 From the Project ManagerProject Galileo is doing great! Congratulations to the Project Team and to the DSN and Multi-Mission Ground Data System (MGDS) personnel for their continuing superb performance. Ganymede-2 was another grand success. Most remarkably, this encounter was truly saved by the most timely anomaly recovery yet. On Saturday morning, August 24, the spacecraft entered safing just 8 days before the encounter sequence was to begin. The Command and Data Subsystem (CDS) A-String was down. Due to the press of all the other Orbital Phase Flight Software work, we did not yet have the contingency packages ready for a "String Down" recovery. Just a week before, we had estimated such a recovery would take 2 to 3 weeks! Everyone turned to and worked at flank speed to save the encounter. By the following Thursday, just 5 days later and 2 days before we had to uplink the encounter sequence, the CDS dual-string operation and science processing was fully recovered without our yet knowing what had caused the problem. Later that very day, the Flight Software Team found the problem. During one of the ten computational cycles (RTI-6) in the CDS, the time tags of all the waiting Delayed Action Commands (DACs) must be checked. There were too many DACs for RTI-6 to finish its new Orbital Phase work after checking them--the processor time overrun properly resulted in the privileged error flag that takes the faulted string down to protect the spacecraft from dangerous erroneous commands. What a relief! We immediately knew how to prevent this problem from happening again. Until that moment, even though the CDS was back up, we were very concerned that whatever had happened might happen again in a few days when it would be impossible to recover in time to do the encounter. In fact, without the joint expertise of the mission operations people (including the testers) and the development people working as a team, this recovery would not have been possible--there would have been no Ganymede-2 science. Last spring, realizing the possibility we might have to do an Orbit Trim Maneuver (OTM) before recovering a down string, we validated that procedure. An OTM was required before Ganymede-2; otherwise the propellant penalties might preclude several of the last orbits of the tour. The OTM was performed flawlessly, single-string, just 3 days after the safing. The last 8 days in August were quite something! There's no substitute for experience. The last of the priority patches to the Flight Software has just been installed on the spacecraft. All the known liens on the playback process are now fixed and the real-time Heavy Ion Counter (HIC) capability is working well. Now approaching the midpoint of the Ganymede-2 tape playback, we can be guardedly optimistic that the Flight Software residual problems have been solved. On September 10-11 the online spacecraft receiver rest frequency drifted anomalously such that the standard DSN uplink acquisition procedure did not lock the uplink. This was promptly resolved by the DSN using a wider sweep. Now the receiver is essentially back to normal, and we suspect Jupiter radiation caused the drift. We'll be watching closely for this at the next encounter. The Near-Infrared Mapping Spectrometer (NIMS) problem also appears to be radiation related. The onboard NIMS reloading effectively mitigated this at Ganymede-2, and we plan to continue that technique. Attempts to move the Photo-Polarimeter Radiometer (PPR) filter wheel were unsuccessful. At Callisto-3, PPR will do radiometry only, and further attempts to move the wheel are TBD. With the sole exception of 1 of the 11 Orbiter science instruments, everything is working very well. All things considered, Project Galileo is fulfilling its promise at Jupiter superbly!
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