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Cassini Significant Events 10/29/2014 - 11/04/2014 Cassini is currently orbiting Saturn with a 47.8-day period in a plane inclined 33.1 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on Nov. 4 using the 70-meter diameter
Deep Space Network (DSN) station 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. Information on the present position of the Cassini spacecraft may be found on "Eyes
on the Solar System." Saturn's gravitation slowed Cassini this week as it continued to climb toward a Nov. 14 apoapsis. While the laws of celestial mechanics controlled the spacecraft's path, the 10-week command sequence known as S86 orchestrated Cassini's activities
from onboard memory. Back on Earth, sequence implementation teams worked on developing sequences S87 and S88, while passionate scientists and engineers worked to define activities for the Grand Finale Mission events of 2017. Many of the key decisions regarding
this phase of the mission were made during last week's Project Science Group meeting at JPL. Wednesday, Oct. 29 (DOY 302) Saturn and Cassini start to slip around behind the Sun in our sky this week toward superior conjunction on Nov. 18, so the intervening distance is reaching its yearly maximum from Earth. Given that the total distance is 10.9 astronomical
units (AU; the range from Earth to Sun), round-trip radio communications take three hours two minutes at the speed of light. Saturn currently happens to be at a distance of 9.9 AU from the Sun in its 29.7-year solar orbit, and that distance is increasing toward
aphelion at 10.1 AU in April 2018. Thursday, Oct. 30 (DOY 303) The Composite Infrared Spectrometer (CIRS) observed Saturn’s atmosphere for 12 hours to help scientists understand its composition. The Visible and Infrared Mapping Spectrometer (VIMS) took advantage of the pointing and made ride-along
observations. Next, the Imaging Science Subsystem (ISS) made an hour-long observation in the satellite orbit campaign, looking to find small objects near the planet. After ISS finished, CIRS took control of pointing again to begin a 23-hour long observation
covering approximately two rotations of Saturn’s atmosphere in the mid-infrared range of the spectrum, to determine upper troposphere and tropopause temperatures. A news feature released today describes some results from Cassini's T-104 encounter with Titan 70 days ago. This giant moon's surface has remained hidden because of thick haze in the atmosphere. Humans can't perceive infrared (IR) light,
such as the signals from a television's remote control, and longer wavelengths, but Cassini's Visible and Infrared Mapping Spectrometer (VIMS) does a spectacular job of investigating Titan's surface at certain IR wavelengths that penetrate its atmosphere.
VIMS was designated the prime instrument to control spacecraft pointing beginning at the T-104 closest-approach point. In this remarkable view, IR sunlight is illuminating clouds and producing specular reflections off the liquid surface of the great lake known
as Kraken Mare:
http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20141030 Friday, Oct. 31 (DOY 304) As soon as CIRS completed its 23-hour observation, Cassini turned to point its high-gain antenna dish to Earth, stepped up the downlink telemetry data rate, and began playing back the data from its solid-state recorder (SSR). The 70-meter
diameter DSN antenna in California had long ago been scheduled to support Cassini for 2.75 hours today. However, due to a mutual arrangement to support the STEREO-B spacecraft emergency, the station was pointing elsewhere when the signals arrived at Earth.
Cassini's telemetry was not captured until later in the day when the Canberra 70-meter DSN station began tracking. New data from ongoing observations over-wrote the older data on the SSR. Saturday, Nov. 1 (DOY 305) The Magnetospheric and Plasma Science (MAPS) instruments were given the day to collect data for their survey campaign, while the spacecraft maintained an Earth-pointed attitude. The current distance of nearly 3.5 million kilometers from
the planet provides good views of the Saturn system for the Magnetospheric Imaging Instrument (MIMI). Sunday, Nov. 2 (DOY 306) Late in the day following the MAPS survey, ISS began a 24-hour long observation of Saturn's irregular moon Kiviuq. A very dark-surfaced object only about 14 kilometers in diameter, Kiviuq follows an inclined, eccentric orbit as far as 11.11
million kilometers out from the planet. Cassini's Ultraviolet Imaging Spectrograph (UVIS) acquired data in ride-along mode. An image showing some satellites and parts of the rings that are familiar to followers of Cassini were selected for today's Astronomy Picture of the Day:
http://apod.nasa.gov/apod/ap141102.html Monday, Nov. 3 (DOY 307) ISS's 24-hour long observation of Kiviuq continued throughout the day. An image featured today catches Saturn's atmosphere and Titan's, both illuminated at very high phase-angle; the shadowed rings appear ghostly dark:
http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=5107 Tuesday, Nov. 4 (DOY 308) ISS made another one-hour observation in the satellite orbit campaign. Following this activity, the spacecraft turned so that CIRS could stare at the sunlit side of the rings for 10 hours to obtain spectra in the thermal infrared part of
the spectrum for studying ring particle composition. Then, near the end of the day, UVIS began an observation that would take 37.75 hours to complete, studying Saturn's northern auroral region. VIMS rode along. Saturn is a daylight object these days, and to the unaided eye it is not visible in the bright sky. When the Deep Space Network (DSN) tracked Cassini today, their dish antennas were trained about twelve degrees due east of the Sun. As expected,
the Doppler signal and ranging data, which are used for navigation, were starting to get a little noisy due to the plasma in the Sun's corona. However, one team's noise is another team's data: today Cassini's Radio Science team began a four-week Superior Conjunction
Experiment, which is a campaign to study the solar corona itself by measuring its effects on the microwave radio signals from the spacecraft. NASA's SOHO spacecraft constantly observes this same solar-wind plasma, and publishes images of it such as this one:
http://sohowww.nascom.nasa.gov/data/realtime/c3/512
(The bright object to the left of the Sun is Venus; Saturn will be in its field of view later this month as the distant planet goes around behind our central star.) This week, the DSN communicated with and tracked Cassini on four occasions, using stations in Australia and California. A total of 12 individual commands were uplinked, and about 550 megabytes of telemetry data were downlinked and captured
at rates as high as 110,601 bits per second. 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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