Cassini Significant Events 02/24/10 – 03/02/10

The most recent spacecraft telemetry was acquired on Mar. 2 from the Deep Space Network tracking complex at Canberra, Australia. 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, Feb. 24 (DOY 055)

A major five-part BBC TV series entitled "Wonders of the Solar System" begins Sunday, Mar. 7. Part 1 is about the Sun but Part 2 is about the Rings of Saturn and Enceladus; Part 3 is about the Lakes of Titan. As you can imagine, Cassini features prominently in Parts 2 and 3. Discovery Science will show the series in the US, perhaps starting in August. For more information on the series, link to: http://www.bbc.co.uk/programmes/b00qyxfb .

Cassini's "Make your own Cassini Presentation" webpage provides museums, planetariums, outreach groups and educators with a toolbox of content to develop and present Saturn viewing events, planetarium and museum shows, lectures, classroom and after school activities.

Thursday, Feb. 25 (DOY 056)

The S62 Engineering Activities Review took place today. At this review, Spacecraft Office personnel take a look at all spacecraft activities to be performed during the S62 sequence.

An Inertial Reference Unit calibration took place on board the spacecraft today. The activity ran for just over 3 hours and rolled the spacecraft in both directions about each of the X, Y, and Z axes. The quick-look analysis looks good and a more detailed analysis will follow in a few weeks.

Cassini Science League: Agreement at Hotei Regio Two of Cassini's instruments, RADAR and the Visible and Infrared Mapping Spectrometer (VIMS), usually see different characteristics when looking at the same place on Titan. But at one area called Hotei Regio, they are in agreement that several geological processes, from a large impact to floods, debris flows and ice volcanoes, appear to have shaped this curious landscape.

Friday, Feb. 26 (DOY 057)

In addition to sending up the S58 background sequence, Uplink Operations sent commands to the spacecraft for a real-time end-of-sequence wheel bias, setting the wheel speeds to –1075, -710, and -948 rpm in preparation for S58. Instrument commands went to the Cosmic Dust Analyzer (CDA) to customize the instrument's visibility to bigger particles during the upcoming Rhea flyby on Mar. 2.

Saturday, Feb. 27 (DOY 058)

The predicted miss from the target for the Rhea flyby on Mar. 2 is less than one km. The uncertainty in this value is dominated by the uncertainty in the Rhea ephemeris and this uncertainty will not improve until after the flyby.
Since the flyby conditions without the final approach maneuver were pronounced acceptable by Science Planning, OTM-238, the Rhea 2 approach maneuver scheduled for Feb. 27, was cancelled.

Sunday, Feb. 28 (DOY 059)

The main engine cover was closed today. It will be reopened on Mar. 3, completing the 58th cover cycle since launch.

At the end of S57, Imaging Science (ISS) observed Iapetus, Saturn's outer satellite Skoll, and the transit of Dione across Enceladus. The Composite Infrared Spectrometer (CIRS) created a mid-infrared thermal map of Saturn to determine upper troposphere and tropopause temperatures, and measured oxygen compounds in Saturn's stratosphere. VIMS observed Saturn's E and G rings.

Monday, March 1 (DOY 060)

The S57 sequence concluded and S58 began execution today. The sequence will run for 34 days and conclude on Apr. 4. During that time there will be two targeted encounters, one each of Rhea and Helene, and ten non-targeted flybys, one each of Pan, Calypso, Titan, Telesto, Atlas, Prometheus, Daphnis, Methone, Pallene, and Polyduces. Three maneuvers are scheduled, numbered 239 through 241.

The S58 sequence began with an ISS observation of the plume on Enceladus. This activity was part of the ongoing campaign to determine the phase function of the plume and to look for time-variability. In combination with ISS, UVIS used its extreme ultra-violet and far ultra-violet channels to observe the plume at high phase.

One of the leads for the Satellite Orbiter Science Team wrote a blog post previewing the March 2 Rhea flyby. It was noted that this flyby would be the closest encounter yet with Saturn's second largest moon and that scientists hope the flyby will help them answer questions about potential debris that could make up a ring around the moon and the composition of its surface. http://blogs.jpl.nasa.gov/?p=62 .

Tuesday, March 2 (DOY 061)

Traveling at a speed of 8.6 km/sec, Cassini performed the Rhea 2 flyby, passing the satellite at an altitude of 100 km. The last targeted flyby of Rhea occurred in November 2005. Approaching Rhea, RADAR performed a raster scan of the moon's surface to obtain simultaneous scatterometry and radiometry measurements to understand the texture and composition of the surface. The Cassini Plasma Spectrometer (CAPS) took over prime pointing 45 minutes before closest approach to observe the interaction between Rhea and the magnetosphere of Saturn. After closest approach, VIMS and CIRS imaged Rhea at visible and infrared wavelengths to better understand its geologic history and composition, and CIRS continued to observe while Rhea went into eclipse. For more information link to: http://saturn.jpl.nasa.gov/mission/flybys/rhea20100302/ .

After the cancellation of OTM-238, the live update analysis based on the final orbit determination solution showed an error of 8.38 mrad for the ISS observation of Helene on Mar. 3. An unplanned live Inertial Vector Propagator update would be required. ISS, UVIS, CIRS, and VIMS requested a go for the update so the files were built and uplinked today in preparation for tomorrow's non-targeted flybys of Pan, Calypso, and Helene.

Coming Up:

Following a day after the targeted flyby of Rhea, the Cassini spacecraft will make its closest approach of the mission to Helene at about 1,800 kilometers. The small moon is referred to as a Trojan moon because it is gravitationally tied to the much larger moon Dione. For more information go to the flyby page at: http://saturn.jpl.nasa.gov/mission/flybys/helene20100303/ .