Cassini Significant Events for 06/20/06 - 06/28/06

Cassini Significant Events for 06/20/06 - 06/28/06

The most recent spacecraft telemetry was acquired Wednesday, June 28, from the Goldstone tracking stations. The Cassini spacecraft is in an excellent state of health and is operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the “Present Position” web page located at .

Tuesday, June 20 (171):

Members of the Cassini Outreach and the Saturn Observation Campaign gave talks on the summer skies, visible planets, and our Milky Way Galaxy in Arizona’s Kaibab National Forest, and at the Grand Canyon Lodge on June 19 and 20.

Wednesday, June 21 (DOY 172):

A Solid State Power Switch (SSPS) trip on the Stellar Reference Unit (SRU) -B replacement heater occurred on June 21. This is the 17th occurrence of an SSPS trip since launch, and the third this year. The other two occurred on March 2 and May 1. These trips are expected to occur at a rate of about two per year and are attributed to Galactic Cosmic Rays. When the trip occurred today, the heater was “off.” On-board CDS fault protection (FP) autonomously reset the switch. There are no thermal issues and no further action is necessary. Spacecraft Operations will be sending commands to the spacecraft for a memory readout (MRO) to obtain further insight into the trip and for documentation purposes.

The official product input port occurred today for the S24 Science Operations Plan update process. The products have been merged and now reside in the on-line file repository where they are accessible for review by the team.

Cassini Outreach presented a sunset talk about the Cassini Mission followed by gorgeous views of Saturn and its moons at the North Rim of the Grand Canyon National Park in Arizona on Wednesday, June 21. This was part of the annual Grand Canyon Star party, held on both the north and south rims of the Grand Canyon each June.

Still images and five short movie sequences acquired over the past six months are being released today by JPL in a media image advisory entitled “moons in motion.” In addition to their drama and visual interest, scientists use the movies to refine their understanding of the orbits of Saturn’s moons. Engineers use the same images, and the orbital positions of the moons, to help them navigate Cassini. You can view both images and movies by linking to:

Thursday, June 22 (173):

The Magnetospheric and Plasma Science (MAPS) instruments became “prime” for today and tomorrow in order to continue the campaign to study the magnetotail portion of Saturn’s Magnetosphere.

Friday, June 23 (DOY 174):

Uplink Operations sent commands to the spacecraft today to power on the Cosmic Dust Analyzer (CDA), execute an MRO of the SSPS table, and establish a new nominal delta-v telemetry schedule prior to OTM-64 execution on June 28. The MRO indicated that an address would need to be updated. Those commands will be sent next week. The CDA mini-sequence has been properly received and will start executing on 175T20:00:00, over the DSS-25 pass.

Today is the last day of the Project Science Group (PSG) meeting being held in Nantes, France. One of the most important topics of discussion was the selection of an extended mission tour. The five PSG Discipline Working Groups were asked to produce and report to the PSG on their criteria for rating tours, a list of liens of specific features of individual tours which made them “unattractive,” rate the tours, and provide a narrative as to how well selected tours might meet the environmental knowledge desires of future Titan and Enceladus missions. Gathering this information is no small matter. The NASA Announcement of Opportunity for the Cassini Orbiter specified five areas of science and explicitly stated that they were of equal priority. With the information above, the project must balance the different scientific interests, then evaluate the labor impact of carrying the various tour groups forward. There is still much work to be done with a final tour selection planned for February of 2007. You can expect to see reports on the updates to the tour selection process after each PSG meeting.

Saturday, June 24 (DOY 175):

Today and tomorrow the Imaging Science Subsystem (ISS) will perform a block of observations including observations of Iapetus. After returning control to the MAPS instruments for several hours, ISS will then perform a satellite transit observation, this time of Epimetheus across Dione. Each day will end with the Composite Infrared Spectrometer (CIRS) observing Saturn in the mid-infrared wavelength. These “mid-IR maps” are atmospheric studies of Saturn, creating a temperature map of Saturn’s upper troposphere and tropopause.

Monday, June 26 (DOY 177):

Monday, June 26, begins with a series of Visual and Infrared Mapping Spectrometer (VIMS) observations of the rings of Saturn. Both the “E” and “G” rings will be targeted at a phase angle of 135 degrees. At this angle, the spacecraft is pointed such that if the Sun is at 12 O’clock, the spacecraft is between the 4 and 5 O’clock angle, with the rings lying in a plane across the 3 to 9 O’clock position. At this particular orientation, sunlight on the rings will be clearly visible as sunlight is scattered by the ring particles.

Tuesday, June 27 (DOY 178):

A Cassini-Huygens Analysis and Results of the Mission (CHARM) teleconference was held today. The topic was the Cassini-Huygens second anniversary. An overview of the mission was given covering launch, cruise, science objectives, and spacecraft status. This was followed by key science results obtained in the first two years.

The actual anniversary date for the start of the Cassini tour is July 1, 2004. In recognition of this event, JPL has put out a news release marking the halfway point of the primary mission. Discoveries made during the first two years have scientists revved up to find out what’s in store for the second half of the mission. The spacecraft has spent a considerable amount of time studying Titan during 15 separate flybys so far. In the next 11 months there will be 17 more Titan encounters, and 51 spacecraft maneuvers - more than one a week - to adjust the flight path. Later in July, navigators will begin to change the spacecraft’s orbit orientation, resulting in a bird’s-eye view of Saturn’s rings. For more information on what is in store, link to:

Wednesday, June 28 (DOY 179):

Science acquisition today began with an Imaging Science Subsystem (ISS) observation of Hyperion followed by a Visual and Infrared Mapping Spectrometer (VIMS) Saturn “feature track” observation. Feature track observations target a particular feature in Saturn’s atmosphere. After VIMS completes this observation, spacecraft control is returned to ISS to continue the Hyperion observations.

Orbit Trim Maneuver (OTM) #64 was performed today. This is the approach maneuver setting up for the Titan 15 encounter on July 2, DOY 183. This maneuver is the first use of the version 6.0 Maneuver Automation Software, and the new ACS reaction control subsystem (RCS) Delta-V telemetry schedule which corrected a discrepancy between the actual post-hydrazine tank recharge tail-off time and the value in ACS flight software. The RCS burn began at 4:30 PM PST. Telemetry immediately after the maneuver showed a burn duration of 47.9 seconds, giving a delta-V of approximately 0.069 m/s. All subsystems reported nominal performance after the maneuver.

A delivery coordination meeting was held today for version 2.21 of the Flight Software Development System (FSDS) implemented by the Spacecraft Operations Office. FSDS is a simulation environment for the Cassini ACS subsystem. It provides the user a command line interface for visibility into the spacecraft simulation, the flight software and the ground interface. Users can retrieve and set variables in the hardware, peek and poke global variables in the flight software, send 7-commands and check telemetry values. Execution time is dependent on the host Unix workstation CPU. Currently, our Ultra-10s can run the ACS flight software and FSDS at about four times real-time.

Wrap up:

Check out the Cassini web site at for the latest press releases and images.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter.