Cassini Significant Events 05/14/08 - 05/20/08

May 22, 2008

(Source: Cassini Project)

The most recent spacecraft telemetry was acquired on Tuesday, May 20, from the Goldstone, California 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:

Wednesday, May 14 (DOY 135)

Yesterday at 3:06 PM, part one of the S40 background sequence ended and part two began execution. S40 will continue to run until Friday, May 30. 

Science this week took advantage of auroral crossings that allowed the Magnetospheric and Plasma Science (MAPS) instruments to observe energetic particle interactions in Saturn's polar regions. The Cassini Plasma Spectrometer (CAPS) and Magnetometer Subsystem (MAG) measured the vertical structure and dynamics of the inner magnetosphere. MAG performed unique observations of Saturn's internal magnetic field over a unique orbit track in latitude and longitude space. Meanwhile, the Radio and Plasma Wave Science (RPWS) instrument observed the auroral magnetosphere and Saturn kilometric radiation source regions, as well as watching for wideband evidence of lightning whistlers. These would verify the existence of lightning already suspected from Saturn electrostatic discharges, and would provide information on the electron density along the field line to the source. 

Friday, May 16 (DOY 137):

Orbit Trim Maneuver (OTM) #155 was performed today. This is the cleanup maneuver after the Titan 43 encounter on May 11. The main engine burn began at 7:36 PM PDT. Telemetry immediately after the maneuver showed the burn duration was 7.1 seconds, giving a delta-V of 1.16 m/s, as planned. All subsystems reported nominal performance after the maneuver.

Saturday, May 17 (DOY 138):

Non-targeted flybys of Calypso and Methone occurred today and will be followed tomorrow by an Epimetheus flyby.

The Composite Infrared Spectrometer (CIRS) began science activities today by leading a joint Optical Remote Sensing (ORS) observation of a Dione solar eclipse. The Visual and Infrared Mapping Spectrometer (VIMS) observed a stellar occultation by Saturn with Imaging Science (ISS) riding along, and then recorded a Saturn polar movie. CIRS also led a joint ORS observation of Janus.

Cassini Radio Science conducted two special observations today: the first North-South Saturn atmospheric occultation, and the second and last Saturn gravity experiment in the prime mission. The activities started with a gravity inbound experiment, then occultation ingress followed by egress, and finally, gravity outbound.

Collectively, the occultations will provide important information about the winds in Saturn's atmosphere. They also provide information about the large and small scale structure of the atmosphere, the temperature/pressure profile, abundance of microwave absorbing species, and the electron number density profile in the ionosphere. The gravity field observation was conducted by Doppler tracking of the spacecraft during time periods both before and after the occultation event. The measured frequency residuals provide key information about Saturn's gravitational harmonic coefficients and hence the interior structure of the planet. Madrid's DSS-55 and DSS-63 and Goldstone's DSS-25, DSS-26 and DSS-15 antennas provided support for these events. The experiments were completed as planned, and high quality data were acquired.

Monday, May 19 (DOY 140):

Today the Navigation team released an update to the reference trajectory. Trajectory 080520 reflects changes beginning in orbit 68 and continuing through to the end of the extended mission in 2010. The primary purpose of the update was to change the Enceladus 5 B-plane angle from 70 to 90 degrees, and to move three maneuver locations to accommodate Discipline Working Group and Navigation Team requests. The maneuvers affected are #162, #168, and #177.

Tuesday, May 20 (DOY 141):

A delivery coordination meeting was held today for the Cassini Information Management System (CIMS) Version 3.4. CIMS 3.4 provides many new features and updates to align the product with the current Science Planning process.

The Cassini Imaging Team released the third in its series of atlases of Saturn's icy satellites, this one charting the fractured 1125 km wide moon Dione. The team has previously released atlases of Enceladus and Phoebe. Atlases of other moons will be released as Cassini's mission continues. Iapetus and Tethys are next in line. All atlases are simultaneously released to the public and to the scientific community via the NASA Planetary Data System (PDS).

It is important for planetary scientists to have accurate maps of the worlds they study. They serve as the basis for geologic interpretations, estimates of the ages of surface regions, and deciphering the processes that formed the moons' landscapes. Most importantly, with their accurate reckoning in latitude and longitude, these maps make it easy for scientists to find and refer to features of interest on the moon's surface.

For links to the full article and the maps go to: