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Posted by baalke on March 9, 2007, 3:52 pm
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Cassini Significant Events
for 02/28/07 - 03/06/07
The most recent spacecraft telemetry was acquired on Tuesday, March 6,
from
the Madrid 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, February 28 (DOY 059):
Part two of the S28 background sequence was uplinked to the spacecraft
today. Due to its size, the sequence was split in order to avoid
having to
remove any science or engineering activities. Part two is registered
on
board, will begin execution on March 15, and will clock out for the
remaining 14 days of the sequence.
As reported last week, an AACS Inertial Reference Unit (IRU)
calibration
completed yesterday. This calibration was performed with the IRU-A
scale
factor corrections that were uplinked recently with the A8.7.5 AACS
flight
software (FSW) update. After examining telemetry from the spacecraft,
it
has been determined that the new values reduce the residual per-axis
gyro
scale factor errors by at least a factor of eight. This improvement
will be
seen when a star id suspend period ends, and attitude propagated by
the gyro
and that determined from the SRU are compared. AACS expects these
values to
remain valid for about two years.
As part of the Cassini Extended Mission NASA Senior Review, held on
February
15, four Cassini scientists gave presentations on the value of the
science
that will be obtained during the two-year period from 2008 to 2010.
The
presentations were extremely captivating. As a result, Science
Planning
requested that these four individuals give their presentations to the
flight
team. The first occurred today as part of the Program internal Tour
Science
Talks. The other three presentations will occur over the next several
weeks.
Thursday, March 1 (DOY 060):
On March 14, a naming ceremony for the Huygens Probe landing site will
be
held at the European Space Agency (ESA) Headquarters. ESA, the
international
Committee for Space Research (COSPAR), and NASA have decided to honor
Professor Hubert Curien's contribution to European space activities by
naming the Huygens landing site on Titan after him. The part played by
ESA
in the Huygens landing, in cooperation with NASA and the Italian Space
Agency (ASI), was made possible thanks to the commitment of Curien
who, for
several decades, worked to promote and strengthen the role of
scientific
research in his home country - France - and in Europe. Among his
numerous
responsibilities, Hubert Curien was French Minister of Research and
Space
under four Prime Ministers. For more information link to the ESA and
Cassini websites.
Friday, March 2 (DOY 061):
Orbit Trim Maneuver (OTM) #96 was performed today. This is the
apoapsis
maneuver setting up for the Titan 26 encounter on March 10. The main
engine
burn began at 11:59 PM PST. Telemetry immediately after the maneuver
showed
the burn duration was 4.08 seconds, giving a delta-V of 0.67 m/s. All
subsystems reported nominal performance after the maneuver.
Sunday, March 4 (DOY 063):
Flight Software (FSW) A8.7.5 normalization was successfully completed
on
board the spacecraft today. Although the software was uplinked in
early
February of this year, the Spacecraft Team decided to wait till after
the
IRU calibration on Wednesday, Feb. 28, before performing
normalization. The
process of normalization involves placing identical copies of the
software
on all four partitions on the SSR, then performing memory readouts to
verify
all copies are correct. AACS now has A8.7.5-32 on default partitions
0
through 3 on both SSR-A and SSR-B. The next update to AACS flight
software
is scheduled for early 2008.
Monday, March 5 (DOY 064):
The Aftermarket Process for the S33 sequence covering orbits 49 and 50
begins today. This 5-week process will address proposed changes that
require re-integration of the science segments contained in the S33
sequence. All proposed changes are to be submitted by end-of-day
today. If
all of the requested changes do not fit, there will be an assessment
meeting
held on March 7, where the Project Scientist will review the
requests. If
necessary, on Tuesday, March 20, a final decision meeting will be held
to
decide what changes will be made to the S33 plan. The approved changes
will
then be integrated by the appropriate target working teams or orbiter
science teams.
In support of S30, a test has been planned in the Integrated Test
Laboratory
for solar occultation ingress & egress and rings egress on DOY 130 for
Radio
Science, the Titan 30 flyby on DOY132 for RADAR and Spacecraft
Operations
(SCO), and Titan 31 ingress & egress on DOY148 for Radio Science. The
tests
are currently scheduled for March 23-29. The details are yet to be
worked
and will be addressed at the S30 Simulation Coordination Meeting. The
length of the test is unusually long and as a result, the S30
development
process will be compressed to accommodate it.
A delivery coordination meeting was held today for the SCO tool
Maneuver
Automation Software (MAS) version 6.1.1. MAS is an application used
to
generate maneuvers based on maneuver parameters, and generate reaction
wheel
bias (RWA) commands. With this software, the maneuver commands and
RWA
biasing may also be merged with a specified background sequence.
Output
products and comparison reports are created throughout these
processes. The
MAS software automates and verifies as much of the maneuver, RWA bias,
and
merge generation processes as possible.
Tuesday, March 6 (DOY 065):
The orbit determination solution using tracking data through 3 PM
today
converged sufficiently to allow the OTM-97 maneuver decision to be
based on
today's orbit solution. Using today's data, OTM-97 has a delta-V of 6
mm/s.
The cost of cancellation on the downstream maneuvers is estimated to
be
about 0.4 m/s. Given the reasonable delta-V cost of canceling the
maneuver,
and the difficulties associated with implementing such a small
maneuver, the
Program manager has decided to cancel the maneuver. There will be a
command
approval meeting tomorrow for an RWA bias in lieu of OTM-97.
Last week images and movies were released of views of Saturn and the
rings
taken from a highly inclined orbit. Today one of those images was
showcased
as Astronomy Picture of the Day. The direct link to the image may be
found
at:
http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=2509
The high inclination views of Saturn mentioned for the last few weeks
are
the visible documentation of a pi transfer completed with the Titan 25
flyby. Cassini's orbital inclination between T24 and T25 was
approximately
59 degrees. From T25 through T33, the inclination will be lowered back
nearly into Saturn's equatorial plane. Prior to the pi-transfer,
Titan
flybys and apoapsis, the farthest distance of Cassini from Saturn in a
given
orbit, had occurred on the night side of Saturn in order to support
magnetotail observations. Now they occur on the dayside of Saturn
offering
several low altitude Titan flybys and favorable ring observation
geometry to
the science community.
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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