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Cassini Significant Events 11/03/10 - 11/09/10 The most recent spacecraft telemetry was acquired on Nov. 9
from the Deep Space Network tracking complex at Madrid, Spain. The Cassini
spacecraft is on course, is being reconfigured after last week's safing event,
and all subsystems are 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: http://saturn.jpl.nasa.gov/mission/presentposition/. Wednesday, Nov. 3 (DOY 307) On Tuesday, DOY 306, the Spacecraft Operations team was
performing a real time command procedure to load the backup AACS Flight
Computer-A (AFC-A) with the new AACS A8.8.0 flight software from the Solid
State Recorder (SSR) when a sudden loss of downlink occurred, halting the
procedure. The DSN station at Canberra, Australia, DSS-45, provided support
during the loss of downlink and confirmed execution of High Gain Antenna (HGA)
safing. It was later determined that a command had been corrupted by a flipped
bit and caused a non-maskable interrupt error in the prime Command and Data
Subsystem A (CDS-A). CDS-A performed a reset which correctly resulted in CDS-B
becoming prime. The spacecraft safing algorithm was run, which terminated all
active programs and shut down all nonessential power loads, including all
science instruments, and resulting in deactivation of the executing S64
background sequence. The spacecraft then turned to Sun-point and switched to
the low gain antenna. This caused DSS-45 to lose lock on the downlink signal at
2010-306T23:56 UTC / Tuesday, Nov. 2 at 4:56 pm PST. An hour later, the HGA
Swap response executed and communication was restored through the high gain
antenna and DSS-45 was able to acquire the 1896 bps engineering telemetry
downlink. Recovery efforts continued today, with 12 command files
being sent to the spacecraft. These files set the uplink rate back to 500 bps,
turned on ranging, powered on the Visual and Infrared Mapping Spectrometer
(VIMS) instrument to get it to a safe thermal state, turned on the prime pressurant
control assembly line heater, enabled Autonomous Thermal Control #6, enabled
the HGA Swap monitor, cleared system fault protection statistics, and read out
various AACS and CDS memories for diagnostic purposes. Thursday, Nov. 4 (DOY 308) Recovery efforts continued today with six command files
being sent to the spacecraft. These files were sent to play back engineering
data around the time of the safing incident, read out more CDS memory, clear
AACS high watermarks, and open propulsion latch valve 40, which had been closed
by the safing event. The commands also cleared system fault protection and CDS
error logs, and put on board a mini-sequence to control the telemetry modes
until the S65 background sequence goes active on Nov. 24. Cassini personnel continue to support the office moves
within the Project area. So far, 26 out of 60 office moves have been completed.
This effort is scheduled to continue through next month, when it's projected
that all 60 moves will be complete. This is an ongoing task driven by the
Project's staff reduction as part of its transition to the new, descoped
Solstice mission and the accommodation of other Projects moving into the
operations building. Friday, Nov. 5 (DOY 309) The working group for the Distributed Object Manager (DOM)
transition to the Network File System (NFS) has successfully set up a test DOM
NFS server inside the firewall, ready for testing except for those outside of
the firewall. Currently, DOM is on the legacy Andrew File System (AFS), a
distributed network file system which is no longer supported by the Laboratory.
This effort to move the DOM from AFS to NFS is still ongoing and slated for
completion early in 2011. Monday, Nov. 8 (DOY 312) Orbit Trim Maneuver (OTM) #265 was performed today. This was
a Reaction Control Subsystem (RCS) burn which began at 3:15 AM PST. Telemetry
immediately after the maneuver showed a burn duration of 157.5 seconds, giving
a total delta-V of 176.92 mm/sec, as planned. This was executed using the all
RCS maneuver block which means the roll and yaw turns to and from the maneuver
attitude were done under RCS control instead of the normal reaction wheel
control as a consequence of the earlier spacecraft safing event. This was the
first OTM to be done using a pmxfile interface in place of the Maneuver
Operations Program Set/Maneuver Automation Software (MOPS/MAS) listener
interface. The switch to pmxfiles was done in preparation for the Navigation
Team's switch to the MONTE software set next year. All subsystems reported
nominal performance after the maneuver. Recovery efforts today included uplinking a file with AACS
vectors and clear high water mark commands and a file to deregister seven
programs from the new prime CDS-B. A status update titled "Cassini to Resume Normal
Operations" was released today and posted on the Cassini web site.
Engineers at JPL expect the Cassini spacecraft to resume normal operations on
Nov. 24. They have traced the steps taken by an onboard computer when Cassini
put itself in precautionary 'safe mode' last week. Engineers determined that
the spacecraft went into safe mode because of a flip of a bit in the command
and data system computer. For more information on this subject link to: http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease20101109/ Tuesday, Nov. 9 (DOY 313) Cassini supported telemetry testing of the DSN's new Data
Capture and Delivery (DCD) software by participating in DSN-DCD Project
Interface Tests (PIT) in mid-September and late October. Review of DCD PIT
results revealed that average latency for Cassini increases for DCD, and that
some gaps in data are difficult to determine because of different hardware
paths. Further analysis to explain latency and data issues is still ongoing. DCD
installation at the DSN complexes is scheduled to start today with the upgrade
at the Madrid, Spain complex, to be completed by Nov. 10. The Goldstone complex
is tentatively scheduled for the DCD upgrade on Nov. 29, followed by the
Canberra complex on Dec. 14. As part of the Mission Control, Data Management and
Accountability and Spacecraft Analysis (MDAS) 5.0.5 delivery, a fix to correct
the lack of notifications when valid telemetry red alarms occur was included.
Cassini supported testing of this new AAN v32/Solaris-10 version, which was
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