TOMIKI ATSUSHI

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.

©2018. American Geophysical Union. All Rights Reserved. Radio occultation (RO) is one of the most efficient techniques for studying fine vertical structures in planetary atmospheres. However, the geometrical optics (GO) method, which has been used for the analysis of RO data, suffers blurring by the finite width (Fresnel scale) of the radio ray and cannot decipher multipath propagation, which also prevents retrieval of fine structures. Here we apply Full Spectrum Inversion (FSI), which is one of the radio holographic methods, to RO data taken in Venus Express and Akatsuki missions to retrieve fine structures in Venus' cloud-level atmosphere. The temperature profiles obtained by FSI achieve vertical resolutions of ~150 m, which is much higher than the typical resolution of 400–700 m in GO, and resolve structures in multipath regions. Thin, near-neutral layers are found to be ubiquitous at cloud heights; we suggest here that those layers are caused by the mixing associated with the breaking of short-wavelength gravity waves. The wavenumber spectra of small-scale structures are consistent with the semiempirical spectrum of saturated gravity waves and show larger amplitudes at higher latitudes. Temperature profiles in the high latitudes frequently show a sharp temperature minimum near the cloud top, below which the vertical temperature gradient is near adiabat, implying that the sharp temperature minimum is created by adiabatic cooling associated with convective plumes that impinge on the overlying stable 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.

The more technologies advance, the higher mission achievements are demanded in small satellite missions. In this study, we have been developing X-band deep space telecommunication systems for 50kg-class small satellites of Category-B missions.

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.

This paper describes measurement and characterization of radio propagation and transmission-particularly of ultra wideband (UWB) signals-within spacecrafts with a view to partly replacing on-board data buses with wireless connections. Adaption of wireless technologies within spacecraft could contribute to reduction of cable weight and resulting launching costs, and more reliable connections at rotary, moving, and sliding joints. This paper presents measurements and characteristics of radio propagation and transmission and addresses the effects of apertures perforated on the outer surface of satellites on the UWB propagation and transmission for low-and high-band UWB within a shield box. Channel responses, spatial distributions of UWB and narrowband propagation gains, delay spreads, and throughputs were derived from measurements. On the effects of apertures, the larger total area of apertures resulted in lower UWB propagation gains, shorter delay spreads, and (slightly) higher link throughput. The propagation study was followed up with experimental evaluation of UWB link throughput within a simulated spacecraft. Commercially off-the-shelf UWB devices were used in the experiments of ultra wideband technology to facilitate a high data rate (e.g. maximum of 400 Mb/s per node attained with SpaceWire, equaling the standards of a wired onboard data bus) and to reduce the fading margin. © 2013 IEEE.

Ultra wideband (UWB) technology has been expected to communicate in very high data rates by wireless within closed environments, such as spacecrafts. With a view to replacing onboard wired interface buses by wireless connection, UWB and narrowband propagation were measured in a UWB frequency band (from 3.1 to 10.6 GHz) within a small spacecraft. While narrowband propagation resulted in considerable spatial variations in path gain due to interferences caused by multipaths, UWB yielded nearly no fading. This suggests that the UWB systems have an advantage over narrowband from a viewpoint of reducing fading margins. Propagation gains were measured with full-, low-, and high-band UWBs, and narrowband (20 MHz bandwidth) for various antenna settings and polarization configurations for transmission and reception. Polarization configurations were found to produce almost no effect on average power delay profiles. Throughputs were also measured with a WiMedia UWB device. More than 85-Mb/s throughputs were observed for all antenna settings and propagation configurations.

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.

The more technologies advance, the higher mission achievements are demanded in small satellite missions. In addition, these missions require more performance of telecommunication at Category-A (such as the lunar orbiter, halo orbiter and Lagrange point missions). We have been developing such an S-band transponder for small satellites of Category-A missions. It weighs about 1kg, has dimensions of 110×110×90mm^3, consumes less than 10W, and keeps sensitivity of transponder detection at the Lagrange points. Therefore, the development of our transponder plays a significant role in small satelli...

Ultra wideband (UWB) propagation was measured and characterized within spacecrafts, with a view to partly replacing onboard data buses with wireless connections. Spatial distributions of UWB and narrowband propagation in frequency (from 3.1 to 10.6 GHz) and time domains were measured with a microwave vector network analyzer. While narrowband resulted in a number of dead spots (deep fading points) within the conductive enclosures, UWB yielded none. This implies the UWB systems have an advantage over narrowband ones from the viewpoint of reducing fading margins. It was also found that delay spreads can be suppressed by partially panelling a radio absorber on the inner surfaces to facilitate high data rate transmission. © 2009 IEEE.

Ultra wideband (UWB) propagation was measured and characterized within spacecrafts, with a view to partly replacing onboard data buses with wireless connections. Spatial distributions of UWB and narrowband propagation in frequency (from 3.1 to 10.6GHz) and time domains were measured with a microwave vector network analyzer. While narrowband resulted in a number of dead spots (deep fading points) within the conductive enclosures, UWB yielded none. This implies the UWB systems have an advantage over narrowband ones from a viewpoint of reducing fading margins. It was also found that delay spre...