NASA Cassini Significant Events 11/24/10 – 11/30/10

The most recent spacecraft telemetry was acquired on Nov. 30 from the Deep Space Network tracking complex at Madrid, Spain. The Cassini spacecraft is in an excellent state of health and all subsystems are operating normally. 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/.

Wednesday, Nov. 24 (DOY 328)

A status update titled “Cassini Back to Normal, Ready for Enceladus” was released today and posted on the Cassini web site. The Cassini spacecraft resumed normal operations today. All science instruments have been turned back on, the spacecraft is properly configured, and Cassini is in good health. Mission managers expect to get a full stream of data during the upcoming flyby of the Saturnian moon Enceladus on Tuesday, Nov. 30. Cassini went into safe mode on Nov. 2, when one bit flipped in the onboard command and data subsystem computer. Engineers have determined that all spacecraft responses were proper when it entered into a standby mode, but still do not know why the bit flipped. The recovery from safing is complete. For more information on this subject link to: http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20101124/

The Stellar Reference Unit (SRU) calibration that was originally scheduled to take place via the S64 background sequence on Nov. 17, but was not due to the safing, was executed today via a real time command.

The S65 sequence began execution today at 2010-328T19:35:00. The sequence will run for 54 days and conclude on Jan. 17. During that time there will be two targeted encounters of Enceladus and one of Rhea, and fourteen non-targeted flybys – five of Titan, two of Pandora, and one each of Hyperion, Atlas, Janus, Dione, Pan, Daphnis, and Methone. Eight OTMs are scheduled, numbered 268 through 275.

This week, the first week of the S65 background sequence, the science observations began during the apoapse portion of Orbit 141, inbound to periapsis. Included were a 13 hour interstellar dust campaign by the Cosmic Dust Analyzer (CDA) and a 13.5 hour observation of the low latitude plasma environment by the Cassini Plasma Spectrometer (CAPS). Next, the Composite Infrared Spectrometer (CIRS), the Imaging Science Subsystem (ISS), and the Visual and Infrared Mapping Spectrometer (VIMS) performed an observation of Titan as part of the Titan monitoring campaign to search for variability in the thick atmosphere of this large moon. The Ultraviolet Imaging Spectrograph (UVIS), CIRS, ISS and VIMS performed an 11 hour observation of Saturn’s aurora. Unique observations of the spongy-looking, chaotically spinning moon Hyperion were made in a 13 hour block and a 5 hour block by ISS, UVIS, VIMS and CIRS. UVIS performed an 11 hour observation of Rhea to map ultraviolet albedo as a function of longitude and phase angle; CIRS and VIMS participated in the observation as well. Approaching periapsis, at a distance of about 7 Saturn radii, CDA made an observation of a ring shadow crossing.

Thursday, Nov. 25 (DOY 329)

Office moves continued this week within the Cassini Project area. So far, 55 out of 60 office moves have been completed. This task is slated for completion by next month, when all 60 moves will be completed in support of the transition to the new, descoped Solstice mission, and the accommodation of other Projects moving into the operations building.

Judges have selected U.S. winners for the Cassini Scientist for a Day essay contest. There were nine U.S. winners (one winner per essay topic per grade category) out of 1,000 students from 67 classrooms in 23 states who entered the essay contest. The winning students come from Virginia, Connecticut, Nebraska, California, New Jersey, Illinois, Missouri, and New York. Names will be announced next week following the live Ustream webcast on Dec. 7. Students are emailing their Saturn questions to scientistforaday@jpl.nasa.gov by December 1, to be answered during the December 7 Ustream event.

Friday, Nov. 26 (DOY 330)

A feature story called “Thin Air: Cassini Finds Ethereal Atmosphere at Rhea” is available on the Cassini web site. It describes how Cassini has detected a very tenuous atmosphere known as an exosphere, infused with oxygen and carbon dioxide, around Saturn’s icy moon Rhea. This is the first time a spacecraft has directly captured molecules of an oxygen atmosphere albeit a very thin one — at a world other than Earth. The oxygen appears to arise when Saturn’s magnetic field rotates over Rhea. For more information on this subject link to: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20101126/

Saturday, Nov. 27 (DOY 331)

Orbit Trim Maneuver (OTM) #268 was performed today. This was the approach maneuver setting up for the Enceladus 12 (E12) encounter on Nov. 30. The Reaction Control Subsystem (RCS) burn began at 9:44 AM PST. Telemetry immediately after the maneuver showed a burn duration of 55.875 seconds, giving a delta-V of 0.064 m/s. All subsystems reported nominal performance after the maneuver.

Sunday, Nov 28 (DOY 332)

The main engine cover was closed today for the periapsis dust crossing, and the Attitude and Articulation Control Subsystem (AACS) secondary safe table value was set to 170 degrees in preparation for the E12 flyby.

Monday, Nov. 29 (DOY 333)

A lunchtime seminar titled “Microwaving Titan” was presented today by a Cassini RADAR team member. This talk described the present understanding of Titan’s surface and how the radar and radiometer worked together to better understand the nature of its surface. This event was sponsored by the Science Division.

Tuesday, Nov. 30 (DOY 334)

Today Cassini flew by Enceladus at an altitude of 47.9 kilometers and a speed of 6.3 km/sec. Closest approach occurred at 2010-334T11:53 at latitude of 61.1*N. This flyby was optimized for Radio Science (RSS) gravity observations. There were two 3-hour “wing” observations before and after closest approach, and then three more hours centered directly around closest approach. Between RSS observations, ISS and CIRS observed this moon on the inbound leg, and CIRS and VIMS took data on the outbound leg. The focus of this ~50 kilometer altitude, northern hemisphere flyby is the study of Enceladus’s gravity and interior. The Cassini radio science subsystem (RSS) measured subtle variations in the Enceladus gravity field as the Cassini spacecraft flew by. For more information link to: http://saturn.jpl.nasa.gov/mission/flybys/enceladus20101130/

The most recent Cassini-Huygens Analysis and Results of the Mission (CHARM) teleconference was held today. The topic: “Unveiling Titan: A World Strange and Familiar”. The Cassini mission has unveiled a world that experiences surface temperatures about 200 degrees colder than Earth’s, receives 100 times less sunlight, where hydrocarbon molecules rain from the sky and water ice is as hard as rock. This presentation is a review of the discoveries of the recent flybys of Titan with focus on what has been learned about its lakes, their seasonal evolution, and the hypothesis that they undergo cyclic changes over tens of thousands of years, analogous to (Croll) Milankovitch climate cycles on Earth. A PDF of the presentation package may be obtained at: http://saturn.jpl.nasa.gov/video/products/MultimediaProductsCharm/

A news release called “Cassini Finds Warm Cracks on Enceladus” is available on the Cassini web site. New images and data from the Cassini spacecraft give scientists a unique Saturn-lit view of active fissures through the south polar region of Saturn’s moon Enceladus. They reveal a more complicated web of warm fractures than previously thought. For more information on this subject and images, link to: http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20101130/