1、Lessons Learned Entry: 0584Lesson Info:a71 Lesson Number: 0584a71 Lesson Date: 1998-03-05a71 Submitting Organization: JPLa71 Submitted by: C. Whetsel/D. OberhettingerSubject: Mars Global Surveyor (MGS) Aerobraking Extra Burn Anomaly (1997) Abstract: Following Mars encounter, an unintended repetition
2、 of MGSs Aerobraking Maneuver #5 occurred after the intentional burn. Installation of a new version of the ground data system software one day earlier than planned without adequate review of the consequences of the schedule change caused an incompatibility between ground and flight software.Configur
3、ation control procedures must ensure that the spacecraft and sequence teams are properly notified of changes to planned ground software updates affecting the spacecraft. In particular, uplink sequences must be consistent with memory partitions onboard the spacecraft. Description of Driving Event: Mi
4、ssions using aerobraking employ atmospheric drag to reduce the spacecraft orbit period and lower its apoapsis altitude. The technique requires tight control both on the attitude pointing of the spacecraft while in the atmosphere, and especially on the altitude during each aerobraking drag pass at pe
5、riapsis (the orbits closest approach to the planet). Targeting periapsis altitudes is critical to assure that the proper orbital conditions are achieved. The periapsis altitude is controlled by periodically performing small propulsive aerobraking trim Provided by IHSNot for ResaleNo reproduction or
6、networking permitted without license from IHS-,-,-maneuvers (ABMs) one-half of the orbit period earlier. This places the spacecraft at the other side of the orbit, near apoapsis, the point in an orbit at which the spacecraft is at furthest distance from the planet. A portion of the Mars Global Surve
7、yor (MGS) spacecraft memory was allocated and managed as storage space for command sequences and programs uplinked from Earth, such as aerobraking maneuvers. These sequence loads are typically created by the flight projects sequence team with inputs from the spacecraft and science operations teams.E
8、xtra Burn Anomaly. An unintended repetition of MGS Aerobraking Maneuver #5 occurred after the intentional burn on November 12, 1997. The planned maneuvers objective was to decelerate the spacecraft 0.1 meters per second (m/s) to enable an aerobraking pass 17 hours later. This maneuver executed as ex
9、pected.refer to D descriptionD Aerobraking Operations Approximately 3 hours later, the spacecraft unexpectedly repeated the aerobraking maneuver, imparting an additional delta-v to the spacecraft. To avoid a deeper penetration into the Martian atmosphere, the flight team designed, uploaded, and succ
10、essfully commanded a third “antidote“ maneuver, which counteracted the effect of the unplanned second maneuver. Although the mission impact of this incident was limited to expenditure of propellant in the 0.5 m/s remedial burn, occurrence at another time could have been mission catastrophic.The caus
11、e of the incident was traced to an incompatibility between ground and flight software. A new version of the ground software had been installed in the ground data system one day earlier than planned without adequate review of the consequences of the schedule change. This new software had been redesig
12、ned to improve programming and command efficiency. Certain memory partitions were reassigned in on-board memory, and this software package needed to be installed on the ground system at the previously agreed to time relative to the command uploads. Due to the address changes, the recently executed A
13、erobraking Maneuver #5 was loaded into the partition originally intended for the next science sequence. Hence, when the spacecraft command data subsystem (CDS) executed Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-“Next Sequence,“ the Aerobraking
14、Maneuver #5 sequence was still present in memory, and it was performed instead of the science sequence.Reference(s): JPL Incident/Surprise/Anomaly (ISA) Number Z44658, November 23, 1997Lesson(s) Learned: Configuration control procedures must ensure that the spacecraft and sequence teams are properly
15、 notified of changes to planned ground software updates affecting the spacecraft. In particular, uplink sequences must be consistent with memory partitions onboard the spacecraft.Recommendation(s): 1. Prior to implementing any change in command and control software, verify that the configurations of
16、 ground and flight software are compatible.2. Provide a method for identifying the time-criticality of any flight software configuration change.3. When approved mission plans must be changed in real time, review and reconsider all factors which were weighed in developing the original plan.4. Softwar
17、e design and implementation should minimize the possibility of accessing onboard stored command sequences at inappropriate times.5. Development and use of flight and ground software should be closely coordinated from the very beginning and throughout the life of the project.Evidence of Recurrence Co
18、ntrol Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Configuration Managementa71 SoftwareProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Additional Info: Approval Info: a71 Approval Date: 1998-03-13a71 Approval Name: Carol Dumaina71 Approval Organization: JPLa71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
