NASA Cassini Significant Events 06/30/10 – 07/06/10
The most recent spacecraft telemetry was acquired on July 6 from the Deep Space Network tracking complex at Canberra, Australia. 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 30 (DOY 181)
An encounter strategy meeting was held today to cover the period between July 7 and Aug. 13, covering Titan flyby T71, Enceladus flyby E11, and maneuvers 257-259.
Based on the latest Navigation orbit determination solution, Science Planning is recommending a NO-GO on the DOY 186 Live Inertial Vector Propagator update. None of the targets called out during the update period from 2010-186T04:20:00 – 2010-186T08:15:00 SCET has pointing differences above the required threshold. The Sequence leads have cancelled the update after reviewing the input from Science Planning.
Orbit Trim Maneuver (OTM) #255 was performed today. This was the apoapsis maneuver setting up for the Titan 71 encounter on July 7. The main engine burn began at 2:00 AM PDT. Telemetry immediately after the maneuver showed a burn duration of 36.208 seconds, giving a delta-V of 6.251 m/s. All subsystems reported nominal performance after the maneuver.
Thursday, July 1 (DOY 182)
July 1 represents a number of significant milestones for Cassini. This year is the second anniversary of the end of Prime Mission and the start of the Equinox Mission. It is also the 6th anniversary of Saturn Orbit Insertion in 2004.
A feature story called “Saturn System moves Oxygen from Enceladus to Titan” is available on the Cassini web site. It describes a comprehensive model based on research by scientists using the Cassini plasma spectrometer that could explain how oxygen may end up on the surface of Titan. The presence of these oxygen atoms could potentially provide the basis for pre-biological chemistry. For more information link to: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20100701/
Friday, July 2 (DOY 183)
This week science observations were very much about the rings. Imaging Science (ISS) took data for a spoke movie and searched for propellers in the A-Ring. The Composite Infrared Spectrometer (CIRS) took data for a temperature map of the rings. The Visual and Infrared Mapping Spectrometer (VIMS) performed a high-resolution observation of the rings’ lit face at low phase. The Ultraviolet Imaging Spectrograph (UVIS) observed a ring and atmospheric ingress occultation of the star ALP VIR at low incidence angle, and performed spectral mapping of the rings. ISS, CIRS, and VIMS jointly observed the D-ring.
Additional science activities included CIRS, ISS, UVIS and VIMS scanning the southern hemisphere of Enceladus to monitor thermal output. UVIS and the Magnetometer searched for Enceladus’s auroral footprint by repeatedly slewing across Saturn’s auroral zone. VIMS and ISS observed Daphnis during a relatively close fly-by at ~77,300 kilometers. The Radio and Plasma Wave Science (RPWS) instrument began a three-day campaign to explore Titan’s ionosphere and its interaction with the Saturnian magnetosphere. RPWS also searched for lightning in the atmosphere of Titan.
Saturday, July 3 (DOY 184)
Orbit Trim Maneuver (OTM) #256 was performed today. This was the approach maneuver setting up for the Titan 71 encounter on July 7. The reaction control subsystem burn began at 7:29 PM PDT. Telemetry immediately after the maneuver showed a burn duration of 14.625 seconds, giving a delta-V of 0.022 m/s. All subsystems reported nominal performance after the maneuver.
Monday, July 5 (DOY 186)
Non-targeted flybys of Calypso, Enceladus, and Daphnis occurred today.
Tuesday, July 6 (DOY 187)
Cassini flew by Titan at an altitude of 1005 kilometers and a speed of 5.9 km/sec. Closest approach occurred at 12:22AM SCET on the 7th – or 5:22PM PDT on the 6th – at a latitude of 56.1* S.
ISS rode along with VIMS outbound from closest-approach to observe Titan’s anti-Saturn hemisphere and track any clouds that might be present. ISS also rode along with CIRS on the day following closest approach to continue to monitor clouds and their evolution.
The day after closest approach was a caboose period with the Cassini Plasma Spectrometer as the prime instrument during a Magnetospheric and Plasma Science campaign.
CIRS obtained a vertical profile for trace species in the stratosphere of Titan via mid-IR limb sounding, and continued a long-term campaign of global mapping in the far-IR
UVIS obtained an image cube of Titan’s atmosphere at extreme ultraviolet and far ultraviolet 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.
RWPS measured thermal plasmas in Titan’s ionosphere and surrounding environment, searched for lightning in Titan’s atmosphere, and investigated the interaction of Titan with Saturn’s magnetosphere.
At the Mission Planning Forum this week, a presentation was given on high level strategic planning for the 22 proximal orbits planned for the end of the Solstice Mission. It was decided to initiate this planning effort while the project is still fully funded, and retains the maximum of mission expertise. The proximal orbits span the period from April 23, 2017 to September 15, 2017, and are numbered 271-293. They will occur during the execution of sequences S99-S101. Some topics of discussion included science activities, possible dust hazards, atmospheric drag, hydrazine use, performance of engineering activities such as analysis of active hardware, and possible pyro firing and ejection of the main engine cover to demonstrate performance after 20 years in flight. The flight team has a lot to talk about before 2017.
A release titled “A Closer Look at Daphnis” highlighted raw images obtained by Cassini on July 5. The images are the closest images of Saturn’s moon Daphnis to date. For the full release link to: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20100706b/
