Cassini Significant Events 03/21/07 - 03/27/07

March 29, 2007

(Source: Cassini Project)

The most recent spacecraft telemetry was acquired on Tuesday, March 27, from the Goldstone tracking complex. 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" web page at .

Wednesday, March 21 (DOY 080):

This week Uplink Operations sent instrument expanded block files to the spacecraft along
with part one of the S29 background sequence. S29 will begin execution next week. In addition, the mini-sequence for Composite Infrared Spectrometer (CIRS) V5.0 flight software check out was sent along with the Radio Science live update block mini-sequence.

Over the past several years this report has mentioned Live Movable Block activities. This
is the first time a Live Update Block has been reported. The difference is that a Live Moveable Block (LMB) is an update to the start time of a set of commands and the Inertial Vector Propagator (IVP) vectors, after the sequence has been uplinked. The delta time between the commands inside the moveable block remains unchanged. A Live Update Block (LUB) is when Radio Science needs the Live Update of their commands and vectors, but they don't move the start time.

Thursday, March 22 (DOY 081):

Cassini Outreach presented Reading, Writing, and Rings at the National After School Conference in Phoenix, Arizona, on March 22-23. Twenty education professionals attended the workshop, and an additional 2,000 stopped by the booth to speak with members of the Outreach team and view materials.

A delivery coordination meeting was held today for Instrument Operations Multi-mission Image Processing Laboratory (MIPL) uplink software upgrades, and Navigation ground software. The MIPL V35.1 delivery contents, test process, and the test report were reviewed. The delivery was accepted for operations and will be used in support of S30 by the Imaging Science Subsystem (ISS) and Visual and Infrared Mapping Spectrometer (VIMS) instruments. NAV T2.5 was a delivery of Navigation software for operations.

Orbit Trim Maneuver (OTM) #100, the Titan 27 approach maneuver, was performed today. The reaction control subsystem burn began at 2:40 PM PST. Telemetry immediately after the maneuver showed the burn duration was 49.75 seconds, giving a delta-V of 0.069 m/s. All subsystems reported nominal performance after the maneuver.

A new study of Cassini data reported this week in the online version of the journal "Science" determined that Saturn's magnetic field lines appear to be slipping relative to the rotation of the planet due to the torque imparted by electrically charged particles originating from geysers spewing water vapor and ice from Enceladus. As the geyser material becomes electrically charged, it is accelerated by the magnetic field. The force required to accelerate these ions and charged dust particles is counteracted by a force that produces the torque on the magnetic field, forcing it to slip in Saturn's ionosphere. Presently, the moon Enceladus is "weighing" down Saturn's magnetic field so much that the field is rotating somewhat slower than the planet. For more information on this news release link to: .

The Titan Orbiter Science Team (TOST) held a 2-day workshop at JPL to complete the extended mission jumpstart integration activity for the period of +/- 30 minutes around each Titan flyby. TOST was successful in completing this integration activity and will be providing AACS with the spacecraft attitude around each Titan closest approach.

Friday, March 23 (DOY 082):

TOST hosted a Titan 28-34 science preview. The presentations covered the science of greatest interest to the instrument teams for these seven flybys. These flybys are at the tail end of the 180-degree orbit transfer sequence, and at the start of the petal swing around to enable the flight team to achieve the Iapetus flyby this September. During this period there are three RADAR prime passes through closest approach (C/A), three with RSS prime through C/A, the T32 Solar Occultation ingress, and one C/A pass for Ion and Neutral Mass Spectrometer (INMS) observations.

Sunday, March 25 (DOY 084):

The Titan 27 flyby occurred today with closest approach at approximately 5:30 PM PDT at an altitude of 1010 km.

Since Wednesday, March 14, the RSS instrument team has performed five Operational Readiness Tests in order to prepare for its observations at T27. The flyby was capped by RSS high northern latitude observations examining polar vortex winds, tropospheric temperature profile, and surface reflectivity with bistatic inbound and outbound observations with an Earth occultation at closest approach. For the first time ever, the high southern and mid-northern latitude regions of Titan's atmosphere and ionosphere have been probed by radio occultation.

In addition to Radio Science, ISS contributed global mapping in a dark region and full disk color mosaics, CIRS performed stratospheric mapping and composition, and VIMS monitored cloud motion on Titan, and mapped mid-latitude regions at moderate solar phase angles.

Monday, March 26 (DOY 085):

As of Monday morning, telemetry and tracking data indicated that the Navigation delivery to the target point at Titan for the Titan 27 flyby came within 160 meters and 0.1 sec of
the intended flyby position, less than the length of two football fields, and all this is happening over 1.5 billion km from Earth. The Titan 19 delivery came within 340 meters of its target, and Titan 24 within 210 meters. All this indicates extremely accurate orbit estimations and maneuver execution, and very fine Navigation and Spacecraft teams. Just business as usual. (:>)

Tuesday, March 27 (DOY 086):

An odd, six-sided, honeycomb-shaped feature circling the entire north pole of Saturn has captured the interest of Cassini scientists. The fact that it has appeared in Cassini images as well as in Voyager images from well over two decades ago indicates that it is a long-lived feature. A second hexagon, significantly darker than the brighter historical feature, is also visible in the Cassini pictures. For more information and associated images and movies, link to: .

An image of Enceladus interacting with Saturn's E ring is Astronomy Picture of the Day today.

DSN schedulers have provided a fully negotiated DSN allocation file to the sequence leads for S30. This means that a Science Allocation Panel meeting for the allocation of sponge bits could be held today, which is more or less on schedule for this sequence. DSN personnel are still recovering from the effects of changes to the allocations as a result of the Stereo launch slips back in the last quarter of 2006. The good news is that over time they are gradually returning to the planned schedule of when to release allocation files to Cassini. It is hoped that we will be back in sync by June and the beginning of development for S37.

The kickoff meeting for the S29 Live IVP update for Saturn and Dione on DOY-097 was held today so that the orbit determination solution for OTM-101 could be incorporated into the process. The driving instruments for this update are CIRS, VIMS and ISS. The go/no go meeting for this activity will be held next Monday, April 2.