Large Satellite Research Articles

Morphology and Kinematics of the Gas in M51: How Interaction with NGC 5195 Has Molded the Structure of Its Arms

The Whirlpool Galaxy is a well-studied grand design galaxy with two major spiral arms, and a large satellite NGC 5195. The arms both show long uniform sections with perturbations (“kinks” or sharp turns) in specific regions. Comparing the two arms shows a small radial offset between the main kinked regions. We analyzed the morphology and also the velocity field in the disk of M51 using kinematic maps based on Hα and CO line emission. These sample complementary radial ranges, with the CO map covering the central zone and the Hα map extending to cover the outer zone. We looked for indicators of density wave resonance, zones where radial flows of gas in the disk plane reverse their sign. These were present in both velocity maps; their 2D localization placed them along or closely parallel to the spiral arms, at a set of well-defined galactocentric radii, and notably more concentrated along the southern, stronger arm. The results can be well interpreted quantitatively, using a numerical model of the interaction of M51 and NGC 5195 in which the satellite has made two relatively recent passes through the disk plane of M51. During the first pass the pair of dominant spiral arms was stimulated, and during the second pass the strong kinks in both arms were formed at about the same time. The second interaction is particularly well characterized, because the timescale corresponding to the production of the kinks and the recovery of the original pitch angle is identical for the two arms.

Feasibility of high temperature superconducting cables for energy harvesting in large space-based solar power satellite applications: Electromagnetic, thermal and cost considerations

The aim of this paper is to present feasibility of application of High Temperature Superconducting (HTS) cables for Space-Based Solar Power (SBSP) application. SBSP is a promising technology that can deliver an infinite amount of clean and eco-friendly energy to the Earth. To deliver the harvested solar energy to the power systems on Earth, efficient energy transmission is critically important. To address the challenges of conventional transmission means, an ideal solution would be using HTS cables. In this research, the design procedure of a Direct Current (DC) HTS cable considering electromagnetic, thermal, and cost constraints is presented. The study considered a 2 MW bipolar DC HTS cable in five operational temperatures: 20 K, 30 K, 50 K, 65 K, and 77 K. The results were showed that the cost and weight of the designed HTS cables were increased by operational temperature increase. However, the cooling cost of HTS cable in higher temperatures, was less than lower temperatures. Also, the total efficiency of the HTS cable and cooling system were increased, when operational temperatures were changed from 20 K to 77 K, from 99.70% to 99.97%, respectively.

Poverty Detection Using Satellite Imagery

As the universe finds it challenging to define poverty, the world bank views poverty as anyone living below $2 per day. Government and international organizations are working to eradicate this poverty. The study reviews some research on satellite images on the prediction of poverty through the concept of CNN. The study split the datasets satellite images of four (4) countries: Nigeria, Mali, Malawi, and Ethiopia obtained from Kaggle in 90% for training with 15% of it for validation and 10% for testing. The datasets were analyzed using CNN, VGG16, ResNet50, which shows that the VGG16 model performs better than the other two models with the validation accuracy of 94%, while CNN has 91%. ResNet has the lowest validation accuracy of 62%. The rise of high-resolution satellite images that contain extensive data of regions or countries' patterns, features, and landscapes can be applied to determine the economic livelihood of people or nations. The application of satellite images to the prediction of poverty is much easier, faster, and less expensive compared to more the prediction becomes more accessible. This study recommends the need for the availability of large satellites images for every region or country. Future researchers should focus on satellite images to predict poverty and the application of satellite images in detecting crime, road traffic, agricultural soil, and the like. Key Words: Convolutional Neural Network, Residual Network, Satellite Images, Architectural Neural Network, Support Vector Machine, Visual Geometry Group.

Multi-objective integrated attitude control of large solar power satellite: A distributed incremental predictive approach

This paper addresses the multi-objective integrated attitude control problem of a large solar power satellite (SPS) in the presence of time-varying parameters, disturbances, and actuator saturation. The attitude coupling dynamic model, which could accurately describe the rotational motion of different SPS components, is firstly obtained. The gravity gradient, solar radiation pressure, microwave radiation reflection, and friction torques are investigated to evaluate their influence on attitude control accuracy. The coupling dynamic model is linearized and discretized, which provides a subsystem model for distributed controller design. A distributed incremental predictive controller is designed for each rotation channel to form a distributed system. The augmented system state is defined to solve the complex constraint problem, and the predicted value with feedback correction is introduced to deal with the disturbances. Besides, the stability of the system is analyzed by considering external disturbances and actuator failure. Comparative analysis with centralized methods under the same prediction horizon is provided, and the results demonstrate a tenfold solution performance enhancement while maintaining accuracy. Furthermore, the controller is integrated with feedback correction, which could improve control accuracy by at least one order of magnitude. The proposed controller reduces the adjusting time for attitude stabilization by 56.8 % in the presence of actuator failure. The simulation results demonstrate that the proposed controller has good robustness and fault tolerance, which provides a feasible solution for SPS multiple attitude control missions.

Satellite Visibility During the 2024 April Total Eclipse

On 2024 April 8, tens of millions of people across North America will be able to view a total solar eclipse. Such astronomical events have been important throughout history, but with nearly 10,000 satellites in orbit, we question whether total eclipses will now reveal a sky full of satellites, fundamentally changing this experience for humanity. Using the current population of Starlink satellites, we find that the brightest satellites would be naked-eye visible in dark skies, but the high sky brightness during totality will make them undetectable to the unaided eye. Our model does not take into account the effects of chance reflections from large, flat surfaces like solar panels, which we expect will cause glints and flares that could be visible from large satellites and abandoned rocket bodies. Time-lapse all-sky imaging might reveal satellites during the eclipse.

An Automated Wayfinding Algorithm to Find Rovers' Path on the Lunar South Pole

As a part of the upcoming Artemis mission, NASA released a large satellite dataset (latitude, longitude, height, and slope) of the lunar south pole, around the area of the lunar module landing site and rover exploration site near the Shackleton Crater. While designing the rover, it’s important to understand the minimum power the rover needs (the amount of slope it can overcome) to navigate the terrain. Our goal was to process the data, visualize the data in 2-D and 3-D, and develop an algorithm that would automatically map the shortest possible path (or no possible path) between two coordinates according to the lunar terrain and rover parameters. To accomplish that, we processed a large unorganized dataset into an equally spaced and sequential matrix of latitude, longitude, height, and slope. The matrix was then converted into a go/no-go maze of the terrain and the Breadth First Search (BSF) and A* algorithms were applied to the maze to find the optimal path. The terrain and the optimal path were plotted in 2-D using Matplotlib and interactively displayed in 3D using Plotly. We developed a Jupyter Notebook web-based app that will allow a user to interactively use the algorithm and visualize the lunar terrain. The results identify the minimum rover slope and various paths depending on higher rover slopes. The algorithm and the rover paths were validated by the NASA SCaN (Satellite Communication and Navigation) team of engineers and the application can be used for design, validation, and training purposes.

Clues to the Origin of Jovian Outer Irregular Satellites from Reflectance Spectra

Visible/near-infrared narrowband spectroscopy (dispersion per element ∼ 6 Å) was obtained of the Jovian irregular satellites JVI Himalia, JVII Elara, JVIII Pasiphae, JIX Sinope, JX Lysithea, JXI Carme, JXII Ananke, and JXVII Callirrhoe in 2006, 2009, and 2010 using the MMT Observatory Red Channel spectrograph. These spectra sample three prograde (i = 28°), four retrograde (i = 149° and 165°), and one independent satellite. Our results suggest that the prograde cluster satellites represent fragments probing the cluster’s original parent body, with the largest satellite, Himalia, being the core of the parent body, while Elara preserves the geochemical/mineralogical transition between the core and an outer layer of the body, and Lysithea formed farther from the center of the parent body. The spectral signatures suggest that the prograde parent body fragmented in the early stages of aqueous alteration. This supports the change from more organic-rich material at Lysithea to more carbonized material at Himalia, consistent with weathering/processing of a carbon-bearing material at Himalia. At twice the distance from Jupiter, the retrograde cluster anchored by Pasiphae also suggests that Ananke preserves the transition between the core and an outer layer of a parent body. Both Sinope and Carme are similar to D-class asteroids. Bluing/flattening near 0.4–0.5 μm in Carme’s spectrum suggests a carbonized component to Carme’s surface material, consistent with greater levels of weathering/processing. Sinope’s red spectrum is consistent with broadband photometry and does not confirm or negate the proposal that it had a common parent body with the Pasiphae cluster.

Continuum Modeling and Boundary Control of a Satellite with a Large Space Truss Structure

Due to its advantages of easy deployment and high stiffness-to-mass ratio, the utilization of truss structures for constructing large satellites presents an appealing solution for modern space missions, including Earth observation and astronomy. However, the dimensions of the traditional finite element model for a satellite with a large space truss structure become exceedingly large as the structure’s size increases. The control system design process based on the finite element model is complex and time-consuming. This paper employs the continuum modeling method to represent the truss structure as a continuous entity. The bending vibrations of the truss structure are encapsulated by a simplified partial differential equation (PDE), as opposed to the more intricate traditional finite element model. Simultaneously, the satellite’s attitude motion is characterized by an ordinary differential equation (ODE). Building upon this coupled PDE-ODE model, a boundary control law that only requires sensors/actuators at the boundary is formulated to effectively mitigate structural vibrations and regulate the satellite’s attitude. The exponential stability of this closed-loop system is scrutinized using Lyapunov’s direct method. The simulation results affirm that the continuum modeling method is indeed well-suited for satellites endowed with substantial truss structures, and the proposed boundary law proves to be highly effective in both attitude tracking and vibration suppression.

Guidance and Control Systems for Multi-Satellite Assembly using Decentralized Nonlinear Model Predictive Control

Assembly of multiple satellites enables to replace the functionality of one large satellite by multiple smaller satellites for many applications and missions such as formation flying, multi robot planetary exploration, and satellites warms. In this paper, a novel decentralized guidance and control (G&C) algorithms is developed for multi-satellite assembly in proximity operations based on Non linear Model Predictive Control (NMPC).The two-body relative motion model is utilized in designing the G&C systems. Decentralization avoids the single point of failure (i.e., the leader satellite), which enhances the robustness of the system. The NMPC is utilized because of itsability to handle the output and the input constraints. Collision avoidance is ensured by defining a quadratic constraint equation. Moreover, the optimal thrust vector is computed while considering the control input saturation. The mission is to assemblemultiple satellites into a cubic configuration, where each satellite approaches a cube vertex. Totes the algorithms’ effectiveness and to increase the level of confidence prior flight, the proposed closed-loop G&C system is demonstrated by using MATLAB andtested for a relative motion model with J2 perturbation. The simulation results showsmooth conversion of all satellites to the target while satisfying the input and outputconstraints.

On the Origin of the Moon and the Continents

All astronomical bodies originate inside clouds of gas and dust, therefore there should be a common process that leads to their condensation. In a galactic cloud there is always a gradient of speeds from point to point. Thanks to it, vortices originate that rake the material of the surrounding cloud gradually forming large gaseous disks, inside which vortices of second order develop that concentrate the matter of their orbits forming smaller and much denser disks, within which third order vortices further concentrate the matter. The dense cores of these vortices finally condense in massive bodies: sun, planets and satellites. The result should be a well ordered planetary system with no “debris” around and where both planets and satellites obey to a precise rule of the distances from their central body. The solar system complies with these conditions with three main exceptions. First, in an orbit where a large planet should be there is only a huge number of scattered asteroids. Second, Earth and its moon with all evidence were not formed in the same vortex, which means that Moon originated somewhere else. Third, Neptune’s satellite system has been shattered by the intrusion of a foreign body, Triton, and its largest satellites are missing. These exceptions seem to be strictly connected to each other and all due to a unique event, that is: Triton has diverted the largest Neptune satellite towards the Sun. This satellite impacted at high speed against the missing planet, scattering myriads of fragments from its mantle and pushing it towards the sun, where it eventually fell. The planet had at least 4 satellites some of which remained in their previous orbit, but two of them were dragged towards the sun and were captured by Earth. The largest became its lonely moon while the second fell on its surface giving origin to the continents. This event happened about 3,96 billion of years ago, as it is proven by the ages of the numerous samples brought from the moon.

SatERR: A Community Error Inventory for Satellite Microwave Observation Error Representation and Uncertainty Quantification

Abstract Satellite observations are indispensable for weather forecasting, climate change monitoring, and environmental studies. Understanding and quantifying errors and uncertainties associated with satellite observations are essential for hardware calibration, data assimilation, and developing environmental and climate data records. Satellite observation errors can be classified into four categories: measurement, observation operator, representativeness, and preprocessing errors. Current methods for diagnosing observation errors still yield large uncertainties due to these complex errors. When simulating satellite errors, empirical errors are usually used, which do not always accurately represent the truth. We address these challenges by developing an error inventory simulator, the Satellite Error Representation and Realization (SatERR). SatERR can simulate a wide range of observation errors, from instrument measurement errors to model assimilation errors. Most of these errors are based on physical models, including existing and newly developed algorithms. SatERR takes a bottom-up approach: errors are generated from root sources and forward propagate through radiance and science products. This is different from, but complementary to, the top-down approach of current diagnostics, which inversely solves unknown errors. The impact of different errors can be quantified and partitioned, and a ground-truth testbed can be produced to test and refine diagnostic methods. SatERR is a community error inventory, open-source on GitHub, which can be expanded and refined with input from engineers, scientists, and modelers. This debut version of SatERR is centered on microwave sensors, covering traditional large satellites and small satellites operated by NOAA, NASA, and EUMETSAT.

Anti-satellite weapon tests to disrupt large satellite constellations

Anti-satellite weapon tests to disrupt large satellite constellations

Hybrid control of attitude maneuver and structural vibration for a large phased array antenna satellite

This paper focuses on the study about hybrid control strategy of attitude maneuver and structural vibration for a large phased array antenna satellite. The satellite system is equipped with cable actuators in the antenna structure and control moment gyros on the central satellite. Firstly, the rigid-flexible coupling dynamic model of the entire satellite system is established based on the hybrid coordinate method. Then a control strategy is presented which could realize the ideal attitude maneuver of satellite while suppressing the structural vibration simultaneously. The proposed strategy is contained of two parts: the attitude controller is designed based on the computed torque method, and the vibration controller is achieved by using a piecewise cost function which could ensure the unidirectional and saturated constraints of cable actuators. Finally, numerical simulations of a large antenna satellite model demonstrate that the structural vibration during the attitude maneuver process can be suppressed effectively by applying the proposed control strategy.

DSHFS: a new hybrid approach that detects structures with their spatial location from large volume satellite images using CNN, GeoServer and TileCache

DSHFS: a new hybrid approach that detects structures with their spatial location from large volume satellite images using CNN, GeoServer and TileCache

Processes Controlling the Seasonally Varying Emergence of Forced Arctic Longwave Radiation Changes

Abstract Most observed patterns of recent Arctic surface warming and sea ice loss lie outside of unforced internal climate variability. In contrast, human influence on related changes in outgoing longwave radiation has not been assessed. Outgoing longwave radiation captures the flow of thermal energy from the surface through the atmosphere to space, making it an essential indicator of Arctic change. Furthermore, satellites have measured pan-Arctic radiation for two decades while surface temperature observations remain spatially and temporally sparse. Here, two climate model initial-condition large ensembles and satellite observations are used to investigate when and why twenty-first-century Arctic outgoing longwave radiation changes emerge from unforced internal climate variability. Observationally, outgoing longwave radiation changes from 2001 to 2021 are within the range of unforced internal variability for all months except October. The model-predicted timing of Arctic longwave radiation emergence varies throughout the year. Specifically, fall emergence occurs a decade earlier than spring emergence. These large emergence timing differences result from seasonally dependent sea ice loss and surface warming. The atmosphere and clouds then widen these seasonal differences by delaying emergence more in the spring and winter than in the fall. Finally, comparison of the two ensembles shows that more sea ice and a more transparent atmosphere during the melt season led to an earlier emergence of forced longwave radiation changes. Overall, these findings demonstrate that attributing changes in Arctic outgoing longwave radiation to human influence requires understanding the seasonality of both forced change and internal climate variability.

Radiation Oncology Practice Changes during the COVID-19 Pandemic

The purpose of this study was to characterize the effects of institutional policies routine SARS-CoV-2 testing before treatment starts with mandatory quarantine periods for COVID-positive patients during the first year of the COVID19 pandemic across radiation oncology sections at our tertiary cancer center. Electronic medical databases were queried to identify all patients treated with curative intent at a large urban cancer center and regional satellites a year prior to the pandemic (02/11/19-12/30/19; pre-pandemic) and the first year of the pandemic (03/11/20-12/30/20; post-pandemic). New treatment starts were filtered for those undergoing treatment under a single ICD-10 diagnosis and the first treatment in each time period for each patient. Chi-square tests were used for categorical variables, and the t-test was used for continuous variables to correlate differences in demographic and clinical factors before and during the pandemic. The total number of new treatment starts were similar between the pre-pandemic (2,218 patients) and post-pandemic (2,130 patients) periods, but there was a 26% decrease in treatments in April 2020 compared to April 2019 and a 40% increase in treatments in November 2020 compared to November 2019. Post-pandemic patients had higher minimum Charlson Comorbidity Index scores (mean 46.0 vs 42.6, P = 0.0013) and were younger (62.8 yo vs 64.3 yo, P = 0.0001). The proportion of patients being treated from the same state as our institution was higher in the post-pandemic period compared to pre-pandemic (77.8% vs 72.43%, P = 0.0259). Distribution of treatments across department disease-site sections were significantly different (P<0.0001), with the proportion of patients treated by the Breast service having increased by 22% whereas the metropolitan area regional satellites experienced a 18% reduction. There were no statistically significant differences amongst pre- and post-pandemic patients with respect to race, marital status, or smoking status. Post-pandemic patients had less total radiation-related clinical visits (mean 24.8 vs 28.6, P<0.0001), lower administered dose (4329 cGy vs 4533 cGy, P<0.0001), and lower radiation fraction count (17 vs 19, P<0.0001). There was no statistically significant difference in the duration between CT simulation and treatment start, but post-pandemic patients had shorter duration of elapsed days during treatment (27 days vs 29 days, P = 0.0001). A disease-site-specific analysis demonstrated that these differences were most pronounced in patients treated for breast cancer. In the first year of the COVID19 pandemic, our institution saw a dynamic change in the number of new radiation treatments. Additional analyses across individual disease-specific services may reveal insight into dose, fractionation, and technique, which may account for the observed differences.

Moving morphable components structural optimum approach considering wire arc additive manufacturing constraint and its application in satellite

The thin-walled reinforced structure is important for achieving structural lightweight in spacecraft. With the rapid development of additive manufacturing technology, large-size, thin-walled, stiffened structures with complex structural forms can be manufactured. However, topology optimization considering manufacturing constraints has always been difficult in this field. This paper proposes a design method for reinforced structures that enables control over structural connectivity based on the Moving Morphable Components (MMC) method, which uses reinforced components with explicit geometrical parameters as primitives for topology optimization. The proposed method solves the challenges of rapidly designing complex geometric reinforcements, forming clear force transfer paths, and effectively reduces the structural topology optimization challenges caused by process constraints associated with the arc start/quench process of wire arc additive manufacturing (WAAM). This method was used to design a core load-bearing structure of a large satellite, i.e., the 3.5-meter tank supporting structure, which was fabricated by the WAAM process for the first time in the spacecraft field. The structure passed the mechanical test and eventually achieved a weight reduction of 31.6%.

Single Object Tracking in Satellite Videos Based on Feature Enhancement and Multi-Level Matching Strategy

Despite significant advancements in remote sensing object tracking (RSOT) in recent years, achieving accurate and continuous tracking of tiny-sized targets remains a challenging task due to similar object interference and other related issues. In this paper, from the perspective of feature enhancement and a better feature matching strategy, we present a tracker SiamTM specifically designed for RSOT, which is mainly based on a new target information enhancement (TIE) module and a multi-level matching strategy. First, we propose a TIE module to address the challenge of tiny object sizes in satellite videos. The proposed TIE module goes along two spatial directions to capture orientation and position-aware information, respectively, while capturing inter-channel information at the global 2D image level. The TIE module enables the network to extract discriminative features of the targets more effectively from satellite images. Furthermore, we introduce a multi-level matching (MM) module that is better suited for satellite video targets. The MM module firstly embeds the target feature map after ROI Align into each position of the search region feature map to obtain a preliminary response map. Subsequently, the preliminary response map and the template region feature map are subjected to the Depth-wise Cross Correlation operation to get a more refined response map. Through this coarse-to-fine approach, the tracker obtains a response map with a more accurate position, which lays a good foundation for the prediction operation of the subsequent sub-networks. We conducted extensive experiments on two large satellite video single-object tracking datasets: SatSOT and SV248S. Without bells and whistles, the proposed tracker SiamTM achieved competitive results on both datasets while running at real-time speed.

Energetic material characterization and ignition study of MEMS based micro-thruster for multi spacecrafts missions

Over the past few years, there has been a growing recognition of the importance of multi-spacecraft missions for a variety of purposes, including Earth observation, navigation, guidance, climate monitoring, and environmental monitoring. The trend amongst agencies is to favour constellations of smaller satellites, which can aggregate data from various sources, rather than relying on larger satellites. The numerous benefits of multi-spacecraft formation flying missions have led to an increasingly growing interest to explore its propulsion technologies, i.e., micro propulsion. Thoroughly characterising and studying the behaviour of the energetic materials is essential to ensure the safe and effective use of these micro-thrusters. Through the optimisation of micro-thruster design, the current research aims to generate outcomes that can be utilised to enhance the design and optimisation processes. Consequently, this will facilitate the widespread utilisation of micro-thrusters in multi-spacecraft missions. To optimise the performance of pyrotechnic micro-electromechanical systems, an efficient heater design, appropriate base material, channel dimensions, and electrical resistance must be considered based on available power and heat transfer requirements. A unique firing and monitoring test setup has been developed to produce a current-time plot for the device. Additionally, different micro-heater configurations, including spiral, loop, and meander types, were designed for the igniter. Experimental observations indicate that the spiral micro-heater design resulted in the lowest ignition delay and produced highly reliable combustion. The proposed microthruster design demonstrated efficient combustion and yielded promising results when tested with energetic materials such as Zirconium Potassium Perchlorate (ZPP) and Boron Potassium Perchlorate (BPN).

Explanation of the Anomalous Outburst Activity of Comet 29P/Schwassmann–Wachmann 1: The Hypothesis about the Existence of Large Satellites

Explanation of the Anomalous Outburst Activity of Comet 29P/Schwassmann–Wachmann 1: The Hypothesis about the Existence of Large Satellites