NASA Cassini Significant Events for 05/20/04 – 05/26/04

The most recent spacecraft telemetry was acquired from the Madrid tracking
station on Wednesday, May 26. 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
http://saturn.jpl.nasa.gov/operations/present-position.cfm .

On-board activities this week included the Imaging Science Subsystem (ISS)
Titan movie which searches for evidence of cloud motion to measure winds.
ISS also continued to study the orbits of the ring-region satellites to
improve our understanding of short- and long-term dynamical evolution. The
Ultraviolet Imaging Spectrograph (UVIS) continues to map the Saturn
magnetosphere in neutral and ion photon emissions to derive the distribution
and density of atomic and molecular species. Deep space calibrations were
performed for the Composite Infrared Spectrometer (CIRS), and a high
frequency calibration for the Radio and Plasma Wave Science (RPWS)
instrument. The ISS NAC was commanded to perform a power-on reset to clear
any possible residual problems prior to some critical Optical Navigation
activities. These activities then occurred without incident.

Remaining on-board activities centered on preparations for Trajectory
Correction Maneuver 20. This maneuver is significant in that it adjusts the
spacecraft’s orbit for its approach to Saturn, and is the same type of
maneuver that will be used for Saturn Orbit Insertion (SOI). This week a
checkout was performed for Rocket Engine Assembly-B, the main engine cover
was opened, and the oxidizer side of the propulsion system un-isolated. The
spacecraft is now ready to support TCM-20 on May 27, 2004.

Starting on Monday, May 24, the Cassini Imaging Team increased the frequency
of its postings of images to one per day (five days per week) for the
enjoyment of scientists and members of the public alike.

The Multi Mission Image Processing Laboratory (MIPL) supported the
generation and delivery of three sets of ‘critical’ Optical Navigation
images in the last week. Two of the events occurred on non-prime-shift and
were staffed for potential manual intervention. All these deliveries were
made successfully and on-time by the automated processes – no intervention
required.

In the last week, 625 ISS images arrived and were distributed along with 369
Visual and Infrared Mapping Spectrometer (VIMS) cubes. The total number of
ISS images acquired since the start of Approach Science is now 7413, and the
number of VIMS cubes is 1311.

In support of the Phoebe encounter, the flight team is holding an Operations
Readiness Test (ORT) for the Phoebe Live Update Process. This week the
files generated during last week’s live update process were run through the
Integrated Test Laboratory for validation. In addition, it was decided to
forgo the remaining portions of the ORT to allow for an earlier Navigation
convergence and a more relaxed schedule for actual Phoebe operations.

The port #1 end-to-end pointing analysis for tour sequences S29 and S30 has
been completed. The Teams will now review the analysis reports and correct
any problems in time for preliminary port #2 on June 7.

The science operations plan implementation process for tour sequences S31
and S32 began this week. A Tour Process meeting was held Wednesday, May 26,
to discuss the impacts the new reference trajectory has on the integrated
science plan and the possible options available to deal with those changes.

A sequence change request approval meeting was held as part of the process
to develop tour sequence S03. Four requests were approved.

A delivery coordination meeting was held for Navigation software version
T1.4. During last week’s internal SOI review, Navigation identified two
“must-do” fixes for this software. One was for ARDVARC, the automated
radiometric data visualization and real-time correction software, and the
other for PVTOEXP which converts spacecraft trajectory “P” files from NAV-IO
format to “Export” DSN format. The 4.1 version was approved and has been
installed for operations use.

The Saturn Observation Campaign (SOC) is a Cassini informal education
program, comprised of about 300 mostly amateur astronomers in 43 states
around the US and in 42 countries around the world. A Saturn Observation
Campaign observing event will be held at Monrovia’s Library Park at the
corners of Myrtle and Lime Streets, in Monrovia, California from 7:30 p.m.
to 10:00 p.m. Saturday May 29. There will be at least two and maybe more
telescopes aimed at Saturn and Jupiter or the moon. A local middle school
science class has been invited and a nice crowd is expected. Saturn will
look best earlier rather than later in the evening.

Saturday night is also the date of the Griffith Observatory Star Party,
hosted by the Los Angeles Amateur Astronomers and the LA Sidewalk
Astronomers. The Griffith Observatory event runs from 2:00 p.m. for solar to
10:00 p.m. once a month. The Griffith Observatory satellite is located
immediately south of the LA Zoo and the Autry Museum in the northeast corner
of Griffith Park. Glendale, California.
http://www.griffithobs.org/satellite.html

Saturn is getting low in the western sky, and by next month, it won’t be
visible again – at least at a decent hour for viewing – until late 2004.
This weekend will be a great time to see Saturn, with Mars nearby, Venus and
Jupiter and even the 3-day waxing moon.

As Saturn grows closer through the eyes of the Cassini spacecraft, both
Cassini and the Earth-orbiting Hubble Space Telescope snapped spectacular
pictures of the planet and its magnificent rings.

Cassini is approaching Saturn at an oblique angle to the Sun and from below
the ecliptic plane. Cassini has a very different view of Saturn than
Hubble’s Earth-centered view. For the first time, astronomers can compare
views of equal sharpness of Saturn from two very different perspectives.
For more information go to: http://saturn.jpl.nasa.gov and
http://hubblesite.org/news/2004/18

Five Cassini images were released in the past week. These images are
available on the gallery section of the Cassini website
http://saturn.jpl.nasa.gov/multimedia/images/latest/index.cfm

Cassini is a cooperative project of NASA, the European Space Agency and the
Italian Space Agency. The Jet Propulsion Laboratory, a division of the
California Institute of Technology in Pasadena, Calif., manages the Cassini
mission for NASA’s Office of Space Science, Washington, D.C.