Cassini Significant Events 06/15/11 – 06/21/11

The most recent spacecraft telemetry was acquired on June 21 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, June 15 (DOY 166)

A news release called "Cassini Plasma Spectrometer Operations on Hold" was issued today. Mission managers for the Cassini spacecraft suspended operation of the Cassini plasma spectrometer (CAPS) instrument on Tuesday, June 14, after a series of voltage shifts occurred on the spacecraft that were attributed to the instrument. The spacecraft's power subsystem continues to function normally and all of the other science instruments as well as the engineering subsystems are unaffected by this. The Cassini engineering team and the CAPS instrument team are actively working the problem and hope to resume instrument operations shortly.

Thursday, June 16 (DOY 167)

Orbit Trim Maneuver (OTM) #286 was performed today. This was the approach maneuver setting up for the Titan 77 encounter on June 20. The Reaction Control Subsystem (RCS) burn began at 9:14 PM PDT. Telemetry immediately after the maneuver showed a burn duration of 8.75 seconds, giving a delta-V of 0.015 m/s. All subsystems reported nominal performance after the maneuver. OTM-287, the Titan 77 cleanup maneuver, is scheduled for June 24. OTM287 is the last planned maneuver until August 22.

Friday, June 17 (DOY 168)

The Cassini Project Science Group (PSG) concluded its meetings in Noordwijk, The Netherlands, today. Topics of discussion during the week included spacecraft status, science plans as the Solstice Mission continues, and plenty of science results. The Radar and Radio Science teams held team meetings, the Titan, Icy Satellites, Saturn, Rings, and Magnetospheres-and-Plasma-Science Working Groups met, and an all-day icy satellites workshop was held today.

Saturday, June 18 (DOY 169)

The Live IVP Update for Helene executed today. An image of Helene is available from today’s observations, and may be seen at: http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS68/N00172880.jpg.

Today the Cassini Outreach team showed Saturn and the moons Titan and Rhea to 150 of JPL/Caltech's Child Education Center parents and teachers at a Starry Night event.

Sunday, June 19 (DOY 170)

This week’s science activities began with a 12 hour Saturn observation by the Composite Infrared Spectrometer (CIRS) to measure oxygen compounds in the stratosphere, and a 10 hour observation of Saturn’s aurora by the Ultraviolet Imaging Spectrograph (UVIS). The Imaging Science Subsystem (ISS) took images of the transit of Rhea across Titan. The periapsis period was dominated by Cosmic Dust Analyzer (CDA) measurements of the radial profile of Saturn’s E ring to constrain the overall asymmetry with respect to the solar direction; these measurements complement the set of CDA observations made in March 2010. The CDA-dedicated periapsis was interrupted for 2.5 hours in order for the Optical Remote Sensing (ORS) instruments to perform observations during a 7000 kilometer flyby of Helene, the highest resolution opportunity of the Solstice Mission to capture this interesting co-orbital moon of Dione. Helene was observed at high phase on approach and lower phase near closest approach.

Monday, June 20 (DOY 171)

Cassini encountered Titan (T-77) today at an altitude of 1,359 kilometers and a speed of 5.9 km/sec. Closest approach occurred at 18:32:01 SCET at a latitude of 0.1 degrees N. The T-77 flyby began with UVIS obtaining an image cube of Titan's atmosphere at Extreme Ultraviolet (EUV) and Far Ultraviolet (FUV) wavelengths by sweeping its slit across the disk. These cubes 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 cubes gathered over the course of the mission to provide latitude and seasonal coverage of Titan's middle atmosphere and stratosphere. RADAR measurements were the focus of the T-77 flyby. RADAR conducted a long altimetry observation over the Shangri-La/Xanadu boundary for global shape and Xanadu characterization, and a Synthetic Aperture Radar (SAR) scan of northern Xanadu. On the outbound leg of the flyby, CIRS performed temperature mapping in the stratosphere to monitor seasonal change, and VIMS observed Titan to continue its mapping of the cloud coverage to detect any seasonal change in the cloud distribution after equinox.

A feature story called “Cassini Captures Ice Queen Helene” is available on the Cassini web site. The Cassini spacecraft completed its second-closest encounter with Saturn’s icy moon Helene, beaming down images of the small moon. At closest approach on June 18, Cassini flew within 6,968 kilometers of Helene’s surface. For images and more information on this subject, link to: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20110620/.

Tuesday, June 21 (DOY 172)

A set of instrument expanded block (IEB) files was radiated to the spacecraft today over Goldstone’s DSS-15 station in support of the S69 background sequence, with all Memory Readouts (MROs) verified and indicating they were nominally loaded and executed without incident.