Cassini Significant Events
for 04/20/06 - 04/25/06
The most recent spacecraft telemetry was acquired Tuesday, April 25,
the Goldstone tracking stations. The Cassini spacecraft is in an
state of health and is operating normally. Information on the present
position and speed of the Cassini spacecraft may be found on the
Position” web page located at
Cassini Significant Events 04/20/06 - 04/25/06
Thursday, April 20 (DOY 110)
Radio Science performed periodic instrument maintenance today along
Ultra Stable Oscillator characterization.
The Software Requirements and Certification Review for the CDS Command
Timer (CLT) flight software patch occurred today. Since a formal
was not required, the documentation was submitted directly to the
Engineering Office. This patch is planned for uplink on May 8-11. It
corrects a code error found last September.
Friday, April 21 (DOY 111)
The Mission Support & Services Office has provided some approximate
of the amount of science data that has been collected since January 1,
The data is complete through April 19, 2006.
Total science data is 138,574,587kbytes or roughly 132 gbytes.
The final real-time command executed during S19 was an end of sequence
reaction wheel assembly bias.
As S19 drew to a close, the Composite Infrared Spectrometer (CIRS)
with 60N latitude Saturn composition measurements and their first
hemisphere temperature map of Saturn at 10N latitude, the Cosmic Dust
Analyzer (CDA) continued with a search for Saturnian dust stream
and the Ion and Neutral Mass Spectrometer (INMS) with scans for dense
particle regions far from Saturn.
Saturday, April 22, (DOY 112):
S20 began execution on Friday, April 21, at 11:30PM Pacific Time. The
sequence will run for a little over 41 days and will conclude on June
During this time, five orbit trim maneuvers (OTM) are scheduled,
through 62. Status at this time is that OTMs 58 and 59 will execute as
planned, and OTM-060 has been deleted. There will be two targeted
Titan during S20 numbered Titan 13 and Titan 14. The one live update
sequence beginning on DOY 115 was cancelled when existing pointing met
science requirements. This is the first time a sequence has been flown
has been split using software developed for that purpose.
At the top of S20, science observations included three Imaging Science
Subsystem (ISS) observations of mutual events capturing a transit of
Enceladus across Janus, a transit of Enceladus across Epimetheus, and a
transit of Janus across Epimetheus. In addition, the Ultraviolet
Spectrograph (UVIS) performed a stellar calibration with the star Alpha
Virginis, and then observed Hyperion in order to measure its UV albedo
across longitude and phase space, and CIRS completed a mid-infrared
of Saturn to determine upper troposphere and tropopause temperature.
Observing temperature gradients and thermal eddies above troposhperic
and waves will give information about the dynamical activity and its
propagation or decay into the stratosphere.
Monday, April 24 (DOY 114):
At the weekly Project Science Meeting one of the topics of discussion
request from the Titan Orbiter Science Team (TOST) to the Cassini
think about a data recovery strategy for Titan 13. The unique data
captured at T13 includes a UVIS solar occultation and a full synthetic
aperture RADAR swath.
At this time, the most desirable option appears to be that if a DSN
occurs during the middle of the downlink, and the project recovers
capability before the end of the pass, then science would like to
uplinking commands to zero-out the Data Policing Table to prevent TOST
from being overwritten by cross discipline data during the following
Observation Period and the following downlink.
The PRIME observations that would be zeroed out are a series of Icy
Satellite Observations, all at about 1 to 2 million km distance, and
high phase. The Magnetospheric and Plasma Science (MAPS) and rider
instruments would also be affected.
There will be a technical coordination meeting tomorrow with the S20
sequence leads, Spacecraft Operations, Mission Planning, and Science
Planning to discuss implementation of this request.
FOLLOWUP: After the Project Science Meeting, the rings group appealed
the Project Scientist to reevaluate the decision of what data should be
preserved in the event of a DSN outage during playback. The fact that
observations would also be played back during the time of concern had
unintentionally overlooked at the meeting. The final decision will be
Tuesday, April 25 (DOY 115):
The remaining files for the April 1 Archive delivery have been
All teams have now delivered 100% of the data.
Check out the Cassini web site at http://saturn.jpl.nasa.gov for the
press releases and images.
The Cassini-Huygens mission is a cooperative project of NASA, the
Space Agency and the Italian Space Agency. The Jet Propulsion
division of the California Institute of Technology in Pasadena, manages
Cassini-Huygens mission for NASA’s Science Mission Directorate,
D.C. JPL designed, developed and assembled the Cassini orbiter.