Cassini Significant Events -- 08/18/05 - 08/24/05

August 26, 2005

(Source: Cassini Project)


The most recent spacecraft telemetry was acquired Wednesday, August 24, 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
http://saturn.jpl.nasa.gov/operations/present-position.cfm .

Thursday, August 18 (DOY 230):

A sponge bit meeting was held today as part of S15 sequence development.
Sponge bits represent available data volume that is given away to the
science teams during the first cycle of preliminary sequence development in
the Science and Sequence Update Process (SSUP). No further changes are
expected to DSN allocations, so much of the data volume that was being held
as margin is given to the teams for science. Prior to the meeting, the
Science Planning lead determines how much extra data volume is available and
teams request data volume that they need. If more data volume is requested
than is available, negotiations are made during the meeting.

Friday, August 19 (DOY 231):

Just prior to periapsis, which will occur tomorrow at 232T11:15, the
Composite and Infrared Spectrometer (CIRS) along with the Imaging Science
Subsystem (ISS) and the Ultraviolet Imaging Spectrograph (UVIS) tracked
cloud and storm features across the face of Saturn. Slow scans with the
infrared detectors were used to determine tropospheric thermal structure at
high spatial resolution. Temperature anomalies will be correlated with
motions and features in images taken by ISS.

A talk was given at noon today in Von Karman Auditorium entitled "26Al in
Iapetus - Consequences for the Formation and Evolution of the Saturnian
System." This seminar was about the dynamics and shape of Iapetus, a
distant satellite of Saturn, and how it turns out to yield crucial clues for
unveiling the history of the Saturnian nebulae and the Solar System. With
its short half-life, 26Al has been used as a fine-scale chronometer to date
events occurring in the early history of the Solar System. Iapetus is the
first case among planetary satellites where other models cannot suffice and
heat from Calcium-Aluminum Inclusions (CAI) is absolutely required. This
allows us to date the age of Iapetus as 4.565 8 ± 0.000 6 Gy. This sets a
lower bound on the age of Saturn, the upper bound being the age of the CAIs.
This result has important consequences for our understanding of the
Saturnian system and provides new constraints for models for the formation
of the outer Solar System. Implications for the geology of Iapetus and the
other Saturnian satellites was also discussed.

A test of the Titan-7 flyby sequence was successfully performed in the
Integrated Test Laboratory (ITL) using the new 050720 reference trajectory,
incorporating the higher T-7 flyby altitude. The T-7 flyby will occur on
September 7.

The Main Engine cover was fully deployed or "closed" this morning. Telemetry
values are consistent with a nominal deployment. The deployment telemetry
data will be queried for subsequent analysis and sent to JPL Division 35
personnel for modeling and tracking the use of this hardware.

The official delivery port occurred as part of the Science Operations Plan
Update process for S16. The merged products are currently being run through
the end-to-end pointing validation process by ACS. A Project Briefing and
Waiver Disposition Meeting is scheduled for August 31.

Saturday, August 20 (DOY 232):

Non-targeted Flybys occurred today of Tethys at 122,750 km and Telesto at
105,340 km.

Sunday, August 21 (DOY 233):

Six of the eight scheduled Ion and Neutral Mass Spectrometer (INMS) SSR
Instrument Expanded Block (IEB) loads for S14 were uplinked today. Normally
these IEBs would have gone up later in the week along with the other
instrument IEBs and background sequence. The files were sent up early due to
a scheduling conflict with uplink of OTM-029 and the resulting shortened
uplink window. The remaining IEB files and background sequence will be sent
up beginning on Friday August 28.

The S14 DOY 248 live update schedule for the Pandora/Titan Inertial Vector
Propagator (IVP) update and the Radio Science (RSS) DOY 250 Saturn
occultation Live Movable Block was sent out to the S14 distribution list.
The kickoff meeting for this process is scheduled for Monday August 29.

The four Sequence Change Requests (SCR) approved at the S14 final SCR/waiver
approval meeting earlier this week were incorporated into the "g" version of
the background sequence. The sequence products were then published to the
program file repository, and the sequence of events, space flight operations
schedule, and DSN keywords files will be published tomorrow. The RSS Live
Movable block remained at its PSIV2 "b" version since no changes were needed
in the final sequence development phase.

Monday, August 22 (DOY 234):

The T6 flyby of Titan today was outbound with a closest distance of 3660 km
at 08:54 GMT. This is one of the few flybys of Titan with opportunities for
far-infrared limb sounding by CIRS both inbound and outbound. Unlike nadir
measurements that intercept the surface, limb sounding allows the instrument
to measure temperatures in the lower stratosphere region. The temperature
data, along with pressure and aerosol measurements, was collected near 55
degrees south latitude.

For the Dual Technique Magnetometer (MAG), this flyby was an opportunity to
study an exotic dayside wake/tail region. During T6, the upstream side of
magnetospheric flow relative to Titan was also the night side. These
conditions may allow the frozen-in magnetic field to convect through the
night side ionosphere and interact with Titan's interior afterwards.

Additional science activities for this encounter included the acquisition by
ISS of high-resolution images also at high southern latitudes south of
Xanadu. UVIS, riding on the CIRS observations, performed spectroscopy for
constituent identification, and the Cosmic Dust Analyzer continued to map
dust densities and dust dynamical properties within Titan's orbit.

At closest approach, the Optical Remote Sensing instruments scanned across
the South Pole conducting the first detailed investigation of the southern
polar region, an area noted for cloud formation and evolution and possibly
even a lake.

Tuesday, August 23 (DOY 235):

An Encounter Strategy Meeting for Titan-6 and Titan-7 was held today. This
will cover Orbit Trim Maneuvers 29-31, and a period from the T6 flyby on
August 22, to the T7 flyby on September 7.

Signatures have been obtained for all three RADAR archive Software Interface
Specification (SIS) documents. At this time, all outstanding archive SISs
have been approved. This marks a formal transition of the Archiving task
from development to operations. The initial delivery of data products was
on July 1, with future deliveries scheduled every three months.

Wednesday, August 24 (DOY 236)

A Cassini picture of Epimetheus, a small moon of Saturn, was selected as
Astronomy Picture of the Day today. A query on the APOD website yielded
over 100 images from Cassini.

Members of the Spacecraft Operations Office (SCO) have placed files for
OTM-29 in the program file repository. As of today, Navigation has
delivered the final maneuver solution, ACS has begun Flight Software
Development System testing, the sequence leads have merged the maneuver
files with the background sequence, and all SCO subsystems have begin their
checklists on the merged products. OTM-29 is scheduled to be uplinked to
the spacecraft and executed on Thursday, August 25.

The final sequence approval meeting for S14 was held today. Uplink of
sequence products will continue as scheduled on Friday.

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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