Explore the vast range of titles available.

This study examines how a spacecraft reacts to constant body-fixed torques and a gyrostatic moment (GM), as well as the impact of energy dissipation. The spacecraft model being studied includes a spherical slug near the center of mass covered by a viscid layer. The problem’s difficulty lies in solving its governing equations of motion (EOMs), which are derived through Euler nonlinear equations. Understanding the behavior of this model can offer insights into how spacecraft respond to external torques, aiding in the development of more efficient and stable systems for aerospace and robotics applications. The research delves into the relationship between energy dissipation and GM on the spacecraft motion in three different scenarios involving constant torques around three various axes. Detailed analysis, as well as novel solution and simulation results, are presented for different energy dissipation possibilities. The influence of manipulating the value of the GM and the viscosity of the layer has been approached. These findings are crucial for comprehending, maintaining, and controlling the motion of spacecraft influenced by external forces in space. The study promises to have a significant impact on the aerospace industry, particularly in the design and operation of spaceships and satellites, by enhancing our knowledge of rotational motion and celestial bodies’ behavior. A comprehensive report will be produced to elucidate the complexities of rotational and orbital motion discovered during this research.

The planar motion of a particle within an arbitrary potential field is considered. The particle is additionally subject to an external force wherein the applied thrust-acceleration is constrained to remain normal to the velocity vector. The system is thus non-conservative but since the thrust force is non-working, the total energy is a conserved quantity. Under this setting, a major result of fundamental importance is established in this paper: that the flight direction angle (more precisely, the sine of the angle between the position and velocity vectors) is shown to always satisfy a linear first-order differential equation with variable coefficients that depend upon the underlying potential function. As a consequence, an analytical solution for the flight direction angle can be obtained directly in terms of the particle's distance from the center of the field for a significant number of special cases for the potential function. In the case of J2 perturbed spacecraft motion within equatorial orbits, the problem is reduced to that of solving an incomplete elliptic integral. Another important implication of the main result established here is that motion problems subject to velocity-normal thrusting can always be reduced to the study of equivalent single degree-of-freedom conservative systems with an effective potential function. The paper concludes with various examples of both academic and practical interest including the study of bounded two-body Keplerian orbits and hodograph interpretetions.

The Europa Thermal Emission Imaging System (E-THEMIS) on the Europa Clipper spacecraft will investigate the temperature and physical properties of Europa using thermal infrared (TIR) images in three wavelength bands centered from 7-14 μm, 14-28 μm and 28-80 μm. E-THEMIS will map >80% of the surface Europa at multiple times of day at a resolution of 8-km per pixel, ∼32% percent of the surface at ≤1 km/pixel resolution, and ∼6% percent at ≤100 m/pixel resolution. The specific objectives of the investigation are to 1) understand the formation of surface features, including sites of recent or current geologic activity, in order to understand regional and global processes and evolution and 2) to identify safe sites for future landed missions. E-THEMIS uses an uncooled microbolometer detector array for the IR focal plane. The E-THEMIS focal plane has 920 cross-track pixels (896 active) and 140 along-track pixels in each of the three spectral bands. The image data are collected at 14-bits per pixel at a frame rate of 60 Hz. The instrument can operate in framing mode, where full frame images are collected, and optionally co-added in time, in each band, or in time-delay-integration (TDI) mode where consecutive rows from each band are offset spatially to remove the spacecraft motion and then summed. In addition, the data in each band can be spatially aggregated from 2 × 2 to 5 × 5 pixels. These modes will be varied throughout each Europa flyby to optimize the data precision while fitting within the E-THEMIS data allocation. The expected temperature precision, measured as the noise equivalent spectral radiance, is 1.2 K at scene temperatures ≥90 K for a TDI of 16 with 4 × 4 pixel coaggregation in Band 2. The absolute accuracy at 90 K is 2−3 K in Band 2. E-THEMIS is an all-reflective, three-mirror anastigmat telescope with a 6.45-cm effective aperture and a speed of f/1.34 cross-track and 1.92 along-track. The mass of instrument Sensor Assembly, mounted on the spacecraft nadir deck, is 11.4 kg, the vault electronics are 1.8 kg, and the two are connected through a 3.1 kg harness. The Sensor volume is 23.7 cm x 31.8 cm x 29.8 cm. E-THEMIS consumes an average operation power of 34.8 W at 28 V. E-THEMIS was developed by Arizona State University with Raytheon Vision Systems developing the microbolometer focal plane assembly and Ball Aerospace developing the electronics. E-THEMIS was integrated, tested, and radiometrically calibrated on the Arizona State University campus in Tempe, AZ.

This paper presents a novel rigid-body navigation and control architecture within the framework of special Euclidean group SE ( 3 ) and its tangent bundle TSE ( 3 ) while considering stochastic processes in the system. The proposed framework combines the orbit-attitude motions of the rigid body into a single, compact set. The stochastic state filter is designed based on the unscented Kalman filter (UKF) which uses a special retraction function to encode the sigma points onto the manifold. The navigation system is then integrated and evaluated with two different control techniques on TSE ( 3 ) : An almost globally asymptotically stabilizing Morse–Lyapunov-based control system with backstepping and a robust sliding mode-based control system. Also, the performance of the UKF in TSE ( 3 ) proposed here is compared with similar filters in the literature to demonstrate the robustness and accuracy of the proposed filter in a realistic setting. Numerical simulations are conducted to demonstrate the effectiveness of the proposed navigation filter for the full state estimation. In addition, the navigation and control systems are tested in the nonlinear gravity field of a small celestial body with an irregular shape. In particular, the performance of the closed-loop systems is studied in a tracking problem of spacecraft motion near the asteroid Bennu based on OSIRIS-REx mission data.

Observation of growing phase space density (PSD) peak in the outer electron radiation belt has been considered evidence for local wave‐driven acceleration as a primary cause of radiation belt enhancement. However, recent studies showed that strong substorm‐associated MeV electron injections can also cause significant radiation belt enhancements on fast timescales (∼10s min). Such rapid enhancements pose challenges for determining true spatial PSD profiles. To address this, we conduct a detailed spatiotemporal analysis of electron flux and PSD during an enhancement event, using Van Allen Probes data. Our analysis reveals rapid and intermittent flux enhancements. During these rapid enhancements, inbound spacecraft observed false PSD peaks, due to spacecraft's relatively slow movement. However, we identify time intervals of stable fluxes between enhancements, enabling us to determine quasi‐stationary PSD profiles with no noticeable peaks. This study provides new insights into accurate PSD analysis, critical for understanding the mechanisms underlying radiation belt enhancements. Plain Language Summary Radiation belt physics studies the origin and dynamics of high‐energy electrons trapped in the Earth's radiation belts. The radial profiles of these electrons' phase space density (PSD) are essential parameters for investigating their origin and dynamics. Outward‐increasing PSD profiles indicate that electrons have been transported radially (injections) from outside the radiation belt, while locally peaked profiles suggest that they were generated locally within the belt. Obtaining accurate PSD profiles is challenging due to significant temporal changes in electron flux, particularly rapid flux enhancements from injections as observed in recent studies. To examine the impact of rapid flux enhancements on PSD analysis, we closely tracked electron flux changes in space and time during an enhancement event using data from NASA's Van Allen Probes. Our results show that inbound spacecraft can observe falsely peaked PSD profiles during rapid flux enhancements, which are temporal artifacts from relatively slower spacecraft motion. By identifying time intervals of stable electron flux between enhancements, we were able to determine the true spatial PSD profiles, which overall exhibited outward‐increasing trends, consistent with injections. Our findings offer new perspective on accurately determining PSD radial profiles, which is essential for unraveling the origins of high‐energy electrons in the Earth's radiation belts. Key Points Rapid and intermittent electron enhancement pattern significantly impacts phase space density (PSD) analysis Inbound spacecraft can observe a temporal PSD peak during rapid electron enhancements driven by injections Quasi‐stationary time intervals between enhancements enable accurate determination of PSD radial profiles

The work simulates the operation of the motion control system of a small spacecraft. The main Executive body of this system is the engine-flywheel. It is proposed to use an electrothermal micro-motor to reduce the kinetic moment of the flywheel motor. In emergency situations, it can be used as the main Executive body of the management system. A comparative analysis of the advantages and disadvantages of using magnetic actuators and electrothermal micro-motor to reduce the kinetic moment of the flywheel motor. Conclusions are drawn on the feasibility of their application for various small spacecrafts.

In the domain of space rendezvous and docking, visual navigation plays a crucial role. However, practical applications frequently encounter issues with poor image quality. Factors such as lighting uncertainties, spacecraft motion, uneven illumination, and excessively dark environments collectively pose significant challenges, rendering recognition and measurement tasks during visual navigation nearly infeasible. The existing image enhancement methods, while visually appealing, compromise the authenticity of the original images. In the specific context of visual navigation, space image enhancement’s primary aim is the faithful restoration of the spacecraft’s mechanical structure with high-quality outcomes. To address these issues, our study introduces, for the first time, a dedicated unsupervised framework named SpaceLight for enhancing on-orbit navigation images. The framework integrates a spacecraft semantic parsing network, utilizing it to generate attention maps that pinpoint structural elements of spacecraft in poorly illuminated regions for subsequent enhancement. To more effectively recover fine structural details within these dark areas, we propose the definition of a global structure loss and the incorporation of a pre-enhancement module. The proposed SpaceLight framework adeptly restores structural details in extremely dark areas while distinguishing spacecraft structures from the deep-space background, demonstrating practical viability when applied to visual navigation. This paper is grounded in space on-orbit servicing engineering projects, aiming to address visual navigation practical issues. It pioneers the utilization of authentic on-orbit navigation images in the research, resulting in highly promising and unprecedented outcomes. Comprehensive experiments demonstrate SpaceLight’s superiority over state-of-the-art low-light enhancement algorithms, facilitating enhanced on-orbit navigation image quality. This advancement offers robust support for subsequent visual navigation.

Coupling between the rotational and translational motion of a rigid body can have a profound effect on spacecraft motion in complex dynamical environments. While there is a substantial amount of study of rigid-body coupling in a non-uniform gravitational field, the spacecraft is often considered as a point-mass vehicle. By contrast, the full-N body problem (FNBP) evaluates the mutual gravitational potential of the rigid-body celestial objects and any other body, such as a spacecraft, under their influence and treats all bodies, including the spacecraft, as a rigid body. Furthermore, the perturbing effects of the FNBP become more pronounced as the celestial bodies become smaller and/or more significantly aspherical. Utilizing the comprehensive framework of dynamics and gravitational influences within the FNBP, this research investigates the dynamics of spacecraft modeled as rigid bodies in binary systems characterized by nearly circular mutual orbits. The paper presents an examination of the perturbation effects that arise in this circular restricted full three-body problem (CRF3BP), aiming to assess and validate the extent of these effects on the spacecraft’s overall motion. Numerical results provided for spacecraft motion in the CRF3BP in a binary asteroid system demonstrate non-negligible trajectory divergence when utilizing rigid-body versus point mass spacecraft models. These results also investigate the effects of shape and inertia tensors of the bodies and solar radiation pressure in those models.

Research on the dynamics of multi-body motion in the Earth-Moon space is a crucial area in current spacecraft motion studies. Distant Retrograde Orbits (DROs) are highly valuable trajectories in the Earth-Moon space. Under the ephemeris model, DROs will become quasi-periodic. Efficiently computing quasi-periodic DROs in the ephemeris model is a pressing issue. This paper addresses the problems of high computational time cost and significant divergence over multiple orbit cycles when calculating quasi-periodic DROs under the ephemeris model and proposes an adaptive two-level differential correction algorithm based on differential evolution. The traditional two-level differential correction selects patch points at equal intervals, while the DRO states are different with different amplitudes, choosing patch points at equal intervals is simple but not suitable for most DRO. Each quasi-periodic DRO should have its own patch points position. The adaptive two-level differential correction algorithm firstly uses differential evolution to obtain the optimal solution of the position of the patch points and then two-level differential correction is played. This algorithm significantly improving both computational efficiency and orbital convergence. Simulation results show that this algorithm significantly reduces computational costs and achieves better convergence compared to traditional two-level differential correction algorithm. This study has a reference value for the design of long-term quasi-periodic DRO, and provides a new idea for the selection strategy of patch points in the two-level differential correction algorithm and the multiple shooting algorithm.

The problem of controlling the relative position and velocity in multi-spacecraft formation flying in the planetary orbits is an enabling technology for current and future research. This paper proposes a family of tracking controllers for different dynamics of Spacecraft Formation Flying (SFF) in the framework of port-Hamiltonian (pH) systems through application of timed Interconnection and Damping Assignment Passivity-Based Control (IDA-PBC). The leader–multi-follower architecture is used to address this problem. In this regard, first we model the spacecraft motion in the pH framework in the Earth Centered Inertial frame and then transform it to the Hill frame which is a special local coordinate system. By this technique, we may present a unified structure which encompasses linear/nonlinear dynamics, with/without perturbation. Then, using the timed IDA-PBC method and the contraction analysis, a new method for controlling a family of SFF dynamics is developed. The numerical simulations show the efficiency of the approach in two different cases of missions.