Early in operational testing for the InSight mission to Mars, it was discovered that the final maneuver to target the entry-interface point was unexpectedly sensitive to planned atmosphere updates that would be based on real-time measurements of the Martian atmosphere by Mars Reconnaissance Orbiter. Upon investigation, the team realized that the Phoenix mission also discovered this sensitivity during operational testing. Further investigation identified that the sensitivity was a result of the fact that both the entry flight path angle and ground target were being held fixed in the maneuver design process, constraining the maneuver in a way that forced the entry time to change to compensate for changes to the nominal trajectory from updating the atmosphere model. The final maneuver was planned for 22 h before entry, at which point it is very expensive to change entry time. The study also revealed that any unguided Mars entry, descent, and landing mission would be impacted by this sensitivity if it used real-time atmosphere observations to model the nominal expected atmosphere used for maneuver targeting of the entry-interface point. This paper discusses the results of that investigation and presents a number of mitigations as well as the consequences of ignoring the sensitivity.

在 InSight 火星任务的早期运行测试中，发现以入口接口点为目标的最终机动对计划中的大气更新非常敏感，这些更新将基于火星侦察轨道器对火星大气的实时测量。经过调查，该团队意识到凤凰号任务在操作测试期间也发现了这种敏感性。进一步的调查发现，敏感性是由于在机动设计过程中进入飞行路径角度和地面目标都保持固定，以某种方式限制机动，迫使进入时间改变以补偿改变来自更新大气模型的名义轨迹。最后一次机动计划在进入前 22 小时进行，在这一点上改变进入时间是非常昂贵的。该研究还表明，如果使用实时大气观测来模拟用于进入接口点机动瞄准的名义预期大气，那么任何非制导的火星进入、下降和着陆任务都会受到这种敏感性的影响。本文讨论了该调查的结果，并提出了一些缓解措施以及忽略敏感性的后果。