Cassini Significant Events -- 04/08/09

The most recent spacecraft telemetry was acquired on Apr. 14 from the Deep
Space Network tracking complex at Goldstone, California. The Cassini
spacecraft is in an excellent state of health and all subsystems are
operating normally. 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/operations/present-position.cfm

Wednesday, April 8 (DOY 098)

The Cassini Mission Website is a 2009 Webby nominee. As one of only five
nominees in its category, the Cassini mission site is eligible for the
internet industry's two most sought-after awards: The Webby Award and The
Webby People's Voice Award. While the Academy selects The Webby Award
winners, the online public selects The People's Voice Award winners. Webby
People's Voice voting starts April 14th and ends April 30th. Each individual
can only vote once. Wired magazine seems to be running neck and neck with
Cassini. Webby Award and Webby People's Voice Award Winners will be
announced on May 5, 2009. Winners will be honored at the 13th Annual Webby
Awards in New York City on June 8, 2009. To register to vote for the
People's Choice, go to http://www.webbyawards.com/

Members of Science Planning gave a presentation today to personnel from the
Advanced Multi-Mission Operations System (AMMOS) Working Group. AMMOS asked for the presentation to assist in understanding what the Cassini flight team
is doing and what AMMOS-provided capabilities need continuing support. The
presentation was designed to provide insight on the complexity of Cassini
operations and what tools are currently in use for uplink planning.

The first science observation today was an Imaging Science (ISS) movie of
the mysterious "spoke feature" on Saturn's rings. For almost six hours,
ISS, along with the Composite Infrared Spectrometer and the Visual and
Infrared Mapping Spectrometer, took advantage of the lit side of the rings
to look for periodicities of the feature. After the spoke movie, ISS imaged
the smaller satellites as part of an orbit determination series. Finally,
Titan came back into the field of view and a 7 hour 24 minute observation of
Titan's clouds occurred.

A non-targeted flyby of Titan occurred on Saturday, Apr. 11.

Orbit Trim Maneuver (OTM) #189 was performed today. This was a periapsis
maneuver setting up for the Titan 53 encounter on Apr. 19 and reflects the
first use of updated Maneuver Automation Software version 8.1. The main
engine burn began at 6:15 AM PDT. Telemetry immediately after the maneuver
showed the burn duration was 42.2 seconds, giving a delta-V of 7.12 m/s. All
subsystems reported nominal performance after the maneuver.

A week-long end-to-end test began today for the AACS flight software (FSW)
A8.7.7 update planned for uplink at the end of May 2009. This version of FSW
will cover the period from June 2009 through July of 2010, and will update
the default safing attitude and the default thruster magnitudes.

All delivered files received for port 1 of the S53 Science Operations Plan
process have been merged. Science Planning has released its assessment of
the product with comments and areas that need to be revised. In addition, a
presentation was given on the science highlights for this sequence with a
focus on what is unique, and what observations have the highest priority.
This information will help the flight team as the sequence goes through the
development process, and assist the team in making trades should the need
arise.

three tracks scheduled to be supported by DSS-14 during this period. These
occur on DOY 105, 110 and 114. The track on DOY-114 was of particular
concern as it was scheduled to support playback of data from the Titan 53
flyby. There is no health and safety issue for the spacecraft but the loss
of this station does represent an impact to science data return. The DSN
scheduler supporting Cassini has acquired partial tracks at DSS-43 on DOY
105 and 106 to assist with playback. In addition, the telemetry modes and
on-board data policing strategy will be updated by real time commands to
insure return of higher priority data. Having ensured that the maximum
feasible has been done for DOY 105, Uplink Operations and Science Planning
will now turn their efforts to the tracks on DOY 110 and 114. Negotiations
to work around problems such as this one are never easy since the other
flight projects planning on being supported by DSS-14 have the same concerns
as Cassini. Stay tuned next week for an update.

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Cassini Significant Events -- 04/08/09 - 04/14/09