NASA Cassini Significant Events for 10/30/2013 – 11/05/2013
Cassini is orbiting Saturn with a 47.9-day period in a plane inclined 49.7 degrees from the planet’s equatorial plane. The most recent spacecraft tracking, telemetry, and radio science data were obtained on Nov. 6 using the 70-meter diameter Deep Space Network (DSN) station at Goldstone, California. Except for the 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/ .
Cassini normally spends much of its time making turns about its three axes, keeping the optical remote-sensing instruments trained on their moving targets, all under control of the Attitude and Articulation Control Subsystem (AACS) Reaction Wheel Assemblies (RWAs). This week though, the radio-noisy Sun drifted near the line-of-sight communications path to Earth, so commands in the S81 on-board sequence stepped down Cassini’s telemetry bit rate to maintain error-free reception. Accordingly, the science observations acquired and stored fewer bits in need of downlinking with the reduced capability; this week the Imaging Science Subsystem (ISS) acquired only eleven images and the Visible and Infrared Mapping Spectrometer (VIMS) acquired only six cubes. By comparison two weeks ago 436 images and 249 cubes were taken and downlinked. There was no lack of high-value science data, though. The Magnetospheric and Plasma Science (MAPS) instruments remained prime for Cassini’s long-planned passage through Saturn’s magnetotail, which is the anti-sunward extension of the planet’s vast magnetic envelope. And the Radio Science team continued to study the Sun itself, with Cassini’s tenth Superior Conjunction Experiment (SCE) to probe the solar corona during two-way communications periods with the DSN.
Wednesday, Oct. 30 (DOY 303)
Today was day six in the eleven-day campaign to study Saturn’s magnetotail. The MAPS instruments continued loading data onto Cassini’s solid-state data recorder for subsequent playback in telemetry.
Thursday, Oct. 31 (DOY 304)
One of the 34-meter aperture DSN stations at Goldstone, California captured Cassini’s X-band (8 GHz) and Ka-band (32 GHz) signals for the Radio Science SCE, meanwhile carrying out routine communications and tracking. Freshly generated commands for Saturday’s Orbit Trim Maneuver (OTM)-363 were uplinked and confirmed on-board.
Friday, Nov. 1 (DOY 305)
Today it was Spain’s turn to participate in the SCE; Madrid’s 70-meter aperture DSN station captured Cassini’s X-band and S-band (2 GHz) signals for Radio Science, again amid routine digital communications and radiometric tracking.
Saturday, Nov. 2 (DOY 306)
The OTM-363 commands turned the spacecraft and fired its bi-propellant-fed main rocket engine for two seconds. Cassini is near apoapsis in its longest-period orbit since 2004, and the resulting change in velocity of 0.36 meters per second set the course for the T-96 flyby of Titan coming up on the first of December, just before periapsis passage.
Sunday, Nov. 3 (DOY 307)
On this tenth day of the magnetotail study ISS, VIMS, and the Composite Infrared Spectrometer (CIRS) had the spacecraft turn to perform an observation in the Titan monitoring campaign from a distance of 3.9 million kilometers.
Monday, Nov. 4 (DOY 308)
The surfaces of Saturn’s moons vary widely in their morphology. By their nature Titan and Enceladus have relatively fresh surfaces, while other moons that don’t have active methods of resurfacing retain craters from past eons’ impacts just like our own Moon. A view of Tethys’ ancient craters was featured today: http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=4913
Tuesday, Nov. 5 (DOY 309)
Commands in the S81 sequence had AACS switch off the RWAs to give them a rest, and switched on the small hydrazine-fuelled rocket thrusters. Cassini will maintain a constant High Gain Antenna (HGA)-to-Earth orientation for the remainder of superior conjunction; AACS will go back to RWA control on Nov. 9. While the spacecraft’s longitudinal axis points to Earth, the secondary axis was chosen to help the MAPS instruments’ continue to obtain additional magnetotail data.
Visit the JPL Cassini home page for more information about the Cassini Project: http://saturn.jpl.nasa.gov/
