Cassini Significant Event Report

For Week Ending 02/23/01

The most recent spacecraft telemetry was acquired from the Goldstone
tracking station on Wednesday, February 21. The Cassini spacecraft is in
an excellent state of health and is operating normally. Cassini is
currently traveling at 46,799 kph relative to the sun, and is 51.2 million
kilometers away from Jupiter. The speed of the
spacecraft can be viewed on the
"Present Position"
web page.


Post Jupiter science operations continued this week with the spacecraft
alternating between Optical Remote Sensing (ORS) movies / atmosphere and
torus observations, and Magnetospheric Imaging Instrument (MIMI) magnetospheric
data collection. Activities included uplinks of a mini-sequence to modify the
Composite Infrared Spectrometer (CIRS) Instrument Expanded Block (IEB), Radio
and Plasma Wave Science (RPWS) commands to change to the EZ sensor for dust
impact detection, a patch to the MIMI Low Energy Magnetospheric Measurement
Subsystem (LEMMS) motor flight software, and activation of the MIMI Ion
and Neutral Camera (INCA) sensor. Additional activities included a CDS-B
automatic SSR repair, a Reaction Wheel Assembly (RWA) momentum unload, RWA
Slow Time Memory Read-out, and a Radio Science Subsystem (RSS) Test.


The RSS Team conducted a test this week to help characterize a discrepancy
observed in one-way data by Cassini's Navigation Team. The open-loop
receiver (the DSP) was used to record one-way data. This was repeated on
three occasions. During the test the one-way signal appeared in the RF
spectrum where it was predicted to be. Since no error was detected in
the one-way data using the open-loop receiver, it is presumed that the
cause of the problem is in the closed-loop receiver system on the ground.
Investigation is continuing.


The Cassini Instrument Operations (IO) Team and the Multi Mission Image
Processing Laboratory have produced and delivered 23,864 ISS images -
16,699 from the NAC and 7,165 from the WAC - and 4,963 Visual and Infrared
Mapping Spectrometer (VIMS) cubes since Jupiter encounter began.


The Spacecraft Office developed and tested Trajectory Correction Maneuver
(TCM)-17 products this past week. The TCM will be used to meet the
flushing requirement for the bi-propellant propulsion system. The
requirement specifies a main engine burn of 5 seconds or greater to be
performed every 400 days and ensures that oxidation buildup from the
oxidizer is "flushed" through the propulsion system. This course
correction, originally placed as a Jupiter fly-by cleanup maneuver, is a
Main Engine burn of 5.4 seconds duration and will be performed next week
on Wednesday, February 28, 2001.


The second and final C26 Science Planning Virtual Team (SPVT) product
delivery port closed this week. Science Planning is now in the process of
merging the files and will deliver them to AACS for the final end-to-end
pointing check.


The Atmospheres Working Group (AWG) held a telecon to work on science and
orbit priorities for Tour. The group made assignments to its members
asking them to examine in more detail the periods of interest to the AWG.
A Titan Orbiter Science Team (TOST) meeting was also held this week.
Members examined the integration of observations associated with the first
ten Titan flybys for the period around +/- 1 day from Titan closest
approach.


Mission Support & Services Office (MSSO) staff has begun preparation of a
"Jupiter Fly-by" network analysis report. This report will be used by
Cassini's hardware infrastructure group to determine what type of problems
and network usage may be expected during tour.


Mission Sequence Subsystem (MSS) D7.4.1 Patch Delivery for the Sequence of
Events Generator (SEG) was held this week. The new version is able to read
the configuration code for the new Radio Science equipment at DSS-25 and
issues keywords based on that code to the DSN to configure the equipment.


A Delivery Coordination Meeting for Cosmic Dust Analyzer FSW was also held
this week. The delivered version 8.4.0 will correct an error in version
8.0.0 that caused the instrument to default to a previous FSW load.



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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