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Cassini Significant Events 03/17/10 – 03/23/10

The most recent spacecraft telemetry was acquired on Mar. 23 from the Deep Space Network tracking complex at Madrid, Spain. 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/mission/presentposition/.

Wednesday, March 17 (DOY 076)

An encounter strategy meeting was held today to cover the period between Apr. 5 and Apr. 28, Titan flyby T67 and Enceladus flyby E9, and maneuvers 242-244.

The Solar System Language Arts product ”Through the Eyes of Scientists” debuted at the National Science Teachers Association (NSTA) conference this week. More than 1,000 DVDs of educator materials were handed out at the NASA booth. Based on a Cassini award winning language arts product, “Through the Eyes of Scientists” integrates language arts with solar system science, math, and technology. NASA scientists are featured who are experts in various fields, including volcanoes, ice, moons and more. Students learn to think like scientists – keeping notebooks in which to observe and record their observations. The program includes video-biographies of scientists working in the field and lab to supplement written materials.

Thursday, March 18 (DOY 077)

The Command Loss Timer (CLT) value was increased to 5 days today as a precautionary measure. The Cassini DSN pass today ends at around noon Pacific Time. The next pass does not occur until the morning of Mar. 22. If the project were to lose that pass for any reason, the limit of the CLT would be exceeded and the spacecraft would execute fault protection. The value will be returned to the nominal value of 90 hours on Mar. 22.

This week the Composite Infrared Spectrometer (CIRS) observed Titan, and measured the oxygen compounds in Saturn’s stratosphere as a function of latitude. The Ultraviolet Imaging Spectrograph (UVIS) mapped volatiles near Enceladus to study the correlation between volatile fluctuations and plume eruptions, and observed an ingress solar occultation by Saturn. The Cassini Plasma Spectrometer led the Magnetospheric and Plasma Science (MAPS) instruments in a 14.5h dusk magnetosphere observation. The Cosmic Dust Analyzer (CDA) performed an almost continuous 2.7-day observation of E-ring dust particles. The Visual and Infrared Mapping Spectrometer (VIMS) observed Saturn atmosphere occultations of the stars alpha Orionis, alpha Canis Majoris, and alpha Canis Minoris, otherwise known as Betelgeuse, Sirius, and Procyon. RADAR performed distant Titan radiometry and collected instrument calibration data. Imaging Science (ISS) performed a satellite orbit campaign observation and imaged the transit of Dione across Tethys. In joint observations, VIMS and CIRS observed the E and G rings, and ISS, CIRS and UVIS performed several observations as part of the Titan monitoring campaign.

Two review papers to be published in the March 19 issue of the journal Science synthesize Cassini science findings since arriving at Saturn in 2004. In a paper describing the elegant mess of activity in the rings, the author describes how Cassini has shown that collisions are routine and chunks of ice leave trails of debris in their wakes. Spacecraft data have also revealed how small moons play tug-of-war with ring material and how bits of rubble that would otherwise join together to become moons are ultimately ripped apart by the gravitational pull that Saturn exerts. In a paper on Saturn's atmosphere, ionosphere, and magnetosphere, the author describes how Cassini helped scientists understand a south polar vortex that has a diameter 20 to 40 times that of a terrestrial hurricane, and the bizarrely stable hexagon-shaped jet stream at the planet's north pole. Cassini scientists have also calculated a variation in Saturn's wind speeds at different altitudes and latitudes that is 10 times greater than the wind speed variation on Earth. For the full text of this article link to: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20100318/

Friday, March 19 (DOY 078)

The spacecraft thermal team reported that the bus heaters turned off this morning as expected. No unexpected behavior has been observed from the recent test. As was reported last week, SCO took advantage of a six day period from March 13 to 19 to turn on spacecraft bus heaters while the main engine cover was closed in order to use the resulting propellant temperature rise to better estimate remaining propellant in each of the tanks. The tanks will now begin the cool down period and will continue the cool down once the main engine cover is opened on Monday morning.

A non-targeted flyby of Titan occurred today along with an unplanned live Inertial Vector Propagator update of Titan vectors that was deemed necessary after the cancellation of Orbit Trim Maneuver 239.

Saturday, March 20 (DOY 079)

Non-targeted flybys of Telesto, Atlas, Prometheus, Daphnis, and Methone occurred on Saturday, Mar. 20, and non-targeted flybys of Pallene, and Polydeuces occurred on Sunday, Mar. 21.

Monday, March 22 (DOY 081)

The main engine cover was opened today and concludes the 59th in-flight cycle. The stow angle returned to its most recent position of 33.3 degrees, which is 1 DN higher, or less open, than the past two years’ stow angle. This is of no concern. The stow angle has been higher in the past without incident.

The 30th Solid State Power Switch (SSPS) trip since launch occurred today. It affected the Magnetospheric Imaging Instrument (MIMI) Low Energy Magnetospheric Measurement Subsystem replacement heater. Fault protection cleared the trip, powered off the MIMI instrument, and powered on the replacement heater. The instrument will be powered back on tomorrow over the next DSN pass. This marks the fourth SSPS trip in four months. The SSPS trip log sheet has been updated for the latest incident.

The kickoff meeting for the S63 Science Operations Plan process was held today. S63 is the final sequence in the Equinox Mission. S64 will be the first sequence of the Extended Extended or Solstice Mission.

Tuesday, March 23 (DOY 082)

Uplink Operations and the Spacecraft Office sent commands to the spacecraft today to power on the MIMI instrument, clear the SSPS trip counter, and perform memory readouts both before and after the clear.

Passes of Cassini through Saturn’s E ring have yielded insights on the exchange of ice particles between Enceladus and the ring. Some of the moon’s jets are successful in shooting ice grains far enough to become part of the E ring. But even the ice grains that make it to the E ring tend to be recaptured by Enceladus within a few orbits as the moon moves around Saturn.