News | July 10, 2013
Cassini Significant Events 07/03/2013 - 07/09/2013
Cassini is orbiting Saturn with a 12-day period in a plane inclined 59.4 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained early on July 9 using the 70-meter diameter Deep Space Network stations at Madrid, Spain. Except for some science instrument issues described in previous reports (for more information search the Cassini website for CAPS and USO), the spacecraft continues to be in an excellent state of health with all of its subsystems operating normally. Information on the present position of the Cassini spacecraft may be found on the "Present Position" page at: http://saturn.jpl.nasa.gov/mission/presentposition/.
Although Cassini's many types of observations this week did not involve Titan at all, Cassini is right on track for an important close flyby of this largest of Saturn's moons on July 10. The Titan T-92 Encounter page offers more detail here: http://saturn.jpl.nasa.gov/mission/flybys/titan20130710.
Wednesday, July 3 (DOY 184)
The Visible and Infrared Mapping Spectrometer (VIMS) observed the garnet-red star Mu Cephei for three and a half hours while it was occulted by the Saturn's rings.
The Realtime Operations team uplinked Part 2 of the S79 command sequence using a Deep Space Network (DSN) station in Australia. All 8375 individual commands were confirmed aboard after a round-trip light time of two hours thirty-six minutes. The S79 sequence will continue executing until Aug. 14.
Thursday, July 4 (DOY 185)
The Composite Infrared Spectrometer (CIRS) has a unique ability to map temperatures. Today it observed ring particles revolving into Saturn's shadow, to assist in determining their thermal inertia. CIRS repeated this sort of observation again on Friday with nearly ideal viewing geometry, and then twice again on Sunday. At the end of the day, VIMS began an observation of nearly six hours watching an occultation of the red star R Cassiopeia as it made a radial egress pass behind the entire ring system, going from the innermost D ring out past the narrow F ring.
Friday, July 5 (DOY 186)
The DSN typically provides flawless two-way digital communications with Cassini, as well as precise radiometric tracking of the line-of-sight speed and distance. Today's DSN "track" lasted the usual nine hours, and was one of a dozen tracking sessions this week.
Saturday, July 6 (DOY 187)
The spacecraft flew behind Saturn's rings today as viewed from Earth. The Radio Science Subsystem team (RSS) had Cassini turn on its S-band and Ka-band radio transmitters, and shut off telemetry and ranging tones on the X-band downlink. DSN stations in Goldstone, California and Canberra, Australia pointed with high precision to track the three pure, continuous tones as they actively probed Saturn's rings. RSS made high-resolution recordings of the signals for later analysis to determine ring properties. This experiment only involved the rings, but was in many respects similar to the one illustrated here, which included Saturn's atmosphere: /resources/15816
The Cosmic Dust Analyzer (CDA) spent nearly nine hours collecting and analyzing dust that impacted the instrument while the spacecraft ascended through Saturn's ring plane, on a path well outside the orbit of Rhea. Next, the Imaging Science Subsystem (ISS) made a close-up observation of the D ring, to monitor time-variable features such as corrugation in the outer part of this innermost ring.
Sunday, July 7 (DOY 188)
Orbit Trim Maneuver 352, the Titan T-92 approach maneuver, executed today using Cassini's small rocket thrusters. The 54-second burn provided Cassini a change in velocity of 57 millimeters per second. This fine-tuned the spacecraft's trajectory for a Titan flyby altitude of 964 kilometers on July 10.
ISS retargeted and tracked the orbits of known propellers (http://go.usa.gov/YyGR) in Saturn’s rings, including the one known as Bleriot. About an hour later the spacecraft passed periapsis, going 33,243 kilometers per hour relative to Saturn.
The massive star Eta Carina is a fascinating object in its own right, but today it served simply as the light source for an occultation of Saturn's rings. For nearly four hours CIRS led Cassini's pointing to watch the star traverse behind the main rings A through C, due of course to the spacecraft's motion in orbit.
Monday, July 8 (DOY 189)
CIRS conducted a ring observation measuring the thermal phase curve with a solar-elevation angle that could not be observed until this point in the mission.
Occultations provide highly valuable opportunities for studying the ring system. Today the Ultraviolet Imaging Spectrograph (UVIS) led an observation of the bright blue star Delta Centauri as it passed behind the A and B rings, providing data that will be particularly useful in understanding wake structure in the rings. Next it was VIMS's turn to lead an occultation observation, as a reddish star called 2 Centauri followed a chord track behind most of the ring system.
Some of the stripes visible in Saturn's A ring are actually waves: bending into ripples like a flag, or waves of varying density, most likely due to gravitational interaction with various moons. Such waves can be seen in an image of the small moon Pan, which orbits within the A ring's Enke Gap, that was featured today: /resources/15847
Tuesday, July 9 (DOY 190)
CIRS made a ring observation, one in a series from specific latitudes and phases of illumination; the observation also served to watch the ring particles as they exited the planet's shadow into sunlight. UVIS then led the other optical instruments in a high-priority observation of Enceladus as its phase of illumination came down as low as one degree, meaning the Sun came almost directly behind the spacecraft. This geometry is useful for understanding Enceladus's surface texture, composition, and other properties. As the day ended, the spacecraft turned to prepare for its T-92 close encounter with Titan.