Planned Space Missions Research Articles

Predicting the Energetic Proton Flux with a Machine Learning Regression Algorithm

The need for real-time monitoring and alerting systems for space weather hazards has grown significantly in the last two decades. One of the most important challenges for space mission operations and planning is the prediction of solar proton events (SPEs). In this context, artificial intelligence and machine learning techniques have opened a new frontier, providing a new paradigm for statistical forecasting algorithms. The great majority of these models aim to predict the occurrence of an SPE, i.e., they are based on the classification approach. This work is oriented toward the successful implementation of onboard prediction systems, which is essential for the future of space exploration. We present a simple and efficient machine learning regression algorithm that is able to forecast the energetic proton flux up to 1 hr ahead by exploiting features derived from the electron flux only. This approach could be helpful in improving monitoring systems of the radiation risk in both deep space and near-Earth environments. The model is very relevant for mission operations and planning, especially when flare characteristics and source location are not available in real time, as at Mars distance.

Development of a low-power Hall thruster with permanent magnets and a dual trigger electrode hollow cathode for the Qilu satellite constellation

A low-power Hall effect thruster (LpHet-100) has been installed on the Qilu-3 satellite and has been launched by the Long March 2D rocket in January 2023. The specific features of LpHet-100 are presented in this article. An innovative dual trigger electrode poison-resistant hollow cathode and an effective magnetic shielding configuration with permanent magnets, additive manufacturing gas distributor are designed and experimentally verified. The prominent characteristics of a shorter starting time, lower ignition shock, and self-healing have been shown in tests of the dual trigger electrode hollow cathode. Thrust performance tests proved that LpHet-100 can work stably in the power range of 50–230 W and generate a thrust of 2.9–10.8 mN, with the maximum specific impulse of 1594 s and maximum thrust efficiency of 38 %. Rigorous environmental tests were conducted to verify the thruster design scheme. In addition, Torque measurement of Hall thrusters is incorporated into the ground tests for the first time. A plasma torque of 5.65–9.88 μN·m is obtained when LpHet-100 operated in 132–228 W. It provides a critical guideline for the attitude and orbit control schemes of the Qilu-3 satellite, which is an essential part of space mission planning. Generally, this study proposes new design of the thruster body and hollow cathode, providing an exhaustive reference for the development process and application of low-power Hall thrusters.

International Legal Regulation and Management of Space Waste on Celestial Bodies

The present article explores the international legal regulation of space waste on celestial bodies and the ecological challenges that space missions will pose in the near future. The lack of a shared vision of whether space waste production should be minimized on celestial bodies is causing uncertainty in the planning of future space missions. Leading private space companies are proposing the transfer of dangerous space waste produced from Earth into outer space. The excessive generation of space waste would increase the risks of activities such as space tourism, and space research and will threaten scientific fields such as radio astronomy. The political alliances that exclude a priori third parties will increase the risk of a generation of unnecessary orbital space debris and space waste on celestial bodies because of the development of several space missions in the same field. The sustainability of space missions on celestial bodies and the protection of the outer space environment should become a guiding principle for both national and international legal regulation of space activities. This article argues for the urgent need to establish comprehensive international regulations and monitoring mechanisms to manage space waste on celestial bodies, emphasizing sustainability and cooperation among space-faring nations.

Icy ocean worlds - astrobiology research in Germany

Icy bodies with subsurface oceans are a prime target for astrobiology investigations, with an increasing number of scientists participating in the planning, development, and realization of space missions to these worlds. Within Germany, the Ocean Worlds and Icy Moons working group of the German Astrobiology Society provides an invaluable platform for scientists and engineers from universities and other organizations with a passion for icy ocean worlds to share knowledge and start collaborations. We here present an overview about astrobiology research activities related to icy ocean worlds conducted either in Germany or in strong collaboration with scientists in Germany. With recent developments, Germany offers itself as a partner to contribute to icy ocean world missions.

Simulation of Human Movement in Zero Gravity.

In the era of expanding manned space missions, understanding the biomechanical impacts of zero gravity on human movement is pivotal. This study introduces a novel and cost-effective framework that demonstrates the application of Microsoft's Azure Kinect body tracking technology as a motion input generator for subsequent OpenSim simulations in weightlessness. Testing rotations, locomotion, coordination, and martial arts movements, we validate the results' realism under the constraints of angular and linear momentum conservation. While complex, full-body coordination tasks face limitations in a zero gravity environment, our findings suggest possible approaches to device-free exercise routines for astronauts and reveal insights into the feasibility of hand-to-hand combat in space. However, some challenges remain in distinguishing zero gravity effects in the simulations from discrepancies in the captured motion input or forward dynamics calculations, making a comprehensive validation difficult. The paper concludes by highlighting the framework's practical potential for the future of space mission planning and related research endeavors, while also providing recommendations for further refinement.

Emulation and Testbed Prototyping of Laser Beam Propagation Characteristics through Atmospheric Turbulence for Optical Satellite Feeder Links

Two classical scenarios in space communications can be examined to evaluate the link performance of free space optical communications (FSO). These scenarios include the downlink and uplink between earth ground stations and near earth geostationary (GEO) satellites, as well as between the earth and spacecraft that are located a significant distance from the earth (i.e., one or more astronomical units (AU) away). Deep space is often defined as being more than 0.01 AU, or around 1,500,000 km, from Earth. In the first part of this analytical research, various practical system characteristics for optical lasers, telescopes, transmitters, receivers, and atmospheric disturbances, including absorption and scintillation, are taken into consideration. The simulation outcomes were compared to significant experimental data from DLR & JAXA’s OICETS/Kirari-Japan to validate the extended simulation model. Additionally, this work will propose a synthetic effects-based optical turbulence generator in order to deeply investigate atmospheric turbulence disturbances in free-space optical communication systems and support the advancement of artificial intelligence processing-based mitigation solutions. Worth mentioning, the initial outcomes and analytical comparisons demonstrate the preliminary viability of the simulation model for the link budget and scintillation estimation for FSO investigations, which can give deep insight into the development of the proposed testbed prototyping, machine learning-based laboratory measurement system, and enhancement possibility for FSO project design and execution for longand medium-term space mission planning.

A Compact Particle Detector for Space-Based Applications: Development of a Low-Energy Module (LEM) for the NUSES Space Mission

NUSES is a planned space mission aiming to test new observational and technological approaches related to the study of relatively low-energy cosmic rays, gamma rays, and high-energy astrophysical neutrinos. Two scientific payloads will be hosted onboard the NUSES space mission: Terzina and Zirè. Terzina will be an optical telescope readout by SiPM arrays, for the detection and study of Cerenkov light emitted by Extensive Air Showers generated by high-energy cosmic rays and neutrinos in the atmosphere. Zirè will focus on the detection of protons and electrons up to a few hundred MeV and to 0.1–10 MeV photons and will include the Low Energy Module (LEM). The LEM will be a particle spectrometer devoted to the observation of fluxes of relatively low-energy electrons in the 0.1–7-MeV range and protons in the 3–50 MeV range along the Low Earth Orbit (LEO) followed by the hosting platform. The detection of Particle Bursts (PBs) in this Physics channel of interest could give new insight into the understanding of complex phenomena such as eventual correlations between seismic events or volcanic activity with the collective motion of particles in the plasma populating van Allen belts. With its compact sizes and limited acceptance, the LEM will allow the exploration of hostile environments such as the South Atlantic Anomaly (SAA) and the inner Van Allen Belt, in which the anticipated electron fluxes are on the order of 106 to 107 electrons per square centimeter per steradian per second. Concerning the vast literature of space-based particle spectrometers, the innovative aspect of the LEM resides in its compactness, within 10 × 10 × 10 cm3, and in its “active collimation” approach dealing with the problem of multiple scattering at these very relatively low energies. In this work, the geometry of the detector, its detection concept, its operation modes, and the hardware adopted will be presented. Some preliminary results from the Monte Carlo simulation (Geant4) will be shown.

Diplomatic, geopolitical and economic consequences of an impending asteroid threat

The Planetary Defense Conference 2023 addressed an asteroid threat scenario as difficult to confront. This article examines potential actions of relevant stakeholders, including States, the International Asteroid Warning Network, the Space Mission Planning Advisory Group, Committee on the Peaceful Uses of Outer Space, and the United Nations Security Council.To that effect, different sources are taken into consideration in this analyisis, such as the legal international framework, the practice of States in multilateral fora and the opinion of scholars. The conclusions shed light on the challenges that the international community will have to face and proposes a preventive approach to mitigate the impact of such a potential catastrophe.

Planetary defense governance: Thirty years of development and the multilateral future

Planetary defense (PD) is a well-established program that refers to activities and actions to predict and mitigate a potential impact by an asteroid or comet on the Earth. States are discussing possible deflection scenarios based on their scientific knowledge and technology capacities at the UN-endorsed Space Mission Planning Advisory Group (SMPAG) and at the General Assembly. Even though PD is being formally recognized as an inherently global challenge requiring international cooperation at the level of UN COPUOS, the current state of the global PD governance depends on particular space-faring states and their willingness to fund and execute planetary defense missions. Political representatives consider PD mostly as scientific efforts, respectively efforts conducted mostly by the community of scientists. However, this would change the day an asteroid on a collision course is detected and without solid PD governance in place, behavior of decision-makers could be contingent leading to the possibly unpredictable supranational policy above national security agendas but with inherent implications to the national security of sovereign states. This situation has historical reasons. This paper, firstly, studies the evolution of PD governance from the 80s up to today, to identify the reasons for the current state-oriented (or inter-governmental in the case of ESA) PD governance. Then, secondly, I propose a multilateral PD security regime as an answer to the current state of PD governance. As the threat of being hit by an asteroid is a low probability, high impact natural phenomenon involving the whole Earth, it requires a multigenerational, financially sustainable, and scientifically beneficial planetary-wide program that covers all without exception and does not cause national security concerns of any sovereign state. As asteroids do not discriminate, the planet Earth should consider establishing a multilateral planetary defense security regime to provide security assurances to all, develop trust in the related technology development that all can oversee, and provide an environment to which all entities contribute with their scientific and industrial capacities.

Influence of the interstellar magnetic field and 11-year cycle of solar activity on the heliopause nose location

Context. The heliosphere is formed by the interaction between the solar wind (SW) plasma emanating from the Sun and a magnetised component of local interstellar medium (LISM) inflowing on the Sun. A separation surface called the heliopause (HP) forms between the SW and the LISM. Aims. In this article, we define the nose of the HP and investigate the variations in its location. These result from a dependence on the intensity and direction of the interstellar magnetic field (ISMF), which is still not well known but has a significant impact on the movement of the HP nose, as we try to demonstrate in this paper. Methods. We used a parametric study method based on numerical simulations of various forms of the heliosphere using a time-dependent three-dimensional magnetohydrodynamic (3D MHD) model of the heliosphere. Results. The results confirm that the nose of the HP is always in a direction that is perpendicular to the maximum ISMF intensity directly behind the HP. The displacement of the HP nose depends on the direction and intensity of the ISMF, with the structure of the heliosphere and the shape of the HP depending on the 11-year cycle of solar activity. Conclusions. In the context of the planned space mission to send the Interstellar Probe (IP) to a distance of 1000 AU from the Sun, our study may shed light on the question as to which direction the IP should be sent. Further research is needed that introduces elements such as current sheet, reconnection, cosmic rays, instability, or turbulence into the models.

Analytical Optimal Solution for the Reachable Domain of Low-Thrust Spacecraft

Low-thrust electric propulsion system has drawn increasing attention from researchers because of its high propellant efficiency. The reachable domain of low-thrust spacecraft can provide a geometric insight for space mission planning. In this paper, analytical solutions of the envelope of reachable domain are obtained by employing the Pontryagin’s maximum principle in the well-known linearized model of relative motion, the Tschauner–Hempel equations. Specifically, this study focuses on two contributions. First, an analytical solution of the envelope of reachable domain is obtained, and the associated optimal control profile is derived. Second, an ellipsoid approximation of the reachable domain is proposed to represent the envelope directly based on the analytical solution. Numerical simulations are conducted to demonstrate the accuracy of the proposed solutions. The results show that the reachable domain obtained analytically coincides well with that solved by the numerical indirect method based on the two-body model with low thrust.

Advancing Space Weather Research and Mission Planning: OSEs, OSSEs, and Related Methods

Advancing Space Weather Research and Mission Planning: OSEs, OSSEs, and Related Methods

RANS-Based CFD Simulation of Jet-Induced Mixing and Jet Impingement on Large Bubble in Microgravity

For National Aeronautics and Space Administration’s space mission planning, tons of cryogenic propellants need to be stored under microgravity conditions. Because of heat leaks into cryogenic propellant tanks, thermal stratification develops from lack of natural convection leading to boil-off of precious propellants. A thermodynamic vent system operates with a jet mixer to reduce thermal gradients within the fluid and control pressure inside the tank. In this work, a Reynolds-averaged Navier-Stokes–based computational fluid dynamics model was developed to study the fluid dynamics of jet-induced mixing and jet impingement on the large ullage bubble in the Tank Pressure Control Experiment (TPCE) under microgravity conditions. First, the computational model was benchmarked against existing experimental flow visualization data on the jet impingement. The jet mixing was then compared quantitatively with correlations for the jet radius to analyze the volumetric flow rate of the jet due to entrainment in the near field of the nozzle. The findings show that the confinement of the jet due to the ullage and the walls contributes positively to the jet entrainment rate, thus increasing the jet volumetric flow rate. In addition, the turbulence parameters are plotted to study the flow development for the TPCE case where the jet does not penetrate the ullage. Last, the model was used to determine the jet Weber number for penetration on the ullage bubble by varying jet inlet velocities. Numerical results show that the jet can penetrate the ullage when the jet Weber number is greater than 1.3.

The Remodeling of Dermal Collagen Fibrous Structures in Mice under Zero Gravity: The Role of Mast Cells.

Mechanisms of adaptive rearrangements of the fibrous extracellular matrix of connective tissues under microgravity practically remain unexplored, despite the most essential functions of the stroma existing to ensure the physiological activity of internal organs. Here we analyzed the biomaterial (the skin dermis) of C57BL/6J mice from the Rodent Research-4 experiment after a long stay in space flight. The biomaterial was fixed onboard the International Space Station. It was found that weightlessness resulted in a relative increase in type III collagen-rich fibers compared to other fibrous collagens in the skin. The number of mast cells in the skin did not change, but their secretory activity increased. At the same time, co-localization of mast cells with fibroblasts, as well as impregnated fibers, was reduced. Potential molecular-cellular causes of changes in the activity of fibrillogenesis under zero-gravity conditions and the slowdown of the polymerization of tropocollagen molecules into supramolecular fibrous structures, as well as a relative decrease in the number of fibrous structures with a predominant content of type-I collagen, are discussed. The data obtained evidence of the different sensitivity levels of the fibrous and cellular components of a specific tissue microenvironment of the skin to zero-gravity conditions. The obtained data should be taken into account in the systematic planning of long-term space missions in order to improve the prevention of undesirable effects of weightlessness.

Exploring the Limits of Synthetic Creation of Solar EUV Images via Image-to-image Translation

The Solar Dynamics Observatory (SDO), a NASA multispectral decade-long mission that has been daily producing terabytes of observational data from the Sun, has been recently used as a use case to demonstrate the potential of machine-learning methodologies and to pave the way for future deep space mission planning. In particular, the idea of using image-to-image translation to virtually produce extreme ultraviolet channels has been proposed in several recent studies, as a way to both enhance missions with fewer available channels and to alleviate the challenges due to the low downlink rate in deep space. This paper investigates the potential and the limitations of such a deep learning approach by focusing on the permutation of four channels and an encoder–decoder based architecture, with particular attention to how morphological traits and brightness of the solar surface affect the neural network predictions. In this work we want to answer the question: can synthetic images of the solar corona produced via image-to-image translation be used for scientific studies of the Sun? The analysis highlights that the neural network produces high-quality images over 3 orders of magnitude in count rate (pixel intensity) and can generally reproduce the covariance across channels within a 1% error. However, the model performance drastically diminishes in correspondence to extremely high energetic events like flares, and we argue that the reason is related to the rareness of such events posing a challenge to model training.

Analysis of Technology, Economic, and Legislation Readiness Levels of Asteroid Mining Industry: A Base for the Future Space Resource Utilization Missions

From their initial discovery in 1848, asteroids have been recognized as valuable resources. Although not yet economically viable, asteroid mining is becoming increasingly technologically feasible. The ongoing missions, such as Lucy, Psyche 16, Hayabusa-2, and OSIRIS-REx developed by students, scientists, space agencies, and private companies, continue to improve the technology and cost readiness levels of the space mining industry. This article contextualizes the advances and prospects for the development of asteroid mining activities by building on the success of previous space resource exploration missions and predicting the future of resource utilization in development of space habitats. More than just providing a state of the art, this article highlights the importance of sustainable investments in asteroid mining projects, the strategies in vogue, and identifies the mission feasibility factors. First, this article provides an analysis of space resource exploration missions and the type of asteroids cataloged by space agencies, the International Asteroid Warning Network (IAWN) and the United Nations Office for Outer Space Affairs. Second, this article presents key factors influencing legal, ethical, economic logistics, and technological advancements of asteroid mining missions. This also includes technoeconomic analysis of key technological factors such as accurate trajectory calculation and prediction, maneuvering capabilities, where simple performance improvements bring the asteroid and Moon mining projects nearer to their economic attainability. Finally, the impact of cost, technology readiness levels, and mission feasibility on recent unmanned space resource missions is presented, providing recommendations to bridge the existing gaps for mission execution and implementation levels. The growing threats of an asteroid impact, coupled with rapid depletion of natural resources on Earth, make asteroid mining an increasingly urgent subject. Since the existing state of technology does not meet appropriate standards, this work not only identifies and lists the current and past successful techniques and potential alternatives to gain maturity for asteroid mining missions but also presents the specific logistic aspects such as bridging the gaps in terms of legislation, in-orbit construction, and servicing using the mined resources based on existing literature. This article supports the IAWN, Impact Disaster Planning Advisory Group, Space Mission Planning Advisory Group, Space agencies, educational institutions, and interested stakeholders by providing a critical analysis of state of the art for optimal future development of the space mining industry.

Predictions of Astrometric Jitter for Sun-like Stars. III. Fast Rotators

A breakthrough in exoplanet detections is foreseen with the unprecedented astrometric measurement capabilities offered by instrumentation aboard the Gaia space observatory. Besides, astrometric discoveries of exoplanets are expected from the planned space mission, Small-JASMINE. In this setting, the present series of papers focuses on estimating the effect of the magnetic activity of G2V-type host stars on the astrometric signal. This effect interferes with the astrometric detections of Earth-mass planets. While the first two papers considered stars rotating at the solar rotation rate, this paper focuses on stars having solar effective temperature and metallicity but rotating faster than the Sun, and consequently more active. By simulating the distribution of active regions on such stars using the Flux Emergence And Transport model, we show that the contribution of magnetic activity to the astrometric measurements becomes increasingly significant with increasing rotation rates. We further show that the jitter for the most variable periodic Kepler stars is high enough to be detected by Gaia. Furthermore, due to a decrease in the facula-to-spot area ratio for more active stars, the magnetic jitter is found to be spot dominated for rapid rotators. Our simulations of the astrometric jitter have the potential to aid the interpretation of data from Gaia and upcoming space astrometry missions.

Multidisciplinary Design Optimization Approach to Integrated Space Mission Planning and Spacecraft Design

Space mission planning and spacecraft design are tightly coupled and need to be considered together for optimal performance; however, this integrated optimization problem results in a large-scale mixed-integer nonlinear programming (MINLP) problem, which is challenging to solve. In response to this challenge, this paper proposes a new solution approach to this problem based on decomposition-based optimization via augmented Lagrangian coordination. The proposed approach leverages the unique structure of the problem that enables its decomposition into a set of coupled subproblems of different types: a mixed-integer quadratic programming (MIQP) subproblem for mission planning, and one or more nonlinear programming (NLP) subproblem(s) for spacecraft design. Because specialized MIQP or NLP solvers can be applied to each subproblem, the proposed approach can efficiently solve the otherwise intractable integrated MINLP problem. An automatic and effective method to find an initial solution for this iterative approach is also proposed so that the optimization can be performed without a user-defined initial guess. The demonstration case study shows that, compared to the state-of-the-art method, the proposed formulation converges substantially faster and the converged solution is at least the same or better given the same computational time limit.

Hierarchical Optimization Algorithm and Applications of Spacecraft Trajectory Optimization

The pursuit of excellent performance in meta-heuristic algorithms has led to a myriad of extensive and profound research and achievements. Notably, many space mission planning problems are solved with the help of meta-heuristic algorithms, and relevant studies continue to appear. This paper introduces a hierarchical optimization frame in which two types of particles—B-particles and S-particles—synergistically search for the optima. Global exploration relies on B-particles, whose motional direction and step length are designed independently. S-particles are for fine local exploitation near the current best B-particle. Two specific algorithms are designed according to this frame. New variants of classical benchmark functions are used to better test the proposed algorithms. Furthermore, two spacecraft trajectory optimization problems, spacecraft multi-impulse orbit transfer and the pursuit-evasion game of two spacecraft, are employed to examine the applicability of the proposed algorithms. The simulation results indicate that the hierarchical optimization algorithms perform well on given trials and have great potential for space mission planning.

The optical geometry definition of the total deflection angleof a light ray in curved spacetime

Assuming a static and spherically symmetric spacetime,we propose a novel concept of the total deflection angleof a light ray in terms of the optical geometry which is theRiemannian geometry experienced by the light ray.The total deflection angle is defined by the difference betweenthe sum of internal angles of two triangles; one of the triangles lieson curved spacetime distorted by a gravitating body and the otheron its background. The triangle required to define the totaldeflection angle can be realized by setting three laser-beambaselines as in planned space missions such as LATOR, ASTROD-GW,and LISA. Accordingly, the new total deflection angle is, in principle,measurable by gauging the internal angles of the triangles.The new definition of the total deflection angle can providea geometrically and intuitively clear interpretation.Two formulas are proposed to calculate the total deflection angleon the basis of the Gauss-Bonnet theorem.It is shown that in the case of the Schwarzschild spacetime,the expression for the total deflection angle αSchreduces to Epstein-Shapiro's formula when the source of a light rayand the observer are located in an asymptotically flat region.Additionally, in the case of the Schwarzschild-de Sitter spacetime,the expression for the total deflection angle αSdScomprises the Schwarzschild-like parts and coupling terms ofthe central mass m and the cosmological constant Λ inthe form of O(Λ m) instead of O(Λ/m).Furthermore, αSdS does not include the terms characterizedonly by the cosmological constant Λ.