Cassini is orbiting Saturn with a 23.9-day period in a plane inclined 53.4 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on Aug.12 using one of the 34-meter diameter Deep Space Network stations at Canberra, Australia. 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/.
The on-board sequence S79 issued the last of its commands controlling Cassini this week, so next week commands from S80 will begin to take effect. Meanwhile, work proceeded on commands for the ten-week sequences S81 and S82, and on planning for the 2016 start of the F-ring and Proximal Orbits phase. Most of Cassini's observations have the attitude control system constantly changing the spacecraft's orientation. Interspersed with these, there are typically calibrations of science instruments, and reaction-wheel speed maintenance activities taking place.
Wednesday, Aug. 7 (DOY 219)
Commands were sent to Cassini to perform an Orbit Trim Maneuver. Just before two o'clock in the morning Pacific time, members of the flight team were in place to watch as OTM 357 turned the spacecraft and fired the 400-newton main engine for 21 seconds. The change in velocity of 3.6 meters per second put Cassini nicely on time and on target for the Titan T-94 flyby coming up on Sept. 12.
Thursday, Aug. 8 (DOY 220)
Earth passed behind Saturn’s rings today from Cassini’s dynamic perspective. The Radio Science team was well prepared; they had all three of the spacecraft's radio transmitters operating, generating pure sine wave emissions in harmony at S-band (2 GHz), X-band (8 GHz with telemetry turned off, because its phase-symbols "perturb" the pure tones), and Ka-band (32 GHz). The invisible radio beams made a chord ring occultation, cutting across all but the D ring and the innermost part of the C ring. High-definition recordings of the signals made on the ground will be studied long into the future to reveal more about the nature of Saturn's icy rings.
Late in the day, the Cosmic Dust Analyzer (CDA) began a 25-hour long observation, capturing and reporting on samples of the interstellar dust (ISD) that can be found passing through our solar system.
Friday, Aug. 9 (DOY 221)
Today belonged to CDA for the ISD observation. At day's end, the first half of the S80 command sequence was uplinked across the distance to Cassini. After a round-trip light time of two hours forty-six minutes, all 6,733 individually timed commands were acknowledged as properly received and stored aboard the spacecraft. The second half of S80 will go up next month after more memory is available on the flight system.
Saturday, Aug. 10 (DOY 222)
Cassini turned back to Saturn, and the Composite Infrared Spectrometer (CIRS) watched for nearly nine hours to discern atmospheric composition. Next, the Ultraviolet Imaging Spectrograph (UVIS) trained its telescopes on the bright blue star Epsilon Orionis, which is also called Alnilam, and is familiar to skywatchers as the middle star in Orion's belt. Saturn's enigmatic moon Iapetus passed right in front of the star due to Cassini's motion, and UVIS was looking for gassy evidence of any possible exosphere, or tenuous atmosphere, around Iapetus. Last, UVIS began an observation lasting sixteen hours to capture Saturn in the extreme-ultraviolet and the far-ultraviolet parts of the spectrum, with ISS riding along to make visible-light images.
Sunday, Aug. 11 (DOY 223)
CIRS made another Saturn observation, looking at atmospheric composition.
Monday, Aug. 12 (DOY 224)
Today through the end of Tuesday, the Visible and Infrared Mapping Spectrometer (VIMS) traded off with CIRS, making several observations of the night side of Saturn. Each observation lasted five or six hours; VIMS mapped the planet's winds, and CIRS studied composition. The other optical instruments also acquired data while CIRS and VIMS had their turns at the helm.
An image featured today poses an optical illusion with rings and tiny moon: http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=4877
Tuesday, Aug. 13 (DOY 225)
Cassini was one of the Deep Space Network (DSN)'s best customers this week; on ten occasions since Wednesday, a DSN station in Spain, Australia, and/or California had its large aperture trained on the Saturn orbiter to carry out two-way communications, radiometric tracking, and/or Radio Science experiments.