Cassini is orbiting Saturn with a 35.8-day period in a plane inclined 40.7 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on April 16 using one of the 34-meter diameter Deep Space Network (DSN) stations 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 "Eyes on the Solar System."
The 10-week command sequence known as S83 controlled most of Cassini's activities this week (the exception was an Orbit Trim Maneuver (OTM) that was accomplished using commands created and uplinked close to realtime). Meanwhile, Cassini's Navigation team continued to determine, refine and publish numeric descriptions of Cassini's orbital path, and worked on upcoming OTM opportunities. The Sequence Implementation Process teams made progress on the 10-week command sequences S84 and S85, and set task deadlines for S86. Planning also proceeded for the 2016 start of the F Ring and Proximal Orbits phase.
Wednesday, April 9 (DOY 099)
The direct-sensing Magnetospheric and Plasma Science (MAPS) instruments studied Saturn’s inner magnetosphere today while Cassini was approaching periapsis. At the same time, the Visible and Infrared Mapping Spectrometer (VIMS) completed a mosaic of the planet's southern hemisphere, from the south pole up to its mid-southern latitudes, while the Composite Infrared Spectrometer (CIRS) and the Ultraviolet Imaging Spectrograph (UVIS) rode along to take data as well; the observation lasted eight hours 39 minutes. As part of a high priority, coordinated study of Saturn’s aurora, control of the spacecraft was then handed off to UVIS for nine hours to execute several slow slews across the southern auroral oval. CIRS and VIMS also acquired data, as did some of the MAPS instruments; room for their data had been allocated in on-board storage for these (and other) ride-along activities.
The spacecraft sped through periapsis midday going 32,904 kilometers per hour relative to the planet, and coming within 686,000 kilometers of the cloud tops.
The day’s science activities concluded with a VIMS observation of Saturn’s southern polar region, staring at 70 degrees south latitude on the planet’s night side. The observation lasted eight hours, 10 minutes, during which time all the other optical remote-sensing (telescopic) instruments also observed.
Thursday, April 10 (DOY 100)
Cassini dedicated the first half of the day to downlinking telemetry containing the science data obtained on the previous day, and returning precise radiometric signals for navigation. Following this, the spacecraft again focused attention on Saturn, with CIRS mapping out the southern hemisphere in the mid to far-infrared for just over 11 hours. UVIS and VIMS rode along the whole time collecting data.
Today the Cassini Program Outreach Office initiated a naming contest. All are invited to suggest a name for Cassini's final mission segment, during which the spacecraft is planned to make 22 very daring and very fast-moving plunges between Saturn's innermost rings and upper atmosphere. Join the contest here: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20140414/
Friday, April 11 (DOY 101)
The first science activity of the day was a "mutual event," making observations of the planet Uranus as it appeared to skirt Saturn’s F ring for 1.5 hours from Cassini’s perspective. The Imaging Science Subsystem (ISS), CIRS, UVIS and VIMS all captured the moment. The Radio and Plasma Wave Science instrument (RPWS) intensified its data collection as the spacecraft flew into Saturn’s magnetotail.
During today's communications session with the Deep Space Network (one of five this week), flight team members uplinked commands to turn the spacecraft and fire its thrusters for 33 seconds. This Orbit Trim Maneuver #377 produced the required 36 millimeters per second change in velocity to clean up Cassini's trajectory following Monday's flyby of Titan.
Saturday, April 12 (DOY 102)
ISS reacquired and tracked the orbits of known "propeller" features (http://go.usa.gov/YyGR) in Saturn’s rings for an hour, with CIRS watching in ride-along mode. CIRS then controlled pointing to stare at the lit side of the rings for seven hours to study ring particle composition, with VIMS riding along. Late in the day CIRS began another seven-hour stare at the same target, this time with ISS riding.
Sunday, April 13 (DOY 103)
ISS spent 16 hours capturing images to create a low-resolution movie of Saturn's F ring, with CIRS and VIMS riding along to take data as well.
NASA's Astronomy Picture of the Day featured one of Cassini images that captured Saturn's clear blue sky in levels of the atmosphere up above the browner haze and clouds: http://apod.nasa.gov/apod/ap140413.html
Monday, April 14 (DOY 104)
ISS, CIRS and VIMS performed a 1.5-hour observation in the Titan monitoring campaign from a distance of 1.7 million kilometers. When that observation completed, ISS began to view the irregular moon Fornjot for just less than 36 hours, in an effort to measure its rotation. With a diameter estimated to be around six kilometers, this icy little object orbits Saturn in the retrograde direction just over 25 million kilometers from the planet, taking four years to go around the planet.
Saturn's rings serve as a laboratory for studying orbital mechanics. In a news feature released today, a clump in the outer part of the main rings might be showing evidence for a process by which moonlets (and moons, and planets in young solar systems) can be formed: http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20140414/
Many compelling aspects of the atmosphere in Saturn's windy northern hemisphere are visible in an image featured today: http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=5009
Tuesday, April 15 (DOY 105)
ISS uses its wide-angle telescope (a 5.7-cm aperture refractor) and its narrow angle telescope (a 19-cm Cassegrain reflector) to capture images while the spacecraft's Attitude and Articulation Control Subsystem provides fine pointing using electrically driven reaction wheels. As soon as Cassini sends the results to Earth, they are viewable almost instantly on Cassini's Raw Images web page: http://saturn.jpl.nasa.gov/photos/raw (for convenience, look for the "Newest" button, directly under the "Observation Time" link, below the "Search Raw Images" gray header). This week, 642 ISS images were received and distributed, as well as 1,198 VIMS cubes.