Cassini Significant Events 01/28/09 - 02/03/09
Title: Cassini Significant Events 01/28/09 -
Cassini Significant Events
01/28/09 - 02/03/09
The most recent spacecraft telemetry was acquired on Feb. 3 from
Deep Space Network tracking complex at Goldstone, California. The
Cassini spacecraft is in an excellent state of health. Information on
the present position and speed of the Cassini spacecraft may be found
on the "Present Position" page at:
Wednesday, Jan. 28 (DOY 028):
An encounter strategy meeting was held today to cover the period
between Feb. 7 and Mar. 27, Titan flybys T50 and T51, and
Thursday, Jan. 29 (DOY 029):
Today at the Executive Session of the Cassini Project Science
meeting, a tour was selected from among four candidates to be part
a proposal to be made to NASA next week for a follow-on mission
the current extended Cassini mission is complete.
Friday, Jan. 30 (DOY 030):
An analysis published in the journal Geophysical Research Letters
recent pictures of Titan's south polar region reveals new lake
features not seen in images of the same region
taken a year earlier. The presence of extensive cloud systems
the area in the intervening year suggests that the new lakes could
the result of a large rainstorm and that some lakes may thus owe
presence, size and distribution across Titan's surface to the
weather and changing seasons. For more information on this
Monday, Feb. 2 (DOY 033):
A non-targeted flyby of Rhea occurred today.
Science Planning (SP) hosted a kick-off meeting today for the S52
Science Operations Plan (SOP) process. The SOP process is
to yield a conflict-free sequence, including both science and
engineering activities, down to the command level. Cassini
participating in this process include: the Project Science Group,
Instrument Teams, SP, the Spacecraft Office, Mission Planning,
Operations, the Instrument Operations Team, and Navigation.
from this process are an integrated conflict-free time-ordered
of all science observations, supporting engineering events to
mission objectives, a constraint-checked pointing profile, and
volume allocations for the science observations contained in the
plan. At the end of this process, all products are turned over
Uplink Operations for the final sequence development process along
with any liens and actions remaining unresolved.
Today a Cassini-Huygens Mission Status Report was published to
the Cassini web site:
The story reported on the project's decision to swap from the
Control Subsystem thruster branch A to branch B. To give you a
the technical information:
Chamber pressure roughness, a measure of efficiency for thrusters,
been increasing on thrusters Z3A and Z4A, as shown in telemetry
and as evidenced in the underburn at maneuver-169. Small
in chamber pressure roughness and thrust are normal for hydrazine
thrusters, but this recent increase could indicate thruster
degradation. At a Technical Interchange meeting on Jan. 22,
Lockheed Martin Space Systems, the propulsion module contractor,
Aerojet, the thruster manufacturer, and technical experts from the
Propulsion section of Division 35 recommended to the Cassini
that a swap be made to the backup thruster set B as soon as
practical. This recommendation has been accepted and a time
March 12-18 is being worked.
The latest status from Spacecraft Operations (SCO) is that work is
continuing on planning the thruster branch swap in mid-March.
Preliminary reviews and file testing will occur in late February.
early March an end-to-end test will occur exercising both files
team procedures. An uplink readiness review is tentatively
for Mar. 6. During the actual uplink
and hardware swap, the
background sequence will be deactivated. This means that all
and engineering activity will cease on board. Sequence leads
contacted the instrument teams to determine what states the
instruments should be left in - off, sleep, other - when the
background sequence halts. The science data collected prior to
071 will be preserved on the SSR and will be played back after the
thruster swap procedure has completed. Deactivation is currently
planned for Mar. 10. The B-branch thruster swap is planned for Mar.
followed by various checkout and calibration activities until the
background sequence is re-activated Mar. 18. The B-branch latch
and the B-branch catalyst bed heaters will be placed into their
correct configurations for B-branch operations before the actual
Tuesday, Feb. 3 (DOY 034):
The Orbit Determination (OD) and Maneuver solutions for Orbit Trim
Maneuver (OTM)-181 are very stable and very little movement is
expected in the next few days. Without an OTM, the flyby at
is predicted to be about 9.3 km high. The OTM has a magnitude
about 40 mm/sec, however cancellation would save about 1.2 m/s.
no OTM solution has been provided to science, and RADAR -
the most impacted team - found it to be acceptable. SCO
cancellation due to concerns related to the A-branch thrusters.
Navigation recommended and the project has concurred with the
cancelation of OTM 181.
The sequence leads for S49 reported that the Titan 51 and Titan 52
Radio Science bistatic observations would be tested in the
Test Laboratory prior to being executed. A Simulation
meeting was held today to support this activity. On Thursday the
will review the procedures for these tests. S49 begins
board the spacecraft on Mar. 26.
Activity has now begun for the fourth Live Inertial Vector
Update in S47. The update will be based on the maneuver #182
solution. The OD will be published by end-of-day Monday. Execution
planned for DOY 44-45 with vector updates for Saturn and Titan.
schedule is very tight - there are less than two days to turn
and process this update. The Kickoff Meeting is scheduled for
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