Cassini Significant Event Report

For Week Ending 04/02/04

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Monday, March 29. 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

Science observations this week included Saturn approach movies to study the planet's atmosphere and its temporal variations, searches for new satellites, observations of Titan and searches for diffuse ring material, and solar wind observations. The Magnetometer Subsystem performed a Science Calibration Subsystem flight calibration, and commands were sent to the spacecraft to power on the Cassini Plasma Spectrometer and perform Real Time Interrupt testing.

The primary activity this week was the execution of the 13th in-flight Huygens probe checkout and a special test of the Probe Mission Timing Unit (MTU). The performance of the Huygens engineering subsystems and instruments during the checkout was as expected. The flow of data from JPL to the Huygens Probe Operating Center in Darmstadt went very smoothly. The MTU is the timer which is set just prior to probe release. Drawing minimal power, it counts down to a fixed time before probe entry at Titan and then initiates the powering on of the Huygens avionics and instruments. The test validated the ground system's process for setting the timer and also measured the timer's drift rate. All aspects of the test were nominal.

Files for C44 were uplinked to the spacecraft this week. They included the background sequence, instrument expanded blocks, and an absolute timed Immediate/Delayed Action Program to perform an ACS Reaction Wheel Assembly bias. C44 begins execution on Thursday, April 1.

Sequence development activities for C44 concluded this week. The Final Sequence Integration and Validation (FSIV) phase sequence change request (SCR) and waiver approval meeting was held with two SCRs and one waiver approved. A Command Approval Meeting was held for Instrument Expanded Block (IEB) files to be uplinked to the spacecraft for Composite Infrared Spectrometer (CIRS), CAPS, Ultraviolet Imaging Spectrograph (UVIS), Visual and Infrared Mapping Spectrometer (VIMS), Imaging Science Subsystem (ISS), Radio and Plasma Wave Science (RPWS), and INMS. The C44 final sequence approval meeting was also held this week. Uplink of IEBs is scheduled for March 25, and the background sequence on March 27. C44 will go active on April 1.

During C44 the first time event "rocking downlink" will be performed for the Cosmic Dust Analyzer (CDA). During the downlink, the spacecraft rolls about the Z-axis in a back and forth manner. CDA will be performing rocking downlinks on 13 April.
Spacecraft Operations completed the Integrated Test Lab (ITL) dry run for the ACS flight software update version A8.6.7 on Thursday, 4/1/04. The test was important because this is the first time in flight an ACS computer will be reset and loaded with a flight software update during an on-going background sequence. The test was successful in that it did catch a missing vector needed for the C44 background. The missing vector has been added and the test will be re-run next week.

Since the start of approach science in January of this year, 1597 ISS images have been acquired along with 627 VIMS cubes.

The Science Operations Plan Update process for S02, which includes the science occurring during and after the Saturn Orbit Insertion burn, had its preliminary port 1 delivery this week.

The Sequence Team released the preliminary version of the S01 background sequence and Phoebe Live Movable Block. Team members are in the process of reviewing the integrated sequence.

In the last week, 265 Imaging Science Subsystem (ISS) images and 36 Visual and Infrared Mapping Spectrometer (VIMS) cubes were returned and distributed, bringing the total of images acquired since the start of Approach Science up to 1969, and the number of cubes up to 663.

The Science Operations Plan Update process for S02, which includes the science occurring during and after the Saturn Orbit Insertion burn, had its official port 1 delivery this week. The team and engineering input products were merged and the merged product was handed off to ACS to perform the end-to-end pointing analysis. The S02 product will be handed off to the SSUP process on April 9.
Tour Science Plan presentation #5 to the flight team this week was part 2 of two parts on the Titan Orbiter Science Team plans for tour. This team was responsible for integration of science activities for the 44 targeted Titan flybys during the prime mission.

Delivery coordination meetings were held this week for Version 5.2 of AP_DOWNLINK consisting of bug fixes and new telemetry predicts, version 10.3 of Kinematic Prediction Tool and Inertial Vector Propagator, and Radio Science Subsystem tools LMBTRK Version 1.2 which incorporated the hard-limb approximation for faster calculations in the cases of large bending angles, for which high accuracy is not needed, POSTLM Version 1.1 which incorporated optimization and the capability to handle both ingress and egress, and BISTAT Version 1.1 which incorporated atmospheric effects on the ray path.

A Delivery Review was held for the Multi Mission Image Processing Laboratory point delivery D32.0.1. Testing results were reported and no issues were brought up. Operations were then halted for a validation and switchover period. This integrated system was then brought on-line as the operational system for Tour.

New content and graphics were released to the Saturn Observation Campaign website. Enhancements include compliance with the design features of the NASA portal, new information, and announcement of application process for new SOC members. The site can be accessed at:

Cassini Outreach is performed not only by members of the Outreach staff located at JPL, but also by members of the flight team. A Radio and Plasma Wave Science instrument team member gave a series of talks in his local community to 22 first grade students at Weber Elementary School in Iowa City as well as 15 members of a Girl Scout Troop in Iowa City. In addition, a member of the Spacecraft Operations Office gave a talk to 21 3rd grade students at Paradise Canyon Elementary School in La Ca¿ada.

Wind-blown clouds and haze high in Saturn's atmosphere are captured in a movie made from images taken by the Cassini narrow angle camera between Feb. 15 and Feb. 19, 2004. This is the first movie ever made showing Saturn in these near-infrared wavelengths. The images were made using a filter sensitive to a narrow range of wavelengths centered at 889 nanometers, where methane in Saturn's atmosphere absorbs sunlight. For more information go to: or

In the week that sees the 375th anniversary of the birth of the Dutch astronomer Christiaan Huygens, an international conference entitled "Titan: From Discovery to Encounter" is taking place, from 13 to 17 April, at ESA's European Space Research and Technology Centre (ESTEC), Noordwijk, the Netherlands.

The conference will bring together an international team of space scientists and historians to discuss topics such as: - Christiaan Huygens and his connection with other 17th century scientists, such as Cassini, Descartes and Newton; - observation of Saturn and its moons from the 17th century to today; - the scientific objectives of the Cassini/Huygens mission and its latest observations on the way to the Saturnian system.

Additional information about Cassini-Huygens is online at

Cassini will begin orbiting Saturn on July 1, 2004, and release its piggybacked Huygens probe about six months later for descent through the thick atmosphere of the moon Titan. Cassini-Huygens is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Office of Space Science, Washington, D.C.

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