Cassini Significant Events -- for 06/23/05 -- 06/28/05

June 30, 2005

(Source: Cassini Project)

The most recent spacecraft telemetry was acquired Wednesday 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:

The entire suite of Magnetospheric and Plasma Science (MAPS) instruments
conducted surveys to measure the properties of interactions between Titan
and its torus.  Measurements included the composition, density, spatial, and
temporal variation in the torus region when Titan is not close by and
perturbing it.

The Magnetospheric Imaging Instrument (MIMI) imaged the dynamics of the
inner magnetosphere, and the Composite Infrared Spectrometer (CIRS) mapped
Titan to obtain measurements of nitriles, hydrocarbons, and carbon dioxide
as a function of latitude and emission angle.

At this time the Radio and Plasma Wave Science (RPWS) instrument is on a
campaign to obtain the highest resolution observations of Saturn
Electrostatic Discharges (SED) within a distance of 6 Saturn radii.  Results
will help to verify the source as lightning, or provide evidence that the
SEDs could be of some other origin such as Saturn's rings.

The fourth of eight Radio Science Subsystem (RSS) occultation observations
occurred this week.  Skip ahead to June 26 for specific details of that and
other science events for that day.

Thursday, June 23 (DOY 174):

The live movable block mini-sequence was uplinked today over the Goldstone
tracking complex.  Confirmation has been received from the spacecraft that
the program has registered properly on board.  The mini-sequence will begin
execution on Sunday, June 26.

A member of the Spacecraft Operations Office (SCO) gave a Cassini talk to 30
members of the Altadena Rotary Club in Altadena, California.

Friday, June 24  (DOY 175):

Delivery Coordination Meetings were held today for Navigation Software T2,
and Maneuver Automation Software (MAS) version 5.  This version of
Navigation Software includes the move to Red Hat 8.0 & Enterprise 4 Linux,
MAS/MOPS changes, multi-mission changes and new utilities. The MAS release
provides needed capabilities to support current and future OTMs.

The S12 Preliminary Sequence Integration and Validation 1 sequence change
request approval meeting was held today.

A command to enable RPWS Sounder Operations was uplinked to the spacecraft.
Sounder operations were confirmed to have begun around 17:50 Spacecraft
Event Time (SCET), about a one-way light time after the command was sent.

RSS personnel participated in an Occultation Operational Readiness Test
(ORT) today.  This is the last test prior to the occultation observations
that will occur on Sunday.

Sunday, June 26  (DOY 177):

Today there were non-targeted flybys of Tethys, Pan, and Telesto.

The RSS Saturn/Rings Ingress and Egress occultation completed successfully
this evening.  The occultation occurred over three antennas at the Goldstone
DSN complex and was the fourth of eight occultation observation periods
planned between May and September.

This was one of the best diametric occultations primarily because of the
high elevation angles at the tracking station leading to better
Signal-to-Noise-Ratio (SNR) and less perturbations of the signal phase by
Earth's atmosphere. In addition, the occultation was entirely covered by
what's considered to be the best Ka-band receiving antenna, DSS-25, for both
ingress and egress. Based on real-time monitoring of signal levels, the limb
track maneuver seemed to have executed well.  This will be verified once the
team receives the ACS reconstructed C-Kernel.

Additional observations included RPWS measurements at the Ring Plane
Crossing to determine the equatorial dust flux and scale height as a
function of radial distance, while also obtaining high-resolution
measurements of plasma waves at the magnetic equator.  The Imaging Science
Subsystem (ISS) obtained a movie of the outer B ring edge and
performed an azimuthal scan of the Cassini Division and Encke Gap, and the
Ultraviolet Imaging Spectrograph (UVIS) obtained a high-resolution radial
profile of the B ring optical depth by making measurements of the star 26
Tau as it passed behind the B Ring. Finally, all the Optical Remote Sensing
instruments performed joint studies of the rings at zero phase angle.

Monday, June 27 (DOY 178):

The main engine cover was successfully opened in preparation for Orbital
Trim Maneuver (OTM) 25.  The cover has been closed since April 30.  SCO also
performed an Attitude Control System reaction wheel bias.

Commands were sent to the spacecraft by Uplink Operations to set up and
perform the Visual and Infrared Mapping Spectrometer (VIMS) S12 instrument
expanded block SSR load #2, to clean up after this operation, and to disable
RPWS Sounder Operations.

RSS performed a Saturn Gravity Science experiment today.

Tuesday, June 28 (DOY 179):

A Planetary Data System archive peer review was held for the Ion and Neutral
Mass Spectrometer (INMS) and RADAR instruments.  The review went well with
only minor liens identified.  Archive software interface specification
documents for the Cosmic Dust Analyzer (CDA), INMS and RADAR are in the
signature cycle.

A press release is now available regarding the lake-like feature recently
observed on Saturn's moon Titan.  Cassini captured a series of images,
released today, showing a marking, darker than anything else around it. It
is remarkably lake-like, with smooth, shore-like boundaries unlike any seen
previously on Titan.   The site has been identified as the best candidate
seen so far for a liquid hydrocarbon lake on Titan.  For more information
link to .

Instrument Operations successfully completed analyzing the results of the
ISS flight software (FSW) checkout performed on June 14.  A sequence to
permanently switch to FSW version 1.4 has been built, reviewed and approved.
Negotiations are underway to upload it in early July in time to be used for
the Enceladus encounter.

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.