Status Report

NASA Cassini Significant Events 07/27/06 – 08/02/06

By SpaceRef Editor
August 5, 2006
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NASA Cassini Significant Events 07/27/06 – 08/02/06

It was reported in the Cassini Significant Events last week that the atmospheric density measured at Titan 16 was higher than expected. The Titan Atmospheric Modeling Working Group (TAMWG) met this morning to discuss this result and assess whether the altitudes selected for upcoming encounters are still acceptable. At the conclusion of the meeting, the TAMWG recommended no changes to the altitudes of upcoming encounters. The new T16 data point has not fundamentally changed our understanding of Titan’s atmospheric profile, except to indicate a less steep falloff in density at high latitudes. Cassini only has one future Titan flyby at very high latitude, Titan 32. Much like T16, this encounter is at 84 deg N latitude with a closest approach at 950 km, so it should be safe as well.

One of the things that presents a challenge to Cassini scientists and sequence developers is attempting to respond to new scientific discoveries as they arise. Background sequence S24 completed Science Operations Plan Implementation in March 2004. At that time the basic sequence was delivered to the project file repository. Science Planning was chartered to archive a sequence that if necessary would fly on the spacecraft “as is.” Now roll the clocks forward to July 27, 2006. S24 has been through both the Aftermarket Process and the Science Operations Plan Update Process. It is currently in final development prior to uplink. The first of four phases of that development process is complete. But, due to the discovery of lakes near Titan’s north pole over the weekend, RADAR has requested re-pointing of their T19 observation to cover more of the same region. What to do?

It was decided to stick with the process and have RADAR submit their pointing changes in the third phase. Although this decreases the number of iterations available to get the pointing right, it allows the other instruments and AACS time to properly assess any impacts they might have. To support the development of this observation, an interim set of sequence products was produced with the new RADAR pointing, to give the Attitude and Articulation Control Subsystem (AACS) time to evaluate it and make a c-kernel available to teams that might wish to examine it. At this time S24 is on track for final approval in September, and it is hoped to have lakes in its future.

Friday, July 28 (DOY 209):

Science data archive deliveries for data acquired during the period of July through September 2005 are now complete. The next archive delivery port is October 1.

The official port occurred today for S25 as part of the Science Operations Plan (SOP) Update process. The merged products are currently being run through end-to-end pointing validation by AACS. The Project Briefing and Waiver Disposition Meeting is scheduled for August 9. The SOP Update product is handed off to the sequence leads on August 11 for the final development process.

Monday, July 31 (DOY 212):

The Cassini RADAR image of Titan’s methane lakes is Astronomy Picture of the Day today.

Tuesday, August 1 (DOY 213):

Orbit Trim Maneuver (OTM) #69, an apoapsis maneuver setting up for the Titan 17 encounter on September 7, was performed today. This main engine burn began at 2:30 PM PDT. Telemetry immediately after the maneuver showed a burn duration of 33.8 seconds, giving a delta-V of 5.4 m/sec. All subsystems reported nominal performance after the maneuver. A contingency DSS-15 track that had been retained for the DOY 214 backup OTM-69 window in case the DSS-14 antenna went red was released at the successful completion of the burn. Cassini thanks MGS, MER and Odyssey for their help in making this track available. The next OTM is scheduled for September 4.

Solar Conjunction occurs when the Sun is between the spacecraft and Earth. This year it will last from August 2 through August 12, and is a time of reduced commanding and downlink capability. Cassini enters Solar Conjunction tomorrow with a separation angle of 4 degrees. During conjunction, communications with the spacecraft become degraded due to interference from the sun. For the next ten days the Spacecraft Operations and Mission Support and Services offices will participate in a campaign where a command file consisting of 10 no-op commands will be uplinked to the spacecraft ten times daily. This will allow the teams to obtain link characterizations and accumulate statistics for uplink reliability at decreased separation angles. With the exception of these no-op command files, Spacecraft Operations has asked for and received a command moratorium. Additional commands will only be sent in the event of an emergency. On Saturday, the spacecraft will be turned so that the High Gain Antenna is continuously pointed to Earth, and 1896 bps telemetry continues while separation is less than 2 deg. Normal playback downlink rates will resume on August 10.

There is a great write up on conjunction on the Cassini web site. For more information link to:

Cassini’s “For Educators” website has a hands-on activity called “Monitoring the Sun’s Corona.” Scroll down the Saturn in your Kitchen and backyard section to “Saturn System Science” to find it. In this activity, students of all ages will learn how, during solar conjunction, scientists use the relative positions of the Sun, Earth, and a spacecraft to study the Sun’s corona, or outer region.

Wednesday, August 2 (DOY 214):

An artist’s rendition of the methane rain on Titan is Astronomy Picture of the Day today

The data obtained by the six Huygens experiments is now archived in the European Space Agency (ESA) Planetary Science Archive (PSA). A copy of the archived data set is also available in the NASA Planetary Data System (PDS). The data is now accessible by the scientific community and the general public for downloads. This represents a major milestone in the Huygens mission. Data from the Aerosol Collector and Pyrolyser (ACP), Doppler Wind Experiment (DWE), Gas Chromatograph Mass Spectrometer (GCMS), and Huygens Atmospheric Structure Instrument (HASI) is accessible along with housekeeping data, calibration information, and documentation necessary to understand and process the products, and to carry out scientific analyses. Data from the Descent Imager Spectral Radiometer (DISR), Surface Science Package (SSP), and the final Huygens entry and descent trajectory data is to be released in the September-October timeframe. To access the data, link to:

A Cassini Saturn Orbit Insertion +2 Years celebration was held in Von Karman auditorium today for the Cassini Flight team. Talks were given by the laboratory director Charles Elachi, and by two surprise celebrities, Robert Picardo and Bill Nye. An additional presentation was given by Outreach who read to the flight team some of the comments that the public has sent to the Cassini web site letting us know how much they appreciate what Cassini is doing, and looking forward to the next two years of prime mission and extended mission after that. The flight team says “THANKS” back to the public. We are looking forward to it too!

Your coffee table will never be the same. Outreach has promised the flight team that they will let us know as books on Cassini/Saturn are published. The first one is a beauty called Saturn: A New View in hardcover. The pictures are phenomenal. The book has not yet been released but may be ordered and will ship as it arrives at distributors. See your local bookstore – either electronic or traditional.

The July 20 “Cassini Real-time Operations” presentation from the Von Karman Lecture Series is online at the JPL public website as a RealPlayer downloadable:

Wrap up:

The most recent spacecraft telemetry was acquired on Wednesday, August 2, from the Goldstone tracking complex. The Cassini spacecraft is in an excellent state of health and all subsystems are operating normally. Check out the Cassini web site at for the latest press releases and images.

SpaceRef staff editor.