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This paper highlights the power system design of the equilibrium lunar–Earth point 6-unit spacecraft (EQUULEUS), which will fly to the second Earth–Moon Lagrange point and perform a variety of scientific and technological missions. The limited power generation and high uncertainties of power generation and consumption are major difficulties encountered by the electrical power system of EQUULEUS for ensuring the feasibility of its mission. To address these issues, some methodologies are described in this paper in detail, which include the unique component arrangement, maximum power-point tracking function, and probabilistic analysis of power management. For the probabilistic analysis, Monte Carlo simulations are conducted based on a numerical model, and the feasibility of the power balance between generation and consumption is verified. [ABSTRACT FROM AUTHOR]

Earth remote sensing from geostationary orbit (GEO) can realize high temporal resolution; however, the spatial resolution is commonly worse than observation from low Earth orbit. In order to achieve high-frequency and high-resolution GEO remote sensing, a "Formation Flying Synthetic Aperture Telescope (FFSAT)" with multiple micro-satellites has been proposed. The FFSAT greatly improves the spatial resolution using a synthetic aperture technique. Therefore the relative positions and attitudes between the optical units of each satellite must be controlled with an accuracy better than 1/10 of the observation wavelength. However, even mm-class accuracy control has not been demonstrated on orbit. As a first practical application of the FFSAT, a forest fire monitoring mission using infrared rays is being considered, in which control accuracy requirement is relaxed as its wavelength is longer than visible light. We proposed a point spread function optimization method for controlling formation flying with an accuracy of approximately 1-1,000 times the wavelength (1µm-1 mm) in the absence of sensors, which can measure absolute distance with µm-accuracy. The effectiveness of the method was demonstrated through simulations in which the satellites' system and the optical system are coupled. The simulation results show that the method can control the formation within the wavelength order. [ABSTRACT FROM AUTHOR]

DELPHINUS is a camera system mounted on EQUULEUS, which is planned to be launched using NASA's Space Launch System EM-1 in 2021. DELPHINUS aims to investigate size distribution, influx ratio, and daily variation of meteoroids in the cislunar space through observations of lunar impact flashes (LIFs) from the far side of the moon. DELPHINUS will observe the moon's surface with the 60-fps camera modules to capture the flashes that are short duration phenomena. All image data cannot be downlinked due to constraints in memory size and communication capability. Therefore, an on-board image processing algorithm was developed to reduce downlinked data size by extracting only necessary pixel data including LIFs. Three experiments using three simulators were demonstrated to verify the real-time processing performance and detection capability. This paper reports the details of the proposed algorithm and the verification results. [ABSTRACT FROM AUTHOR]

he amount of debris in space is increasing every year, and its e↵ect on satellite missions is worsening. In this research, a method for removing debris using laser radiation pressure from a ground station is proposed. This method does not require a satellite to be launched to remove debris, and the system applied is less likely to be considered as a threat because it is relatively safe even if the laser erroneously irradiates another satellite, because the laser intensity is no more than 108 W/m2. However, the power applied to debris is small, such that it requires a great deal of time and energy to deorbit the debris. Therefore, this study aims to evaluate the feasibility of debris removal by laser radiation pressure from the viewpoint of energy consumption and time. In addition, in order to increase the feasibility of this method, a sub-optimized laser irradiation method for reducing the time and energy consumption required for removal is proposed. This study addresses how much energy and time is needed for a particular piece of debris to be removed by laser under three parameters: power of the laser, time that the laser is powered, and the location of the laser ground station. By sub-optimizing these parameters, the energy needed to remove a particular piece of space debris within a particular time is minimized. Furthermore, a laser irradiation method for deorbiting multiple pieces of debris using multiple laser ground stations is discussed. This study contributes to show that the new debris removal method using laser radiation pressure from laser ground station can e↵ectively and practically remove multiple debris in terms of time and energy cost. [ABSTRACT FROM AUTHOR]

Recently, a spatial resolution of several meters from LEO has been realized in small satellite remote sensing. However, it is difficult to increase a temporal resolution in LEO remote sensing. Therefore, GEO remote sensing which enables observation of high temporal resolution from GEO or its nearby orbit is getting important. In order to obtain enough spatial resolution in GEO remote sensing, an optical system having a diameter of several meters is required because of the diffraction limit. It takes huge cost to realize the optical system with such a large diameter due to manufacturability and required accuracy. To solve these problems, we propose a synthetic aperture telescope by small satellites formation flying. The synthetic aperture telescope is composed of mirror satellites constituting a primary mirror of the telescope and an imaging satellite having a focal plane assembly. By optically synthesizing the light collected by mirror satellites with the imaging satellite, a virtual large aperture telescope is constructed in orbit. In this paper, observations at near infrared to short wavelength infrared are assumed and required specifications are shown. Moreover, we describe optical performance of the synthetic aperture telescope and an adjustment method of the optical system by applying the adaptive optics technique. [ABSTRACT FROM AUTHOR]

This paper proposes an accurate aerodynamic model for membrane structures in free-molecular flow that allows the calculation of torque and force exerted on them, and which can be used for precise analysis of the attitudes and orbital dynamics of the structures. Recently, various types of deployable thin membrane structures attached to satellites for deorbit purposes have been developed and demonstrated on low-Earth orbits (LEOs), and their attitude dynamics have also been investigated. However, in early studies, deorbit sails were modeled as simple flat plates because there were no precise models for membranes that could express wrinkles, billowing, and asymmetric shapes. In this paper, a calculation method using tensor expressions of aerodynamic disturbance is proposed for the design of deorbit devices using high-fidelity membrane models. The proposed method is tested in the attitude stability analysis of membranes on LEOs, and the results show that the asymmetric shapes of the membranes affect their attitude stability. [ABSTRACT FROM AUTHOR]

This paper describes development strategies and on-orbit results of the attitude determination and control system (ADCS) for the world's first interplanetary micro-spacecraft, PROCYON, whose advanced mission objectives are optical navigation or an asteroid close flyby. Although earth-orbiting micro-satellites already have ADCSs for practical missions, these ADCSs cannot be used for interplanetary micro-spacecraft due to differences in the space environments of their orbits. To develop a new practical ADCS, four issues for practical interplanetary micro-spacecraft are discussed: initial Sun acquisition without magnetic components, angular momentum management using a new propulsion system, the robustness realized using a fault detection, isolation, and recovery (FDIR) system, and precise attitude control. These issues have not been demonstrated on orbit by interplanetary micro-spacecraft. In order to overcome these issues, the authors developed a reliable and precise ADCS, a FDIR system without magnetic components, and ground-based evaluation systems. The four issues were evaluated before launch using the developed ground-based evaluation systems. Furthermore, they were successfully demonstrated on orbit. The architectures and simulation and on-orbit results for the developed attitude control system are proposed in this paper. [ABSTRACT FROM AUTHOR]