Cassini Significant Event Report

For Week Ending 01/12/01

The most recent spacecraft telemetry was acquired from the Madrid tracking
station on Wednesday, January 10. The Cassini spacecraft is in an
excellent state of health and is operating normally. The speed of the
spacecraft can be viewed on the
"Present Position"
web page.

Phase E of the Jupiter subphase continued this week. Activities included
Cassini Plasma Spectrometer (CAPS) solar wind observations, atmospheric cyclic
observations, Io eclipse observation, a ring observation at 90 degree
phase angle, Europa, Callisto, and Ganymede observations, a Ganymede and
Europa eclipse observation, Ultraviolet Imaging Spectrometer (UVIS)
stellar occultation, Composite Infrared Spectrometer (CIRS) feature track
observation, and a UVIS / Hubble Space Telescope aurora observation.

Other activities included uplink of the CAPS, Imaging Science Subsystem
(ISS) and Visual and Infrared Mapping Spectrometer (VIMS) Instrument
Expanded Block (IEB) loads, CAPS IEB load for gain tests and execution of
the tests, command to clear the Solid State Power Switch (SSPS) for the
AACS Valve Drive Electronics Control Unit-B, AACS Reaction Wheel Assembly
(RWA) memory readout (MRO), AACS highwater mark clears, uplink of AACS RWA
unload bias overlay programs, Magnetospheric Imaging Instrument (MIMI) Ion
and Neutral Camera (INCA) collimator high voltage commanded to off, a
reaction wheel momentum unload, CDS-A and CDS-B automatic SSR repairs,
CIRS focal plane assembly control set point to 21, MIMI to science mode
mini-sequence, reset CDS SSPS trip counters, AACS reset of total RPM
counter, and a MIMI processor MRO and turn on of the replacement heater
for the Low Energy Magnetospheric Measurement Subsystem (MIMI LEMMS).

Magnetometer Subsystem (MAG) personnel have been looking at the recent MAG
data in the vicinity of the Jovian bow shock crossings identified recently
by the other Cassini investigations and reported a number of interesting
observations. First, the outbound shock crossing at 365/2212 is very clear
in the field data and is accompanied by a large overshoot indicative of a
supercritical shock. Hydromagnetic waves are also evident upstream of the
shock. Mirror mode waves are present in the magnetosheath for much of the
day. Second, the inbound and outbound shock crossings at 366/0959 and 1219
are also prominent and contain overshoots. There appear to be several
close approaches to the bow shock near 1103, 1115 and 1212 while Cassini
is in the magnetosheath suggesting that the spacecraft is skimming along
the moving shock front.

Radio and Plasma Wave Science (RPWS) personnel reported that Cassini
entered the Jovian magnetosphere around mid day on January 9. RPWS
observed trapped continuum radiation extending down to about 500 Hz,
corresponding to a plasma density of about 3 x 10^-3 at about 1315. The
actual magnetopause crossing time is still in question, however. Based on
previous experience with Galileo in this region of the magnetosphere, it
seems that on occasion, the density gradient can be very gradual and the
location of the boundary not very clear in the wave data. Cassini exited
the magnetosphere that same day reentering the magnetosheath and then went
back in to the magnetosphere at about 0700 on day 10. For the period on
day 9 when Cassini was inside the magnetosphere, Galileo also was still
inside, hence the two spacecraft were inside Jupiter's magnetosphere at
the same time.

Instrument Operations and the Multi Mission Image Processing Laboratory
(MIPL) have produced and delivered 16238 ISS images -10522 Narrow Angle
Camera and 5716 Wide Angle Camera - and 2108 VIMS cubes since Jupiter
encounter began.

The Radio Science Ka-band exciter and traveling wave tube amplifier were
turned on again, after RADAR observations concluded, to support DSS-25
upgrade implementation testing.

The final approval meeting for C24 was held this week. The sequence is
approved for uplink and will begin execution next week. The Sub Sequence
Generation Sequence Change Request meeting was held for C25.

Revision A of the Science Operations and Planning Computer User's
Handbook, and the SPICE Events Kernel Development Plan were completed and
distributed this week.

A draft agenda has been released for the Planetary Science Group meeting
to be held in January at JPL.

Installation of Telemetry, Command & Data Management (TC&DM) 25.2.2
occurred this week. MSS D7.3.1 was deployed on all SOPCs ahead of target
date. Deployment included 150 prerequisite patches and two software

Outreach personnel staffed a poster presentation on Cassini classroom
activities at the joint meeting of the American Association of Physics
Teachers and the American Astronomical Society this week.

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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