Cassini Significant Events -- for 08/11/05 - 08/17/05

August 19, 2005

(Source: Cassini Project)

The most recent spacecraft telemetry was acquired Wednesday, August 17, 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 .

Activities this week:

Thursday, August 11 (DOY 223):

Cassini's orbit passed through apoapsis today and began the 13th orbit of
tour. While in the apoapsis region, the Imaging Science Subsystem (ISS)
made a movie of Saturn's southern hemisphere, and the Visible and Infrared
Mapping Spectrometer (VIMS) studied the rings in a mosaic.

As part of sequence development for S15, the sequence leads released the
preliminary cycle 1 integrated sequence products for review and for ACS
Inertial Vector Propagator (IVP) & Kinematic Prediction Tool analysis.

Friday, August 12 (DOY 224):

A CDS flight software (FSW) patch uplink readiness review was held for the
SSR auto repair correction. This patch will be uplinked in mid-September.

The last time members of the Spacecraft Operations Office (SCO) looked at a
time frame for the first fuel-side bipropellant repressurization planned in
the tour, it appeared that it did not need to be performed until around
December 2005. This repressurization is a procedure required to keep the
main engine operating normally. Several changes have occurred since the last
assessment: trajectory changes have increased the biprop delta-V used
during the last year, as has the decision to lower the delta-V threshold for
RCS thruster vs. main engine use. It is now evident that the activity should
occur before OTM-33. Currently it is planned for mid-September, right
before the CDS FSW patch upload.

Mission Planning has been working on a maneuver cancellation process and
presented the latest version to the Live IVP Update Working Group. This
group has the basic science representation from Radio Science, RADAR, and
the Optical Remote Sensing instruments that deal with trajectories, orbit
determination deliveries, uncertainties, etc.

Sunday, August 14 (DOY 226):

This was the chance to hear Michael Oare's composition "Cassini's Rings"
performed live in its west coast premier. A member of the Cassini flight
team arranged with the composer, and with the conductor of the La Cañada
Community Band, to present this piece on Sunday, August 14th, at Memorial
Park in La Cañada, California. The Grafton Middle School in Yorktown, VA,
originally premiered the piece at a spring concert in June of this year.

SCO reported that a calibration was performed on Inertial Reference Unit-A
over Sunday and Monday. Performance of the unit continues to be excellent.

Monday, August 15 (DOY 227):

VIMS performed an Automated Sequence Processor (ASP) command to update the
command load in the instrument. This update corrects one trigger, which the
science team incorrectly planned and noticed too late to correct in the S13
uplink process. The update was successfully performed.

Members of the ACS and Integrated Test Laboratory teams supported and
presented at the AIAA Guidance, Navigation, and Control conference in San
Francisco, California the week of August 15.

A calibration of the Radio Science Subsystem (RSS) HGA boresight was
performed today.

Instrument Operations and the Multi-Mission Image Processing Laboratory
participated in extensive testing of an engineering version of FEI-5. This
File Exchange Interface system is used by the MER and MRO flight projects.
Their use of this system has significantly impacted Cassini and Spitzer
throughput of instrument science products. Due to the architecture of a
multi-mission facility, missions share resources even if they are running
independent applications. For instance, the applications can be running on
the same CPU, accessing the same database server and/or getting
authentication from the same password server. Resources such as these may
be temporarily held by one project doing its independent work. The other
projects may be locked out or access restricted until the resources again
become available. Testing this week involved baseline tests, problem
reproducibility and problem resolution tests. The engineering version caused
no adverse effects and significantly reduced the impact on Cassini.

Tuesday, August 16 (DOY 228):

A meeting was held today to determine if Orbit Trim Maneuver (OTM)-28,
scheduled for Thursday of this week should be cancelled. The small
magnitude of the maneuver, 50 mm/sec, taken together with a resulting cost
downstream of less than 1 m/sec, indicated that the maneuver was not
required. This along with the necessity of the team working overnight to
perform the maneuver convinced management to cancel it.

All signatories have approved the Cassini Plasma Spectrometer Archive
Software Interface Specification (SIS) document. Only one archive SIS
remains to be completed.

Near the end of this week, Cassini came within 608,000 km of Hyperion. ISS
studied the satellite's geology while Ultraviolet Imaging Spectrograph
measured its ultraviolet albedo. The Composite and Infrared Spectrometer
(CIRS) made high spectral resolution infrared measurements for composition
analysis. These results laid the groundwork for a 1010 km targeted flyby in

Wednesday, August 17 (DOY 229)

The full merged preliminary cycle 2 products for S14 were released today.
This includes files for the background sequence and the live moveable block.
The associated Space Flight Operations Schedule will be released tomorrow.

The final science event this week was a CIRS longitudinal scan of the rings
to study seasonal effects due to elevation of the sun and screening of the


Outreach has released the Cassini Science Highlights for August. A reduced
version of this information has been included below.

Cassini Reveals Saturn's Eerie-Sounding Radio Emissions

Cassini's Latest Findings About Enceladus

Evidence of Ice Volcanism on Enceladus

Nested Craters on Mimas Tell of a Heavily Tortured Past