Institute Of Space And Astronautical Science Research Articles

Measurements of seismic waves induced by high-velocity impacts: Implications for seismic shaking surrounding impact craters on asteroids

On asteroids, impact-induced seismic shaking is an important geological process related to the modifications of the surface features that are due to the movement of regolith grains on the asteroid surface. Mass movements caused by seismic shaking (e.g., landslides and crater erasures) were recently observed by several spacecrafts. To elucidate the seismic shaking areas induced by impacts on asteroids, it is necessary to determine the excitation and the decay processes of impact-induced seismic waves. Here we conducted impact cratering experiments using 500-μm quartz sand to simulate an asteroid surface at the Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA). We used 4.75-mm- and 2-mm-diameter projectiles with density from 14.9 to 1.2 g cm−3; the impact velocity ranged from 7 to 0.2 km s−1. We measured the acceleration waveform by using three to five accelerometers setting on the target surface, and we examined three parameters characterizing the impact-induced seismic wave with varying distances from the impact point: the propagation velocity (Vprop), the maximum acceleration (gmax), and the half period of the first upward peak (Thalf). The Vprop was obtained to be 52.4 ± 7.2 m s−1, regardless of the impact velocity and the projectile properties, and the Thalf slightly depended on the impact velocity as vi0.14 but was independent of the projectile properties. The gmax had a close relationship with the distance from the impact point normalized by the crater rim radius, x/Rrim, regardless of the impact velocity and the projectile properties. The obtained empirical equation was shown as gmax = 102.21(x/Rrim)−3.18. By using the empirical equations we obtained herein, we observed that the seismic energy normalized by the kinetic energy of a projectile, Es/Ek, decreased with the increase of the normalized distance, x/Rrim. We also estimated the area of impact-induced seismic shaking on an idealized small (500 m in diameter) body at the impact velocity of 5 km s−1.

Development and Flight Test of Affordable Scientific Balloon System Suitable for Sea Recovery

A reasonable solution to retrieve a payload of a scientific balloon regardless of safety issues and recoverability is the sea recovery strategy. Sea recovery strategy is a unique retrieval method being pioneered by the Japan Aerospace Exploration Agency (JAXA) and the Institute of Space and Astronautical Science (ISAS) for decades. This strategy has contributed to the achievement of various scientific and engineering research missions in Japan, such as in atmospheric observation and space environment simulation. However, in spite of a long history of conducting sea recovery strategy by JAXA/ISAS, to the best of the author’s knowledge, there have been few published works on designing and manufacturing balloon systems suitable for sea recovery operations due to the rarity of this recovery method. This paper presents a detailed description of a system for a small zero-pressure balloon (ZPB) platform designed for sea recovery operations. For this, a small ZPB platform using affordable commercial off-the-shelf (COTS) products was developed with careful consideration of maritime telecommunication, water resistance, short-circuit prevention, and flotation. In addition to reducing the overall cost by using COTS products, it enabled miniaturization of the telemetry, tracking and command system to enhance portability. The results of the latest flight tests were also described including the sea retrieval strategy to verify the reliability of the developed balloon system.

Design Exploration of Low-Thrust Space Trajectory Problem for DESTINY Mission

The present study focuses on exploring optimal transfer solutions for the Demonstration and Experiment of Space Technology for INterplanetary voYage (DESTINY) mission, which was proposed as an Institute of Space and Astronautical Science (ISAS) Epsilon-class small program in 2013 based on the “Space Science & Exploration Roadmap” proposed by the ISAS and later approved by the government committee on space policy. During the DESTINY mission, the spacecraft will first be injected into a low elliptical orbit by an Epsilon rocket, and its altitude will then be increased to approach the Moon using an ion engine system. Next, the spacecraft will be injected via a transfer orbit to the Halo orbit of the Sun–Earth system by way of gravity assist from the Moon. As the spacecraft revolves around the Earth several hundred times, it gradually increases its altitude. Thus, the launch time and thrust profile must be chosen properly. Note that there are several conflicting requirements, including the reduction of fuel consumption, total flight time, and maximum eclipse time, that must be taken into consideration. To satisfy these requirements, many-objective evolutionary computation is applied to find better orbital designs.

Effect of Fuselage Cross Section on Aerodynamic Characteristics of Reusable Launch Vehicles

An experimental study on examining aerodynamic characteristics of fuselage cross sections for RLVs (Reusable Launch Vehicles) was conducted at Mach number 0.3, 0.9 and 4.0 in the wind tunnel of ISAS (Institute of Space and Astronautical Science), JAXA (Japan Aerospace Exploration Agency). Three bodies, having the same projected area and length, with and without a set of fins, were tested. Their cross sections are a circle, a square and a triangle with rounded corners. The results showed that the fuselage cross sections had large effects on aerodynamic characteristics in subsonic and transonic flow. The lift coefficient of the model having the triangular cross section with a set of the fins was larger than that of the others in high angles of attack region due to contributions of the separation vortices generated from the fuselage expanding to the wing surface.

ASTRO-H CdTe detectors proton irradiation at PIF

Asbstract The French Atomic Energy Commission (CEA), with the support of the European Space Agency (ESA), is partner of the Soft Gamma-Ray Detector (SGD) and the Hard X-ray Imager (HXI) onboard the 6th Japanese X-ray scientific satellite ASTRO-H (JAXA) initiated by the Institute of Space and Astronautical Science (ISAS). Both scientific instruments, one hosting a series of Compton Gamma Cameras and the other being a focal plane of a grazing incidence mirror telescope in the hard X-ray domain, are equipped with Cadmium Telluride based detectors. ASTRO-H will be operated in a Low Earth Orbit with a 31° inclination at ~550 km altitude, thus passing daily through the South Atlantic Anomaly radiation belt, a specially harsh environment where the detectors are suffering the effect of the interaction with trapped high energy protons. As CdTe detector performance might be affected by the irradiation, we investigate the effect of the accumulated proton fluence on their spectral response. To do so, we have characterized and irradiated representative samples of SGD and HXI detector under different conditions. The detectors in question, from ACRORAD, are single-pixels having a size of 2 mm by 2 mm and 750 µm thick. The Schottky contact is either made of an Indium or Aluminum for SGD and HXI respectively. We ran the irradiation test campaign at the Proton Irradiation Facility (PIF) at PSI, and ESA approved equipment to evaluate the radiation hardness of flight hardware. We simulated the proton flux expected on the sensors over the entire mission, and secondary neutrons flux due to primary proton interactions into the surrounding BGO active shielding. We eventually characterized the detector response evolution, emphasizing each detector spectral response as well as its stability by studying the so-called Polarization effect. The latter is provoking a spectral response degradation against time as a charge accumulation process occurs in Schottky type CdTe sensors. In this paper, we report on the test campaigns at PIF and will show up our experimental setup. We will pursue describing the irradiation conditions associated with our GEANT 4 predictions and finally, we report the main results of our campaigns concluding that the proton effect does not severely affect the CdTe response neither the detector stability while the secondary neutrons might be more active to reduce the performance on the long run.

Ejecta Cone Angle and Ejecta Size Following a Non-perforating Hypervelocity Impact

The effects of projectile diameter and impact velocity on ejecta cone angle and ejecta size distribution were investigated by striking aluminum alloy 6061-T6 targets with aluminum alloy 2017-T4 spheres at velocities ranging from 2 to 6km/s. The two-stage light-gas gun at the Institute of Space and Astronautical Science (ISAS)/ Japan Aerospace Exploration Agency (JAXA), and Nagoya Institute of Technology was used for the experiments. To examine the scattering angles of ejecta, a witness plate (150mm × 150mm, 2mm in thickness) made of copper C1100P-1/4H, with a 30-mm hole in the center, was placed 50mm in front of the target.

OS1522-303 超高速衝突により発生するイジェクタサイズ分布の相似性

We examined ejecta size distribution when aluminum alloy 2017-T4 spheres with a diameter of 1.6, 3.2 and 7.0 mm impacted aluminum alloy 6061-T6 targets with a plane surface at several impact velocities. We used a two-stage light-gas gun at the Institute of Space and Astronautical Science (ISAS)/Japan Aerospace Exploration Agency (JAXA) and Nagoya Institute of Technology. The size distributions of the ejecta were examined in detail and we compared the size distribution of the ejecta when impacting on the plane surface target at several impact velocities. The scaling law of ejecta size was discussed.

Ejecta Size Distribution Resulting from Hypervelocity Impacts between Aluminum Alloys

We investigated the effects of impact velocity on ejecta size when aluminum alloy 2017-T4 spheres with a diameter of 3.2 mm impacted aluminum alloy 6061-T6 targets with a thickness of 30 mm at velocities of 2 to 7 km/s. We used a two-stage light-gas gun at the Institute of Space and Astronautical Science (ISAS)/Japan Aerospace Exploration Agency (JAXA). To examine the scattering angles of the ejecta, the following was placed 50 mm in front of the target: a witness plate (150 mm × 150 mm, 2 mm in thickness) made of copper with a hole of 30 mm. The ejection behaviors of fragments were observed using a high-speed video camera. The size distributions of the ejecta were examined in detail. The cumulative number of ejecta was proportional to the square of the impact velocity; in other words, to the impact energy of the projectiles. An experimental formula was created by curve fitting of the cumulative number distribution of the projected areas to a bilinear exponential distribution model when the aluminum alloy spheres struck the aluminum alloy targets.

THE ASTRO-H MISSION

A review of the Astro-H mission is presented here on behalf of the Astro-H collaboration. The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). One of the main uniquenesses of the ASTRO-H satellite is the high sensitivity and imaging capability of the wide energy band from 0.3 keV to 600 keV. The coverage is achieved by combining the four instruments of the SXS, SXI, HXI, and SGD. The other main uniqueness is a spectroscopic capability not only for a point-like source but also for an extended source with high spectral resolution of ΔE~4÷7eV of SXS. Using the unique powers of these instruments, ASTRO-H will address unresolved issues in high-energy astrophysics.

THE ASTRO-H MISSION

A review of the Astro-H mission is presented here on behalf of the Astro-H collaboration. The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). One of the main uniquenesses of the ASTRO-H satellite is the high sensitivity and imaging capability of the wide energy band from 0.3 keV to 600 keV. The coverage is achieved by combining the four instruments of the SXS, SXI, HXI, and SGD. The other main uniqueness is a spectroscopic capability not only for a point-like source but also for an extended source with high spectral resolution of Δ<em>E</em>~4÷7eV of SXS. Using the unique powers of these instruments, ASTRO-H will address unresolved issues in high-energy astrophysics.

Return to Venus of the Japanese Venus Climate Orbiter AKATSUKI

Japanese Venus Climate Orbiter/AKATSUKI was proposed in 2001 with strong support by international Venus science community and approved as an ISAS (The Institute of Space and Astronautical Science) mission soon after the proposal. The mission life we expected was more than two Earth years in Venus orbit. AKATSUKI was successfully launched at 06:58:22JST on May 21, 2010, by H-IIA F17. After the separation from H-IIA, the telemetry from AKATSUKI was normally detected by DSN Goldstone station (10:00JST) and the solar cell paddles’ deployment was confirmed. After a successful cruise, the malfunction happened on the propulsion system during the Venus orbit insertion (VOI) on Dec. 7, 2010. The engine shut down before the planned reduction in speed to achieve. The spacecraft did not enter the Venus orbit but entered an orbit around the Sun with a period of 203 days. Most of the fuel still had remained, but the orbital maneuvering engine was found to be broken and unusable. However, we have found an alternate way of achieving orbit by using only the reaction control system (RSC). We had adopted the alternate way for orbital maneuver and three minor maneuvers in Nov. 2011 were successfully done so that AKATSUKI would meet Venus in 2015. We are considering several scenarios for VOI using only RCS.

OS1914 ターゲット曲面への超高速衝突により生じるイジェクタのサイズ分布

We investigated the effects of shape of the target on ejecta size when aluminum alloy 2017-T4 spheres with a diameter of 3.2 mm impacted aluminum alloy 6061-T6 targets with a plane surface and a curved surface at velocities of 2 to 7 km/s. We used a two-stage light-gas gun at the Institute of Space and Astronautical Science (ISAS)/Japan Aerospace Exploration Agency (JAXA). To examine the scattering angles of the ejecta, the following was placed 50 mm in front of the target: a witness plate (150 mm × 150 mm, 2 mm in thickness) made of copper with a hole of 30 mm. The ejection behaviors of fragments were observed using a high-speed video camera. The size distributions of the ejecta were examined in detail. We compared the size distribution of the ejecta when impacting on the plane surface target and when impacting on the curved surface target.

Fracture behavior of silicon nitride ceramics subjected to hypervelocity impact

A new advanced ceramic thruster made of monolithic silicon nitride ceramics was developed for the planetary exploration spacecraft AKATSUKI (PLANET-C) at Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA). To ensure its operation onboard the spacecraft, the reliability of the ceramic thruster against micrometeoroid hypervelocity impact has been investigated. Silicon nitride plates were impacted by spheres of stainless-steel and other materials with 0.2–0.8-mm diameters in the velocity range up to 8.0 km/s using a two-stage light-gas gun. Using crater depth data under various impact conditions, the penetration equation of silicon nitride was determined. The impacted samples showed fracture patterns of three types: cratering, cratering with spallation, and perforation. These fracture patterns were well categorized by the multiple forms of the penetration equation.

A powerful tool for browsing quick-look data in solar-terrestrial physics: “Conjunction Event Finder”

The “Conjunction Event Finder (CEF)” is a Web tool for seamlessly browsing quick-look (QL) data from many different kinds of satellites and ground-based instruments in solar-terrestrial physics. The QL plots are generally scattered all over the world, so that browsing many of them is so far very troublesome and inefficient. Just a simple procedure on the CEF, however, generates a collection of links to the QL plots for a period of interest, allowing us to check the data much more efficiently than ever. Hence this tool is powerful in finding interesting events of conjunction observations by satellites and ground-based instruments. The CEF is available in the Data ARchives and Transmission System (DARTS) at Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA) in Japan.

Micrometeoroid impact on ceramic thin components for interplanetary probe

Abstract A new advanced ceramic thruster made of monolithic silicon nitride (Si3N4) is under development for the next interplanetary probe of PLANET-C Venus exploration mission in Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA). In order for secure operation of a spacecraft with a ceramic component onboard a real mission, the reliability against micrometeoroid impacts on the ceramic component has to be investigated in addition to the quasi-static mechanical and thermal analyses and verifications. First, the risk probability of the micrometeoroid impacts was evaluated by using an interplanetary flux model, and the risk evaluation in terms of impact energy was proposed by combining the velocity distribution with the flux model. The probability of impacts on the ceramic thruster during the mission was estimated with this model. Second, hypervelocity impact tests were performed with a two-stage light-gas gun. Three types of failure were observed: one was only a crater formed on the impact surface. Another type was crater formation on the front-face and spall fracture on the back-face and in the last type a perforation was formed in addition to cratering and spalling. The samples did not either shatter or breakdown for the impact energies tested in this study. The impact failure morphology observed in this study showed dependency on the plate thicknesses and the projectile kinetic energy. The energy-based risk evaluation together with the series of the hypervelocity impact tests indicated that the silicon nitride ceramic thruster onboard the interplanetary probe would have only a local damage and survive during the mission term.

Lessons from half a century experience of Japanese solid rocketry since Pencil rocket

50 years have passed since a tiny rocket “Pencil” was launched horizontally at Kokubunji near Tokyo in 1955. Though there existed high level of rocket technology in Japan before the end of the second World War, it was not succeeded by the country after the War. Pencil therefore was the substantial start of Japanese rocketry that opened the way to the present stage. In the meantime, a rocket group of the University of Tokyo contributed to the International Geophysical Year in 1957–1958 by developing bigger rockets, and in 1970, the group succeeded in injecting first Japanese satellite OHSUMI into earth orbit. It was just before the launch of OHSUMI that Japan had built up the double feature system of science and applications in space efforts. The former has been pursued by ISAS (the Institute of Space and Astronautical Science) of the University of Tokyo, and the latter by NASDA (National Space Development Agency). This unique system worked quite efficiently because space activities in scientific and applicational areas could develop rather independently without affecting each other. Thus Japan's space science ran up rapidly to the international stage under the support of solid propellant rocket technology, and, after a 20 year technological introduction period from the US, a big liquid propellant launch vehicle, H-II, at last was developed on the basis of Japan's own technology in the early 1990's. On October 1, 2003, as a part of Governmental Reform, three Japanese space agencies were consolidated into a single agency, JAXA (Japan Aerospace Exploration Agency), and Japan's space efforts began to walk toward the future in a globally coordinated fashion, including aeronautics, astronautics, space science, satellite technology, etc., at the same time. This paper surveys the history of Japanese rocketry briefly, and draws out the lessons from it to make a new history of Japan's space efforts more meaningful.

Mission design and integrated guidance and navigation strategy for NEO flyby using ‘interceptor’

Institute of Space and Astronautical Science (ISAS) of Japan Aerospace Exploration Agency (JAXA) is currently planning the missions that the small probe ‘interceptor’ flybys near Earth objects. Interceptor is very small probe. An interceptor observes spectrum, takes close images, and determines mass of an NEO (near earth object) during a flyby. The weight of interceptor is less than 10 kg. This paper shows three types of missions. In general, it is impossible to determine the relative orbit during flyby only with optical information. Thus, the optical navigation needs to be combined with the radio navigation that should provide the relative velocity vector information. In this paper, the integrated guidance and navigation strategy of interceptor is proposed. The interceptor needs the thruster for the attitude and orbit control. This paper introduces the development of the gas-thrust equilibrium thruster for small satellites.

적외선 우주배경복사 관측 실험 국제 공동 연구

A Korean team (Korea Astronomy and Space Science Institute, Korea Basic Science Institute, and Kyung Hee University) takes part in an international cooperation project called CIBER (Cosmic Infrared Background ExpeRiment), which has begun with Jet Propulsion Laboratory (JPL) in USA and Institute of Space and Astronautical Science (ISAS) in Japan. CIBER is a rocket-borne instrument, of which the scientific goal is to measure the cosmic near-infrared extra-galactic background to search for signatures of primordial galaxy formation. CIBER consists of a wide-field two-color camera, a low-resolution absolute spectrometer, and a high-resolution narrow-band imaging spectrometer. The Korean team is in charge of the ground support electronics and manufacturing of optical parts of the narrow-band spectrometer, which will provide excellent opportunities for science and technology to Korean infrared groups.

Akari initial results

A new advanced ceramic thruster made of monolithic silicon nitride ceramics was developed for the planetary exploration spacecraft AKATSUKI (PLANET-C) at Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA). To ensure its operation onboard the spacecraft, the reliability of the ceramic thruster against micrometeoroid hypervelocity impact has been investigated. Silicon nitride plates were impacted by spheres of stainless-steel and other materials with 0.2–0.8-mm diameters in the velocity range up to 8.0 km/s using a two-stage light-gas gun. Using crater depth data under various impact conditions, the penetration equation of silicon nitride was determined. The impacted samples showed fracture patterns of three types: cratering, cratering with spallation, and perforation. These fracture patterns were well categorized by the multiple forms of the penetration equation.

SELENE project status

SELENE (Selenological and Engineering Explorer) project started as a joint mission of the former ISAS (Institute of Space and Astronautical Science) and the former NASDA (National Space Development Agency: the two organizations were merged into JAXA in 2002) of Japan in 1998. The launch target is rescheduled for 2006 due to delay of completion of launch vehicle, H-IIA. The SELENE project is now under a sustained design phase. The flight model components were manufactured, and the interface tests between the bus-system and the mission instruments were completed by the end of March 2004. The functional checks and calibration for the flight model components are being carried out at present. From the beginning of 2005, the final assembly tests will start.