Cassini Significant Event Report

For Week Ending 07/18/03

The most recent spacecraft telemetry was acquired from the Goldstone tracking station on Wednesday, July 16. The Cassini spacecraft is in an excellent state of health and is operating normally. Information on the spacecraft's position and speed can be viewed on the "Present Position" web page.

On-board activities this week included a Radio and Plasma Wave Science (RPWS) high frequency receiver calibration, conclusion of the RPWS cyclic, a Magnetometer Subsystem (MAG) bus interface unit reset, MAG power on reset, Cassini Plasma Spectrometer (CAPS) instrument maintenance, ACS, CDS, Visual and Infrared Mapping Spectrometer (VIMS), and Cosmic Dust Analyzer (CDA) flight software normalization, CDA and VIMS Instrument Expanded Block (IEB) uplink, completion of the Reaction Wheel Assembly (RWA)-4 articulation and checkout activity, Saturn Orbit Insertion (SOI) demo sequence uplink to the SSR, and clearing of the high water marks.


The normalization of ACS and CDS flight software loads on the SSR was in preparation for the SOI Critical sequence demo. Old versions of flight software had been kept in the prime partitions following ACS A8 and CDS V9 checkout. All partitions now reflect the A8 and V9 copies.


The Spacecraft Operations Office (SCO) completed the Articulated Reaction Wheel Mechanism (ARWM) and RWA-4 checkout activities this past week. RWA-4 has now been moved by the ARWM to match the RWA-3 angular momentum position and has been verified to be in the proper position. There was a delay of two days during checkout activities due to questions about the direction to be commanded for the ARWM. After reviewing pre-launch special tests and the original problem failure report on commanded direction, the correct direction was commanded and verified by the remaining tests. A project briefing was held later in the week where Reaction Wheels 1-2-4 were approved as the prime reaction wheels.


The Radio Science Subsystem (RSS) Solar Conjunction Experiment #2 (SCE) concluded this week. Throughout the month of the experiment, the RSS team was unable to move the Ka-Band Translator (KaT) frequency from its current bad region. Given the uncertainty about future KaT performance, Radio Science believes a re-scoped Gravitational Wave Experiment #3 (GWE) plan is appropriate and responsible given the Project's policy of minimizing time spent on reaction wheels. The team has suggested observations only for the last 20 days of the currently allocated 40-day interval. The re-scope does not affect GWE scientific objectives or GWE3's unique geometry for observations of the galactic center.


The official port#3 merged products were delivered to ACS/SCO as part of Science Operations Plan implementation for tour sequences S7 and S8. A wrap-up meeting for this process has been scheduled for July 30.


A Science Planning Team Project Briefing was held for cruise sequence C40. The integrated product has been approved for implementation. At the meeting it was decided that the first 2 hours of the new 20-day GWE#3 would be allocated to ACS to perform an RWA bias. GWE now spans 2003-314T06:42:00 to 2003-334T06:05:00 SCET for a duration of 019T23:02, 37 minutes shy of 20.0 days.


A total of five Sequence Change Requests (SCR) was approved at a Preliminary Sequence Integration and Validation SCR approval meeting for C39. Two were corrections to items previously submitted and the other three were reactions to the removal of the VIMS straylight activities, which were moved from C39 to C40. Implementation of these SCRs was also performed this week, and new input files sent back to the Sequence Team lead by the affected teams.


Events this week for the S14 Science and Sequence Update Process (SSUP) Verification and Validation (V&V) activity included PSIV2 subsequence input port, default Live Movable Block (LMB) and trigger Immediate/Delayed Action Program delivery, distribution of the full merged sequence products with LMB requests included for the V&V PSIV2 phase, updated PSIV2 IEB loads sent to the Sequence Team lead by the instrument teams, publication of updated Sequence Phase List of Ancillary Files (SPLAF) products, conclusion of waypoint analysis and report distribution, and PSIV2 IEB Command Packet File inputs to CDS.


System Engineering gave a presentation on the background, timeline, goals and success criteria, test plan, and open issues for the Live Update V&V. Live Update V&V is part of the SSUP real-time commanding process. The V&V will operationally certify the processes, timeline, and execution of commands in the Integrated Test Laboratory. Live Update V&V will begin after the conclusion of SSUP V&V and will run from mid August to mid September.


All teams and offices supported the Cassini monthly management review.


System Engineering (SE) assisted Science Planning and Mission Planning in generating a SPLAF and associated Pointing Design Tool and Sequence Generator configuration files for both Uplink V&V S14, and for C40. The tools are still being refined, but appear to be time-savers for the Operations Teams. Software Requirements Certification Review delivery meetings were held for the VIMS v7.1, Ion and Neutral Mass Spectrometer V6, and CAPS v4.0 instrument flight software (FSW). The FSW has been delivered to the project software library and approved for processing to uplink as part of the C39 sequence activities.


Delivery coordination meetings were held for BECON V1, Flight System Dynamics Simulator V2.16, and a Cassini Information Management System patch delivery V2.5.1. BECON, the Best fit conic gradient optimizer, uses spacecraft and celestial body ephemeris data to construct the Inertial Vector Propagator conic vector that minimizes the maximum vector fit error over the time interval of the Probe Relay.



Additional information about Cassini-Huygens is online at http://saturn.jpl.nasa.gov.


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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