Asteroid Proximity Operations Research Articles

Overview of Hayabusa2 Asteroid Proximity Operation Planning and Preliminary Results

Hayabusa2 is a Japanese asteroid explorer launched by the H-IIA rocket on Dec. 3, 2014. After the long cruising with the ion engine system, the spacecraft approached its target body, Ryugu, using optical navigation. It arrived at Home Position (HP), 20 km above the sub-Earth point, on Jun. 27, 2018. The spacecraft is now on its way back to Earth. It will reach the Earth by the end of 2020. During the 1.5-year asteroid proximity phase, we performed many kinds of science observations using the remote sensing instruments. We performed several numbers of descent operations to deploy and lander/rovers, to collect the surface samples, and to create an artificial crater using a new small kinetic impactor. Detailed operation planning of the asteroid proximity phase started after the launch, and lots of training for the proximity phase were conducted from one year before the arrival. This paper summarizes the overview of the asteroid proximity operation plan of Hayabusa2 and its preliminary results.

The deep-space multi-object orbit determination system and its application to Hayabusa2’s asteroid proximity operations

The deep-space multi-object orbit determination system (DMOODS) and its application in the asteroid proximity operation of the Hayabusa2 mission are described. DMOODS was developed by the Japan Aerospace Exploration Agency (JAXA) for the primary purpose of determining the trajectory of deep-space spacecraft for JAXA’s planetary missions. The weighted least-squares batch filter is used for the orbit estimator of DMOODS. The orbit estimator supports more than 10 data types, some of which are used for relative trajectory measurements between multiple space objects including natural satellites and small bodies. This system consists of a set of computer programs running on Linux-based consumer PCs on the ground, which are used for orbit determination and the generation of radiometric tracking data, such as delta differential one-way ranging and doppler tracking data. During the asteroid proximity phase of Hayabusa2, this system played an essential role in operations that had very strict navigation requirements or operations in which few optical data were obtained owing to special constraints on the spacecraft attitude or distance from the asteroid. One example is orbit determination during the solar conjunction phase, in which the navigation accuracy is degraded by the effect of the solar corona. The large range bias caused by the solar corona was accurately estimated with DMOODS by combining light detection and ranging (LIDAR) and ranging measurements in the superior solar conjunction phase of Hayabusa2. For the orbiting operations of target markers and the MINERVA-II2 rover, the simultaneous estimation of six trajectories of four artificial objects and a natural object was made by DMOODS. This type of simultaneous orbit determination of multi-artificial objects in deep-space has never been accomplished before.

Hayabusa2 mission status: Landing, roving and cratering on asteroid Ryugu

Hayabusa2 arrived at the C-type asteroid Ryugu in June 2018. During one and a half year of the Ryugu-proximity operation, we succeeded in two rovers landing, one lander landing, two spacecraft touchdown/sample collection, one kinetic impact operation and two tiny reflective balls and one rover orbiting. Among the two successful touchdowns, the second one succeeded in collecting subsurface material exposed by the kinetic impact operation. This paper describes the asteroid proximity operation activity of the Hayabusa2 mission, and gives an overview of the achievements done so far. Some important engineering and scientific activities, which have been done in synchronous with the spacecraft operations to tackle with unexpected Ryugu environment, are also described.

Utilization of Ka-band Communication for Hayabusa2 Asteroid Proximity Operation

Utilization of Ka-band Communication for Hayabusa2 Asteroid Proximity Operation

Relative equilibria and stability of a dumbbell spacecraft about an asteroid

The gravitational orbit-attitude coupling becomes pronounced in spacecraft dynamics about small asteroids, due to the large ratio of the spacecraft's dimension to the orbital radius. In this study, relative equilibria and their stability of the gravitationally coupled orbit-attitude dynamics (full dynamics) of a dumbbell spacecraft about an irregular-shaped asteroid are investigated. The shape of the asteroid is represented by a homogeneous polyhedron, and its non-spherical gravity is calculated accordingly. By using geometric mechanics, the Hamiltonian structure and equations of motion of the full dynamics are derived. Then, the orbit-attitude equilibria about asteroids 4769 Castalia, 433 Eros, and 6489 Golevka are calculated numerically, respectively, and the drift of orbit-attitude equilibria with respect to the dumbbell's varying length is also discussed. By comparing with the equilibria of a point mass, it has been found that a classical point-mass equilibrium can generate three orbit-attitude equilibria located nearby. With the increase of the dumbbell's length, the effects of orbit-attitude coupling become stronger, and the orbit-attitude equilibria diverge further from the classical point-mass equilibria. The spectral stability of the orbit-attitude equilibria is determined numerically and analyzed. It has been found that the gravitational orbit-attitude coupling is likely to make the equilibria unstable in our simulations. The dumbbell is a good approximation of a spacecraft consisting of two modules that are connected by trusses, and its orbit-attitude equilibria have potential applications in asteroid proximity operations, such as body-fixed hovering.

Hayabusa2–Sample return and kinetic impact mission to near-earth asteroid Ryugu

The Japan Aerospace Exploration Agency launched the asteroid sample return spacecraft “Hayabusa2” on December 3, 2014. Hayabusa2 will reach the C-type asteroid 162173 Ryugu in 2018, and return back to the Earth in 2020. Sample collections from three sites, four surface rovers deployment and a 4 MJ-class kinetic impact crater forming are planned in the 1.5 years of the asteroid-proximity operation. The mission objective of Hayabusa2 has three aspects, science, engineering and exploration, all of which would be expanded by the successful round-trip journey. The objectives and technologies used in this mission is not a direct solution for the future planetary defense, but should contribute to this field by increasing general asteroid knowledge and enhancing human capabilities of small body-surface access/roving/sampling/impacting. This paper describes the outline of the Hayabusa2 mission, overviews the kinetic impact technology as an example of planetary defense-related technologies and the current flight status after the two and a half years of the interplanetary cruise.

Robust Adaptive Tracking of Rigid-Body Motion With Applications to Asteroid Proximity Operations

This paper addresses the coupled position- and attitude-tracking control of a rigid spacecraft in the proximity of asteroids, where multiple, complicated, unknown perturbations resulting from highly uncertain environment must be dealt with. Dual quaternions are used to formulate the tracking error dynamics in a compact manner for unified translational and rotational control law design. A robust adaptive control scheme is then developed from an originally model-dependent controller by introducing an adaptive algorithm to dynamically adjust the compensation for perturbations due to parametric uncertainties and external disturbances. The proposed method has a simple structure and is computationally efficient, since it requires no information about the unknown perturbations and involves only two adaptive variables. Numerical simulations for asteroid landing and hovering control are presented to verify the effectiveness of the proposed methods.

Flight status of robotic asteroid sample return mission Hayabusa2

The Japan Aerospace Exploration Agency launched the asteroid sample return spacecraft “Hayabusa2” on December 3, 2014. Hayabusa2 will reach the C-type asteroid 1999 JU3 in 2018, and return back to the Earth in 2020. Sample collections from three sites, four surface rovers deployment and a 4MJ-class kinetic impact crater generation are planned in the 1.5 years of the asteroid-proximity operation. The mission objective of Hayabusa2 has three aspects, science, engineering and exploration, all of which would be expanded by the successful round-trip journey. This paper describes the outline of the Hayabusa2 mission and the current flight status after the seven month of the interplanetary cruise.

System design of the Hayabusa 2—Asteroid sample return mission to 1999 JU3

The Japan Aerospace Exploration Agency is currently developing the second asteroid sample return mission, designated as Hayabusa 2. Following the successful return of Hayabusa from the asteroid “Itokawa”, Hayabusa 2 is designed as a round-trip mission to the asteroid “1999 JU3”. The 1999 JU3 is a C-type asteroid, which is believed to contain organic matter and hydrated minerals. Thus, it is expected that successful sample collection will provide additional knowledge on the origin and evolution of the planets and, in particular, the origin of water and organic matter. The current mission scenario will enable the spacecraft to reach 1999 JU3 in the middle of 2018 and perform an asteroid proximity operation for 1.5 years. Three touch downs for sampling and one 2-m-class crater generation by means of a high-speed impact operation are planned during the asteroid proximity operation. The samples are to be brought back to the Earth by a re-entry capsule. The present paper describes the system design of Hayabusa 2, some key technical challenges of the mission, and the development status.

Capabilities of Furlable Solar Sails for Asteroid Proximity Operations

Missions have beenproposed inwhich a spacecraft equippedwith a large furlable solar sail transfers to amain-belt asteroid using the fully deployed sail for propulsion and then performs an inspectionmission at the asteroid with the sail fully stowed. This paper examinesways inwhich the partially deployed sail could insteadbe used tomaneuver the spacecraft while in the vicinity of the asteroid,with the goal of improving the science observations that could bemade. Methods are presented for quantifying the performance that can be obtained by taking advantage of the freedom to select the active sail area for two types of hovering problems: one in which the spacecraft is to maintain a fixed position in the rotating sun–asteroid frame and the other in which it is to maintain a fixed position relative to a landmark on the rotating asteroid surface. In both of these problems, the ability to adjust the active sail area greatly expands the range of locations at which the spacecraft can satisfy the specified hover conditions.