http://saturn.jpl.nasa.gov/news/features/feature20070129.cfm

and click on the link provided.

Today CIRS made a temperature map in the infrared to obtain information of
the thermal structure of Titan's stratosphere from roughly 70 to 400 km in
altitude. Variations in longitude, latitude, and altitude are all of
interest in understanding the dynamics of the stratosphere.

Upcoming:

Saturn will be at its closest point to Earth this year during the beginning
of February.  As a result, it looks bigger and brighter both visually and
with the aid of a telescope than it will for all the rest of 2007.  Because
Saturn is slowly moving away from the Sun, it will not be this close to
Earth again until 2029.  Saturn Opposition is coming up Feb. 10.  This means
that Saturn will be 180 degrees opposite the Sun as seen from Earth.  Saturn
Observation Campaign members around the globe are organizing observing
events for viewing at opposition.  An event local to JPL is scheduled for
Monrovia Library Park from 6-10 p.m.  Viewing may run later if there are
still interested viewers and decent weather conditions. Saturn viewing in
2007 details here:  http://soc.jpl.nasa.gov/viewing.cfm

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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