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The Galileo spacecraft is performing flawlessly and the Project Team is vigorously working the broad spectrum of activities required for the Jupiter mission. It is most heartening to see all these efforts moving so briskly through the multitude of diverse problems and contingencies. The Team clearly has the knowledge, skills, and dedication to safely deliver Galileo to Jupiter and perform the Jupiter mission. We are doing extensive fault protection and contingency planning--we will be well prepared to properly respond to contingencies.
Some very significant milestones were achieved over the past five months. We completed the SL9 data return as planned in January. In February, the new flight software for Jupiter arrival (Phase 1) was uplinked to the Command and Data Subsystem (CDS) and the Attitude and Articulation Control Subsystem (AACS). This marked the first time a planetary spacecraft central computer was completely reloaded in flight. Because of the great complexity and criticality of this process, we allocated six weeks for it. We were surprised and elated when the whole thing was done without a significant problem within one day of the nominal 25-day schedule.
Also in February, the Probe ground battery testing executed the Probe descent profile and showed adequate capacity for the full-up Probe nominal mission including the pre-entry science measurements. On March 16th the newly loaded Phase 1 Orbiter Flight Software was used to perform the final inflight checkout of the Probe. The checkout results were perfect. Based on the excellent ground battery test results and the Probe checkout, we will command the Probe to perform its nominal mission. This is done by the Orbiter a few days before it releases the Probe. (Once the Probe is released, it can no longer be commanded.)
One of our biggest challenges over the last several months has been the Orbital Operations (Phase 2) Flight Software (FSW) development. We have been very ambitious in working with the science investigators to maximize the capability of this new software to do the best possible job within the limits of the onboard processors and available memory. Near the end of last year, we had fallen seriously behind schedule. Through a most extraordinary effort, the Development team has effectively recovered and now has a version of the Phase 2 FSW containing representations of all core capabilities in system testing in the Spacecraft Testbed. This recovery also involved substantial augmentation of test teams (and very long hours for all involved) and testing platforms--most notably maximum use of the high-speed simulator called FASTSIM developed under the leadership of the late Dr. John Zipse. We now have good reason to expect delivery of the first "flyable" Phase 2 FSW in July as planned.
Over the past year, we have been working intensely with our colleagues at DARA (the German Space Agency) and DASA (Daimler-Benz Aerospace; formerly Messerschmitt-Bolkow-Blohm (MBB)) in preparing to use Galileo's 400N main rocket engine. (Germany is our international partner in Project Galileo, having supplied the entire Galileo propulsion system and several science instruments.) The Orbiter Deflection Maneuver (ODM) which targets the Orbiter to its Jupiter/Io aimpoint is now scheduled for July 27th (two weeks after Probe Release) and this will be the first inflight use of the 400N engine. The JPL/DARA/DASA team has studied every potential engine and feed system fault and developed the most comprehensive contingency action plan feasible. Extensive tests of a flight-identical engine were performed in Germany to demonstrate contingency operating capabilities. Further testing of feed-system components was also performed. Our Plan specifies how we will operate the 400N engine for both ODM and Jupiter Orbit Insertion (JOI) for all credible faults. It has been endorsed and complimented for its thoroughness by a Review Board of outside experts.
The so-called Critical Engineering Sequence, which is designed to perform the Probe-Orbiter Relay and JOI "no-matter-what!", has also been vigorously worked over the past year and is now essentially completed and under Project Change Control. Only vernier adjustments are anticipated.
Concurrent with all the preparations for arrival, development of the detailed spacecraft operating sequences for each of the Jupiter/Satellite encounters of the Orbital Tour has been ongoing since last August. These sequences contain all the scientific observations, the required engineering activities, and planning windows for the orbit trim maneuvers. A very substantial fraction of the Flight Team has been working tirelessly and diligently on this demanding, longer range effort. The sequence for the fourth encounter (E4) of the ten encounter tour is nearing completion. These products are impressive and are the instructions to the spacecraft for meeting our scientific objectives in Jupiter orbit.
Trajectory Correction Maneuver (TCM) 23 was flawlessly performed on schedule April 12th. TCM 23 adjusted the Spacecraft trajectory so that after the Probe is released it will nominally be on a ballistic path to the center of its Jupiter entry corridor. The accuracy of the entry path will now be mainly determined by the accuracy of the prerelease spin-up and the Orbiter-Probe separation springs impulse.
In closing, I am delighted to report that Project Galileo has recently received two more prestigious awards. Aviation Week & Space Technology named Galileo in its 1994 Laurels for our Shoemaker-Levy 9 Jupiter impact observations and our discovery of Ida's moon Dactyl, and we have just received the NASA Group Achievement Award for our Ida encounter and Dactyl discovery.
Jupiter awaits!