吉光 徹雄

This study presents technologies of the triple hybrid landing gear for the OMOTENASHI(Outstanding Moon exploration Technologies demonstrated by Nano Semi-Hard Impactor) spacecraft, which consists of an airbag, a crushable material as a shock absorber, and an impact resistance structure. The inflated airbag has capability to possibly mitigate impact acceleration at the instant of landing and submergence into regolith that covers a planetary surface. The crushable material with lattice structures, manufactured by a metal 3D printer, serves a dual purpose: it dissipates kinetic energy and controls the impact acceleration at landing by compressing itself within a designed deceleration distance. Further, in the impact resistance structure, the protective object is filled with resin and hollow glass beads, and the impact resistance is improved while the weight reduction is maintained. This paper provides the technical details such as the required specification, verification test results, and assembly result of the surface probe as the smallest lander of the OMOTENASHI spacecraft.

The Hayabusa2 spacecraft investigated the C-type (carbonaceous) asteroid (162173) Ryugu. The mission performed two landing operations to collect samples of surface and subsurface material, the latter exposed by an artificial impact. We present images of the second touchdown site, finding that ejecta from the impact crater was present at the sample location. Surface pebbles at both landing sites show morphological variations ranging from rugged to smooth, similar to Ryugu’s boulders, and shapes from quasi-spherical to flattened. The samples were returned to Earth on 6 December 2020. We describe the morphology of >5 grams of returned pebbles and sand. Their diverse color, shape, and structure are consistent with the observed materials of Ryugu; we conclude that they are a representative sample of the asteroid.

The article “Orbit insertion strategy of Hayabusa2’s rover with large release uncertainty around the asteroid Ryugu” written by Yusuke Oki, Kent Yoshikawa, Hiroshi Takeuchi et al., was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 05 November 2020 without open access. After publication in Volume 4, Issue 4, page 309–329, the author(s) decided to opt for Open Choice and to make the article an open access publication. Therefore, the copyright of the article has been changed to © The Author(s) 2020 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

After 3.5 years of cruise, and about 3 months in the vicinity of its target, the MASCOT lander was deployed successfully on October 3, 2018 by the Hayabusa2 spacecraft onto the C-type near-Earth asteroid (162173) Ryugu. After a free-fall of 5 ​min 51 ​s from an altitude of 41 ​m MASCOT experienced its first contact with the asteroid hitting a big boulder. The lander bounced for ~11 ​min 3 ​s before it came to rest. MASCOT was able to perform science measurements with its payload suite at 3 different locations on the surface of Ryugu. It investigated the fine-scale structure, multispectral reflectance, thermal characteristics and magnetic properties. The surface consists of very rugged terrain littered with large surface boulders. The in-situ measurements confirmed the absence of fine particles and dust as already implied by the remote sensing instruments aboard the Hayabusa2 spacecraft. After about 17 ​h of operations, the MASCOT mission terminated with the last communication contact as its primary batteries depleted. This paper summarizes the MASCOT mission covering its four years of in-flight operations, its preparation for the descent, landing and in-situ investigation on the asteroid Ryugu until the end of its operation.

MASCOT (‘Mobile Asteroid Surface Scout’) is a 10 kg mobile surface science package part of JAXA’s Hayabusa2 sample return mission. The mission was launched in December 2014 from Tanegashima Space Center, Japan. The Hayabusa2 spacecraft reached the target asteroid in summer 2018. After a mapping phase of the asteroid and a landing site selection process the MASCOT lander was deployed to the surface on the 3rd of October 2018. MASCOT operated successfully for about 17 h on the surface of Ryugu. It performed three relocation manoeuvres and one “Mini-Move” and returned 128 MBytes of data. MASCOT has been developed by the German Aerospace Center (DLR) in cooperation with the Centre National d’Etudes Spatiales (CNES). The main objectives were to perform in-situ investigations of the asteroid surface and to support the sampling site selection for the mother spacecraft. These objectives could be reached successfully. On 6th December 2020 Hayabusa2 successfully returned asteroid samples to the Earth.

This paper describes the orbit design of the deployable payload Rover 2 of MINERVA-II, installed on the Hayabusa2 spacecraft. Because Rover 2 did not have surface exploration capabilities, the operation team decided to experiment with a new strategy for its deployment to the surface. The rover was ejected at a high altitude and made a semi-hard landing on the surface of the asteroid Ryugu after several orbits. Based on the orbital analysis around Ryugu, the expected collision speed was tolerable for the rover to function post-impact. Because the rover could not control its position, its motion was entirely governed by the initial conditions. Thus, the largest challenge was to insert the rover into a stable orbit (despite its large release uncertainty), and avoid its escape from Ryugu due to an environment strongly perturbed by solar radiation pressure and gravitational irregularities. This study investigates the solution space of the orbit around Ryugu and evaluates the orbit’s robustness by utilizing Monte Carlo simulations to determine the orbit insertion policy. Upon analyzing the flight data of the rover operation, we verified that the rover orbited Ryugu for more than one period and established the possibility of a novel method for estimating the gravity of an asteroid.

Copyright © 2020 by the International Astronautical Federation (IAF). All rights reserved. A 6U CubeSat “OMOTENASHI” will be the world's smallest moon lander which is launched by NASA SLS Artemis-1. Because of its severe mass and size limitation, it will adopt semi-hard landing scheme. That is, OMOTENASHI is decelerated from orbital velocity to less than 50 m/s by a small solid rocket motor and shock absorption mechanism has been developed to withstand the high-speed impact. Ultra small communication system (X-band and P-band) is also developed. It observes radiation environment of Earth and moon region with portable dosimeters. This paper shows the mission outline, the design, and the development results of OMOTENASHI.

The near-Earth asteroid (162173) Ryugu is a 900-m-diameter dark object expected to contain primordial material from the solar nebula. The Mobile Asteroid Surface Scout (MASCOT) landed on Ryugu’s surface on 3 October 2018. We present images from the MASCOT camera (MASCam) taken during the descent and while on the surface. The surface is covered by decimeter- to meter-sized rocks, with no deposits of fine-grained material. Rocks appear either bright, with smooth faces and sharp edges, or dark, with a cauliflower-like, crumbly surface. Close-up images of a rock of the latter type reveal a dark matrix with small, bright, spectrally different inclusions, implying that it did not experience extensive aqueous alteration. The inclusions appear similar to those in carbonaceous chondrite meteorites.

Hayabusa2 is a Japanese asteroid explorer which aims to get some fragments from the C-type asteroid “Ryugu” and bring them back to the Earth. It was launched in December 2014 and arrived at the target asteroid at the end of June 2018 after 3.5 years' interplanetary cruise using an Ion engine propulsion system. The authors developed two tiny twin rovers for Hayabusa2 spacecraft. The rovers had a mass of approximately 1.1 kilograms and were packed into one container. The purposes of the rovers were to make two technical experiments on the asteroid surface. They had a hopping capability fitted for the microgravity environment of small planetary bodies, which was evaluated on the asteroid surface. They were equipped with fully autonomous capability to move over the surface and make some observations such as taking images on the asteroid surface. This autonomous capability was demonstrated on the asteroid surface. The rovers were simultaneously deployed onto the Northern hemisphere of the target asteroid on 21 September 2018 at the altitude of approximately 50 meters above the surface. Both rovers made autonomous surface explorations by hopping as planned. The obtained data and images were transmitted by radio to the relay module of the mother spacecraft which stayed at the altitude of 20 kilometers away from the asteroid, and then downlinked to the Ground. One of the rovers (Rover 1A) survived for 113 Asteroid days after the deployment whereas the other (Rover 1B) worked for 10 Asteroid days. Total of more the 600 images were transmitted to the Ground from both rovers. The images unveiled the detailed surface condition of asteroid Ryugu. This was the World first surface exploration on small planetary body in our Solar System attained by unmanned robot. This paper summarises the explorations by MINERVA-II twin rovers.

This paper presents the current development status of the optional payload named Lunar Excursion Vehicle (LEV) for the Japanese future Lunar landing mission SLIM. The deployable exploration system LEV is released from the lander at the few meters above the Lunar surface after the lander's terminal deceleration is finished. LEV consists of two probes that will move and observe around the landing site autonomously. They also help acquire the evidence of SLIM landing by taking pictures of the final status of the lander.

Copyright © 2019 by the International Astronautical Federation (IAF). All rights reserved. On October 3rd, 2018, the MASCOT lander has been deployed successfully by the Hayabusa2 spacecraft from an altitude of 41m onto the C-type near-Earth asteroid (162173) Ryugu. After a free-fall of approx. 6 minutes MASCOT has experienced its first contact with the asteroid. The lander underwent a bouncing phase of ~ 11 minutes before it finally came to rest at its first settlement point where it entered into its on-surface operational mode. The lander was able to perform science measurements with its payload suite at 3 locations on Ruygu. After about 17 hrs of operations, the MASCOT mission terminated with the last communication contact. The lander was jointly developed by the German Aerospace Centre (DLR) and the Centre National d'Etudes Spatiales (CNES). The payload suite of four scientific instruments is provided by DLR Berlin (MASCam wide-angle camera with colour illumination and MARA thermal IR radiometer), IAS Paris (MicrOmega hyperspectral IR soil microscope) and TU Braunschweig (MASMag magnetometer). The paper will outline the path of the lander on the asteroid and present a summary of the scientific observations. These first results are related to the progress of the Hayabusa2 mission and its MINERVA-II rovers on the background of a recap of the landing site selection process.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Hayabusa2 is an asteroid sample return mission operated by the Japanese space agency, JAXA. It was launched in December 2014. In July 2018 the spacecraft will reach the mission target after a 4-year-long cruise. The objective is a C-type primordial asteroid called Ryugu, in search of organic and hydrated minerals that might give essential clues for the solar system formation. The small lander MASCOT (Mobile Asteroid surface SCOuT) carried aboard Hayabusa2 intends to land on the surface for in-situ investigations while the probe is aiming to study Ryugu on a global scale and to return samples to Earth. MASCOT was jointly developed by the German Aerospace Centre (DLR) and the Centre National d'Etudes Spatiales (CNES). It is equipped with a sensor suite consisting of four fully-fledged instruments. DLR was responsible for developing the MASCOT lander and ground segment, and is in charge of planning and conducting lander operations. CNES supplied the hyperspectral IR spectrometer (MicrOmega, IAS Paris), antennas and electrical power system that would be essential contributors to the on-asteroid operation success. These subsystems are partly inherited from Philae lander onboard Rosetta mission. CNES is responsible for MASCOT flight dynamics and is also providing an operational support for RF and power system, based on the expertise gained on the past science missions. The lander mission is similar to the previous Philae mission nevertheless the timeline and the resources are more constrained than it was for Philae. Indeed the characteristics of the Ryugu asteroid such as the shape and the gravity will be known only after arrival of Hayabusa2 in July 2018. In addition to this, MASCOT’s battery allows to operate only for a few hours. So the time available to prepare those 2 asteroid days of science activities on the surface will be very short and dedicated processes and tools were developped to cope with these constraints. Thus a training phase is mandatory to deal with the different processes and all the teams involved. An expertise and science mission support was developped at CNES Toulouse to prepare the operations and provide a support to the operational team at DLR. Its functionnalities and interfaces will be detailed as well as the specific training put in place. This paper is a complement to the overall MASCOT operations paper submitted by Christian Krause (DLR). It will summarize the performed and planned activities to prepare the CNES team and means for MASCOT operations while focusing on the improvements/adaptations made on the subsystems inherited from Philae. Some specific topics as flight dynamics team’s involvement in landing site selection, visualisation tool, specific RF link tests and power system tests and developped models are also detailed in specific papers submitted for this spaceops in the dedicated sessions.

Hopping rover is one of solution for locomotion on loose and rocky terrain on the moon and planetary surface. The hopping rover jumps over an obstacles. Since the height of hopping is equal to the height which the rover can get over, the traversability of rover becomes higher. In order to design a push plate with a small amount of slip on the granular media for a stable and efficient hopping, it is necessary to know the reaction force received from the ground. In this paper, we describe the force estimation method of shoe plate design of jump rover based on Resistive Force Theory and calculate the reaction force when pressing the shoe plate and find of the shape that is suitable for hopping. The shoe plate is manufactured with a 3D printer, and the pressing test result and the calculation result are compared. Finally, we verify the effectiveness including the hopping motion of the rover, using the dynamics simulator on the moon gravity.

Copyright © 2018 by the International Astronautical Federation (IAF). All rights reserve It will be nearly a four year long journey from launch with the Hayabusa2 spacecraft on Dec 3 rd , 2014, until the beginning of October 2018 when MASCOT ('Mobile Asteroid surface SCOuT') should land on the Near-Earth Asteroid (162173) Ryugu. During cruise phase, MASCOT underwent several inflight and ground based health checks, instrument calibration and subsystem tests to prepare the lander for its biggest challenge: operating autonomously on the asteroid's surface for up to 16 hours. Within this time, MASCOT should provide scientific data of the surface and physical properties of asteroid Ryugu with its 4 scientific instruments: a wide angle camera with night-time colour illumination (MASCAM), an imaging IR spectrometer microscope (MicrOmega), a multichannel radiometer (MARA), and a magnetometer (MasMAG). MASCOT has an internal mobility unit which enables it to self-right, to place itself into the desired science operation orientation and to relocate on the surface in order to explore more than one site. The lander was jointly developed by the German Aerospace Centre (DLR) and the Centre National d'Etudes Spatiales (CNES). The four payloads are provided by DLR Berlin (MASCAM and MARA), IAS Paris (MicrOmega) and TU Braunschweig (MASMAG). The landing of MASCOT is currently scheduled between 2018, October 1 st - 4 th .

Recently, a small size hopping rover is received attention for the moon and planetary exploration society. In a low gravity environment, a lightweight hopping rover might have high traversabilities: by jumping over long distance and obstacles. While a lot of hardware designs for hopping system are presented, few software designs for its system are presented. For the near future, software design for the rover is necessary to satisfy some requirements including sensing and navigation. A hopping rover has more uncertainties than conventional wheeled rover because a hopping movement is fundamentally different from a wheeled movement. Its uncertainties might be risks for the rover, in addition, it is difficult to reduce uncertainties because of its payload and hopping behavior. In this paper, we focus the navigation on hopping software system, and discuss about hopping movement with some uncertainties. Next, we propose the determination method of landing position using the geometric features of the triangle. The method is considered risks for the rover. We confirmed effectiveness of path planning with proposal method by simulation.