Cassini Significant Events 08/22/07 - 08/28/07
August 30, 2007
(Source: Cassini Project)
The most recent spacecraft telemetry was acquired on Tuesday, Aug. 28, from the Goldstone tracking complex. 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" web page located at http://saturn.jpl.nasa.gov/operations/present-position.cfm .
Wednesday, Aug. 22 (DOY 234):
The latest Cassini mission video report is available at: http://www.jpl.nasa.gov/videos/cassini/cassini20070824/
Also just posted is a Huygens probe feature on turbulence. Look for it at:
A memo was released today from the Navigation team documenting the delivery of the proposed 070620 - June 20, 2007 - Cassini Extended Mission (XM) Reference Trajectory database. The current reference database for prime mission will remain in effect until April 11, 2008.
Thursday, Aug. 23 (DOY 235.):
The icy satellites Interdisciplinary Scientists (IDS) met today and allocated the Enceladus flybys for the proposed extended mission to the various instrument teams.
The Aftermarket process for S38 orbits 57-59 began today with the submission of all desired science and engineering changes. The flight team last reviewed this sequence in November of 2004 when it was "archived" at the conclusion of the Science Operations Plan Implementation process. The sequence has been "on the shelf" for a little over 2.5 years.
This long lead-time is typical for a prime mission sequence. Using S01 as an example, the process began in June of 2001 with Science Operations Plan (SOP) Integration. This was followed by SOP Implementation, "archive," the Aftermarket process, SOP Update, and the Science and Sequence Update process. Roughly three years from the start of integration to execution in May of 2004. Why such an extended schedule? The processes and procedures for developing the sequences were not in place at the time of launch. This was a deliberate choice on the part of the developers in order to have the sequence development processes and tools in place when the actual sequence development had to begin. The cruise to Saturn was to last nearly seven years. Approximately the first three years were used to put the sequence processes and tools in place; the next three or so years were used to generate the sequences. Normally for prime mission, four or five sequences are in development on any given day and one is executing on-board the spacecraft.
Now compare this to the sequence development process for the proposed XM. As mentioned in the next paragraph, integration is beginning on orbits 79-80, both contained in S42, the first sequence in XM. That sequence will begin execution on July 1, 2008. In less than a year, science and flight team members must complete the Integration, Science Operations Plan, and Science and Sequence Update processes. For XM, the Aftermarket and Science Operations Update processes are being eliminated in order to compress the over-all development time, and meet a more accelerated schedule. Also note, there is no "on the shelf" time. The team believes this schedule can be supported due to improvements in ground support hardware, software, and lots of hands on experience.
Friday, Aug. 24 (DOY 236):
The first science request delivery milestone for XM occurred today. All requests for orbits 79-80 have been submitted. The next major delivery milestone occurs on September 14. At that time all of the Target Working Teams (TWT) and Orbiter Science Teams (OST) can begin actively integrating the XM.
The Satellite Orbiter Science Team (SOST) hosted an Iapetus flyby preview meeting today to review the science objectives and activities to be performed for the flyby scheduled on Sept. 10.
Navigation has reviewed the consequences of canceling Orbit Trim Maneuver (OTM) 124 scheduled for execution on Monday, Aug. 27. Using the latest orbit determination estimates, the maneuver would have a magnitude of 60 mm/sec and a cancellation cost of 77 mm/sec. There is not a clear improvement in the science return from either the non-targeted Rhea or the targeted Titan flybys next week if the maneuver is performed. After a discussion with program management, it was decided to cancel the maneuver.
Monday, Aug. 27 (DOY 239):
Last week it was reported that Cassini outreach and visualization activities were presented at the European Planetary Science Congress 2007 in Potsdam, Germany. An additional presentation made in this session pertinent to Cassini was one given by the organizer of the on-line Unmanned Spaceflight Forum in which he showed the high level of excitement and participation that has been generated in the public with the near-real-time posting of raw images by Cassini and MER. The raw image area is the most heavily trafficked location on the Cassini web site.
The Solar Conjunction period concluded today when the Sun-Earth-Probe (SEP) angle reached 5 degrees. The Command Loss Timer was set back to its nominal value of 85 hours on Aug. 24, when the SEP angle had increased to about 3 degrees.
Although conjunction officially ended today, near normal operations resumed on Aug. 25, with an Optical Navigation (Opnav) image taken by the Imaging Science Subsystem Narrow Angle Camera. This was followed by an Ultraviolet Imaging Spectrograph (UVIS) mosaic of Saturn's inner magnetosphere, a Composite Infrared Spectrometer (CIRS) F Ring rotation movie, and acquisition of RADAR distant Titan radiometer science and calibration data.
Tuesday, Aug. 28 (DOY 240)
The S33 Rhea/Titan Live Inertial Vector Propagator update for DOY-242 was radiated to the spacecraft earlier this morning over DSS-14. The program has been registered on-board and will begin execution on Wednesday.
The main engine cover was closed today for a dust hazard on Aug. 29. It will be re-opened on Aug. 30 before the Titan 35 flyby. This will be the 35th close/open cycle since launch. The next closure will occur in March 2008.
An encounter strategy meeting was held today to cover the period between Aug. 31 and Sept. 10, Titan T35 through Iapetus I1, and maneuvers 125-127.
The monthly Cassini-Huygens Analysis and Results from the Mission (CHARM) teleconference today featured talks and question and answer sessions on the composition and sponge-like appearance of Saturn's moon, Hyperion. Two articles appeared in the July 5 publication "Nature" on these topics:
Surface composition of Hyperion:
Hyperion's sponge-like appearance:
Rhea and Titan flybys - Thursday, Aug. 30 and Friday, Aug. 31, 2007