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Posted by baalke on August 31, 2007, 6:25 pm
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Cassini Significant Events
for 08/22/07 - 08/28/07
The most recent spacecraft telemetry was acquired on Tuesday, August
28,
from the Goldstone tracking complex. 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" web page located at
http://saturn.jpl.nasa.gov/operations/present-position.cfm.
Wednesday, August 22 (DOY 234):
The latest Cassini mission video report is available at:
http://www.jpl.nasa.gov/videos/cassini/cassini20070824/
Also just posted is a Huygens probe feature on turbulence. Look for
it at:
http://saturn.jpl.nasa.gov/news/features/feature20070828.cfm
A memo was released today from the Navigation team documenting the
delivery
of the proposed 070620 - June 20, 2007 - Cassini Extended Mission (XM)
Reference Trajectory database. The current reference database for
prime
mission will remain in effect until April 11, 2008.
Thursday, August 23 (DOY 235.):
The icy satellites Interdisciplinary Scientists (IDS) met today and
allocated the Enceladus flybys for the proposed extended mission to
the
various instrument teams.
The Aftermarket process for S38 orbits 57-59 began today with the
submission
of all desired science and engineering changes. The flight team last
reviewed this sequence in November of 2004 when it was "archived" at
the
conclusion of the Science Operations Plan Implementation process. The
sequence has been "on the shelf" for a little over 2.5 years.
This long lead-time is typical for a prime mission sequence. Using
S01 as
an example, the process began in June of 2001 with Science Operations
Plan
(SOP) Integration. This was followed by SOP Implementation,
"archive," the
Aftermarket process, SOP Update, and the Science and Sequence Update
process. Roughly three years from the start of integration to
execution in
May of 2004. Why such an extended schedule? The processes and
procedures
for developing the sequences were not in place at the time of launch.
This
was a deliberate choice on the part of the developers in order to have
the
sequence development processes and tools in place when the actual
sequence
development had to begin. The cruise to Saturn was to last nearly
seven
years. Approximately the first three years were used to put the
sequence
processes and tools in place; the next three or so years were used to
generate the sequences. Normally for prime mission, four or five
sequences
are in development on any given day and one is executing on-board the
spacecraft.
Now compare this to the sequence development process for the proposed
XM.
As mentioned in the next paragraph, integration is beginning on orbits
79-80, both contained in S42, the first sequence in XM. That sequence
will
begin execution on July 1, 2008. In less than a year, science and
flight
team members must complete the Integration, Science Operations Plan,
and
Science and Sequence Update processes. For XM, the Aftermarket and
Science
Operations Update processes are being eliminated in order to compress
the
over-all development time, and meet a more accelerated schedule. Also
note,
there is no "on the shelf" time. The team believes this schedule can
be
supported due to improvements in ground support hardware, software,
and lots
of hands on experience.
Friday, August 24 (DOY 236):
The first science request delivery milestone for XM occurred today.
All
requests for orbits 79-80 have been submitted. The next major
delivery
milestone occurs on September 14. At that time all of the Target
Working
Teams (TWT) and Orbiter Science Teams (OST) can begin actively
integrating
the XM.
The Satellite Orbiter Science Team (SOST) hosted an Iapetus flyby
preview
meeting today to review the science objectives and activities to be
performed for the flyby scheduled on Sept. 10.
Navigation has reviewed the consequences of canceling Orbit Trim
Maneuver
(OTM) 124 scheduled for execution on Monday, Aug. 27. Using the
latest
orbit determination estimates, the maneuver would have a magnitude of
60
mm/sec and a cancellation cost of 77 mm/sec. There is not a clear
improvement in the science return from either the non-targeted Rhea or
the
targeted Titan flybys next week if the maneuver is performed. After
a
discussion with program management, it was decided to cancel the
maneuver.
Monday, August 27 (DOY 239):
Last week it was reported that Cassini outreach and visualization
activities
were presented at the European Planetary Science Congress 2007 in
Potsdam,
Germany. An additional presentation made in this session pertinent to
Cassini was one given by the organizer of the on-line Unmanned
Spaceflight
Forum in which he showed the high level of excitement and
participation that
has been generated in the public with the near-real-time posting of
raw
images by Cassini and MER. The raw image area is the most heavily
trafficked
location on the Cassini web site.
The Solar Conjunction period concluded today when the Sun-Earth-Probe
(SEP)
angle reached 5 degrees. The Command Loss Timer was set back to its
nominal
value of 85 hours on Aug. 24, when the SEP angle had increased to
about 3
degrees.
Although conjunction officially ended today, near normal operations
resumed
on Aug. 25, with an Optical Navigation (Opnav) image taken by the
Imaging
Science Subsystem Narrow Angle Camera. This was followed by an
Ultraviolet
Imaging Spectrograph (UVIS) mosaic of Saturn's inner magnetosphere, a
Composite Infrared Spectrometer (CIRS) F Ring rotation movie, and
acquisition of RADAR distant Titan radiometer science and calibration
data.
Tuesday, August 28 (DOY 240)
The S33 Rhea/Titan Live Inertial Vector Propagator update for DOY-242
was
radiated to the spacecraft earlier this morning over DSS-14. The
program
has been registered on-board and will begin execution on Wednesday.
The main engine cover was closed today for a dust hazard on Aug. 29.
It
will be re-opened on Aug. 30 before the Titan 35 flyby. This will be
the
35th close/open cycle since launch. The next closure will occur in
March
2008.
An encounter strategy meeting was held today to cover the period
between
Aug. 31 and Sept. 10, Titan T35 through Iapetus I1, and maneuvers
125-127.
The monthly Cassini-Huygens Analysis and Results from the Mission
(CHARM)
teleconference today featured talks and question and answer sessions
on the
composition and sponge-like appearance of Saturn's moon, Hyperion.
Two
articles appeared in the July 5 publication "Nature" on these topics:
Surface composition of Hyperion:
http://www.nature.com/nature/journal/v448/n7149/abs/nature05948.html
Hyperion's sponge-like appearance:
http://www.nature.com/nature/journal/v448/n7149/abs/nature05779.html
COMING UP:
Rhea and Titan flybys - Thursday, Aug. 30 and Friday, Aug. 31, 2007
http://saturn.jpl.nasa.gov/news/events/t35-rhea/index.cfm
Wrap up:
Check out the Cassini web site at http://saturn.jpl.nasa.gov for the
latest
press releases and images.
The Cassini-Huygens mission 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,
manages the
Cassini-Huygens mission for NASA's Science Mission Directorate,
Washington,
D.C. JPL designed, developed and assembled the Cassini orbiter.
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