News | November 14, 2012
Cassini Significant Events 11/07/2012 - 11/13/2012
Cassini is orbiting Saturn with a period of 15.9 days and inclined 46.3 degrees from the equatorial plane. The most recent spacecraft tracking and telemetry data were collected on Nov. 14 by the Deep Space Network's 70 meter Station 14 at Goldstone, California. With the exception of a couple of instrument issues noted previously, the spacecraft continues to be in an excellent state of health with all 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/.
Tuesday morning's T-87 encounter measured the density of Titan's atmosphere in three different ways as Cassini skimmed through its thin upper reaches 973 kilometers above the surface. The Titan Flyby T-87 page has all the details here: http://saturn.jpl.nasa.gov/mission/flybys/titan20121113/
Back on Earth, the Science Planning and Sequence Team started forming a working group at JPL to identify and address engineering issues connected with Cassini's F ring and Proximal orbits in 2016 and 2017.
Wednesday, Nov. 7 (DOY 312)
The Magnetometer performed an eight-hour calibration while rotating the spacecraft about its X-axis, in preparation for the upcoming Titan T-87 flyby.
The Radio Science team continued this year's Superior Conjunction Experiment, measuring the solar corona's effects on Cassini's S-band, X-band and Ka-band downlink carrier signals, two bands at a time depending on the supporting Deep Space Network (DSN) stations' capabilities. Today, a DSN station in Madrid, Spain, participated. On Thursday, it will be a station at Goldstone, California, and again on Monday, a station in Spain.
The Imaging Science Subsystem (ISS) began an 11.7 hour movie of the lit face of the rings at high phase angle, looking for periodicities in the spokes.
Thursday, Nov. 8 (DOY 313)
The Attitude and Articulation Control Subsystem team executed a Reaction Wheel Assembly bias maneuver to adjust wheel speeds, while thrusters stabilized the spacecraft. Another one was done on Monday, prior to the T-87 flyby. Neither one was tracked by the DSN in real time, but the Navigation team will rely on telemetry to model the thrusters' effects on the trajectory. (Similar maneuvers by other spacecraft are variously described as momentum unloading or reaction wheel desaturation maneuvers. The difference is that for Cassini, these maneuvers are not for the purpose of removing momentum, but rather to manage momentum, i.e., keeping wheel speeds within a specified speed range.)
Friday, Nov. 9 (DOY 314)
ISS created a 15-hour movie of streamer-channel features in the F ring, which are raised by the 135 kilometer-long moon Prometheus when it passes through its apoapses, which are near, and sometimes go into, the F ring.
Orbit Trim Maneuver (OTM) 334, the Titan T-87 approach maneuver, was performed today using the RCS thrusters. The 56 second burn provided a delta-V of about 58 millimeters per second.
The Visible and Infrared Mapping Spectrometer (VIMS) observed the red star Chi Cygni for an instrument calibration.
Saturday, Nov. 10 (DOY 315)
The Radio Science team carried out a radio occultation experiment today whose geometry complements that of experiments completed during Cassini's Primary and Equinox Missions. Sampling a new range of ring opening angles, today's occultation chord was nearly radial, probing from the outer A ring to about mid C ring on ingress as the Earth-pointed spacecraft passed behind the ring system. Measurements at Cassini's three radio bands (0.94, 3.6, and 13 centimeters wavelength) were collected, and the data are expected to yield high resolution radial profiles of ring structure, particle sizes, aggregate of sizes or wakes, wake orientation, packing fraction, ring thickness, and more. The occultation continued into Saturn's ionosphere and upper atmosphere.
VIMS made an observation pointing at several locations within the ring system while the Sun illuminated them at high phase. VIMS then observed a chord occultation of the bright star Alpha Ceti as Cassini's motion made it pass from the F ring, in as far as the middle C ring, and then back out to the inner A ring. Finally, ISS made a close-up observation of the D ring to monitor time-variable features.
Sunday, Nov. 11 (DOY 316)
The Ultraviolet Imaging Spectrograph (UVIS) observed for three and a half hours while the star Epsilon Canis Majoris passed behind the rings.
Cassini passed through periapsis going almost 42,000 kilometers per hour, at about 410,000 kilometers above the cloud tops. This is near the E ring's outer edge.
ISS made a survey of the outer A ring with full longitudinal coverage to reacquire giant propeller features (see http://go.usa.gov/YyGR) whose orbits may have changed. The Composite Infrared Spectrometer (CIRS) was next to observe the rings, taking data to assemble thermal emission phase curves by making radial scans on the left and right ansae.
Monday, Nov. 12 (DOY 317)
CIRS spent five hours mapping Titan's stratospheric temperatures to monitor seasonal changes. VIMS then did a global map to monitor post-equinox climatic changes and look for specular reflection from the northern lakes. ISS rode along with CIRS and VIMS to image Titan's atmosphere.
An image was featured today showing the south polar vortex high in Titan's atmosphere that Cassini continues to monitor. It may be seen here: /resources/15664
Tuesday, Nov. 13 (DOY 318)
The T-87 Titan encounter executed at 973 kilometers altitude, both studying Titan and providing the gravity assist to bring Cassini's orbital inclination up to 46.3 degrees. INMS and realtime Doppler data were prime around closest approach to measure atmospheric density, with the optical remote sensing instruments observing on approach and departure.