Cassini Significant Events 01/30/08 - 02/05/08

February 7, 2008

(Source: Cassini Project)


The most recent spacecraft telemetry was acquired on Tuesday, Feb. 5, from the Madrid 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" page at: http://saturn.jpl.nasa.gov/operations/present-position.cfm.


Wednesday, Jan. 30 (DOY 030):


Science observations this week begin with the Imaging Science Subsystem's (ISS) Narrow Angle Camera capturing images as part of the ongoing orbit determination campaign for various Saturnian satellites. At the same time, the Cassini Plasma Spectrometer (CAPS) and the Magnetospheric Imaging Instrument (MIMI) will be taking data to contribute to the ongoing study of Saturn's magnetospheric boundaries on the dusk-side at a variety of latitudes, and near noon on highly inclined orbits. In addition, the Ultra-Violet Imaging Spectrograph (UVIS) will be collecting data at a low rate continuously as part of an interplanetary hydrogen survey.


Thursday, Jan. 31 (DOY 031):


Journey to Saturn From Your Computer
Want a peek at Saturn as seen from space? A new interactive 3-D viewer that uses a game engine and allows users to travel to Saturn and see it the way the Cassini spacecraft sees it is now online at
http://saturn.jpl.nasa.gov/multimedia/CASSIE
The full article on CASSIE and additional links are available at:
http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=811


NOTE: Use of the software will require the installation of a plugin/webplayer. Recommended browsers are Firefox, Safari, and Internet Explorer. Netscape will crash with the plug in. Outreach is still tinkering with the system, as there are still a few bugs to be worked out. Feel free to send comments by using the +Contact Us link at the very bottom of the page.


An AACS Periodic Engineering Maintenance was completed Jan. 31. Performed every 90 days, this activity exercises the engine gimbal actuators, the backup Reaction Wheel Assembly (RWA), wheel #3, and scrubs the Backdoor Assisted Load Format Injection Loader memory. In the RWA exercise, the wheel is commanded to +100 rpm, -100 rpm, 0 rpm, then turned off.


Based on the latest orbit determination solution and the consensus amongst participating teams, the live Inertial Vector Propagator (IVP) Update has been given the GO for generation and uplink. The pointing errors for the Radio Science (RSS) Live Movable Block are also large enough to warrant an update in order to get satisfactory pointing for the RSS Saturn occultation. The merge product is in the process of being built by the sequence lead and will be delivered to AACS for Kinematic Prediction Tool (KPT) validation shortly. The KPT c-kernel predicts will be released by Monday for review by RSS.


Friday, Feb. 1 (DOY 032):


Two of Saturn's rings have been found to contain orderly lines of densely grouped, boulder-size icy particles that extend outward across the rings like ripples from a rock dropped in a calm pond. Normally, the distances between particles change with their velocity. In the case of Saturn's rings, the distances between these ring particles stay relatively equal even though their velocities may change. This type of pattern is completely new. For the full text of this article, link to: http://saturn.jpl.nasa.gov/news/features/feature20080131.cfm


On Saturday, Feb. 2, RSS will perform a Ka-band TWTA periodic instrument maintenance activity. This will be followed by an RSS 5-hour high-gain antenna (HGA) boresight calibration where the antenna is pointed at Earth, and a crosshair maneuver is executed for which telemetry will be recorded. Finally, RSS will perform an Operational Readiness Test to demonstrate preparedness to support the Rings/Saturn Occultation experiment on Feb. 8.


Monday, Feb. 4 (DOY 035):


CDS V10 flight software (FSW) normalization was successfully completed Feb. 4. This completes the V10 FSW update begun Sept. 24, 2007.


Unlike all previous maneuvers, Orbit Trim Maneuver (OTM) #144 was sent to the spacecraft on the DSN pass prior to the primary uplink window. OTM-144 is the biggest maneuver since the Periapsis Raise Maneuver in August of 2004, and the spacecraft's orbit period is very short, just under 12 days. Because of this, the backup location isn't as efficient as the prime location. If for some reason the backup window was used instead of the primary, a lot of additional propellant would needed. Not only would the backup maneuver be 5 m/s larger, but also the trajectory asymptotes would deviate by quite a bit from the reference trajectory. This means that maneuvers after the backup would also be larger, as they would need to correct the asymptotes back to the reference trajectory. The maneuver analysts looked a few revs ahead and found that the cost would be 15 m/s, and the asymptotes still aren't completely corrected. We decided to uplink this maneuver early to increase our probability of execution and thereby decrease the risk of excess propellant consumption.


Today ISS will check out a couple of Saturn's lesser-known moons, Helene and Atlas. ISS will image the satellites every 10 minutes for about 13 hours. The following day, the Composite Infrared Spectrometer (CIRS) will execute radial scans of Saturn's unlit face at various local times, while ISS tags along to do a slow scan azimuthally around Saturn's B-ring.


S41, the final sequence of the Cassini Prime Mission, kicked off today as part of the Science Operations Plan Update process. This process completes March 14 at which time S41 will move on to final sequence development.


Tuesday, Feb. 5 (DOY 036):


Orbit Trim Maneuver (OTM) #144 was performed today. This is the apoapsis maneuver setting up for the Titan 41 encounter on Feb. 22. The main engine burn began at 7:15 PM PST. Telemetry immediately after the maneuver showed the burn duration was 227.9 seconds, giving a delta-V of 37.39 m/s. All subsystems reported nominal performance after the maneuver.