From: Jet Propulsion Laboratory
Posted: Friday, June 13, 2008
The most recent spacecraft telemetry was acquired on Tuesday, June 10, 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: http://saturn.jpl.nasa.gov/operations/present-position.cfm.
Wednesday, June 4 (DOY 156)
This week begins by continuing to focus on ring science. During the bulk of the week, the Magnetospheric and Plasma Science (MAPS) instruments took advantage of opportunities to observe the auroras and the processes driving them. In addition, a number of occultation experiments were performed. On DOY 160, the Visual and Infrared Mapping Spectrometer (VIMS) observed the occultation of the star Gamma Cru with the Magnetospheric Imaging Instrument (MIMI), Composite Infrared Spectrometer (CIRS) and Ultraviolet Imaging Spectrograph (UVIS) riding along. On DOY 161, UVIS observed a solar occultation. The solar occultation port boresight was centered on the sun as it entered Saturn's atmosphere. The camera slit was aligned tangent to Saturn's limb. On DOY 162, CIRS observed a stellar ring occultation, and UVIS observed a stellar ring occultation on DOY 163 to close out the week.
Thursday, June 5 (DOY 157)
Today Uplink Operations sent commands to the spacecraft for the S41 live Mimas Inertial Vector Propagator (IVP) update, and commands to modify Radio and Plasma Wave Science (RPWS) direction finding. Both commands will execute on Sunday, June 8.
Saturn's F ring has long been of interest to scientists as its features change on timescales from hours to years and it is probably the only location in the solar system where large-scale collisions happen on a daily basis. Understanding these processes helps scientists understand the early stages of planet formation. A team of scientists led from the UK has discovered that the rapid changes in Saturn's F ring can be attributed to small moonlets colliding with their constituent particles and causing perturbations. Images obtained by Cassini in 2006 and 2007 show the formation and evolution of a series of structures called "jets" that are the result of collisions between small nearby moonlets and the core of the F ring. A paper on these findings has been published in "Nature." Title: "The determination of the structure of Saturn's F ring by nearby moonlets." For the complete article about these findings link to: http://www.scitech.ac.uk/PMC/PRel/STFC/CassColl.aspx Images may be found at: http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageI...
Friday, June 6 (DOY 158):
The Command Loss Timer was set back to the nominal 90 hours in the background sequence today. It had been set to a value of five days back on May 6 in order to accommodate potential Cassini DSN pass losses should any problems arise during the Entry/Descent/Landing phase of the Phoenix Mission.
The third DSS-47 proficiency test with Cassini using a Radio Science Receiver (RSR) in Narrabri, Australia, was completed today. The ~2.5 hour track overlapped additional supports over Goldstone's DSS-25 and Canberra's DSS-34 stations. The entire DSS-47 support was in 3-way mode with DSS-25 providing the uplink.
Since the last Cassini Narrabri test on DOY 126, station personnel have been running a series of tests to try to identify and repair the source of two issues that were reported by the RSS team: Spurious spectral spikes around the carrier and poor short- and long-term frequency stability. One of the issues seems to have "gone away," and the test today was unable to provide insight to the cause of the other.
The next planned DSS-47 Cassini support is on DOY 168 during an RSS Saturn atmospheric occultation. The occultation will also be covered by Goldstone's DSS-25 and DSS-26 and Canberra's DSS-34 in addition to the 70-m antennas at both sites, making it the first time ever four antennas will be tracking Ka-band simultaneously! Previously the most has been three antennas.
Saturday, June 7 (DOY 159):
This weekend the moon glides past several planetary waypoints, one of which is Saturn. All you'll need to enjoy this show is a clear evening sky. On Saturday, June 7, the crescent moon will be visible just below Mars. On the 8th, the moon is closer to Saturn, forming a little triangle with Regulus. And on the 9th, the waxing crescent is higher still above Saturn, tracing an imaginary line along the ecliptic plane. Over the next few weeks, Mars and Saturn draw closer together. On July 10 and 11, both planets will be visible in the same telescope field-of view. A star chart for Saturn and Mars can be found at: http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=2109
Sunday, June 8 (DOY 160):
June 8 is noted for Saturn periapsis for Cassini, and for the fact that it is the 383rd birthday of Giovanni Domenico Cassini. Born in 1625, Cassini, an Italian-French astronomer, discovered several of Saturn's satellites: Iapetus, Rhea, Tethys and Dione. In 1675, he discovered what is today called the "Cassini Division," the gap between two of the main rings of Saturn.
Monday, June 9 (DOY 161):
Non-targeted flybys of Pan and Pandora occurred today.
A weeklong series of meetings has begun as part of the #45 PSG meeting being held in Rome. The primary focus will be on the various science discipline sessions, and on discussion of post Equinox Mission activities.
An image of Saturn's rings from the "other side" is Astronomy Picture of the Day today. In this instance, "other side" means 17 degrees above the ring plane. Check it out at: http://antwrp.gsfc.nasa.gov/apod/ap080609.html
Live IVP/ Live Movable Block (LMB) activities in S41 continued today with the kickoff meeting for the third update process of the sequence. The orbit determination solution will be released tomorrow, and a go/no go given on Wednesday. If it's a go, the files will be uplinked to the spacecraft on Friday. UPDATE: It's a go. Based on analysis by Science Planning and concurrence from ISS, CIRS, VIMS and UVIS, the Saturn and Mimas vectors will be updated and the Dione vectors will not. The live movable block for RSS to execute on June 15 will also be updated.
The sequence leads for S42 currently have their hands full. After receiving the Instrument Expanded Block (IEBs) files from the instrument teams, the end result will be 15 loads to be sent to the spacecraft for this sequence. Eight are for the Ion and Neutral Mass Spectrometer (INMS) and the ISS load was large enough that it had to be split in two. This is not counting getting the background sequence up as well. This is a record for the number of IEBs to be uplinked. This could also present some scheduling issues since the first uplink track on DOY 177 only has three hours of usable uplink time, and the second uplink track the next day has an RSS boresight calibration resulting in one hour without telemetry.
The most recent spacecraft telemetry was acquired on Tuesday, June 10, from the Goldstone, California 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 http://saturn.jpl.nasa.gov for the latest press releases and images.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter.
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