Cassini Significant Events -- for 04/21/05 - 04/27/05

April 29, 2005

(Source: JPL)

The most recent spacecraft telemetry was acquired Wednesday from the
Goldstone tracking station. 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 .

Something new for this week:

Uplink Operations, Science Planning, and the Spacecraft Operations Office
use day-of-year (DOY) instead of dates from the Julian calendar when
planning activities or referring to events. This is part of the "project
speak" of Cassini, as well as all other flight projects at JPL. Beginning
this week, DOY has been included as part of the header for each day. This
will help you orient yourself for future events as they are mentioned in
this report.

Activities this week:

On Saturday, April 23, Cassini will pass apoapsis and begin Rev 7. During
this period the Visual and Infrared Mapping Spectrometer and other Optical
Remote Sensing instruments will take data for a mosaic of the rings, the
Ultraviolet Imaging Spectrograph (UVIS) will perform a stellar calibration,
and the Imaging Science Subsystem will look for spokes in the rings. UVIS
will also be observing the rings in the hopes of detecting flashes from
meter-sized interplanetary impactors.

As a follow-up to the Titan-5 flyby on April 16, the Spacecraft Operations
Office (SCO) reported that ACS is working to estimate the angular momentum
imparted on the S/C due to atmospheric torque. This data will be presented
at the Titan Atmospheric Working Group on May 16.

Thursday, April 21 (DOY 111):

An updated version of the S10 Live Inertial Vector Propagator (IVP) Update
overlay vectors for Dione, Tethys, Titan and Saturn (DOYs 122-125) has been
placed in the Program file repository. Once on-board, the overlay will be
stored in the background sequencing region. This item is an example of how
even though a background sequence is "final" and currently executing on
board the spacecraft, sequence development may continue to within days of
the end of execution.

For the S11 sequence, the Preliminary Sequence Integration and Validation 2
Cycle 1 initial merged sequence products were also delivered to the file
repository. Both the S11 background sequence and the two scheduled live
moveable blocks were included. The sequence of events file and space flight
operations schedule will be released by end of day Friday, April 22.

The Program has approved an Enceladus tweak to the reference trajectory that
will retarget the E2 flyby to 175 km. Additional changes as a result of the
tweak include the b-plane angle at -215 degrees, Mimas at 62,700 km and the
time has shifted about 22 min later, Rev 12 begins 24 minutes later, Rev 13
begins 1 minute later, etc.

Friday, April 22 (DOY 112):

A Software Review/Certification Requirements delivery meeting was held for
ISS flight software. Version V1.4.0 contained corrections that otherwise
would have resulted in loss of science data and diagnostic information,
reduced operational complexity, and fixed some things that had the potential
of causing problems in future.

A verification and validation exercise concluded today in the Integrated
Test Laboratory (ITL) for the Radio Science Subsystem (RSS) Inertial Vector
Definition (IVD) Update. The V&V was successful and commands will be
uplinked as planned to the spacecraft.

The RSS team reported that even though Canberra's DSS-34 was not scheduled
to return to service with Ka-band downlink capability until April 25, an RSS
DSS-34 Ka-band checkout test was scheduled today with the understanding that
it would be supported on a best efforts basis. The station locked up on
Ka-band shortly after the beginning of the pass, and enabled monopulse
immediately after. DSS-34 Radio Science Receiver (RSR) Ka-band data has now
been recorded for the first time ever!

Monday, April 25 (DOY 114):

Uplink Operations sent commands to the spacecraft for a Cassini Plasma
Spectrometer (CAPS) Power-on reset that will be executed on DOY 118, and to
perform a CDS memory readout and verification of all partitions.

Preliminary port #1 for the S13 Science Operations Plan Update process
occurred today. The products were merged and reports published. Official
port #2 is scheduled for Friday, April 29.

Tuesday, April 26 (DOY 115):

Jack O'Connell, California State Superintendent of Public Instruction,
visited JPL at the invitation of the JPL Education Office and the
encouragement of Congressman Adam Shiff, who also attended. The Education
Office provided a briefing on JPL education activities including the Cassini
Reading, Writing and Rings program.

An Assessment meeting was held to review all of the requested changes to the
S15 sequence. With the exception of one request, it appears that all of the
remaining changes will fit within the available resources. Unless the
Target Working Teams (TWTs) and Orbiter Science Teams (OSTs) recommendations
change over the next couple of weeks, it is likely that the Decision meeting
scheduled for May 17 will be canceled.

Wednesday, April 27 (DOY 116):

The maneuver approval meeting was held today for Orbit Trim Maneuver #24.

The S11 sequence leads will be asking for an ITL V&V test for a live
moveable block to execute during that sequence. Today a joint
Simulation/V&V meeting was held to review the files necessary and to develop
a schedule.

Cassini Outreach, along with the JPL Astronomy club, concluded the fourth
Saturn viewing night at JPL this week. JPL employees were invited to bring
their families back to JPL at sunset for views of Saturn and other visible
objects. Several hundred employees and their families participated and
received Cassini outreach material.

Uplink Operations sent commands to the spacecraft for the Live IVP Update
overlay vectors for Dione, Tethys, Titan and Saturn. The mini-sequence has
been properly received by the S/C. The file will begin execution on
2005-122T02:35:59 and will continue for approximately 3 days and 16 hours

In addition, SCO radiated the OTM 24 file which will execute on

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.

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