Cassini Update - October 24, 2008
- From: baalke@xxxxxxxxxxxxx
- Date: Fri, 24 Oct 2008 17:08:28 -0700 (PDT)
Cassini Significant Events
for 10/15/08 - 10/21/08
The most recent spacecraft telemetry was acquired on Oct. 21 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, Oct. 15 (DOY 289):
Today the Cassini flight team celebrated the 11th anniversary of
launch.
Today was relatively quiet for science activities. The beginning of
the day was devoted to completing the long F ring movie started the
day before. Afterwards the spacecraft turned toward Earth to
downlink science data to Goldstone DSN stations. The day finished
with a short Composite Infrared Spectrometer (CIRS) thermal map of
the main rings.
The S45 background sequence was radiated to the spacecraft over the
Goldstone DSS-15 pass today. Execution will begin on Saturday at
2008-292T20:21 Spacecraft Event Time (SCET).
Thursday, Oct. 16 (DOY 290):
The spacecraft is approaching periapsis and the level of science
activity is increasing. This makes sense if you remember that each
time the spacecraft reaches periapsis, it is the closest it will be
to Saturn for that orbit.
Today CIRS took data for a thermal map of the main rings. The Visual
and Infrared Mapping Spectrometer (VIMS) observed the bright star
Gamma Crucis as it passed behind rings F through D, and later scanned
the shaded portion of the unlit side of the rings. The imaging
cameras (ISS) had a short retargetable activity to search for
yet-undiscovered moons or ring features, and the Ultraviolet Imaging
Spectrograph (UVIS) observed a stellar-ring occultation, this time of
a bright ultra-violet star. After the Optical Remote Sensing (ORS)
instruments completed their observations, the Magnetospheric and
Plasma Science (MAPS) teams observed the auroral magnetosphere and
Saturn Kilometric Radiation source region.
Friday, Oct. 17 (DOY 291):
Non-targeted flybys of Palene and Epimetheus occurred today.
Orbit Trim Maneuver (OTM) #168 was performed today. This was a large
periapsis maneuver setting up for the Enceladus 6 flyby on Oct. 31,
and targeted Titan 46 encounter on Nov. 3. The main engine burn
began at 3:34 AM PDT. Telemetry immediately after the maneuver showed
the burn duration was 41.7 seconds, giving a delta-V of 7.0 m/s. All
subsystems reported nominal performance after the maneuver.
The maneuver was preceded by one of the early Extended Mission Radio
Science (RSS) ring occultations spanning a chord of the ring system.
For this observation, RSS observed at Ka, X and S band frequencies.
An unusually long 14-hour downlink block to accommodate a series of
navigation and engineering events followed. Prior to the maneuver,
Spacecraft Operations received telemetry confirming that the main
engine (ME) cover was open. The ME cover is used to protect the
engines from small particulates during ring plane crossings. Once the
OTM was complete, a real time Radio and Plasma Wave Science Whistler
observation was performed on thrusters during the backup maneuver
pass. These observations are designed to obtain wideband evidence of
lightning whistlers, would verify the existence of lightning already
suspected from Saturn Electrostatic Discharges (SED), and would
provide information on the electron density along the field line to
the source. The cover was closed again at the end of the pass for a
dust hazard that will occur on October 24. This was cycle #49 for
the ME cover.
Saturday, Oct. 18 (DOY 292):
The last science activities of the S44 sequence were a small
satellite orbit determination campaign by ISS, a CIRS thermal map of
the rings, and three optical navigation images for the Navigation
team. The spacecraft then turned toward Earth to downlink the
remainder of S44 science data before handing off to the next day and
next sequence.
The S44 sequence concluded and S45 began execution today at
2008-292T14:44 Pacific Time. The sequence will run for 40 days and
conclude on Nov. 26. During that time there will be two targeted
encounters of Titan and sixteen non-targeted flybys - two each of
Enceladus and Tethys, and one each of Titan, Janus, Pan, Mimas,
Methone, Pandora, Daphnis, Atlas, Epimetheus, Polydeuces, Telesto,
and Helene. Five OTMs are scheduled, numbered 169 through 173.
Sunday, Oct. 19 (DOY 293):
A non-targeted flyby of Titan occurred today.
The first day of the S45 sequence featured rings observations led by
VIMS and CIRS. VIMS made a mosaic of the lit side of the rings while
CIRS watched as the star CW Leo, a bright infrared source, passed
behind the rings. The Cassini Plasma Spectrometer (CAPS) ended the
day with almost two hours of dedicated studies of the Saturnian
magnetosphere.
Monday, Oct. 20 (DOY 294):
A beautiful image of Saturn with moons and rings is Astronomy Picture
of the Day today. Check it out at:
<http://antwrp.gsfc.nasa.gov/apod/ap081020.html>http://
antwrp.gsfc.nasa.gov/apod/ap081020.html
Today is the first day of a week-long Cassini Project Science Group
meeting. This is the 46th assembly of this group since the project
began its early stages of development back in the mid 1980s. This
week, Cassini scientists will come to JPL to participate in Saturn,
Icy satellite, Titan, Rings, and Magnetospheric working groups,
instrument team meetings, and to give status reports to those
assembled on work in progress.
Much of the day's science activities involved ISS observations of
Mimas, Tethys, Titan and Saturn's small satellites, as well as
Saturn's G ring. In addition, UVIS studied the volatiles in the
vicinity of Enceladus to determine the nature of the relationship
between the very tenuous atmosphere at Enceladus and the plumes
emanating from that moon's southern pole. To better study Saturn's
magnetosphere, CAPS oriented the spacecraft for MAPS observations for
nearly five hours
Tuesday, Oct. 21 (DOY 295):
Closing out this week, ISS imaged Saturn's main rings through a
combination of its filters to produce high-resolution color scans in
addition to continuing campaigns to monitor Saturn's small satellites
and its F ring. UVIS performed a two-hour observation of the surface
of Dione.
Visit the JPL Cassini home page for more information about the
Cassini Project: <http://saturn.jpl.nasa.gov/>
.
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