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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 19, using one
of the 34-meter diameter Deep Space Network stations in California. 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 .
Cassini spent this week near the top of its "roller-coaster ride" of an orbit about Saturn, moving relatively slowly more than three million kilometers away from the gas giant. By Monday it had passed apoapsis, the high point in orbit,
and had begun gathering speed towards a May 4 periapsis passage. Cassini's "ticket" is good for 58 more rides around Saturn before end of mission in September 2017.
Wednesday, April 13 (DOY 104)
The spacecraft's largest-aperture telescope is a 50-centimeter diameter Cassegrain reflector that serves the Composite Infrared Spectrometer (CIRS). Today, the spacecraft's attitude-control wheels kept CIRS pointed at Saturn for 23
hours. Spectra collected will help scientists understand the composition of the gas giant's atmosphere. The Visible and Infrared Mapping Spectrometer (VIMS) and the Ultraviolet Imaging Spectrograph (UVIS) rode along with CIRS, taking data as well.
Thursday, April 14 (DOY 105)
The Imaging Science Subsystem (ISS) made a 60-minute observation in the satellite orbit campaign, looking for small objects orbiting near Saturn. Next, using the 70-meter diameter Deep Space Network (DSN) station in Australia, the
flight team sent commands to Cassini comprising the S94 background sequence. All 6,655 individual timed commands were received, as reported in telemetry after a round-trip time of 156 minutes at the speed of light. While the spacecraft held its high-gain antenna
pointed towards Earth for this session with the DSN, the Magnetospheric and Plasma Science (MAPS) instruments continued to collect in-situ data.
Findings from a long study by another in-situ direct-sensing instrument, Cassini's Cosmic Dust Analyzer, were featured in a news article just released:
http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20160414 .
Today is the 388th birthday of the 17th century astronomer Christiaan Huygens, who made several discoveries regarding Saturn, including the discovery of Saturn's largest moon Titan in 1655.
Friday, April 15 (DOY 106)
Saturn is rising just before midnight these nights, offering a beautiful view to anyone with at least a small telescope. Yellowish Titan can also be spotted easily, as well as some of Saturn's other moons.
Saturday, April 16 (DOY 107)
ISS, CIRS and VIMS performed a 90-minute observation in the Titan monitoring campaign today while the planet-like moon was at a distance of 4.4 million km. This observation was repeated on Tuesday from a distance of 3.7 million km.
Right on the heels of today's observation came a 60-minute ISS satellite orbit campaign observation. Finally, CIRS observed the northern, sunlit side of Saturn's rings, obtaining spectra at thermal-infrared wavelengths to study ring-particle composition. UVIS
and VIMS took data as well.
Sunday, April 17 (DOY 108)
ISS began a 30-hour observation of the irregular moon Ijiraq. Named after a creature in Inuit mythology, this very dark-surfaced object is about ten km in diameter, and occupies an inclined orbit that reaches as far as 14.6 million
km from Saturn.
Cassini scientists gathered at the European Geophysical Union (EGU) meeting in Vienna, Austria, today to begin a week of discussions. Included topics are the most recent findings from Cassini's dive through Enceladus’ plume last October,
updates on Titan's seasonal changes and cloud monitoring, the composition of Titan’s hydrocarbon seas, the case for massive, ancient rings around Saturn, and the unique science coming up in Cassini's final orbits in 2017.
Monday, April 18 (DOY 109)
With the completion of ISS's Ijiraq observation and another session with the DSN, the 10-week command sequence S93 came to an end, and S94 took the reins until June 26. Meanwhile, Cassini coasted through apoapsis, marking the start
of Saturn orbit #235. It had reached an altitude of 3.3 million km from Saturn, and slowed to 6,058 km per hour relative to the planet. S96's first science activity was a seven-hour observation by CDA of exogenous dust.
An image featured today shows some relatively fresh surface terrain of Saturn's anomalous moon Enceladus:
http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=5327 .
Tuesday, April 19 (DOY 110)
CIRS observed infrared spectra from Saturn’s atmosphere for 11 hours to measure its composition. Two of the other telescopic instruments rode along: VIMS and UVIS.
On five occasions during this week, while Cassini's optical instruments were pointing at or near Saturn, ISS carried out a two-minute Storm Watch observation. VIMS rode along with one of them.
The Deep Space Network communicated with and tracked Cassini five times this week, using stations in Australia and California. A total of 6,691 individual commands were uplinked, and about 1,338 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 19:
http://go.nasa.gov/1RGpQnj . 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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