Cassini is orbiting Saturn with a 31.9-day period in a plane inclined 48.1 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on March 5 using the 70-meter diameter Deep Space Network (DSN) station at Canberra, Australia. 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 "Eyes on the Solar System."
Each time one of Cassini's telescopic remote-sensing instruments is allotted time to control the spacecraft's pointing and make an observation, one or more of the other optical instruments, which are all co-aligned, might also observe at the same time if storage space for their data has also been allocated. This was true for most of this week's optical remote-sensing activities. On the other hand, the direct-sensing magnetospheric and plasma science instruments can take data almost continuously, since they can generally make useful observations regardless of orientation.
Wednesday, Feb. 26 (DOY 057)
The Imaging Science Subsystem (ISS) performed an observation in the satellite orbit campaign to sight objects orbiting near the planet; this was repeated on Friday. The Visible and Infrared Mapping Spectrometer (VIMS) squeezed in a two-minute storm-watch observation of Saturn, and then the Composite Infrared Spectrometer (CIRS) began a 23-hour observation of Saturn’s atmosphere to better define its composition.
Thursday, Feb. 27 (DOY 058)
After developing and thoroughly testing a set of commands on the ground, the flight team sent them to Cassini today to carry out a special procedure. Following the two-hour 40-minute round-trip travel time at the speed of light, the flight team watched as the commands turned on and off pairs of the electrical catalyst-bed heaters within the backup-branch propulsion system's hydrazine thrusters. The data confirmed the predicted results, validating the team's novel contingency plan for operating thrusters in a power-saving mode should it ever become necessary to use non-standard cross-branch thruster operations.
Friday, Feb. 28 (DOY 059)
VIMS executed another quick storm watch, then spent six hours creating a mosaic of the sunlit side of the rings from far "above" their north side.
Saturday, March 1 (DOY 060)
DSN stations in Australia and California participated in four operations readiness tests this week, preparing for realtime Radio Science measurements of Titan's gravitational field during the T-99 encounter coming up next Thursday. (Spain had participated last week.) The tests coincided with routine command, telemetry, and tracking activities; there were a total of eight DSN passes this week.
ISS began 13.5 hours of low resolution observations of Saturn's narrow F ring. They will later be processed on the ground into a movie.
Sunday, March 2 (DOY 061)
CIRS performed the first of three long-duration observations this week of Titan, from as far as about two million kilometers. This one lasted 15 hours. The one on the following day was also 15 hours, and Tuesday's lasted 13 and one-half hours.
Monday, March 3 (DOY 062)
Orbit Trim Maneuver (OTM) 373, an approach maneuver for the upcoming Titan T-99 flyby, turned the spacecraft and fired the small hydrazine-fed thrusters for 20 seconds. The burn provided the desired change in velocity of 24 millimeters per second to fine-tune the flyby trajectory.
An image featured today dramatically shows Saturn's rings being lit from behind. In this viewing geometry the finest particles shine brightly by forward-scattering the sunlight. Of note are the bright outer part of the A ring and the narrow F ring just beyond. Portions of the D ring near the planet are just barely visible, and spoke-like features (http://go.usa.gov/4WGP) can be seen in the dark B ring: http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=4990.
Tuesday, March 4 (DOY 063)
Today the flight team uplinked four files of instrument-expanded-block commands that will support execution of the S83 command sequence, which begins on March 13. After a round-trip light time, telemetry confirmed that each of the 6,752 individual commands was properly received and stored on board.