Cassini Significant Events 01/26/06 - 02/01/06

February 3, 2006

(Source: Cassini Project)

Thursday, Jan. 26 (DOY 026):

Picking a target for a spacecraft to observe is usually a task for a select group of mission scientists. This past fall, however, a group of California third, fourth and fifth graders got to put themselves in the scientists' place and select where to point Cassini's cameras as the spacecraft continues its tour of the Saturnian region.

The students were given ten days to study three target options and decide which opportunity would make the most sense scientifically. After a lively debate, they voted to take an image of the rings. The opportunity arose as Cassini mission planners were weeding out a few extra optical navigation images (OPNAVs) built in the mission plan. OPNAV images are images that the navigators use to learn the exact orbits of the various moons orbiting the ringed planet, as well as the orbit of the spacecraft itself.

The Cassini Program generally builds in a few more images for optical navigation purposes than are absolutely necessary as a contingency measure in case of outages. Since current performance has been excellent, the Program was able to free up a small number of these images for this purpose, with no cost and no impact to the mission.

The students who got to step into Cassini scientists' shoes attend Shirley Avenue Elementary School in Reseda, California, part of the NASA Explorer School network. The school was selected to pilot this educational program that challenges students to experience first-hand the kind of decisions scientists make on a daily bases. On Wednesday, January 25, these students were able to be present at JPL when their image was received and displayed. In February, a similar activity will be open to all 150 NASA Explorer schools.

Friday, Jan. 27 (DOY 027):

The official input port for S20 development occurred today as part of the Science Operations Plan (SOP) update process. The merged products are currently being run through the end-to-end pointing validation process by AACS. The Project Briefing and Waiver Disposition meeting is scheduled for Wednesday, February 8. The SOP Update product is handed off to the sequence leads on Friday, February 10.

A Reaction Wheel Assembly (RWA) friction test was performed today on the backup wheel. In this test, the RWA is spun up to 600 RPM in both directions and is timed as it coasts down to 0 rpm. The results of this test were favorable and showed no significant change since early 2004.

Sequence leads for S18 were informed today that DSS-15 is ready for nominal operations. Contingency commanding and possible data loss mentioned in last week's Significant Events report was avoided. Cassini has returned to the planned downlink schedule.

An image of a new storm on Saturn is Astronomy Picture of the day today. But this time, the image was taken, not by Cassini, but by two ground-based astronomers near Paris, France. Interestingly enough, the storm seems to correspond with an outburst of radio noise detected by the Cassini spacecraft. The phenomenon is likely similar to the Dragon Storm recorded by Cassini's instruments early last year. That storm is thought to be analogous to a terrestrial thunderstorm, with radio noise produced in high-voltage lightning discharges. Kudos to the guys in France!

Background sequence S18 began execution today. The sequence will run for 42 days, concluding on March 10. Operations during that time include Orbit Trim Maneuvers 51, 52, 53, and 54, one targeted outbound flyby of Titan at an altitude of 1,813 km, one non-targeted flyby of Helene at an altitude of 67,669 km, two potential live updates, 50 DSN tracks, and a periodic instrument maintenance activity performed by the Spacecraft Operations Office.

Saturday, Jan. 28 (DOY 028):

Using Deep Space Network station DSS-25, the Radio Science Subsystem executed a High Gain Antenna Boresight Calibration in preparation for their Titan gravity experiment later in the sequence.

A member of the Cassini Mission Support and Services Office gave a Cassini talk to 20 educators from the Midwest. The educators were visiting Pasadena as part of a workshop hosted by Space Education Initiatives.

Monday, Jan. 30 (DOY 030):

The Saturn Observation Campaign (SOC) web pages have been updated for Saturn viewing in 2006. Saturn is back in the early evening sky, and is easily visible rising in the eastern sky after sunset. Look to the members page to find a Saturn Observation Campaign participant who can help you see Saturn. If there is no one in your area, consider participating in this excellent Cassini Mission Outreach program. Find Saturn viewing information, member roster and participation guidelines on the SOC website at

Weather permitting, public viewing of Saturn will be provided by Saturn Observation Campaign and Cassini Outreach volunteers with telescopes on Friday, February 3, on Colorado Blvd in Pasadena, CA and Saturday, February 4, at Library Park, Myrtle and Lime Streets, Monrovia, CA. Saturn, just past opposition, will be in our evening sky until June. For more information access the following URL:,

The Satellite Orbiter Science Team sponsored a 2-day Icy Satellite Workshop on January 30-31st in honor of the late JPL scientist Damon Simonelli. This was a very productive science meeting to discuss collaborative science on the icy Saturnian satellites.

Tuesday, Jan. 31 (DOY 031):

The Aftermarket Process for the S22 sequence began today. This 5-week process will address proposed - discretionary - changes that require re-integration of the segments contained in the S22 sequence. All such changes were submitted today and an assessment package released by the Science Planning Team. It appears that all of the requested changes can fit within the available resources. Unless the Target Working Teams and Orbiter Science Teams' recommendations change over the next couple of weeks, it is likely that the Decision meeting scheduled for February 15 will be canceled.

Outreach presented Cassini education materials, with an emphasis on Reading, Writing, and Rings, to more than 300 educators in Orange County. The event was sponsored by the Discovery Science Center in Santa Ana, California.

An illustration of the Huygens Probe on Titan's surface was Astronomy Picture of the Day today. This illustration is based on data returned from the Probe.

All teams and offices participated in this month's NASA Quarterly Review. In addition to the standard template, special presentations were given on the upcoming changes to the reference trajectory and the resulting science/sequence re-integration required, spacecraft status and activities, science data archiving, outreach, status of meeting level-one science requirements, and science highlights for the quarter.

Uplink Operations sent commands to the spacecraft for the Cosmic Dust Analyzer decontamination mini-sequence. The mini-sequence will execute on Friday, February 3.

Wednesday, Feb. 1 (DOY 032):

During this first week of S18, Cassini was outbound from Saturn. Optical Remote Sensing activities included Imaging Science Subsystem (ISS) spectrophotometry and phase coverage study of Iapetus with the Ultraviolet Imaging Spectrograph (UVIS) riding along to measure the ultraviolet albedo. The distance from Cassini to Iapetus was 942,300 km with the Sun-Iapetus-Cassini or phase angle at 135 degrees. This was followed by a lightning search by ISS and the Visible and Infrared Mapping Spectrometer (VIMS) in the Saturn northern hemisphere.

ISS also observed three satellite mutual events in which the path of one satellite crosses another during the period of observation. With rapid shuttering, the time of exact alignment can be captured and incorporated into the astrometric measurements that are a key part of orbit improvement calculations. The transits observed this week were Rhea across Enceladus, Titan across Telesto, and Janus across Enceladus. Other images of satellites, namely Enceladus and Dione, were taken against a star background by the Optical Navigation team. This returned data will be analyzed to refine knowledge of the spacecraft trajectory as well as the orbits of these bodies.

The Composite Infrared Spectrometer conducted a lengthy observation of Saturn measuring oxygen compounds such as H20 and CO2 and hydrocarbons as a function of altitude, particularly in Saturn's stratosphere. Different latitudes were sampled during the segments of the analysis.

VIMS made a number of stellar calibrations of bright IR stars. These will be used to build a library of up to 70 bright stars. Even though these stars are very bright, they have not been extensively observed in the near IR. Since it is now far beyond Earth's atmosphere, VIMS can measure the 1 to 5 micron spectra of stars without being affected by terrestrial water vapor, CO2, CH4 or other contaminants. Observing stars of different spectral types will establish the variation of near-IR spectra according to type.

The Magnetospheric and Plasma Science instruments were also active this week in performing an outer magnetosphere survey. By continuously taking data, these instruments seek to establish the locations of the magnetospheric boundaries, the global dynamics of the magnetosphere, and the degree of its variability with time.

Wrap up:

The most recent spacecraft telemetry was acquired on Wednesday, February 1, from the Goldstone tracking complex. The Cassini spacecraft is in an excellent state of health and all subsystems are operating normally. Check out the Cassini web site at for the latest press releases and images.