To ensure the successful launch of the Korea pathfinder lunar orbiter (KPLO) mission, the Korea Aerospace Research Institute (KARI) is now performing extensive trajectory design and analysis studies. From the trajectory design perspective, it is crucial to prepare contingency trajectory options for the failure of the first lunar brake or the failure of the first lunar orbit insertion (LOI) maneuver. As part of the early phase trajectory design and analysis activities, the required time of flight (TOF) and associated delta-V magnitudes for each recovery maneuver (RM) to recover the KPLO mission trajectory are analyzed. There are two typical trajectory recovery options, direct recovery and low energy recovery. The current work is focused on the direct recovery option. Results indicate that a quicker execution of the first RM after the failure of the first LOI plays a significant role in saving the magnitudes of the RMs. Under the conditions of the extremely tight delta-V budget that is currently allocated for the KPLO mission, it is found that the recovery of the KPLO without altering the originally planned mission orbit (a 100 km circular orbit) cannot be achieved via direct recovery options. However, feasible recovery options are suggested within the boundaries of the currently planned delta-V budget. By changing the shape and orientation of the recovered final mission orbit, it is expected that the KPLO mission may partially pursue its scientific mission after successful recovery, though it will be limited.

1. INTRODUCTION
 2. CONTINGENCY TRAJECTORY DESIGN METHOD
  2.1 Equations of Motion
  2.2 Recovery Maneuver Computation
 3. SIMULATION BACKGROUNDS
  3.1 Assumptions and Setups
  3.2 Nominal Lunar Orbit Acquisition Phase
 4. RECOVERY OPTION ANALYSIS
  4.1 Case 1 - Insertion into Circular Mission Orbit
  4.2 Case 2 - Insertion into Elliptical Mission Orbit
 5. CONCLUSIONS
 ACKNOWLEDGMENTS
 REFERENCES

• Young-Joo Song(Korea Aerospace Research Institute, Daejeon 34133, Korea) Corresponding Author
• Jonghee Bae(Korea Aerospace Research Institute, Daejeon 34133, Korea)
• Young-Rok Kim(Korea Aerospace Research Institute, Daejeon 34133, Korea)
• Bang-Yeop Kim(Korea Aerospace Research Institute, Daejeon 34133, Korea)