Cassini Significant Events 04/13/11 – 04/19/11

The most recent spacecraft telemetry was acquired on April 18 from the Deep Space Network tracking complex at Goldstone, California. 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, April 13 (DOY 103)

A software patch to the Cassini Information Management System (CIMS) Resource Checker (RC) was delivered and installed today. The RC is a CIMS function that is called by CIMS, but can be altered without the need to deliver a new version of CIMS. Several enhancements were provided to the RC as part of this delivery, which are referenced in approved engineering change request (ECR) 111264.

Files were uplinked to the spacecraft yesterday in support of S67 for the end of sequence reaction wheels bias and for the swap from Reaction Wheel Assembly (RWA) 3 to RWA-4 in preparation for S68. Files were verified as properly received by the spacecraft and will start execution on DOY 115.

An item called “Cassini-Huygens Participating Scientist Announcement of Opportunity” was released today on the European Space Agency (ESA) web site as an invitation to submit proposals for Participating Scientist (PS) positions on the Cassini-Huygens mission. This Announcement of Opportunity was published jointly by ESA, NASA and the Italian Space Agency (ASI). For more information link to: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=48621.

Thursday, April 14 (DOY 104)

Seven instrument expanded block (IEB) files were radiated to the spacecraft today over DSS-43 in support of the S68 background sequence. The S68 sequence will be uplinked on Wednesday, April 20, and go active on Monday, April 25.

A kickoff meeting was held today for the S70 Sequence Implementation Process. Port 1 for the first set of input files from the teams occurs April 29.

Friday, April 15 (DOY 105)

Orbit Trim Maneuver (OTM) #280 was performed today. This was the approach maneuver setting up for the Titan 75 encounter on April 19. The Reaction Control Subsystem (RCS) burn began at 6:00 PM PDT. Telemetry immediately after the maneuver showed a burn duration of 13.125 seconds, giving a delta-V of 0.0212 m/s. All subsystems reported nominal performance after the maneuver.

Sunday, April 17 (DOY 107)

Non-targeted flybys of Aegaeon and Helene occurred today.

Monday, April 18 (DOY 108)

This week in science closed out the long (26 day) period focusing on the Magnetospheric and Plasma Science (MAPS) instruments making measurements of Saturn's magnetosphere. Five optical navigation images were acquired. The Ultraviolet Imaging Spectrograph (UVIS) performed two more of its series of repeated slews across the auroral oval of Saturn for 17 hours each, a special set of observations that were coordinated with Hubble Space Telescope observations of Saturn's aurorae. Just after periapsis, the Visual and Infrared Mapping Spectrometer (VIMS) and the Composite Infrared Spectrometer (CIRS) observed a stellar occultation of a star passing behind Saturn to determine the hydrogen/helium ratio in Saturn's atmosphere. This was followed by the Titan T-75 flyby.

T-75 is a pre-dusk, high altitude equatorial flyby across Titan's induced magnetic tail downstream from the moon. The geometry for T-75 is ideal to study the structure of the magnetotail and possibly the current sheet that separates its two lobes. The Cassini Plasma Spectrometer (CAPS) pointing will lead to important measurements of the ion and electron species escaping from the moon as a result of its interaction with Saturn's magnetospheric flow. UVIS obtained measurements of Titan's atmosphere at Extreme Ultraviolet/Far Ultraviolet (EUV/FUV) wavelengths by sweeping its slit across the disk of the moon. These data provide spectral and spatial information on nitrogen emissions, H emission and absorption, absorption by simple hydrocarbons, and the scattering properties of haze aerosols. This is one of many such datasets gathered over the course of the mission to provide latitudinal and seasonal coverage of Titan's middle atmosphere and stratosphere. CIRS rode along with a slow UVIS scan across the surface to determine seasonally changing surface temperatures at 19 microns.

Tuesday, April 19 (DOY 109)

Cassini flew by Titan today at an altitude of 10,053 kilometers and a speed of 5.6 km/sec. Closest approach occurred at 2011-109T05:00:39, at a latitude of 0.1 degree N. This was one of the two most important Titan flybys in the entire extended mission for two of Cassini's science teams. The radio and plasma wave science (RPWS) instrument team and the Cassini plasma spectrometer (CAPS) instrument team will use this flyby to study how Titan's and Saturn's magnetospheres interact with each other. For more information link to: http://saturn.jpl.nasa.gov/mission/flybys/titan20110419/.

The S68 final sequence approval meeting was held today. The background sequence will go up to the spacecraft on Wednesday, Apr. 20, and will begin execution on Monday, April 25.

A mission planning forum was held today to discuss the science objectives for the F-ring and Proximal orbits. These orbits occur during the last year of Cassini’s Solstice mission and represent unique science opportunities. Science objectives for these orbits include determining the mass of Saturn’s rings, mapping the internal structure of Saturn, and in-situ sampling of Saturn’s atmosphere. The information presented at the forum will be used by the science and engineering teams to plan for the F-ring and Proximal orbits.

The Science Forum for S70 was held today. Topics included an overview of science planned for this sequence followed by highlights, unique activities, and highest priority observations as described by the Target Working Team (TWT) and Orbiter Science Team (OST) leads, with comments from the Investigation Scientists and other instrument team representatives.