Cassini Significant Events 06/20/06 - 06/28/06

June 30, 2006

(Source: Cassini Project)


Cassini Significant Events 06/20/06 - 06/28/06

The most recent spacecraft telemetry was acquired Wednesday, June 28, 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
http://saturn.jpl.nasa.gov/operations/present-position.cfm .

Tuesday, June 20 (171):

Members of the Cassini Outreach and the Saturn Observation Campaign gave
talks on the summer skies, visible planets, and our Milky Way Galaxy in
Arizona's Kaibab National Forest, and at the Grand Canyon Lodge on June 19
and 20.

Wednesday, June 21 (DOY 172):

A Solid State Power Switch (SSPS) trip on the Stellar Reference Unit (SRU)
-B replacement heater occurred on June 21. This is the 17th occurrence of
an SSPS trip since launch, and the third this year. The other two occurred
on March 2 and May 1. These trips are expected to occur at a rate of about
two per year and are attributed to Galactic Cosmic Rays. When the trip
occurred today, the heater was "off." On-board CDS fault protection (FP)
autonomously reset the switch. There are no thermal issues and no further
action is necessary. Spacecraft Operations will be sending commands to the
spacecraft for a memory readout (MRO) to obtain further insight into the
trip and for documentation purposes.

The official product input port occurred today for the S24 Science
Operations Plan update process. The products have been merged and now
reside in the on-line file repository where they are accessible for review
by the team.

Cassini Outreach presented a sunset talk about the Cassini Mission followed
by gorgeous views of Saturn and its moons at the North Rim of the Grand
Canyon National Park in Arizona on Wednesday, June 21. This was part of the
annual Grand Canyon Star party, held on both the north and south rims of the
Grand Canyon each June.

Still images and five short movie sequences acquired over the past six
months are being released today by JPL in a media image advisory entitled
"moons in motion." In addition to their drama and visual interest,
scientists use the movies to refine their understanding of the orbits of
Saturn's moons. Engineers use the same images, and the orbital positions of
the moons, to help them navigate Cassini. You can view both images and
movies by linking to: http://saturn.jpl.nasa.gov

Thursday, June 22 (173):

The Magnetospheric and Plasma Science (MAPS) instruments became "prime" for
today and tomorrow in order to continue the campaign to study the
magnetotail portion of Saturn's Magnetosphere.

Friday, June 23 (DOY 174):

Uplink Operations sent commands to the spacecraft today to power on the
Cosmic Dust Analyzer (CDA), execute an MRO of the SSPS table, and establish
a new nominal delta-v telemetry schedule prior to OTM-64 execution on June
28. The MRO indicated that an address would need to be updated. Those
commands will be sent next week. The CDA mini-sequence has been properly
received and will start executing on 175T20:00:00, over the DSS-25 pass.

Today is the last day of the Project Science Group (PSG) meeting being held
in Nantes, France. One of the most important topics of discussion was the
selection of an extended mission tour. The five PSG Discipline Working
Groups were asked to produce and report to the PSG on their criteria for
rating tours, a list of liens of specific features of individual tours which
made them "unattractive," rate the tours, and provide a narrative as to how
well selected tours might meet the environmental knowledge desires of future
Titan and Enceladus missions. Gathering this information is no small matter.
The NASA Announcement of Opportunity for the Cassini Orbiter specified five
areas of science and explicitly stated that they were of equal priority.
With the information above, the project must balance the different
scientific interests, then evaluate the labor impact of carrying the various
tour groups forward. There is still much work to be done with a final tour
selection planned for February of 2007. You can expect to see reports on
the updates to the tour selection process after each PSG meeting.

Saturday, June 24 (DOY 175):

Today and tomorrow the Imaging Science Subsystem (ISS) will perform a block
of observations including observations of Iapetus. After returning control
to the MAPS instruments for several hours, ISS will then perform a satellite
transit observation, this time of Epimetheus across Dione. Each day will
end with the Composite Infrared Spectrometer (CIRS) observing Saturn in the
mid-infrared wavelength. These "mid-IR maps" are atmospheric studies of
Saturn, creating a temperature map of Saturn's upper troposphere and
tropopause.

Monday, June 26 (DOY 177):

Monday, June 26, begins with a series of Visual and Infrared Mapping
Spectrometer (VIMS) observations of the rings of Saturn. Both the "E" and
"G" rings will be targeted at a phase angle of 135 degrees. At this angle,
the spacecraft is pointed such that if the Sun is at 12 O'clock, the
spacecraft is between the 4 and 5 O'clock angle, with the rings lying in a
plane across the 3 to 9 O'clock position. At this particular orientation,
sunlight on the rings will be clearly visible as sunlight is scattered by
the ring particles.

Tuesday, June 27 (DOY 178):

A Cassini-Huygens Analysis and Results of the Mission (CHARM) teleconference
was held today. The topic was the Cassini-Huygens second anniversary. An
overview of the mission was given covering launch, cruise, science
objectives, and spacecraft status. This was followed by key science results
obtained in the first two years.

The actual anniversary date for the start of the Cassini tour is July 1,
2004. In recognition of this event, JPL has put out a news release marking
the halfway point of the primary mission. Discoveries made during the first
two years have scientists revved up to find out what's in store for the
second half of the mission. The spacecraft has spent a considerable amount
of time studying Titan during 15 separate flybys so far. In the next 11
months there will be 17 more Titan encounters, and 51 spacecraft maneuvers -
more than one a week - to adjust the flight path. Later in July, navigators
will begin to change the spacecraft's orbit orientation, resulting in a
bird's-eye view of Saturn's rings. For more information on what is in
store, link to: http://saturn.jpl.nasa.gov

Wednesday, June 28 (DOY 179):

Science acquisition today began with an Imaging Science Subsystem (ISS)
observation of Hyperion followed by a Visual and Infrared Mapping
Spectrometer (VIMS) Saturn "feature track" observation. Feature track
observations target a particular feature in Saturn's atmosphere. After VIMS
completes this observation, spacecraft control is returned to ISS to
continue the Hyperion observations.

Orbit Trim Maneuver (OTM) #64 was performed today. This is the approach
maneuver setting up for the Titan 15 encounter on July 2, DOY 183. This
maneuver is the first use of the version 6.0 Maneuver Automation Software,
and the new ACS reaction control subsystem (RCS) Delta-V telemetry schedule
which corrected a discrepancy between the actual post-hydrazine tank
recharge tail-off time and the value in ACS flight software. The RCS burn
began at 4:30 PM PST. Telemetry immediately after the maneuver showed a
burn duration of 47.9 seconds, giving a delta-V of approximately 0.069 m/s.
All subsystems reported nominal performance after the maneuver.

A delivery coordination meeting was held today for version 2.21 of the
Flight Software Development System (FSDS) implemented by the Spacecraft
Operations Office. FSDS is a simulation environment for the Cassini ACS
subsystem. It provides the user a command line interface for visibility
into the spacecraft simulation, the flight software and the ground
interface. Users can retrieve and set variables in the hardware, peek and
poke global variables in the flight software, send 7-commands and check
telemetry values. Execution time is dependent on the host Unix workstation
CPU. Currently, our Ultra-10s can run the ACS flight software and FSDS at
about four times real-time.





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