Cassini Significant Events 01/14/2015 – 01/20/2015

Cassini is currently orbiting Saturn with a 31.9-day period in a plane inclined 19.1 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on Jan. 21 using one of the 34-meter diameter Deep Space Network stations 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/ .

Commands from the 10-week-long on-board command sequence S87 directed most of Cassini's activities in flight this week, while the spacecraft proceeded to climb towards apoapsis next month. Meanwhile, development activities proceeded on the sequences S88, S89, and S90. Working plans for the mission's activities in 2016, and for the 2017 Grand Finale, were among the tasks as Cassini's managers and scientists met this week at the Italian Space Agency (ASI) headquarters near Rome for the 65th Project Science Group meeting.

Wednesday, Jan. 14 (DOY 014)

Today marks a decade since the European Space Agency's battery-powered Huygens Probe, which Cassini delivered to the Saturn system, made history by parachuting for two and one-half hours through the dense atmosphere of Titan, Saturn's planet-size moon. Named for the seventeenth Century Dutch astronomer Christiaan Huygens who discovered Titan, this atmospheric-probe spacecraft was designed to survive landing, whether in liquid seas or on solid ground. It encountered a frozen, dry terrain and continued returning data from its surface-science investigations for another 72 minutes at which point, the Cassini orbiter, which was relaying the probe data, disappeared over the horizon. This web page provides more information, as well as a link to the European Space Agency's listing of the "Top 10 Discoveries at Titan":
https://solarsystem.nasa.gov/news/12892/cassini-10-years-at-saturn-top-10-discoveries/.

Cassini's Ultraviolet Imaging Spectrograph (UVIS) led a joint observation of Saturn’s northern aurora, along with participation from the Composite Infrared Spectrometer (CIRS) and the Visible and Infrared Mapping Spectrometer (VIMS).

The S87 command sequence in Cassini's memory reached a planned pause, at which time commands from Earth arrived, created based on the latest tracking data, for Orbit Trim Maneuver (OTM) 401. In response, the spacecraft turned and fired its small hydrazine-fed rocket thrusters for 232 seconds. This burn imparted the needed change in velocity of 230 millimeters per second to correct the spacecraft's trajectory following last Sunday's T-108 Titan fly-by.

Thursday, Jan. 15 (DOY 015)

The Imaging Science Subsystem (ISS) led CIRS and VIMS in a 90-minute Titan monitoring campaign observation while the giant moon was at a distance of 1.7 million kilometers. When this was finished, CIRS took control of spacecraft pointing for 12 hours, observing Saturn in an effort to better determine its atmospheric composition. ISS squeezed in a two-minute storm-watch observation of Saturn both before and after the CIRS-led activity.

Friday, Jan. 16 (DOY 016)

CIRS stared at Saturn's sunlit C ring, the innermost of the three main rings that are visible from Earth in a small telescope. This observation lasted seven hours, and obtained thermal infrared spectra to study ring particle composition. ISS and VIMS took advantage of the pointing and took data while "riding along." Next, ISS took two minutes for a Saturn storm watch, and then CIRS, with ISS and VIMS riding along, began a 23-hour observation of Saturn’s atmosphere to measure temperatures in the upper troposphere and the tropopause.

Four of Huygens's views on approach to Titan's surface were featured as NASA's Astronomy Picture of the Day today:
http://apod.nasa.gov/apod/ap150116.html .

Saturday, Jan. 17 (DOY 017)

ISS and VIMS made a two-minute Saturn storm-watch observation before Cassini turned to communicate with Earth for eight hours. Next, ISS began controlling the spacecraft's attitude for 38 hours so its telescopes could track and observe Saturn's irregular moon Albiorix. UVIS and VIMS rode along. Albiorix is a very dark-surfaced object about 26 kilometers in diameter. This member of the Gallic group of satellites was named for a mythological king of the world and orbits Saturn in an inclined, highly elliptical path that reaches more than 16 million kilometers from the planet.

Sunday, Jan. 18 (DOY 018)

Saturn is well placed before dawn in the eastern sky these days, offering a fine view in almost any telescope. The sunlight reflected from Saturn and its rings, as well as Cassini's signal, take 87 minutes to propagate to Earth; this is decreasing by a few seconds every day as Earth swings eastward around the Sun.

Monday, Jan. 19 (DOY 019)

Saturn's bright-surfaced moon Janus occupies practically the same orbit as smaller Epimetheus, and the two execute an orbit exchanging "dance" about once every four years. A stunning image of the larger of the pair was featured today:
/resources/16142 .

Tuesday, Jan. 20 (DOY 020)

UVIS observed the bluish star beta Canis Majoris for eight hours while it was occulted by Saturn's A ring and then the B Ring. The other telescopic instruments -- ISS, CIRS, and VIMS -- rode along. This was an excellent opportunity for observing wakes and structure in the rings. With this observation complete, ISS and VIMS made another two-minute storm watch of Saturn. The Navigation team then used ISS to take images of the dwarf planet Pluto for optical navigation purposes. This was for the benefit of the New Horizons Pluto-Charon mission, launched nine years ago, which will fly rapidly past these Kuiper-belt objects this coming July. Finally, CIRS turned and stared at Saturn's sunlit A ring -- the outermost of the three main rings -- for six hours with VIMS riding, collecting thermal infrared spectra to study ring particle composition.

During the past week, the Deep Space Network communicated with and tracked Cassini on five occasions, using stations in Australia and California. A total of 148 individual commands were uplinked, and about 840 megabytes of telemetry data were downlinked and captured at rates as high as 124,426 bits per second.