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Cassini is orbiting Saturn with a period of 31.9 days in a plane inclined 28.8 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on April 12, using a 34-meter diameter
Deep Space Network station in Australia. The spacecraft continues to be in an excellent state of health with all of its subsystems operating normally except for the instrument issues described at
http://saturn.jpl.nasa.gov/news/significantevents/anomalies .
Having flown by Saturn's largest moon Titan on Monday April 4, Cassini spent this week climbing "up" from the ringed gas giant, slowing towards an April 18 apoapsis; all the science activities were controlled by the on-board S93 command
sequence. Back on Earth, Sequence Implementation Process teams continued putting together additional 10-week sequences. S94 will be uplinked on April 14 to start executing on April 18. The S95 sequence begins controlling Cassini on June 26, and S96 goes active
on September 8. Development activities for S97 have been scheduled; following that ten-week sequence, only four more remain to be implemented in the mission.
Wednesday, April 6 (DOY 097)
Cassini's Imaging Science Subsystem (ISS) had the spacecraft turn to point its telescopes toward Saturn's dusty G ring, and the diffuse E ring, which Enceladus's geysers constantly feed. These faint rings were sunlit at high phase
angle, meaning backlit, so that their fine particles would show brightly in forward-scattered light. The Visible and Infrared Mapping Spectrometer (VIMS) took advantage of this orientation, and acquired data while riding along. Data taken during this 9.3-hour
observation will be used to make a movie.
Thursday, April 7 (DOY 098)
During a routine session with the Deep Space Network today, Cassini turned and burned its small rocket thrusters on command from the flight team. This Orbit Trim Maneuver (OTM)-446 burn lasted 172 seconds, and imparted the planned
167 millimeters per second change in velocity, serving as a trajectory clean-up maneuver following the recent Titan T-118 fly-by.
When the OTM was done, ISS, VIMS, and the Composite Infrared Spectrometer (CIRS) performed a 90-minute observation in the Titan monitoring campaign, at a distance of 1.6 million kilometers from the planet-like moon. Late in the day,
ISS led CIRS and VIMS as they began a 12.6-hour examination of the Encke gap in Saturn's A ring. Particles in that gap complete an orbit of the planet once every 13.9 hours.
Friday, April 8 (DOY 099)
During recent DSN communications periods, the flight team uplinked commands that will support science instruments' activities in the upcoming S94 sequence. There were a total of 11,788 individual "instrument-expanded block" commands;
all made the journey intact, and their proper reception was confirmed after a round trip of 192 minutes at the speed of light.
Caltech astronomers recently published orbital constraints for an unseen planet in the outer solar system, with an estimated mass an order of magnitude greater than Earth's. The question as to whether the ephemeris of Saturn or Cassini
might show any perturbations from such an object was the subject of a news feature today: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature201604082 .
Saturday, April 9 (DOY 100)
VIMS spent seven hours today making a mosaic of the sunlit side of Saturn's rings, with CIRS and the Ultraviolet Imaging Spectrograph (UVIS) riding along. ISS then made a one-hour observation as part of the satellite orbit campaign,
looking near the planet for small objects. When this was done, the Navigation team used ISS to image Saturn's small active moon Enceladus against the background stars, for optical navigation purposes. Finally, CIRS and VIMS began a 23-hour observation of Saturn’s
atmosphere to determine upper-troposphere and tropopause temperatures.
Sunday, April 10 (DOY 101)
Cassini's Magnetospheric and Plasma Science (MAPS) instruments continued sampling the in-situ environment today, while the spacecraft remained Earth-pointed for communications and tracking.
NASA's Astronomy Picture of the Day featured a view of Saturn and Titan in a Cassini image taken during an engineering test in October 2002, while the spacecraft was still en route to its destination: http://apod.nasa.gov/apod/ap160410.html
.
Monday, April 11 (DOY 102)
A more recent Cassini image featured today is centered on the Cassini Division in Saturn's rings; this space was named after its discoverer, the same 17th-century astronomer for which the spacecraft takes its name: Giovanni Domenico
Cassini. Towards the upper right and outer edge of the A ring in the image, the wide Encke gap, and the narrow Keeler gap near the edge can be identified. At full size, the image is 1020 pixels on a side, matching the native resolution of ISS's imaging-sensor
chip. The image may be seen here: http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=5325 .
Tuesday, April 12 (DOY 103)
CIRS stared at the rings' northern sunlit side for 10 hours today studying ring-particle composition, with VIMS and UVIS participating. Today's viewing geometry from Cassini is illustrated here: http://go.nasa.gov/1NoFJdU .
Five times during the week, while Cassini's optical instruments were pointing at or near Saturn, ISS carried out two-minute Storm Watch observations. VIMS rode along with one of them.
The Deep Space Network communicated with and tracked Cassini five times this week, using stations in Australia. A total of 11,927 individual commands were uplinked, and about 1,020 megabytes of telemetry data were downlinked and captured
at rates as high as 142,201 bits per second.
This illustration shows Cassini's position mid-day on April 12: http://go.nasa.gov/1RGpFbF . The format shows Cassini's path over most of its current orbit up to today; looking down from the north, all depicted objects (except the
background stars of course) revolve counter-clockwise, including Saturn along its orange-colored orbit of the Sun.
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Milestones spanning the whole orbital tour are listed here:
http://saturn.jpl.nasa.gov/mission/saturntourdates .
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For a glossary of technical terms relating to these events, click the "full story" link on this page:
http://saturn.jpl.nasa.gov/news/significantevents/ .
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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/ .
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