Cassini Significant Event Report

For Week Ending 08/31/01

The most recent spacecraft telemetry was acquired from the Madrid tracking
station on Wednesday, August 29. 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.


Recent spacecraft activities include the conclusion of the second Radio
Science Subsystem Gravitational Wave Experiment (GWE) system test, an
Ultraviolet Imaging Spectrometer Interplanetary Hydrogen Survey, a Radio
and Plasma Wave Science (RPWS) High Frequency Receiver calibration, and a
Visual and Infrared Mapping Spectrometer (VIMS) Arcturus observation.
Real-time commands were uplinked to the spacecraft as planned to perform
two clearings of the Attitude and Articulation Control Subsystem high
water marks, test an RPWS trigger command, perform a checkout of the
Composite Infrared Spectrometer (CIRS), set the VIMS Solid State Recorder
equivalency bit to non-equivalent, and de-register the on-board Mission
Sequence Subsystem (MSS) D7.2 modules.


The RADAR instrument collected radiometry calibration data in raster scans
over the Sun, Jupiter, and five microwave sources. The measurement of the
Sun provides the critical data needed to fully calibrate the side lobes of
the antenna beam pattern, while the measurements of Jupiter and the
microwave sources will complete the RADAR team's original instrument
checkout plan, an important part of calibrating the RADAR's radiometer. In
addition to the calibration data, the operation provided valuable thermal
data to understand how the instrument will perform under various thermal
loads, which will help with tour planning.


The Science Planning Team began the tour Science UPlink Verification
(SUPV) activity. This activity will take the integrated plans from the
Titan and Satellite Orbiter Science Teams and the Target Working Teams
(TWTs) to the next level of design detail to understand better how to
build these tour sequences. For the first SUPV activity the group is
developing the detailed pointing designs and power mode transitions for
the Titan-3, Titan-5, and Titan-6 flybys. The TWTs have also begun to
integrate the science and engineering requests associated with tour orbits
4 through 14 based on the Cassini Information Management System inputs
from the Science Teams and the Project.


The Navigation team has delivered a high precision reference trajectory
for the first few orbits of the Cassini Tour. This trajectory includes all
of the changes made to the original baseline for the new Huygens probe
mission including a slightly larger orbit insertion burn, the Titan-a,
Titan-b, and Titan-c encounters, and a probe flyby altitude of 65,000 km
with an orbit delay time of 2.1 hours. Some parts of this trajectory are
still subject to change as the final details of the revised probe mission
are worked out.


The Deep Space Mission System (DSMS) held a delivery review for the DSS-25
Cassini Upgrade Task. This task designed and implemented improvements at
DSS-25 in support of the GWE, including improved frequency stability, a
Ka-band uplink capability, improved pointing, a state-of-the-art media
calibration system, and new open-loop receivers. The Review Board
commended the group for the dramatic progress.


Program training began this week for new Uplink Operations, Science
Planning, and Mission Support and Services Office personnel. Classes
included an overview of the Sequence Virtual Team Uplink Process, services
available from the Cassini Solution Oriented Services help desk, and the
"Helpful Stuff" presentation that provides new Program members with
information on where to go for Cassini documents, forms, schedules, and
general information.


A Software Review Certification Requirement (SRCR) meeting was conducted
by the System Engineering Office to review VIMS Flight Software (FSW)
version 4.2. Test procedures were discussed and the FSW was approved for
check-out in the Integrated Test Laboratory (ITL), with the uplink date of
the software still to be decided.


The Instrument Operations (IO)/RADAR team held a requirements and design
review. Topics included operations processes for uplink; downlink; and
instrument pointing, health and safety; as well as development activities
for the instrument testbed, sequencing software, instrument flight
software, and data processing software. This review completed a series of
reviews of the four facility instruments.


A Mission Assurance website has been established which facilitates mission
assurance awareness, information, and requirements in addition to
providing direct links to both the On-Line Risk Management Tool and the
Problem/Failure Reporting System. The new Risk Management Tool has
recently been filled with data that assigns risks to personnel who are
then responsible for disposition of the risks.



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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