冨木 淳史

A 6U CubeSat “OMOTENASHI” was developed to be the world's smallest moon lander. It was launched by NASA's SLS Artemis-1 on November 16, 2022. However, because of the spacecraft anomaly, the battery was depleted and the communication with the spacecraft had been lost. After we gave up the moon landing experiment, we have been conducting a search and rescue operation till September 2023. But it was unsuccessful, unfortunately. In this article, the mission objective, the spacecraft design, the planed mission scenario, and the in-orbit operation results are presented. Additionally, lessons learned from the development and the in-orbit operation are presented.

This paper presents a collaborative effort between NASA and JAXA to make 3-way Doppler data from JAXA tracking stations available to the Artemis 1 navigation team to improve orbit determination. The paper describes the system configuration and concept of operation of this capability. Testing effort at the three JAXA's ground stations - the Uchinoura's 20-m and 34-m antennas and Usuda's 64-m antenna - are discussed. Both aspects of system testing are highlighted, first on the use of Artemis 1 recorded signal to ensure compatibility between ground and flight systems, and second on the tracking with the Lunar Reconnaissance Orbiter, as a substitute for Artemis before launch, to validate other key operational functions such as ephemeris processing, spacecraft tracking capability, data delivery, and interactions among multiple operational teams in different organizations. Results from actual support to Artemis 1's Orion spacecraft in November-December 2022 are also presented.

This chapter presents an ongoing effort in preparing JAXA Uchinoura station support to the Artemis 1 mission, scheduled for launch in late 2020. The system involves three key participants: JAXA ground station at Uchinoura, the Deep Space Network (DSN) components at the Jet Propulsion Laboratory, California, and the Artemis 1 mission navigation at the NASA Johnson Space Center, Texas.Demonstration of Uchinoura station support to the future Artemis signal relies on the use of a low-cost, highly-portable software-defined radio (SDR) test equipment as well as the tracking of the Lunar Reconnaissance Orbiter (LRO) spacecraft. Using the SDR equipment, we validated the compatibility of signal format between the Artemis flight radio and the Uchinoura ground station without having to send the flight equipment to the station. By tracking an ongoing operational spacecraft such as LRO, we were able to calibrate the performance of the system in real operational conditions. The measured Doppler noise of 0.03 Hz (1-sigma), or 0.002 m/s range rate at S-band, for Uchinoura station is deemed suitable to the Artemis 1 mission navigation needs.This chapter also discusses the test equipment capability and its performance. In addition to being low cost, the equipment offers many advantages compared to the traditional full-scaled test signal simulator. Chief among them is portability making system easy to set up and transport, and the fidelity of the test signal that it captures from spacecraft flight equipment. Some of the lessons learned, such as internal frequency stability of the test signal, are also reflected.

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.

<p>A Fault Detection, Isolation, and Recovery (FDIR) algorithm for attitude control systems is a key technology to increasing the reliability and survivability of spacecraft. Micro/nano interplanetary spacecraft, which are rapidly evolving in recent years, also require robust FDIR algorithms. However, the implementation of FDIR algorithms to these micro/nano spacecraft is difficult because of the limitations of their resources (power, mass, cost, and so on). This paper shows a strategy of how to construct a FDIR algorithm in the limited resources, taking examples from micro deep space probe PROCYON. The strategy focuses on function redundancies and multi-layer FDIR. These ideas are integrated to suit the situation of micro/nano interplanetary spacecraft and demonstrated in orbit by the PROCYON mission. The in-orbit results are discussed in detail to emphasize the effectiveness of the FDIR algorithm. </p>

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.

Communication with spacecraft is essential to every space mission. However, when the estimation or control of the motion of a spacecraft cannot be performed precisely, it is extremely difficult to communicate with the spacecraft in real-time operations. To enable communication in this situation, this paper proposes an off-line signal-processing method to detect the weak signal transmitted from a spacecraft under poor communication conditions. This is achieved by the following process. First, the Doppler shift effect caused by the motion of the spacecraft is removed from the received signal. The signal power is then enhanced by integrating the signal spectrum over a long time period. Moreover, the estimated frequency model, which contains the Doppler shift information, can be used for orbit and attitude determination as well. A coarse-ranging technique based on the detected weak signal is then introduced as a method of improving the orbit-estimation accuracy. The validity and effectiveness of the proposed method are demonstrated by applying these algorithms to actual radio waves transmitted from the IKAROS.

© 2018 IAA This study proposes a solar sailing method for angular momentum control of the interplanetary micro-spacecraft PROCYON (PRoximate Object Close flYby with Optical Navigation). The method presents a simple and facile practical application of control during deep space missions. The developed method is designed to prevent angular momentum saturation in that it controls the direction of the angular momentum by using solar radiation pressure (SRP). The SRP distribution of the spacecraft is modeled as a flat and optically homogeneous plate at a shallow sun angle. The method is obtained by only selecting a single inertially fixed attitude with a bias-momentum state. The results of the numerical analysis indicate that PROCYON's angular momentum is effectively controlled in the desired directions, enabling the spacecraft to survive for at least one month without momentum-desaturation operations by the reaction control system and for two years with very limited fuel usage of less than 10 g. The flight data of PROCYON also indicate that the modeling error of PROCYON's SRP distribution is sufficiently small at a small sun angle (<10°) of the order of 10−9 Nm in terms of its standard deviation and enables the direction of the angular momentum around the target to be maintained.

©2018. American Geophysical Union. All Rights Reserved. Temperature profiles of the Venus atmosphere obtained by the Akatsuki radio occultation measurements showed a prominent local time dependence above 65-km altitude at low latitudes equatorward of 35°. A zonal wavenumber 2 component is predominant in the temperature field, and its phase (i.e., isothermal) surfaces descend with local time, suggesting its downward phase propagation. A general circulation model (GCM) for the Venus atmosphere, AFES-Venus, reproduced the local time-dependent thermal structure qualitatively consistent with the radio occultation measurements. Based on a comparison between the radio occultation measurements and the GCM results, the observed zonal wavenumber 2 structure is attributed to the semidiurnal tide. Applying the dispersion relationship for internal gravity waves to the observed wave structure, the zonally averaged zonal wind speed at 75- to 85-km altitudes was found to be significantly smaller than that at the cloud top. The decrease of the zonal wind speed with altitude is attributed to the momentum deposition by the upwardly propagating semidiurnal tide excited in the cloud layer.

<p>SLIM (Smart Lander for Investigating Moon) is the Lunar Landing Demonstrator which is under development at ISAS/JAXA. SLIM demonstrates not only so-called Pin-Point Landing Technique to the lunar surface, but also demonstrates the design to make the explorer small and lightweight. Realizing the compact explorer is one of the key points to achieve the frequent lunar and planetary explorations. This paper summarizes the preliminary system design of SLIM, especially the way to reduce the size.</p>

<p>Precise determination of antenna phase centers is crucial to reduce the uncertainty in gain when employing the three-antenna method, particularly when the range distances are short-such as a 3-m radio anechoic chamber, where the distance between the phase centers and the open ends of an aperture antenna (the most commonly-used reference) is not negligible compared with the propagation distance. An automatic system to determine the phase centers of aperture antennas in a radio anechoic chamber is developed. In addition, the absolute gain of horn antennas is evaluated using the three-antenna method. The phase centers of an X-band pyramidal horns were found to migrate up to 18 mm from the open end. Uncertainties in the gain were evaluated in accordance with ISO/IEC Guide 93-3: 2008. The 95% confidence interval of the horn antenna gain was reduced from 0.57 to 0.25 dB, when using the phase center location instead of the open end. The phase centers, gains, polarization, and radiation patterns of space-borne antennas are measured: low and medium-gain X-band antennas for an ultra small deep space probe employing the polarization pattern method with use of the horn antenna. The 95% confidence interval in the antenna gain decreased from 0.74 to 0.47 dB.</p>

PROCYON is a first full-scale, 50-kg-class probe featuring most of the key technologies for deep-space exploration. It was developed by the University of Tokyo and ISAS/JAXA and launched with Hayabusa 2 on 3 Dec 2014. PROCYON has a newly developed X-band telecommunication system fully compatible with the frequency range, up- and down-link turn-around ratio, modulation scheme, and DDOR tones following CCSDS-recommended standards, and it can establish X-band coherent two-way communication and ranging links with deep-space stations as larger deep-space probes have done. The total mass of the onboard telecommunication system is 7.3 kg excluding its RF coaxial harness, and total power consumption during two-way communication, 15 W of RF output power at SSPA, is 54.3 W. After launch, PROCYON's telecommunication system has been successfully working according to the system design. These achievements will provide core technologies for nextgeneration deep-space exploration by ultra-small probes.

Experimental evaluation of ultra wideband (UWB) wireless transmission was carried out with a view to replacing wired interface buses in spacecrafts. Application of wireless technologies within the spacecrafts could contribute to reduction in cable weight reduction in the cost of design, manufacture, and test more flexibility in layout of spacecraft subsystems and reliable connections at rotary, moving, and sliding joints. However, multipath propagation in semi-closed conductive enclosures, such as spacecrafts, restricts the link performance. Spatial distributions of UWB and narrowband propagation gains, delay spreads, and throughputs were measured with use of four different-sized shield boxes (simulated miniature satellites). Then UWB link throughput was experimentally evaluated in the boxes with use of connecting off-the-shelf MB-OFDM UWB devices. Increase in the inner volume of boxes resulted in higher UWB propagation gains, but wider delay spreads and hence lower link throughput.

PROCYONは,超小型衛星による小惑星フライバイ探査ミッションを目的として,はやぶさ2のピギーバック搭載機会である2014年12月の打ち上げを目指している.超小型衛星による深宇宙探査ミッションは,大型衛星とは異なる信頼性基準,コストのバランスによって成立させる必要がある.特に搭載重量や発生電力の制約条件は大きく,従来の宇宙用通信コンポーネントの設計概念を大きく変えて積極的な民生部品の活用と小型軽量化に最適な技術の導入が不可欠である.本稿では,PROCYON通信系構成,並びに,各コンポーネントの詳細を紹介する.

Experimental evaluation of ultra wideband (UWB) wireless transmission was carried out with a view to replacing wired interface buses in spacecrafts. Application of wireless technologies within the spacecrafts could contribute to reduction in cable weight; reduction in the cost of design, manufacture, and test; more flexibility in layout of spacecraft subsystems; and reliable connections at rotary, moving, and sliding joints. However, multipath propagation in semi-closed conductive enclosures, such as spacecrafts, restricts the link performance. Spatial distributions of UWB and narrowband propagation gains, delay spreads, and throughputs were measured with use of four different-sized shield boxes (simulated miniature satellites). Then UWB link throughput was experimentally evaluated in the boxes with use of connecting off-the-shelf MB-OFDM UWB devices. Increase in the inner volume of boxes resulted in higher UWB propagation gains, but wider delay spreads and hence lower link throughput.

A high-speed downlink communication system is required to meet various applications for nano/small satellites. The purpose of this research is to develop a high-data-rate X band downlink system with low power consumption. A high efficient RF circuits using GaN-HEMT SSPA and low power consumption digital circuits were important. We developed over 300Mbps with occupied BW150MHz, RF power 2W, power consumption 20W, mass 1.4kg.

This research proposes an X-band high efficiency onboard SSPA (solid-state power amplifier) for deep space missions by focusing on GaN (gallium nitride) HEMT (high electron mobility transistor) whose remarkable material properties, such as high thermal conductivity, wide band gap, and high breakdown voltage, are suitable for high power and high efficiency applications. Developing a high efficiency onboard SSPA is one of the great issues when we consider some missions toward Mars, Jupiter, and much farther planets because of the requirements of both ultra-long distance communication and low power consumption. As a first step toward developing a SSPA for deep space, a breadboard model is fabricated based on preliminary design. It consists of a buffer amplifier, a driver amplifier unit, a high power amplifier unit, an automatic level control unit, a variable attenuator, DC/DC convertors, and an over current protection unit. Here, GaN HEMT is used in both driver amplifier and high power amplifier units. RF (radio frequency) characteristics of these amplifier units are evaluated in experiments. The driver amplifier unit achieves output power of 31.5 dBm with power gain of 33.5 dB and less than -26 dBc of IM3 (third order intermodulation distortion) at P1dB (1dB compression point) at 8.425 GHz. Moreover, the maximum efficiency is up to 35.2%. On the other hand, the high power amplifier unit achieves 42.3 dBm of output power with 46.1% of PAE (power added efficiency) at P3dB (3dB compression point) at 8.40 GHz. In addition, the integrated GaN SSPA bread board model achieves the maximum output power of 41.9 dBm and the maximum total efficiency of 31.0% at 8.40 GHz. At least more than 5% total efficiency improvement can be seen compared to the previous onboard SSPAs. Moreover, space applicability of GaAs (gallium arsenide) MMIC (monolithic microwave integrated circuit), GaN HEMT and DC/DC convertor that are expected to be used in the SSPA are confirmed in total ionizing dose test.

Ka-band communications is one of the most important technologies for increasing the amount of data acquired in deep space missions. As a first step toward developing this technology, a Ka-band extender was attached to an existing X-band transponder. The Ka-band extender can generate Ka-band signals from the transponder's signals. The extender is designed so as to reuse design elements of the X-band transponder. This approach ensures reliability of the extender without additional qualification, lowers production costs, and allows for flexibility in the Ka-band extender configuration. For instance, the minimum configuration is a simple upconverter, which is realized by sharing circuits to the greatest extent possible with the transponder. The extender is compatible with the Ka-band specifications in Consultative Committee for Space Data Systems standards. Properties such as a flexible coherent ratio, high-speed analog and digital modulation, and ultralow phase noise for radio science missions are provided. Here, a breadboard model of the Ka-band extender was evaluated in experiments. The Allan variance of the Ka-band output signal was less than 1 × 10^-12 (at 1 s), 1 × 10^-13 (at 10 s), and 1 × 10^-14 (at >100 s) when an external reference signal was used. The Allan variance degradation and phase noise degradation, which were caused by the internal phase locked loop or frequency translation loop, were also measured. The measured phase noise degradation was about 25 dB from the theoretical value.

IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) is the world's first spacecraft to successfully demonstrate solar-sail technology in interplanetary space. The spacecraft is made of square shape of very thin membrane, whose diagonal dimension is 20m. By changing its attitude toward Sun, radiation pressure of solar photons can be used as propulsive force of the spacecraft. To determine the orbit under the continuous big influence of the nongravitational perturbative force (i.e. solar radiation pressure), Very Long Baseline Interferometry (VLBI) observation is effective because sky plane position of the spacecraft can be directly and instantaneously measured by VLBI observables without (or with less dependence on) a priori assumption for solar radiation pressure model. In order to effectively perform VLBI measurements, a signal generator of Differential One-way Range (DOR) tones, which consist of multiple tones whose spanning bandwidth is about 28MHz, was developed and installed to the spacecraft. A digital backend system for the ground stations which has maximum output performance of 4-Gbps had also developed to sample wideband DOR tones. A total number of 24 international VLBI experiments were carried out by using totally 15 antennas among 8 agencies during July and August in 2010. As a result of initial analysis, measurement accuracy of VLBI delay was confirmed to be 50 pico second level, which is 20 times improved precision compared to the JAXA's conventional deep space spacecraft such as Hayabusa and Akatsuki. © 2011 IEEE.

The Radio Science experiment (RS) in the Akatsuki mission of JAXA aims to determine the vertical structure of the Venus atmosphere, thereby complementing the imaging observations by onboard instruments. The physical quantities to be retrieved are the vertical distributions of the atmospheric temperature, the electron density, the H2SO4 vapor density, and small-scale density fluctuations. The uniqueness of Akatsuki RS as compared to the previous radio occultation experiments at Venus is that low latitudes can be probed many times thanks to the near-equatorial orbit. Systematic sampling in the equatorial region provides an opportunity to observe the propagation of planetary-scale waves that might contribute to the maintenance of the super-rotation via eddy momentum transport. Covering the subsolar region is essential to the understanding of cloud dynamics. Frequent sampling in the subsolar electron density also helps the understanding of ionosphere dynamics. Another unique feature of Akatsuki RS is quasi-simultaneous observations with multi-band cameras dedicated to meteorological study; the locations probed by RS are observed by the cameras a short time before or after the occultations. An ultra-stable oscillator provides a stable reference frequency which is needed to generate the X-band downlink signal used for RS.

The application of Ka band to deep space communication is attractive. It makes profit of either higher bit rate or more compact system depending on what we prefer for our system. We also have tried to introduce Ka band technology to our deep space activities since the beginning of the 21st century. But a decade was needed till the missions actively take the Ka band benefits in their proposal. They are also active to construct a new deep space ground station for Ka band. We will discuss our onboard and ground station system for Ka band that we have prepared for this decade. Among them we will take up a Ka band coherent transmitter attached to the exiting X band transponder and a blueprint of our future Ka band ground station. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

技術の進歩と共に小型衛星に求められるミッション要求は高度化し,衛星は軽量化,低コスト化が求められている.カテゴリ-Aに属する月周回,ハロー軌道,ラグランジュ点などミッションでもより高性能な通信機器が要求されている.本研究では,カテゴリ-Aミッションの小型衛星に向けた,Sバンドトランスポンダを開発している.重量約1kg,寸法110×110×90mm^3,消費電力10w以下,ラグランジュ点でトランスポンダの検波を維持する.本開発により,カテゴリ-Aミッションの小型衛星設計に重要な役割を与える.本稿では開発している月・ラグランジュ点ミッションに向けた小型Sバンドトランスポンダを報告する.

衛星サブシステムのレイアウト自由度の拡大や信号ケーブル質量の軽減と超高速バス接続の両立を実現するために,信号ケーブルの一部を無線化することを提案する.無線システムを衛星構体内部という多くの障害物を含む閉鎖空間に適用するために,超広帯域無線伝搬技術(UWB)を用いることを提案する.UWBは,比帯域幅20%以上取ることで,多重波フェージングを克服することができる.そのため,狭帯域伝送に比べ有利と考えられる.UWBを衛星構体内へ適用するためには,その電波伝搬特性を明らかにする必要がある.小型科学衛星の機械環境試験モデルと,それを模擬した内部空間を用意し,電波伝搬特性を測定した.UWBモノポールアンテナとベクトルネットワークアナライザを使用し,3.1〜10.6GHzの周波数応答からパス利得の空間分布,遅延プロファイル,遅延スプレッドを測定した.その結果,狭帯域伝搬では深いフェージングの落ち込みであるデットスポットが生じ,UWBではこれらが発生しないことが分かった.また,伝送品質の向上を図るため,遅延スプレッドの制御を試みた.結果,電波吸収体による遅延スプレッドの制御が可能であることが分かった.