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Cassini Significant Events 12/18/2013 - 12/31/2013 Cassini is orbiting Saturn with a 31.9-day period in a plane inclined 51.3 degrees from the planet's equatorial plane. The most recent spacecraft tracking and telemetry data were obtained on Jan. 2 using the 70-meter diameter Deep Space
Network station at Canberra, Australia. 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" at
http://1.usa.gov/1arNM5Q. Cassini spends much of its time tracking various targets as its optical remote-sensing (ORS) instruments observe them for science observations, and turning to point its high-gain antenna to Earth for communications and radiometric tracking.
Largely independent of all these twists and turns, however, Cassini's direct-sensing Magnetospheric and Plasma Science (MAPS) instruments, as usual, continue to acquire data about the spacecraft's immediate environment. Wednesday, Dec. 18 (DOY 352) Three of Cassini's ORS instruments, the Imaging Science Subsystem (ISS), the Composite Infrared Spectrometer (CIRS), and the Ultraviolet Imaging Spectrometer (UVIS) created a fifteen-hour movie of Saturn’s rings to search for periodicities
of the spokes (http://go.usa.gov/4WGP). Thursday, Dec. 19 (DOY 353) ISS, CIRS and the Visible and Infrared Mapping Spectrometer (VIMS, the fourth ORS instrument) performed an observation in the Titan monitoring campaign at a distance of 3.75 million kilometers from the target. CIRS began a 24-hour survey
to create a mid-infrared map of Saturn, measuring temperatures in the upper troposphere and tropopause; VIMS rode along. Friday, Dec. 20 (DOY 354) CIRS completed its mid-IR map. ISS and UVIS then began a twelve-hour study of the irregular moon Tarvos. This tiny, dark-surfaced "iceberg" orbits Saturn in a highly eccentric orbit that reaches nearly eighteen million kilometers from Saturn. A mosaic of Cassini's extensive synthetic-aperture radar imaging of Titan's northern region of lakes made NASA's Astronomy Picture of the Day:
http://apod.nasa.gov/apod/ap131220.html Saturday, Dec. 21 (DOY 355) ISS and UVIS started a 25-hour observation of the irregular object Skathi, another small dark object. This one is in a retrograde, inclined orbit that reaches 15.5 million kilometers from Saturn. Sunday, Dec. 22 (DOY 356) ISS, CIRS and VIMS performed another Titan monitoring observation as the distance to the giant moon decreased to 2.8 million kilometers. Monday, Dec. 23 (DOY 357) ISS began another movie of the rings today at high phase illumination searching for spoke periodicities, with CIRS, UVIS, and VIMS also taking advantage of the pointing and recording data. This one lasted 33 hours. Selected images were featured in an article recognizing Cassini's tenth holiday season in orbit at Saturn:
http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20131223 Tuesday, Dec. 24 (DOY 358) The flight team uplinked the first half of the ten-week command sequence S82 today using the 70-meter diameter Deep Space Network (DSN) station in Australia. After a round-trip light time of two hours fifty-six minutes, telemetry from Cassini
showed that each of the 7,328 individually timed commands was properly received and stored aboard. As today marked the fiftieth "birthday" of the DSN, an image taken of the Cassini Mission Controller during this activity was published via Twitter:
https://twitter.com/CassiniSaturn/status/415548994060689408/photo/1 A short video recounts the DSN's history and its importance to planetary exploration:
http://www.youtube.com/watch?v=NGgzq8eXZOQ&feature=youtu.be During 2013, Cassini's education and public outreach effort shared 150 press images and 40 news releases and special features. Of these, Cassini science team members selected a gallery of "top ten" images for the year:
http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20131224 Wednesday, Dec. 25 (DOY 359) CIRS led a 12-hour examination of Saturn to investigate atmospheric composition, with UVIS and VIMS riding along. ISS made an observation in the satellite orbit campaign with VIMS also taking data, looking for an hour at objects near the
planet. VIMS squeezed in a two-minute storm-watch look at Saturn. The navigation team then used ISS to take images of Saturn's moon Mimas against the background stars for optical navigation purposes. Finally, VIMS started an eight-hour ring mosaic. Thursday, Dec. 26 (DOY 360) While most flight team members enjoyed a JPL holiday today, the Cassini Mission Controller supported a routine DSN pass. This was one of ten such sessions during these two weeks that provided flawless two-way digital communications and
radiometric tracking across 1.57 billion kilometers of interplanetary space. Friday, Dec. 27 (DOY 361) ISS led another satellite orbit campaign observation, which VIMS again followed with a two-minute storm watch. CIRS mapped the planet-shadowed rings in the far infrared to measure ring particle temperatures and determine their thermal inertia.
UVIS rode along. The final commands in the 10-week S81 sequence then turned the spacecraft to point its high-gain antenna to Earth for a nine-hour DSN pass. Saturday, Dec. 28 (DOY 362) The S82 command sequence began controlling the spacecraft. Its first action was to turn the spacecraft so that UVIS, CIRS and VIMS could jointly observe Saturn’s northern aurora for 12 hours. Sunday, Dec. 29 (DOY 363) ISS performed a 15-hour observation at low-phase illumination of part of the G ring. The day concluded with Orbit Trim Maneuver (OTM) 367. Commands prepared and uplinked in real time turned the spacecraft and fired its thrusters for 110
seconds, providing a velocity change of 115 millimeters per second to adjust course for the Titan T-97 flyby on Jan. 1. Monday, Dec. 30 (DOY 364) Cassini turned to train ISS's telescope on the irregular moon Siarnaq and track it for 13 and a half hours. Its size, surface brightness, and orbit about Saturn are roughly similar to those of Tarvos. A close-up infrared view of the persistent cyclonic vortex, which is centered right on Saturn's north pole, was featured today:
http://saturn.jpl.nasa.gov/photos/imagedetails/index.cfm?imageId=4953 Tuesday, Dec. 31 (DOY 365) Titan loomed large the day before encounter. ISS spent ten hours monitoring its high northern latitudes, tracking clouds and how they evolve as summer approaches. The T-97 encounter web page was published:
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