1、Lessons Learned Entry: 1484Lesson Info:a71 Lesson Number: 1484a71 Lesson Date: 2004-08-02a71 Submitting Organization: JPLa71 Submitted by: Mark Boyles, David OberhettingerSubject: The Mission Operational Design Should Allow for “Down Days“ (2004) Abstract: Early in the Mars Exploration Rover (MER) d
2、esign phase, and in all modeling for operations and mission science return, planners assumed that each rover would be inoperable every third day, on average, due to problems. This planned margin contributed to mission success by giving operations personnel time to gain an understanding of problems,
3、and to plan high-risk maneuvers, before taking action. For complex missions, provide sufficient margin in the planned mission science return to accommodate likely interruptions in the data flow.Description of Driving Event: Early in the Mars Exploration Rover (MER) design phase, and in all modeling
4、for operations and mission science return, planners assumed that each rover would be inoperable every third day, on average, due to problems. MERs daily command cycle and 90-day prime mission lifetime requirement were factors in deciding to make this assumption. The benefit of making allowances for
5、these hypothetical “down days” was that it provided: 1. Enough margin in the planned mission return to accommodate losses such as the roughly two-week data loss due to the Spirit flash memory problem, and2. A benchmark against which to compare actual lost days of operation. This helped JPL to determ
6、ine whether it was on track to meet mission and science return criteria and contributed to meeting full mission success.This mission design assumption enabled a cautious approach during surface operations when responding to detection of anomalies and when planning the execution of high-risk maneuver
7、s by the MER operations team. Spirit, the first of the two MER rovers, was delayed in its “drive-off” of the lander when airbags hampered the preferred egress path (Figure 1). Later, Spirit experienced a Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-
8、problem with its flash memory for 2 weeks. The operations team for the second rover, Opportunity, spent several days determining the safety of entering the crater Endurance. During these and other surface mission events, operations personnel were not under undue pressure to return to science opera
9、tions, but instead took sufficient time to gain confidence in their understanding of the situation before taking action. refer to D descriptionDAdditional Key Words: operational margin, operations margin, mission planning, operations design Lesson(s) Learned: For complex spaceflight missions, it is
10、very likely that unforeseen factors will cause interruptions in the science data return. Recommendation(s): For complex missions such as landers or rovers, provide sufficient margin in mission return/success operational scenarios to accommodate likely interruptions in the data flow on the order of s
11、everal days. Such margin may be on the order of 30% or more depending on the complexity of the mission. Evidence of Recurrence Control Effectiveness: Corrective Action Notice No. Z85350 was opened by JPL on January 4, 2005 to initiate and document appropriate Laboratory-wide corrective action on the
12、 above recommendation.Documents Related to Lesson: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N/AMission Directorate(s): a71 ScienceAdditional Key Phrase(s): a71 Flight Operationsa71 Hardwarea71 Payloadsa71 Policy & Planninga71 Risk Management/A
13、ssessmenta71 Safety & Mission Assurancea71 SpacecraftAdditional Info: Approval Info: a71 Approval Date: 2004-09-22a71 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-,-,-
