Cassini is orbiting Saturn with a 9.6-day period in a plane inclined 61.7 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on May 22 by the 70-meter diameter Deep Space Network station at Madrid, Spain. Except for some science instrument issues described in previous reports, the spacecraft continues to be in an excellent state of health with all of its subsystems operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the "Present Position" page at: http://saturn.jpl.nasa.gov/mission/presentposition/ .
Titan is almost as massive as a small planet, and it has a great deal of angular momentum as it orbits Saturn. Cassini, also in orbit about Saturn, regularly takes full advantage of Titan's ample gravitation and momentum to shape its own orbit to precisely fit the Mission Planning team's commitments to the Science teams. This week, the Navigation team determined how and when to fire the spacecraft's rocket thrusters to fine-tune the flyby altitude and timing for its next Titan encounter, T-91 on May 23 (see: http://saturn.jpl.nasa.gov/mission/flybys/titan20130523 ). This "elastic collision" will result in a lower-inclination orbit for Cassini as well as a slightly longer orbit period, going from 61.7 degrees and 9.6 days to 59.4 degrees and 12 days. Subsequent Titan flybys will continue adjusting the inclination until early next year when T-110 brings it down to within a degree of Saturn's equatorial plane again.
Wednesday, May 15 (DOY 135)
The Imaging Science Subsystem (ISS), the Composite Infrared Spectrometer (CIRS) and the Visible and Infrared Mapping Spectrometer (VIMS) carried out an observation in the Titan monitoring campaign from a distance of 2.5 million kilometers today, and again on Thursday and Friday. CIRS, the Ultraviolet Imaging Spectrograph (UVIS) and VIMS observed Saturn to better determine its composition.
The first global topographic map of Saturn's largest moon Titan is the subject of today's news feature:
Thursday, May 16 (DOY 136)
Cassini passed through apoapsis, having coasted 1.36 million kilometers from the planet, slowing to 12,498 kilometers per hour relative to Saturn. This marked the beginning of Cassini's orbit #190.
The second half of the ten-week command sequence S78, which was uplinked last week, began controlling the spacecraft's activities. ISS observed Methone and Anthe, which are small objects in faint ring arcs just outside the orbit of Mimas. Some of these objects may be seen here: http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=2675. The Navigation team used ISS to take five images of Saturn's satellite Tethys against the field of background stars for optical navigation purposes. The day concluded with another ISS observation in the Satellite Orbit Campaign.
The news site Reddit.com hosted an "Ask Me Anything" interview today with the "Women of Cassini." A transcript, with pertinent links, may be seen here:
Friday, May 17 (DOY 137)
A multi-wavelength auroral science campaign continued this week, coordinated among Cassini and several Earth-based facilities, to make unprecedented simultaneous observations of the aurora in both of Saturn's hemispheres across UV and IR wavelengths. The spacing of multiple observations over several weeks allows the effects of different solar wind and magnetospheric conditions to be examined. Don't miss the description of this campaign, nor the observers' latest Science Blog entries, available here:
Deep Space Network stations in California and Australia participated in an operations readiness test, helping prepare for the Radio Science occultation experiment coming up on Monday.
UVIS, CIRS and VIMS studied Saturn's aurora today and again on Saturday. ISS reacquired and tracked the orbits of known propellers in Saturn's rings (http://go.usa.gov/YyGR) .
Saturday, May 18 (DOY 138)
This weekend, members of the Cassini Outreach team hosted a dark-sky Saturn viewing event in the Mojave National Preserve, one of California's darkest sites. More than seventy people trekked out to the desert star party. Saturn did not disappoint, showing elusive Iapetus among several other moons. Use this chart to find Iapetus this spring and summer
Closer to Cassini's earthly home, members of Cassini Outreach, the Science Office, and the Pasadena Old Town Sidewalk Astronomers showed views of Saturn and Titan to 120 people at a library park in the nearby town of Monrovia. Saturn viewing will continue to be excellent through August even from a brightly lighted city, as detailed here:
Sunday, May 19 (DOY 139)
Cassini turned its telescopes to Titan and made an observation to monitor its clouds. Next, Orbit Trim Maneuver 349 fired the spacecraft's small rocket thrusters for ten seconds and provided Cassini a velocity change of about 17 millimeters per second, fine-tuning the approach to Titan for the T-91 encounter. Finally, UVIS led another sixteen hours observing Saturn's southern aurora.
Monday, May 20 (DOY 140)
The Radio Science team silenced Cassini's telemetry transmissions, turned on two additional transmitters, and conducted another Saturn atmosphere and ring occultation experiment. Today's experiment probed a Saturn latitude of 69.5 degrees south, and used DSN stations in Australia and California. Otherwise, it was very similar to last week's, which is illustrated here:
The Ion and Neutral Mass Spectrometer (INMS) looked for neutral molecules in Saturn's inner magnetosphere, after which CIRS led an observation of Mimas's nightside leading hemisphere from 200,000 kilometers away. The day finished with northern auroral observations while Cassini passed through periapsis of Orbit #190 going 45,253 kilometers per hour relative to Saturn, at about 316,000 kilometers above the cloud tops.
The spectacular image featured today could only be obtained as summer approaches in the north of Saturn:
Tuesday, May 21 (DOY 141)
UVIS carried out a stellar occultation observation, watching the star Theta Carinae as it passed behind Saturn's rings by virtue of Cassini's motion in orbit. The week concluded when UVIS began leading a 23-hour observation of Saturn's northern auroral region.
A news feature posted today makes some predictions about the weather on Titan, which might possibly include a cold hurricane: