Cassini Significant Events
09/10/08 - 09/16/08
The most recent spacecraft telemetry was acquired on Sept. 16 from
the Deep Space Network tracking complex at Goldstone, California.
The Cassini spacecraft is in an excellent state of health and all
subsystems are operating normally. Information on the present position
and speed of the Cassini spacecraft may be found on the "Present
Position" page at:
http://saturn.jpl.nasa.gov/operations/present-position.cfm.
Wednesday, Sept. 10 (DOY 254):
Science activities today began with the Cassini Plasma Spectrometer
(CAPS) leading a Magnetospheric and Plasma Science (MAPS) auroral
investigation. After turning to Earth and downlinking this data,
the spacecraft stayed Earth pointed as the rings of Saturn passed between
Earth and the spacecraft. This provided an opportunity for a Radio
Science (RSS) ring occultation experiment. Cassini used its radio
transmitter to send multiple frequency radio signals through the rings.
Scientists carefully monitor the signals as they are received on
Earth. This allows them to deduce the structure and composition of
the rings. The day ended with a joint Optical Remote Sensing (ORS)
campaign of Saturn's south polar region.
A non-targeted flyby of Epimetheus occurred today.
Science Planning, Composite Infrared Spectrometer (CIRS), Imaging Science
(ISS), Ultraviolet Imaging Spectrograph (UVIS), and Visual and Infrared
Mapping Spectrometer (VIMS) teams weighed in today at the Go/No Go
meeting for the first S44 Live IVP Update. It's a go for updates to
Saturn, Cassini, and Enceladus vectors to execute on DOY 161.
Uplink of the necessary files is planned for next Monday.
The Cassini Radio Science (RSS) S43 orbit 84 rings chord occultation was
completed on Wednesday, Sept. 10. The experiment was covered by Madrid's
DSS-63 station with X- and S-band support, and DSS-54 with X- and Ka-band
support. This was the last in a family of four fast chord occultations
that probed the rings when the opening angle was small, about 5 to 7
degrees. This was also the first time DSS-54 provided RSS occultation
experiment support. DSS-55 at Madrid is usually scheduled to
support the RSS Ka-band activities, but since that antenna is currently
down for upgrades and maintenance, DSS-54 was scheduled instead.
A nice image of the Anthe ring arc around Saturn was Astronomy Picture of
the Day today. The image may be seen at:
http://antwrp.gsfc.nasa.gov/apod/ap080910.html
Thursday, Sept. 11 (DOY 255):
Sequence Team leads uplinked the S44 background sequence today. In
addition, a CIRS noise test and flight software patches to instrument FSW
version 5.0.4 were also uplinked. The patches will be used to determine
the best way to remove certain types of noise from the CIRS science data.
Following the results of the noise tests, a permanent patch to the CIRS
FSW will be made. The permanent patch will decrease the odds of the CIRS
scan mechanism becoming stuck by increasing a timing constraint the
software uses in controlling the mechanism. The current CIRS
commands will execute on DOY 259.
Saturday, Sept. 13 (DOY 257):
Science activities at the end of S43 included a continuation of an
orbit determination study performed by ISS on some of the lesser-known
Saturnian satellites. Next, UVIS, CIRS, and ISS observed Saturn's
moon Rhea for six and a half hours to look for trace volatile
elements. This was followed by ISS images of the G-Ring arc and an
opportunistic "mutual event" image of Dione transiting across
Enceladus. Finally, CAPS led another MAPS survey of the
magnetic and plasma environment of Saturn.
The S43 sequence concluded and S44 began execution today at
2008-257T23:44 SCET. The sequence will run for 35 days and conclude
on Oct. 18. During that time there will be a targeted encounter of
Enceladus and fifteen non-targeted flybys - two each of Titan, Tethys,
and Pallene, and one each of Pandora, Mimas, Calypso, Daphnis, Atlas,
Pan, Telesto, Janus, and Epimetheus. Five maneuvers are scheduled,
numbered 164A, and 165 through 168,
Monday, Sept. 15 (DOY 259):
A presentation on "Missing Noble Gases from the Titan
Atmosphere" was given today at JPL. The noble gases are a group of
chemical elements with very similar properties; under standard
conditions, they are all odorless, colorless, monatomic gases, with a
very low chemical reactivity. The six noble gases that occur naturally
are helium, neon, argon, krypton, xenon, and the radioactive radon. The
melting and boiling points for each noble gas are close together,
differing by less than 10 degrees Celsius; consequently, they are liquids
only over a small temperature range.
Sequence leads sent commands to the spacecraft today for a Cosmic Dust
Analyzer (CDA) ring plane crossing activity and a noise test, and for the
S44 Live Inertial Vector Propagator (IVP) Update #1. All files have
properly registered on-board the spacecraft.
Tuesday, Sept. 16 (DOY 260):
A non-targeted flyby of Titan occurred today.
The S46 Science Operations Plan product was handed off to the Sequence
Team today and the final sequence development process for S46, the
Science and Sequence Update Process, began. Items still to be
closed are RADAR requests for testing of the T48 and T49 Titan flybys in
the Integrated Test Laboratory, and establishing a schedule and resources
for the three Live IVP updates scheduled in S46.
Today a talk was presented on "Saturn's moon Titan: View from
Cassini's RADAR Mapper." Case studies using Synthetic Aperture
Radar (SAR) and high-resolution radiometry data for geological mapping
and characterization of Titan's surface were presented. Emphasis was on
flows and drainage patterns, geology, crater structures, dunes, lakes,
and evidence of structural control on drainage and flow features in the
Hotei area. Suggestions were also presented on opportunities for data
synergy between SAR/high-resolution radiometry/VIMS for geological
mapping and SAR/altimetry/VIMS for surface and subsurface
studies.
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