Implementation of a Map Relative Localization System for Planetary Landing

Abstract

The Mars 2020 Entry, Descent, and Landing (EDL) system successfully delivered the Perseverance rover to Jezero Crater, the most hazardous landing site ever attempted on Mars. To mitigate the risk of landing hazards, which included cliffs, inescapable dune fields, and rocks, a novel terrain relative navigation system was developed and integrated with the heritage Mars Science Laboratory EDL system. First the hazards were identified using orbital imagery and stored on-board the spacecraft as a hazard map. Then, during parachute descent, the Lander Vision System (LVS) estimated map relative position by fusing landmarks matched between descent imagery and a map of the landing site with inertial measurement unit data. Finally, the position estimate and hazard map were then used by the powered descent system to identify and then fly to the safest and reachable landing target. Postflight analysis indicated that all required systems worked much better than predicted. In particular, the fully autonomous LVS generated a position estimate in 10 s that was in error by only a few meters relative to a 40 m requirement. This paper describes the LVS design, how it was tested before launch, and the LVS performance during EDL.