Cassini Significant Events -- 05/25/06 - 05/31/06

June 2, 2006

(Source: Cassini Project)

The most recent spacecraft telemetry was acquired Wednesday, May 31, from
the Goldstone tracking stations. 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 .

Thursday, May 25 (145):

Science activities this week included Composite Infrared Spectrometer (CIRS)
observations to measure oxygen compounds such as H20 & CO2 in Saturn's
stratosphere as a function of latitude, Ultraviolet Imaging Spectrograph
(UVIS) Saturn auroral observations, and the Visual and Infrared Mapping
Spectrometer (VIMS) observed the E Ring near a phase angle of 145 degrees
for vertical and radial structure. Meanwhile, the MAPS instruments
continued to observe the structure and dynamics of Saturn's magnetotail at
low latitudes and moderate distances downstream.

A delivery coordination meeting was held for Mission Sequence Subsystem
(MSS) D12.0 software set. The software will be used for the first time
during the S24 Science Operations Plan Update process. D12 includes the new
Imaging in the Ring Gap (IGAP) pointing capability. Imaging Science
Subsystem scientists use IGAP to design observations to examine ring
structure, and look for moonlets in the ring gaps. Among many other new and
revised capabilities, it also includes updates to numerous blocks, flight
rule and constraint checks, and supports the new 12B version of the command

Friday, May 26 (DOY 146):

The S21 final sequence approval meeting was held today. Uplink of the
instrument expanded block files and background sequence will begin this
weekend. S21 begins execution on June 3. One issue still open is that the
Titan Orbiter Science Team is working on a plan to request repeat playback
of Titan 15 data from the July 2 flyby in the event of station loss. This
issue will be resolved well before the flyby.

All participating teams delivered their files for the official input port as
part of the Science Operations Plan update process for S23.

Uplink Operations sent commands to the spacecraft for an end of sequence
bias overlay and a Cosmic Dust Analyzer (CDA) threshold noise test. Receipt
of both files was verified over Goldstone's DSS 24.

Monday, May 29 (DOY 149):

JPL was closed for the Memorial Day holiday, but commanding the spacecraft
goes on!

Seven Ion and Neutral Mass Spectrometer (INMS) Instrument Expanded Block
(IEB) files were radiated to the spacecraft Sunday and today. There is one
more INMS IEB that will be uplinked tomorrow along with eight IEBS for the
other instruments and Navigation. Uplink Operations was able to verify that
the files executed properly and the memory readouts were per predict. There
were no dropped packets for these files. There was one bad ALF in the
library region and this was expected.

A Reaction Wheel Assembly (RWA) friction test was performed today for the
prime reaction wheels number 1, 2, and 4. In this activity, the wheels are
spun up to 900 rpm in both directions and are timed as they run down to 0
rpm. This gives an indication of their performance. The longer the
run-down time, the better. The results of this test were mixed. As
compared to the results of the last test in March, RWA-1 was worse in the
clockwise direction, better in the counter clockwise direction, RWA-2 was
essentially unchanged, and RWA-4 was better in both directions. A test of
the backup reaction wheel number 3 will occur Friday, June 2. These
friction tests are repeated every 3 months to monitor the state of the RWAs.

Tuesday, May 30 (DOY 150):

Members of the CDA team sent an Automated Sequence Processor (ASP) command
to prepare their instrument to perform a scheduled noise test. This is a
repeat of the test performed during cruise in February of 2002. CDA will be
reporting next week on the results of the test.

A delivery coordination meeting was held today for the Spacecraft Operations
Office tools Maneuver Automation Software v6.0, and MAPDF_GEN v8.3.

A great close-up image of Rhea was Astronomy Picture of the Day today.

The topic of the Cassini-Huygens Analysis and Results of the Mission (CHARM)
teleconference for May 30, 2006 was the Magnetic Portraits of the Icy
Satellites of Saturn.

Wednesday, May 31 (DOY 151):

The S21 background sequence programs were radiated today at 151T19:21:47.
Uplink Operations has verified that all of the programs and the associated
cyclics have been properly registered onboard the spacecraft. The sequence
will begin execution on 2006-154T02:39:00.

JPL has put out a news release announcing that new research shows Enceladus
may have rolled over, literally, explaining why the moon's hottest spot is
at the south pole. Enceladus recently attracted scientists' attention when
the Cassini spacecraft observed icy jets and plumes indicating active
geysers spewing from the tiny moon's south polar region. The mystery that
investigators set out to explain was how the hot spot could end up at the
pole if it didn't start there. Researchers propose the reorientation of the
moon was driven by warm, low-density material rising to the surface from
within Enceladus. Their findings are in this week's journal Nature. Future
Cassini observations of Enceladus may support this model. Meanwhile,
scientists await the next close flyby of Enceladus in 2008. To access the
full news release link to:

A member of the Magnetometer team gave a science talk to the flight team
today on "Magnetic Observations of Saturn by the Cassini Spacecraft." The
Cassini spacecraft has made many and varied new discoveries about Saturn's
environment. The spectacular images taken of the planet, its rings and its
satellites represent the 'visible' components of this environment. There is
also, however, a much larger 'invisible' component known as the
magnetosphere, which forms as a result of the interaction between Saturn's
magnetic field and the solar wind. This interaction was described and data,
mainly taken by the Cassini magnetometer, was used to illustrate the natural
and dynamic 'boundaries' that form as a result. A similar kind of
interaction between Saturn's rotating magnetosphere and the satellites Titan
and Enceladus was also described.

This Weekend June 3 and 4:

Local viewing by members of the Saturn Observation Campaign (SOC):

Friday, June 2, 7:30 p.m. 'til 10:00 p.m.,
Colorado near Delacey - Pasadena Ave., Pasadena, Calif.

Saturday, June 3, 7:30 p.m. 'til 9:30 p.m.,
Myrtle & Lime, Monrovia, Calif.

What you can see:

This weekend, you will be able to look up and view Saturn and the moon from
your backyard without a telescope!

As the month of June passes you can watch as Mars and Saturn draw closer to
each other. The two planets can be seen to the lower right of the moon on
Friday, June 2nd.

Near the horizon, try to spot Mercury low in the west-northwest 5 degrees
above the horizon after sunset. If you don't see it, don't worry. Mercury
will rise a little higher in June.

Meanwhile, Jupiter reigns all alone over the southern sky -- you can't miss
it -- it's the brightest "star" in the sky.

Contact an SOC member near you, or your local amateur astronomy club or science center for weekend Saturn viewing opportunities. For a list of SOC members, visit