Cassini Significant Events 08/04/04 - 08/10/05

August 12, 2005

(Source: Cassini Project)


Thursday, August 04 (DOY 216):

Information was provided this week regarding the assessment meeting that was held August 3 about S18 aftermarket changes.  It appears that all requested changes can fit within the available resources.  Unless the recommendations of the Target Working Teams and Orbiter Science Teams change over the next couple of weeks, it is likely that the decision meeting scheduled in two weeks will be canceled.

Outreach provided information regarding some events that occurred over the previous weeks.   July 24-30, Outreach presented, "Reading, Writing, and Rings" at the annual conference for students with exceptional needs. Sixty members of the education community who work with students with physical, mental, and emotional disabilities attended the conference, held in Huntsville, Alabama.

The Chabot Space and Science Center in Oakland, California hosted a 3-day workshop focusing on "Reading, Writing, and Rings".  The workshop led teachers through different activities as well as teaching techniques developed in the lessons. Integration with standardized testing plans and state-adopted language arts curricula were included. In addition, a mission overview was presented to introduce teachers to different technical aspects of the mission.  A Q&A session was held afterwards.  The workshop ran August 1-3, 2005 with 18 teachers attending.


Friday, August 05 (DOY 217):

An image advisory was released today on the satellite Mimas.  The Cassini spacecraft found the Saturnian moon looking battered and bruised, with a surface that may be the most heavily cratered in the Saturn system.  The August 2 flyby returned eye-catching images of its most distinctive feature, the spectacular 140 km diameter landslide-filled Herschel crater. Numerous rounded and worn-out craters, craters within other craters and long grooves reminiscent of those seen on asteroids are also seen in the new images.  The new Mimas images are available at http://saturn.jpl.nasa.gov. 

All teams and offices participated today in a Cassini/NASA quarterly review.

The Titan Orbiter Science Team hosted a Preview Meeting covering the Titan T6, T7, & T8 encounters. The meeting was open to anyone on the flight team who was interested in a preview of the science objectives and activities for these three flybys.


Monday, August 08 (DOY 220):

Uplink Operations sent commands to the spacecraft for Visual and Infrared Mapping Spectrometer (VIMS) Instrument Expanded Block files, and for a Cosmic Dust Analyzer decontamination activity that will execute on Friday.

The Composite Infrared Spectrometer (CIRS) and Ultraviolet Imaging Spectrograph (UVIS) instrument teams have now delivered 100 percent of their archive data from launch through September 2004 to the Planetary Data System (PDS)
The second archive delivery on October 1, 2005 will contain data collected from October 2004 to December 2004.  The Magnetospheric Imaging Instrument team has already submitted their data for this period, and it has been accepted by PDS.


Tuesday, August 09 (DOY 221):

A kick-off meeting was held today for the DOY 227 Live Inertial Vector Propagator (IVP) update process.   A Go/No Go meeting will be held tomorrow.   UPDATE:  At the Go / No-Go meeting it was determined that the original satellite and spacecraft ephemeris information used in planning the observation was still very accurate, and the update to the pointing was not necessary.

OK.  So what is all this about Live IVP updates, OD solutions, pointing, etc. that you keep hearing about?  Initial development for a sequence may occur years before it is time to finally dust it off, and execute it on-board the spacecraft.  In early development the Science community will identify satellites they wish to observe, but at the time, the exact details of where to point the spacecraft are not known.  There is too much uncertainty at that time to accurately predict where the satellite is going to be. It requires both the Navigation team's understanding of where the spacecraft is, and our knowledge of the location of the satellites in order to ensure accurate pointing.  Things change over time, hence the uncertainty at the time of sequence development.

To ensure that the satellite data will be acquired when the sequence finally executes, the concept of live movable blocks and vector updates was developed.  Basically, for a limited number of observations, spacecraft pointing for specific targets will be analyzed, and a small portion of the sequence modified to ensure we are looking in the right place.  The vectors that are being updated are superceded - updated - as part of the live update process, thus providing accurate pointing to the satellites. Oh, and this all happens while the sequence is already executing.  That is why it is called a "live" update.

If changes to the spacecraft trajectory based on the Orbit Trim Maneuvers (OTM) leave us with the pointing necessary to acquire the satellites, the Live IVP update process ends at the No/Go meeting.

Wednesday, August 10 (DOY 222)

Orbit trim maneuver #27 (OTM-27), the "Titan 6 targeting" maneuver, was successfully completed on the spacecraft.  The main engine burn began at 07:44 am PDT.  A "quick look" immediately after the maneuver showed the burn duration was 15.5 sec long, giving a delta-V of 2.4 m/s.   AACS, Navigation, Propulsion, Thermal, Power, and Fault Protection teams all reported nominal performance after the event.
Science activities this week included CIRS' continued monitoring of the F-Ring as well as mapping of a region just south of Saturn's equator to determine the local temperatures of the upper troposphere and tropopause.

The Imaging Science Subsystem (ISS) took images of Pandora, Janus, Helene, Telesto, Methone, Prometheus, Epimetheus, and Pan for the purpose of better determining the orbits of these minor satellites.

The Magnetospheric and Plasma Science (MAPS) instruments conducted a magnetospheric boundary campaign looking in the corotation direction.

The VIMS instrument carried out a regional aurora map, and as part of instrument calibration observed Fomalhaut, a bright star with an unexpected amount of infrared radiation from the disk around it.  UVIS also performed instrument calibration by observing Alpha Eri, the ninth brightest star in the sky.

Wrap up:

The most recent spacecraft telemetry was acquired Wednesday, August 10, from the Madrid tracking station.  The Cassini spacecraft is in an excellent state of health and all subsystems are operating normally. Check out the Cassini web site at http://saturn.jpl.nasa.gov for the latest press releases and images.