Elsevier

Icarus

Volume 358, April 2021, 114220
Icarus

Research Paper
Ballistic deployment of the Hayabusa2 artificial landmarks in the microgravity environment of Ryugu

https://doi.org/10.1016/j.icarus.2020.114220Get rights and content
Under a Creative Commons license
open access

Highlights

  • Hayabusa2 deployed two target markers (TMs) on the asteroid Ryugu as artificial landmarks for autonomous landing control.

  • TM trajectories were reconstructed from flight data, demonstrating the performance of the ballistic deployment under microgravity.

  • Beanbag-like structure of the TM successfully dissipated kinetic energy and prevented a rebound after the impact.

  • Impact and gravimetric analyses based on the reconstructed trajectories provided insights on the surface and internal structures of Ryugu.

Abstract

Hayabusa2 deployed two artificial landmarks called “target markers (TMs)” on the asteroid Ryugu for autonomous landing control. To achieve precise deployment on target landing sites, the TMs were designed to dissipate kinetic energy and released near the asteroid surface (with an altitude of less than 40 m). This study evaluates the performance of the ballistic deployment in the actual microgravity environment by reconstructing the trajectories of the TMs from optical, altimetric, and radiometric data. In addition, based on the reconstructed trajectories, low-velocity impacts of the TMs on the surface of Ryugu are characterized with dynamical parameters, such as dissipated energy and a coefficient of restitution. The physical implications of the impact analysis are discussed in comparison with on-ground experimental data. Furthermore, the gravitational environment is investigated using the reconstructed trajectory data and a shape model of Ryugu, providing information on the local gravity anomaly. Consequently, this paper demonstrates the usefulness of deployable artificial landmarks for small-body landings and further offers insight on surface conditions and internal structures near the Hayabusa2 landing sites where samples of Ryugu were collected.

Keywords

Small-body exploration
Orbital motion
Gravity field
Low-velocity impact
Internal structure

Data Availability

The ONC-W1 images that were obtained during the TMD1 and TMD2 operations and used in the current research are provided as supplementary data to this article. The shape models of Ryugu used in this article are archived in the JAXA Data Archives and Transmission System (DARTS). The global shape model Watanabe et al. (2019) is available at www.darts.isas.jaxa.jp/pub/hayabusa2/paper/Watanabe_2019; the local DEM for the TD1 site Morota et al. (2020) is available at www.darts.isas.jaxa.jp/pub/hayabusa2/paper/Morota_2020; and the local DEM for the TD2 site Arakawa et al. (2020) is available at www.darts.isas.jaxa.jp/pub/hayabusa2/paper/Arakawa_2020. Additional data from the mission will be archived in DARTS by the end of 2020.

Cited by (0)

1

Current affiliation: GomSpace Luxembourg, 11 Boulevard du Jazz, L-4370 Esch-Belval, Luxembourg.