Engineering topics

Eric Sahr

Publications and source records attributed to Eric Sahr.

5 records

NASA NTRS2021

OSIRIS-REx Proximity Operations and Navigation Performanceat (101955) Bennu

The NASA Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft began close proximity operations at the small (500-m diameter) B-type asteroid (101955) Bennu in December 2018 and concluded in May 2021. Hundreds of grams of pristine surface regolith were collected on October 20, 2020, when the OSIRIS-REx spacecraft successfully executed the Touch and Go (TAG) sample collection sequence. The spacecraft touched down within 1 meter of the targeted site on the surface of Bennu. TAG was the culmination of over 2 years of navigation performance refinement as a result of extraordinary interagency teamwork between the Flight Dynamics System (FDS), science and spacecraft teams while in close proximity to Bennu. This paper will discuss the navigation processes, planning and performance during the proximity operations at Bennu.

Peter G. Antreasian↗

NASA NTRSDate not supplied

OSIRIS-REx Proximity Operations and Navigation Performance at (101955) Bennu

The NASA Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft began close proximity operations at the small (500-mdiameter) B-type asteroid (101955) Bennu in December 2018 and concluded in May 2021.Hundreds of grams of pristine surface regolith were collected on October 20, 2020, when the OSIRIS-REx spacecraft successfully executed the Touch and Go (TAG) sample collection sequence. The spacecraft touched down within 1 meter of the targeted site on the surface of Bennu. TAG was the culmination of over 2 years of navigation performance refinement as a result of extraordinary interagency teamwork between the Flight Dynamics System (FDS),science and spacecraft teams while in close proximity to Bennu. This paper will discuss the navigation processes, planning and performance during the proximity operations at Bennu.

Peter G Antresian↗

NASA NTRSDate not supplied

Osiris-Rex Post-Tag Observation Trajectory Design and Navigation Performance

NASA’s OSIRIS-REx spacecraft successfully collected a sample of asteroid regolith from the surface of near-Earth asteroid Bennu in October of 2020. Subsequent imaging of the sampler head showed material leaking from the collection mechanism, thus stowage of the sample precluded execution of any planned maneuvers in the following days. Optical navigation imaging also ceased in the days following sample collection. The desire to image the sample site to investigate the results of the spacecraft-to-surface interaction led to the Navigation team designing a trajectory to return to Bennu after several months in order to image the surface one final time. After several iterations a trajectory design was created that satisfied the numerous constraints that were levied in order to place utmost importance on the safety of the spacecraft and stowed sample, while also closely emulating previously obtained imaging conditions to provide a close comparison of site pre- and post-contact. Significant analysis was necessary in order to reliably reacquire the asteroid after several months without optical navigation imagery. The final design required five maneuvers to return the spacecraft to Bennu and perform a final flyby of the asteroid at a distance of 3.8 kilometers. Successful execution of the phase provided key insights regarding the performance of the sample collection activities and the subsurface composition of the asteroid.

Daniel R Wibben↗

NASA NTRSDate not supplied

Lucy Optical Navigation Performance During The (152830) Dinkinesh Encounter

The Lucy Jupiter-Trojan asteroid mission launched in November 2021. Its original mission concept included six small-body encounters over its 12-year primary mission. In the fall of 2022, an additional target of opportunity encounter was proposed to be executed in the fall of 2023. The encounter with (152830) Dinkinesh (previously 1999 VD57) presented myriad imaging, navigation, engineering, and planning challenges, as well as a chance to exercise and further refine the Optical NavigationSystem concept of operations, interfaces, and tools. Dinkinesh would be the smallest and dimmest target Lucy would encounter, with a higher uncertainty in these physical parameters than for other targets. While the Op Nav system and instruments carried a high amount of heritage from the New Horizons and OSIRIS-REx missions, this would be the first use of these systems on Lucy for navigation purposes. Despite these additional challenges, the Lucy Dinkinesh encounter was a resounding success throughout which the navigational system exceeded requirements.1Optical Navigation was successfully performed and fed into the orbit determination and trajectory maneuver activities up to the final knowledge update. The Dinkinesh encounter also proved to be greatly scientifically interesting, if not additionally challenging, as the Dinkinesh system was discovered to be a binary system through imaging during closest approach, and the secondary body was itself found to be a contact binary. This added complexity notwithstanding, the OpNav and OD teams were able to re-construct the close-approach trajectory of Dinkinesh in cooperation and concert with the Lucy Science Team’s shape modelling efforts.

Erik Lessac-Chenen↗

NASA NTRSDate not supplied

Orbit Determination For Lucy's First Asteroid Encounter: The Dinkinesh (1999VD57) Flyby

Lucy, NASA’s 13th Discovery program mission, launched on October 16, 2021, is enroute to explore the Jupiter-Trojan asteroids situated at the L4 and L5 Lagrange points. Along this trajectory, Lucy will conduct flybys of two main belt asteroids and perform three Earth fly-bys. This paper delves into the Orbit Determination (OD) process during the Dinkinesh flyby, marking Lucy’s inaugural encounter with an asteroid. The Dinkinesh flyby achieved a significant milestone, flawlessly completing the engineering systems checkout. The discussion herein encompasses the OD strategy, setup, and computed OD solutions during operations. The paper further explores the impact of solar conjunction on the OD solutions and decisions and sheds light on the discovery of Selam, a contact binary orbiting Dinkinesh. Preliminary reconstructed trajectories for both Lucy and Dinkinesh, and an initial state of Selam, are presented. The close approach radial distance of Lucy from Dinkinesh was 430.63 km±0.02km in formal uncertainty.

Jeroen L. Geeraert↗