Large Satellite Research Articles

Radiometric Normalization Using a Pseudo−Invariant Polygon Features−Based Algorithm with Contemporaneous Sentinel−2A and Landsat−8 OLI Imagery

As sensor parameters and atmospheric conditions create uncertainties for at−sensor radiation detection, radiometric consistency among satellite images is difficult to achieve. Relative radiometric normalization is a method that can improve multi−image consistency with accurate pseudo−invariant features (PIFs), especially over large areas or long time series satellite images. Although there are algorithms that manually or automatically select PIFs, the spatial mismatch of satellite images can affect PIF extraction, particularly with artificial pixels. To alleviate this problem, we proposed to use Landsat−8 OLI as the reference image and Sentinel−2A as the subject image, to apply pseudo−invariant features−based algorithms with polygon features through the single−band and multiple−band regression. Compared to pseudo−invariant point features, hyperspectral library, and histogram matching approaches, the results demonstrate the superiority of the proposed algorithms with correlation coefficients of 0.9948 and 0.9945, and an RMSE of 0.0097 and 0.0095 with multiple− and single−band regression, respectively. We also found more accurate linear fitting and better shape matching through band scattering and reflectance frequency analysis. The proposed algorithms are a significant improvement in radiometric normalization, within artificial pixels, achieving spectral signature consistency.

Numerical Solving of Radiation Geometrical Inverse Problem

Compared to large satellites, on-board electronics of microsatellites, such as microprocessors, are more exposed to radiation and high-energy particles. This problem can lead to single-event upsets, which might generate false commands such as thruster firing or switching heaters on or off. In some cases, these upsets cause the loss of a spacecraft orientation and endanger the whole mission. This makes important to elaborate a reliable and robust attitude determination system which will enable us to correct and recover the spacecraft’s attitude after a failure. It must have a simple design, low mass, and power consumption. In this paper we suggest a new method of determination of spacecraft’s attitude based on heat fluxes analysis that could form the basis of such a system. In order to develop it we have to solve two inverse problems sequentially. The first inverse problem is the estimating of heat fluxes absorbed by the spacecraft surface. The second one is to determine the spacecraft’s attitude based on the estimated values of radiative heat fluxes. This paper is dedicated to the solution of the second inverse problem.

Atmospheric humidity and temperature sounding from the CubeSat TROPICS mission: Early performance evaluation with MiRS

Atmospheric humidity and temperature are the two most important geophysical variables for numerical weather forecasting and relevant Earth studies, contributing to the reduction of over 60% forecast errors. Conventional large satellite microwave radiometers provide the primary sounding data of moisture and temperature, with the V-band (near 50 GHz) and G-band (near 183 GHz) as the main spectra. In recent years, CubeSats are rapidly developing with compact sizes, novel designs, and low cost. The NASA TROPICS is an ongoing CubeSat constellation mission for studying tropical meteorology and storm systems, with the first Pathfinder satellite launched on 30 June 2021, which will provide a median revisit rate better than 60 min. TROPICS has innovative channels at F-band (near 118 GHz) and 205 GHz, providing a new perspective for atmospheric sounding. In this study, we have extended the NOAA MiRS system and applied it to TROPICS Pathfinder early-phase, provisionally calibrated data, focusing on moisture and temperature. We have examined the retrieval quality and compared with the ECMWF analysis and MiRS retrievals from NOAA-20 ATMS. An experiment of subsetting ATMS to match up with TROPICS channels is also conducted. Here we focus on atmospheric humidity and temperature retrievals, since they are of primary importance for microwave sounders and is tied to the core of the TROPICS mission along with precipitation retrieval. Compared to traditional channels, TROPICS F-band and 205 GHz provide new information content with distinct sensitivity to moisture and hydrometeors, showing for example over 20 K larger dynamic range of brightness temperature at 205 GHz compared to 190 GHz. The retrieved total precipitable water compared to ECMWF has a correlation coefficient of 0.955, 0.985, and 0.977 for TROPICS, ATMS, and ATMS subset, respectively. For water vapor profile, the standard deviation of retrieval to ECMWF is 0.93, 0.76, and 0.80 g/kg for the three experiments, respectively, and regarding temperature, it is 2.5, 1.5, and 1.6 K, respectively. The retrieval shows dependence on surface type and clouds, where land and cloudy conditions degrade retrieval compared to ocean and clear condition. The early performance is promising, and the successful MiRS extension paves the way to explore improved data when the calibration validation is complete and from the forthcoming constellation.

Structural Analysis of Airplane Wing Using Composite and Natural Fiber Materials: A Survey

Abstract: Natural fiber-reinforced polymer-based composites are increasingly used in modern society due to their numerous benefits for uses in mechanical engineering. Polymer-based composite materials are widely employed in civil construction, automotive, aerospace, and many other industries due to their many benefits. Natural fibers can be used to create new, highperformance polymer materials because they are affordable, environmentally friendly, renewable, and partially and fully biodegradable. Examples of these fibers include EGR Glass R Glass, Carbon fiber, and S Glass, as well as kenaf, pineapple, sugarcane, hemp, oil palm, flax, and leaf. The purpose of this study is to explore the use of natural fibers and composites in the production of airplane wings, including mechanical characteristics, applications, and potential as well as problems and future demand for natural composite materials for engineering uses. A good 50% of the airspace's components are natural composites. Because natural composites have the ability to lower aircraft weight, they are currently being used to construct helicopters, military fighter aircraft, small and large civil transport aircraft, cockpits, satellites, launch vehicles, and missiles. Rudder, spoilers, LG doors, keel beam, airbrakes, elevators, turbine engine fan blades, propellers, rear bulkhead, wing ribs, main wings, interior fixtures, etc. Composites made of natural fibers are attractive and promising. The use of natural fiber-based composite materials is growing daily due to their strength and integrity. The natural fiber is a renewable, environmentally beneficial, and biodegradable raw material. Both its mechanical and thermal insulation qualities are strong in natural fiber. However, the loading placed on the natural fiber and its youthful modulus determines its strength In addition to discussing the benefits of natural fibers over other materials, this paper provides a description of the several types of natural fiber, their physical and mechanical properties, and their advantages.

Evidence of electron correlation and weak bulk plasmon in SrMoO3

We investigate the electronic structure of highly conducting perovskite SrMoO3 using valence band photoemission spectroscopy and electronic structure calculations. Large intensity corresponding to coherent feature close to Fermi level is captured by density functional theory (DFT) calculation. An additional satellite at ∼3 eV binding energy remains absent in DFT, hybrid functional (DFT-hybrid) and dynamical mean field theory (DFT + DMFT) calculations. Mo 4d spectra obtained with different surface sensitive photoemission spectroscopy suggest different surface and bulk electronic structures. DFT + DMFT spectral function is in excellent agreement with the coherent feature in the bulk Mo 4d spectra, revealing moderate electron correlation strength. A large plasmon satellite and signature of strong electron correlation are observed in the surface spectra, while the bulk spectra exhibits a weak plasmon satellite.

Droplet size distribution in a swirl airstream using in-line holography technique

We investigate the morphology and size distribution of satellite droplets resulting from the interaction of a freely falling water droplet with a swirling airstream of different strengths by employing shadowgraphy and deep-learning-based digital in-line holography techniques. We found that the droplet exhibits vibrational, retracting bag and normal breakup phenomena for the no swirl, low and high swirl strengths for the same aerodynamic field. In the high-swirl scenario, the disintegrations of the nodes, rim and bag-film contribute to the number mean diameter, resulting in smaller satellite droplets. In contrast, in the low-swirl case, the breakup of the rim and nodes only contributes to the size distribution, resulting in larger droplets. The temporal variation of the Sauter mean diameter reveals that for a given aerodynamic force, a high swirl strength produces more surface area and surface energy than a low swirl strength. The theoretical prediction of the number-mean probability density of tiny satellite droplets under swirl conditions agrees with experimental data. However, for the low swirl, the predictions differ from the experimental results, particularly due to the presence of large satellite droplets. Our results reveal that the volume-weighted droplet size distribution exhibits two (bi-modal) and three (multi-model) peaks for low and high swirl strengths, respectively. The analytical model that takes into account various mechanisms, such as the nodes, rim and bag breakups, accurately predicts the shape and characteristic sizes of each mode for the case of high swirl strength.

Quasi-Geostationary Earth Orbits for Space Solar Power Infrastructure and Other Low Area Density Satellites

This paper explains non-Keplerian orbital behavior for thin, large earth-based satellites with very low area density. We demonstrate a unique new solution that produces a new, quasi-geostationary earth orbit (QGEO) that can help with economical deployment of space solar power satellites as well as the mitigation of space debris for all satellites.

SiamMDM: An Adaptive Fusion Network With Dynamic Template for Real-Time Satellite Video Single Object Tracking

Tracking moving targets in satellite videos has attracted wide attention recently. However, the development of target tracking in satellite videos is much slower than that in general videos for the following key reasons. First, typical moving objects in satellite videos consist of few pixels and lose most of their appearance features, making it difficult for the tracker to distinguish the target from the background. Second, the appearance of satellite video objects often changes due to occlusion, illumination variation, or other factors. Classic Siamese tracking networks only use the first frame as the target template, leading to poor tracking results. Third, when the target is fully occluded, it is difficult for the tracker to recapture the target. To address the above problems, we propose a Siamese tracking network based on multiple(M) response map fusion and spatiotemporal constraints in this paper. By generating response maps at different layers of the tracking network and fusing them adaptively, small objects in the satellite videos can be tracked more accurately. Furthermore, a dynamic(D) template update strategy is proposed to cope with possible changes in the appearance of objects in satellite videos, preventing the high dependence on the initial frame. To recapture the target, a score-guided target motion(M) trajectory prediction model is proposed. We call the proposed Siamese tracking network SiamMDM for short. We conducted complete experiments on SatSOT and SV248S, two large satellite video target tracking datasets. The results show that our method achieves state-of-the-art tracking performance while running at over 110 FPS.

A STUDY ON THE RECENT ADVANCES IN THE DESIGN OF MEMS-BASED SOLID MICROTHRUSTERS

In the past few decades, space technology has moved toward using many small satellites working in a cluster instead of making individual satellites for space missions. Nano or microsatellites increase the reliability of the mission while minimizing cost, rather than having one large satellite increasing both the cost and the failure risk for any given space mission. Considering the case of a small satellite cluster, it is easy to manage mission requirements with less complexity during any hazard, compared to an individual satellite. All of this has led to the increasing application of micro and nanosatellites in space engineering. These small satellites are propelled by micropropulsion created by microthrusters. Currently, liquid, gas, and electrical thrusters are the most common. This paper mainly describes the recent advancements in the field of MEMS microthrusters. MEMS (microelectromechanical system) thrusters are used in small satellites in a variety of ways that require very little thrust. In the paper discussion, MEMS-based solid-propellant microthrusters (SPMs) are delineated. All advancements in the MEMS solid thrusters are indicated in the article, dedicated to mounting schemes, designing approaches, and various performance testing experiments. The main challenge in this technology is combustion, which takes place in an exceptionally small volume.

Large Scale LEO Satellite Networks for the Future Internet: Challenges and Solutions to Addressing and Routing

This document analyses the problems and challenges of addressing and routing to Low Earth Orbit (LEO) satellites used for the future Internet. It focuses on the scenario where Inter-Satellite-Links (ISL) are used for massive LEO satellite constellation. Such LEO satellite network is the key to the Non-terrestrial Network (NTN) integration with 5G and beyond. The paper describes two categories of solutions. One is based on IPv6 and another is based on a new protocol, New IP. The two categories of solutions are a) using new types of addresses for LEO satellites and b) new concepts for routing with these addresses. The semantic addressing scheme leverages the characteristics of satellites with known orbit elements; and simplifies the satellite identification by using limited indexes. The routing method combines semantic addressing with source routing and generates a new semantic routing scheme. Compared with traditional methods, the new proposals dramatically reduce the workload in satellite, such as table size, Ternary Content-addressable memory (TCAM) lookups, and packet header size. Thus it is more suitable to networks in space where the harsh environment limits the hardware performance, power consumption, link bandwidth and system complexity.

Transmit Beampattern Design for Distributed Satellite Constellation Based on Space–Time–Frequency DoFs

For distributed satellite constellations, detection performance can be equivalently regarded as a single large satellite by the cooperative operation of multiple small satellites, which is a promising research topic of the Next-Generation Radar (NGR) system. However, dense grating lobes inevitably occur in the synthetic transmit pattern due to its distributed configuration, as a result of which the detection performance of dynamic coherent radar is seriously weakened. In this paper, a novel transmit beampattern optimization method for dynamic coherent radar based on a distributed satellite constellation is presented. Firstly, the effective coherent detection range interval is determined by several influence factors, i.e., coherent detection, far-field, and system link constraints. Then, we discuss the quantitative evaluation method for coherent integration in terms of synchronization error, beam pointing error, and high-speed motion characteristics and we allocate the corresponding terms in a reasonable way from the perspective of engineering. Finally, the space–time–frequency degrees of freedom (DOFs), which can be collected from satellite spacing, carrier frequencies, and platform motion characteristics, are utilized to realize a robust transmit beampattern with low sidelobe by invoking a genetic algorithm (GA). Simulation results validate the effectiveness of our theoretic analysis, and unambiguous coherent transmit beamforming with a satellite constellation of limited scale is accomplished.

REDS: Random ensemble deep spatial prediction

AbstractThere has been a great deal of recent interest in the development of spatial prediction algorithms for very large datasets and/or prediction domains. These methods have primarily been developed in the spatial statistics community, but there has been growing interest in the machine learning community for such methods, primarily driven by the success of deep Gaussian process regression approaches and deep convolutional neural networks. These methods are often computationally expensive to train and implement and consequently, there has been a resurgence of interest in random projections and deep learning models based on random weights—so called reservoir computing methods. Here, we combine several of these ideas to develop the random ensemble deep spatial (REDS) approach to predict spatial data. The procedure uses random Fourier features as inputs to an extreme learning machine (a deep neural model with random weights), and with calibrated ensembles of outputs from this model based on different random weights, it provides a simple uncertainty quantification. The REDS method is demonstrated on simulated data and on a classic large satellite data set.

Satellite Constellation Avoidance with the Rubin Observatory Legacy Survey of Space and Time

We investigate a novel satellite avoidance strategy to mitigate the impact of large commercial satellite constellations in low-Earth orbit on the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). We simulate the orbits of currently planned Starlink and OneWeb constellations (∼40,000 satellites) to test how effectively an upgraded Rubin scheduler algorithm can avoid them, and assess how the overall survey is affected. Given a reasonably accurate satellite orbit forecast, we find it is possible to adjust the scheduler algorithm to effectively avoid some satellites. Overall, sacrificing 10% of LSST observing time to avoid satellites reduces the fraction of LSST visits with streaks by a factor of 2. Whether such a mitigation will be required depends on the overall impact of streaks on science, which is not yet well quantified. This is due to a lack of adequate information about satellite brightness distributions as well as the impact of glints and low surface brightness residuals on alert purity and systematic errors in cosmological parameter estimation. A significant increase in the number of satellites or their brightness during Rubin Operations may make implementing this satellite avoidance strategy worthwhile.

Revisiting the Cassini States of synchronous satellites with an angular momentum approach

AbstractLike our Moon, the large icy satellites of Jupiter are thought to be in a Cassini State, an equilibrium rotation state characterized by a synchronous rotation rate and a precession rate of the rotation axis equal to that of the normal to the orbit. In these equilibrium states (up to four Cassini States are possible for a solid and rigid satellite), the spin axis of the satellite, the normal to its orbit and the normal to the inertial plane remain coplanar with an obliquity that remains theoretically constant. However, as the gravitational torque exerted on the satellite shows small periodic variations, the orientation of the rotation axis will also vary with time and nutations in obliquity will appear.Here we present a dynamical model for the study of the Cassini States. This model includes the coupling between the polar motion and the spin axis precession/nutation which is neglected in the classical studies. We study the influence of the triaxiality of Ganymede on its four possible Cassini States, use a Toy model of the Moon to illustrate the nutations in obliquity obtained with the dynamical model, and investigate the influence of the presence of a subsurface ocean on the Cassini State I of Europa.

GENETIC ALGORITHM BASED FOPID CONTROLLER FOR NANO-SATELLITE ATTITUDE CONTROL

Nano-satellites are very popular among researchers today because they are more affordable and easier to use than most large satellites. The system performance on nano-satellites needs to be improved for better by using fractional order PID (FOPID) controllers which have never been tested on unstable systems on nano-satellite objects. The PID controller development produces two fractional power parameters called the FOPID controller, which makes it even more attractive. The genetic algorithm (GA) produces the optimal computation value on the FOPID controller because it has been proven to have better performance and is improved by the ITAE performance index. Based on the analysis of responses in a steady-state in the form of overshoot, rise time and settling time on the three-axis stabilized nano-satellite attitude control, namely roll, pitch, and yaw is concluded that the FOPID controller is superior to the classic PID controller that has been previously studied. The effect of the two parameters of the FOPID controller on an unstable system for nano-satellite attitude control shows good performance results based on the ITAE performance index using the genetic algorithm (GA) method.

Effective dust growth in laminar circumplanetary discs with magnetic wind-driven accretion

ABSTRACT It has been considered that large satellites around gas planets form in situ circumplanetary discs (CPDs). However, dust particles supplied into CPDs drift toward the central planets before they grow into satellitesimals, building blocks of the satellites. We investigate the dust growth in laminar CPDs with magnetic wind-driven accretion. In such laminar discs, dust particles can settle on to the mid-plane and grow large by mutual collision more efficient than in classical turbulent CPDs. First, we carry out 3D local MHD simulations of a CPD including all the non-ideal MHD effects (Ohmic resistivity, Hall effect, and ambipolar diffusion). We investigate if the disc accretion can be governed by magnetic wind-driven accretion and how laminar the disc can be, in a situation where the magnetic disc wind can be launched from the disc. Secondly, we model 1D steady CPDs consistent with the results of the MHD simulations and calculate the steady radial distributions of the dust profiles in the modelled discs, taking account of the collisional growth, radial drift, fragmentation, and vertical stirring by the Kelvin–Helmholtz instability. We show that satellitesimals can form in such CPDs if the dust-to-gas mass ratio of the inflow to the discs is larger than 0.02, which is 50 times smaller than the critical value in turbulent CPDs. This condition can be satisfied when enough amount of dust piles up at the gas pressure bump created by the planets. This result shows that satellitesimals would form in laminar CPDs with magnetic wind-driven accretion.

A correlation between accreted stellar kinematics and dark-matter halo spin in the artemis simulations

ABSTRACT We report a correlation between the presence of a Gaia-Sausage-Enceladus (GSE) analogue and dark-matter (DM) halo spin in the artemis simulations of Milky Way-like galaxies. The haloes which contain a large population of accreted stars on highly radial orbits (like the GSE) have lower spin on average than their counterparts with more isotropic stellar velocity distributions. The median modified spin parameters λ′ differ by a factor of ∼1.7 at the present day, with a similar value when the haloes far from virial equilibrium are removed. We also show that accreted stars make up a smaller proportion of the stellar populations in haloes containing a GSE analogue, and are stripped from satellites with stellar masses typically ∼4 times smaller. Our findings suggest that the higher spin of DM haloes without a GSE-like feature is due to mergers with large satellites of stellar mass ∼1010 M⊙, which do not result in prominent radially anisotropic features like the GSE.

Optimal deployment of satellite mega-constellation

This paper proposes an optimization framework to deploy a large satellite constellation. The proposed framework consists of two phases: the mission viability evaluation phase and the optimal planning phase. The feasibility of the constellation deployment architecture with given resources is assessed in the first phase. The second phase uses mixed-integer linear programming to optimize the satellite deployment plan based on a dynamic logistics model. The effectiveness of the proposed framework is demonstrated through a case study for optimal deployment planning of a large satellite constellation.

Stellar angular momentum can be controlled from cosmological initial conditions

ABSTRACT The angular momentum of galaxies controls the kinematics of their stars, which in turn drives observable quantities such as the apparent radius, the bulge fraction, and the alignment with other nearby structures. To show how angular momentum of galaxies is determined, we build high (35 pc) resolution numerical experiments in which we increase or decrease the angular momentum of the Lagrangian patches in the early universe. We perform cosmological zoom-in simulations of three galaxies over their histories from z = 200 to z = 2, each with five different choices for the angular momentum (15 simulations in total). Our results show that altering early universe angular momentum changes the timing and orbital parameters of mergers, which in turn changes the total stellar angular momentum within a galaxy’s virial radius in a predictable manner. Of our three galaxies, one has no large satellite at z = 2; in this case, the specific angular momentum is concentrated in the central galaxy. Our changes to the initial conditions result in its stellar angular momentum changing over 0.7 dex (from 61 to ${320}\, {\rm kpc\, km\, s}^{-1}$) at z = 2. This causes its effective radius to grow by 40 per cent, its v/σ parameter to grow by a factor of 2.6, and its bulge fraction to decrease from 0.72 to 0.57. This proof of concept illustrates how causal studies can contribute to a better understanding of the origin of galaxy scaling relations and intrinsic alignments.

Giant quantum anharmonic effects on the stability, vibrational and optical properties of cyclo[4n+2]carbon

Cyclo[ 4 n + 2 ]carbons are sp-bonded carbon rings in which Hückel rule predicts a fully symmetric structure that is, however, in competition with the second order Jahn–Teller (Peierls) distortion. This picture, however, neglects the crucial role played by nuclear quantum effects. Here we investigate the magnitude of nuclear quantum effects on the stability, vibrational and optical properties of cyclo[ 4 n + 2 ]carbons ( n = 1 , 2 , 3 , 4 ) in vacuum. The quantum structural minimization reduces the energy separation between the different isomers and determines that the most stable C 14 isomer is the cumulenic one, setting the transition from the polyyenic to the cumulenic form at n = 3 (at odd with the classical structural optimization setting the transition at n = 2 ). Moreover, the quantum anharmonic effects generate very large frequency shifts, linewidth broadenings and satellites in the phonon spectral weight hindering any possible interpretation based on the non-interacting harmonic spectrum. The optical absorbance is completely reshaped by quantum anharmonic vibrations with redshifts ranging from 0.4 to 1.0 eV in the first excitonic absorption with respect to the static ionic picture. Finally, we also determine the crystal structure of C 18 on a NaCl bilayer to be a buckled polyynic phase in agreement with recent experimental findings. Our work outlines the crucial role of nuclear quantum effects in the understanding of carbon molecular systems.