Optical Navigation Simulation and Performance Analysis for Osiris-Rex Proximity Operations

The OSIRIS-REx mission timeline with OpNav milestones is presented in Figure 1. The first three proximity operations (ProxOps) mission phases focus on Navigation. During these phases, OSIRIS-REx approaches Bennu, conducts equatorial and polar flybys in Preliminary Survey, and inserts into the first mission orbit: Orbit A. During these phases, the OpNav techniques evolve from point-source to resolved-body centroiding to landmark tracking

Early Navigation Performance of the OSIRIS-REx Approach to Bennu

The New Frontiers-class OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) mission is the first American endeavor to return a sample from an asteroid. In preparation for retrieving the sample, OSIRIS-REx is conducting a campaign of challenging proximity-operations maneuvers and scientific observations, bringing the spacecraft closer and closer to the surface of near-Earth asteroid (101955) Bennu. Ultimately, the spacecraft will enter a 900-meter-radius orbit about Bennu and conduct a series of reconnaissance flybys of candidate sample sites before being guided into contact with the surface for the Touch and Go sample collection event. Between August and December 2018, the OSIRIS-REx team acquired the first optical observations of Bennu and used them for navigation. We conducted a series of maneuvers with the main engine, Trajectory Correction Maneuver, and Attitude Control System thruster sets to slow the OSIRIS-REx approach to Bennu and achieve rendezvous on December 3, 2018. This paper describes the trajectory design, navigation conops, and key navigation results from the Approach phase of the OSIRIS-REx mission

Post-flight Evaluation of Lidar-based Digital Terrain Models for OSIRIS-REx Navigation at Bennu

The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft spent more than 2 yr characterizing near-Earth asteroid (101955) Bennu. The OSIRIS-REx Laser Altimeter (OLA) was responsible for producing the most accurate reconstruction of the asteroid’s surface—down to a global resolution of around 5 cm with a data precision of ±1.25 cm. However, the best-quality global OLA digital terrain model (DTM), version 21 (v21), was not available for navigation during proximity operations, nor was the utility of this model evaluated for processing images and altimeter data for navigation. The focus of this paper is the post-flight assessment of the final OLA v21 DTM, its performance for navigation-related analysis, and estimates of corrections needed for the DTM and measurement models. We created 15 cm resolution maplets for processing optical navigation (OpNav) data, and 5 cm resolution DTMs for processing altimeter data, to estimate a combined spacecraft trajectory over five phases of the mission. Our estimated corrections to the OLA instrument model produce altimeter data residuals with a precision of 7.12 cm (1 σ ; one standard deviation from the mean). The OpNav maplets produce image residuals at 0.2 px (1 σ ) and estimated landmark locations accurate to ±6 cm, outperforming DTM navigation-related performance requirements. Finally, our estimate of the global DTM scale is more precise and within 1.1 σ of previously reported values. We find that a slight discrepancy persists between the image and altimeter data, with image data suggesting that the DTM is too small by 0.049%, but nevertheless is exceptional for navigation

Transition from Centroid-Based to Landmark-Based Optical Navigation During OSIRIS-REx Navigation Campaign at Asteroid Bennu

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Stereophotoclinometry for OSIRIS-REx Spacecraft Navigation

We summarize a decade of effort by the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) mission team to build up the unique capabilities, processes, and procedures required to accomplish the unprecedented navigation performance required during proximity operations at asteroid (101955) Bennu. Stereophotoclinometry was a key technology used for digital terrain model (DTM) generation and landmark navigation, enabling estimation of spacecraft trajectories and Bennu’s geophysical parameters. We outline the concept of operations for OSIRIS-REx landmark navigation and the wide array of testing and verification efforts leading up to OSIRIS-REx’s arrival at Bennu. We relate the outcome of these efforts to the experiences during proximity operations. We discuss navigation and DTM performance during operations, including detailed lessons learned to carry forward for future missions