Cassini Significant Events 03/24/05 - 03/30/05

April 1, 2005

(Source: Jet Propulsion Laboratory)

Cassini Significant Events for 03/24/05 - 03/30/05

The most recent spacecraft telemetry was acquired today 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 .

Activities this week:

Science activities this week continued with the acquisition of Ultraviolet
Imaging Spectrograph mosaics of Saturn's inner magnetosphere, Imaging
Science Subsystem (ISS) observations of Iapetus limb topography and geodesy,
and a magnetospheric boundary campaign performed by the Magnetospheric and
Plasma Science instruments.

Thursday, March 24:

Ion and Neutral Mass Spectrometer flight software normalization was
performed last week on the Solid State Recorder (SSR). The SSR has room for
two different versions of flight software for each instrument, as well as
for the software for the engineering computers. Normalization means that
both versions are equivalent. This is actually the first time in flight
that all instrument and engineering flight software copies are equivalent.

Last week, a Conference on Quality in the Space and Defense Industries
(CQSDI) featured a session on mission success at JPL, and how mission
operations assurance contributes to project reliability. The talk began
with a short session illustrating success highlights from 2004 and followed
with a 90-minute panel breakout presentation on Cassini. The presentation
illustrated the Cassini mission operations assurance process and described
how the Cassini flight team prepared for the critical mission events last
year of Saturn orbit insertion and the Huygens Probe release and relay.
Results from the Huygens mission were also shared along with lessons
learned. Attendees were encouraged to learn from the Cassini-Huygens
experiences with respect to integrating mission operations assurance to
increase reliability.

Systems Engineering gave a presentation on the Radio Science Subsystem (RSS)
Inertial Vector Definition (IVD) process at today's Cassini Design Team

Instrument Operations delivered version 2 of the Spacecraft, Planet,
Instruments, C-matrix, and Events Kernel Generation Program, along with
required documentation.

At a Program Change Control Board meeting it was decided to defer the
delivery of Mission Sequence Subsystem version D11 for about two weeks from
the current date of May 25 to allow for another re-delivery of the Inertial
Vector Propagator (IVP) tool to fix an error that impacts RSSIVD
functionality. The first operational use of D11 was identified as S14
Science and Sequence Update Process, which begins on June 20, so the delay
has no impact on operations use of the software.

Friday, March 25:

An image related to Huygens's discovery of Luna Saturni (Titan) was
Astronomy Picture of the Day today.

The Tethys Tweak Assessment/Approval Meeting was held today. This is a
rather complex issue with multiple options. Before a decision could be
made, more information was deemed useful for deciding on the possible
science trades affecting data collection for both Tethys and Saturn. As
time was still available before a final decision must be made, Project
Management agreed to wait until next Tuesday's Mission Planning Forum to
enable the team to continue studying options.

Sequence Development continues for S11. The Preliminary Sequence
Integration and Validation 1 cycle one initial merged sequence products were
published to the project file repository and are now available for review.

Today Navigation delivered the final orbit determination solution for Orbit
Trim Maneuver (OTM) #19. After that, evaluation files were published,
reviewed, and cancellation of the Easter weekend maneuver was approved.
Just a few short weeks ago on March 5, OTM #16 was cancelled. The
Significant Events report for that week discusses why cancellation is
carefully considered, and last week's report goes into some detail on the
process for cancellation.

Monday, March 28:

Official port 2 occurred today for the S12 Science Planning update process.
The team sequence files were merged and delivered to ACS for end-to-end
pointing validation.

Tuesday, March 29:

A Cassini image of the crescents of Titan and Dione was Astronomy Picture of
the Day today.

Events today included an Enceladus non-targeted flyby, Saturn periapsis,
main engine cover close, a ring plane crossing, and a Cosmic Dust Analyzer
(CDA) rocking downlink activity.

Downlinked data was lost over Madrid's station DSS-63 today when station
transmitter problems occurred. CDA reported a loss of considerable data for
the rocking downlink activity on day of year 88. They did succeed, however,
in partially reconstructing the impact rate based on the impact counters
transmitted via housekeeping data.

At the Mission Planning Forum, the decision was made to proceed with the
trajectory adjustment that will reduce the non-targeted Tethys flyby
altitude from about 32,000 km to 1500 km, and to reduce the targeted
Hyperion altitude from 1000 km to 500 km. There were pros and cons for the
science that could be obtained with and without the change, but the
consensus was that there was an overall improvement with the change. The
cost for making the change is around 7 to 8 m/sec.

The Multi-Mission Image Processing Laboratory converted operations to
version D33 software. This date was picked to minimize the impact upon
optical navigation deliveries and scheduled processing requests. The
switch-over involved bringing down the automated processes, making database
updates, changing pointers to the new D33 software set and restarting the
processes. The transition was successful and went very smoothly.

Wednesday March 30:

A Planetary Data System (PDS) peer review was held for a sample ISS team
archive volume. No major liens were identified. The ISS team's goal was to
produce a usable, well-documented data set. They met that goal extremely
well. PDS is currently organizing a review for a recently received CDA peer
review volume.

Today's on-board activities included RSS Titan gravity science, a Radio and
Plasma Wave Science high frequency receiver calibration, and a reaction
wheel biasing activity.

A Software Requirements and Certification Review for CDA flight software
(FSW) version 10.0.0 was held today. The FSW was approved pending support
documentation modifications. The new software will be uplinked to the
spacecraft and a checkout performed in May of this year. The purpose of
this delivery was to implement updated parameters and algorithms for
on-board data processing and data evaluation based on results of the early
inner-Saturnian measurements. This will calibrate the instrument based on
to-date results, allowing for enhanced science return.

Wrap up:

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.