Cassini Significant Events
for 02/18/09 - 02/24/09

The most recent spacecraft telemetry was acquired on Feb. 24 from the
Deep Space Network tracking complex at Goldstone, California.  The
Cassini spacecraft is in an excellent state of health. Information on
the present position and speed of the Cassini spacecraft may be found
on the "Present Position" page at:
http://saturn.jpl.nasa.gov/mission/presentposition/.

Wednesday, Feb. 18 (DOY 049)

Spacecraft Operations hosted the S53 Engineering Activities Review
today.  At this review the team goes over all engineering and health
and safety activities to be performed during sequence execution.

Thursday, Feb. 19 (DOY 050):

Sequence activities began with a series of Optical Navigation images
collected by the Imaging Subsystem (ISS). These images of Saturn's
satellites against the background stars allow the Navigation team to
more accurately determine Cassini's orbit. The day ended with a
thirteen-hour observation of Saturn's E and G rings by the Visual and
Infrared Mapping Spectrometer (VIMS).

Friday, Feb. 20 (DOY 051):

Work continued on preparations for the swap to the RCS thruster
B-branch, scheduled to begin Mar. 12.  A technical review of the
Cassini Thruster Swap and Checkout Plan was held
today.  Representatives from Divisions 31, 34, and 35 participated.

A detailed review of the "Open LV-41 and swap to B-branch" procedure
was also held today.  The Integrated Test Laboratory dry run will be
kicked off Feb. 23.  Both the procedure and various contingency files
will be tested that week.

An AACS friction test of the backup reaction wheel # 3 was performed
today.  In this test, performed every 6 months, the wheel is spun up
to 600 rpm in both the clockwise and counterclockwise directions, and
timed as it is allowed to run down to zero.  Results were unchanged
from previous tests.

Today the Ultraviolet Imaging Spectrograph (UVIS) oriented the
spacecraft to target Enceladus for a three and a half hour
observation designed to map the system in the immediate neighborhood
of Enceladus. Observations tested the connection between volatile
changes and plume eruptions.   Next, ISS targeted a few more icy
satellites in the Saturn system. The day ended with an experiment
conducted by the RADAR instrument where, instead of actively bouncing
RADAR signals off Titan, they passively measured the radio heat
signature of Titan. This type of measurement is referred to as
radiometry.

Science Planning handed off all files and materials to Uplink
Operations to begin final sequence development for S50.

An after-school adaptation of Reading, Writing & Rings was presented
to 60 Los Angeles area educators on February 19 and 20, 2009.

Educator-Astronaut Barbara Morgan will be the keynote speaker at the
International Reading Association's Annual Convention West in
Phoenix, AZ, February 21-25, 2009.  She will feature "Reading,
Writing & Rings" in her address.  Cassini Outreach provided copies of
the RWR CD-ROM to her to distribute to 300 teachers attending the
conference.

Monday, Feb. 23 (DOY 054):

The Target Working Team (TWT)/ Orbiter Science Team (OST) integrated
products for S53, covering orbits 117 through 119, were delivered
today. The integrated products are in their final form and no
re-integration is planned.  The next step in sequence development,
Science Operations Plan (SOP) implementation, will kick off on Mar.
9.  Between now and then, the instrument teams will be working on
pointing designs for the sequence. TWT/OST teams deliver integrated
sequence products for the extended mission about every five weeks.

Tuesday, Feb. 24 (DOY 055):

Contingency planning is one of the many ongoing activities while a
flight project is in the operations phase.  A possible scenario might
be that someday the reaction wheels on board Cassini may fail.  That
scenario and the options for conducting a thrusters-only mission was
the topic of discussion at the Mission Planning Forum today. The
presentation included Reaction Control Subsystem hydrazine budget
with number of turns per day, different options for articulating the
spacecraft at slower rates and accelerations, wider deadbands, etc.

The February Cassini-Huygens Analysis and Results of the Mission
teleconference for the JPL outreach networks featured "Rings around a
moon? The puzzling case of Rhea."  The presentation can be downloaded
from the Cassini website at:
http://saturn.jpl.nasa.gov/video/products/MultimediaProductsCharm/
>http://saturn.jpl.nasa.gov/video/produ
cts/MultimediaProductsCharm/

Each year dozens of Cassini scientists, engineers and educators
volunteer to support Open House.  In 2009, JPL open house takes place
all day Saturday and Sunday, May 2 and 3.  The attached link will
take you to a Cassini specific video from 2008. There are additional
videos on the
page.
http://" target="new">http://www.jpl.nasa.gov/video/index.cfm?id=814>http://
www.jpl.nasa.gov/video/index.cfm?id=814

On Feb. 24, a quadruple transit of Saturn's moons occurred when
Titan, Mimas, Dione and Enceladus passed directly in front of Saturn
as seen from Earth.  The Hubble Space Telescope and amateur
astronomers from along the Pacific coast of North America, Alaska,
Hawaii, Australia and East Asia were able to observe this event.
Transits like these are rare. They only happen every 14 to 15 years
when the orbits of Saturn's moons are nearly edge-on to Earth.  For
more information link to:
http://science.nasa.gov/headlines/
y2009/19feb_quadrupletransit.htm>http://science.nasa.gov/headlines/
y200
9/19feb_quadrupletransit.htm

Visit the JPL Cassini home page for more information about the
Cassini Project: http://" target="new">http://saturn.jpl.nasa.gov/>http://
saturn.jpl.nasa.gov/>
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