Orbital Orientation Research Articles

Spectral Performance Optimization of Small-Diameter Telescopes for Space Object Detection

Successful tracking and detection of resident space objects (RSOs) requires selection of spectral filters that are capable of compensating for the effects of wavelength dependent atmospheric scattering, and material reflectance properties. When operating in an urban environment such as Atlanta, GA the emitted city light pollution is also an important factor. In this study, we perform a multi-spectral optimization for the Georgia Tech Space Object Research Telescope across the visible through infrared spectrum that accounts for atmospheric turbulence, atmospheric transmission, and background sky radiance. The first contribution of this work is the development of a wavelength-dependent performance metric for the detection of RSOs under different atmospheric conditions. The second contribution is the derivation of a simplified model for light pollution that is based on existing astronomy models. This simplified model accounts for double scattering of light and can be used for adding a light pollution component to sky background results that are generated by complex atmospheric simulation tools. The final contribution is the derivation of novel spectral filters that are tuned to the sub-optimal atmospheric seeing conditions of Atlanta, GA and the RSO materials that are considered in this study. While this study is developed for the geographic region of Atlanta, GA and uses simplified bidirectional reflectance distribution models models for spacecraft materials, the framework is generalizable to different geographic regions, weather conditions, and satellite orientations.

Improving the Orbits of Four Visual Binaries Using Gaia DR2 Data and Observations with the 26-inch Refractor of Pulkovo Observatory

We use a modified method of the apparent motion parameters (AMP), in which the initial data from the Gaia DR2 catalog are not only high-precision coordinates, parallaxes, and radial velocities of the components of the studied wide binary stars, but are also their proper motions. The coincidence of the AMP orbits obtained both from the Gaia DR2 data and from the Pulkovo series from 1960–2019 leads to an orbit that is unambiguous in terms of an ascending node. The results for improving the orbits of such visual binaries of the Pulkovo research program as ADS 246, 2757, 10386, and 12169 are presented. Orbits (with periods of 1226, 1075, 4500, and 4900 years), orbital orientation parameters in the Galaxy coordinate frame, and the masses of these systems are obtained (0.59 ± 0.05, 1.7 ± 0.3, 1.7 ± 0.4, and $$2.25 \pm 0.5{{M}_{ \odot }}$$ ). It is shown that dense homogeneous series of ground-based observations, such as CCD observations with the 26-inch refractor of the Pulkovo Observatory, do not lose their relevance, serve as the basis for identifying the best solution based on both Gaia data and our own observations, and should be continued. It was also shown that the Thiele–Innes method is not suitable for determining the orbits of binary stars with a separation of more than 100 AU. The paper is based on a presentation made at the conference “Astrometry yesterday, today, and tomorrow,” which took place on October 14–16, 2019 at the Sternberg Astronomical Institute of Moscow State University.

Spin-resolved atomic orbital model refinement for combined charge and spin density analysis: application to the YTiO3 perovskite.

A new crystallographic method is proposed in order to refine a spin-resolved atomic orbital model against X-ray and polarized neutron diffraction data. This atomic orbital model is applied to the YTiO3 perovskite crystal, where orbital ordering has previously been observed by several techniques: X-ray diffraction, polarized neutron diffraction and nuclear magnetic resonance. This method gives the radial extension, orientation and population of outer atomic orbitals for each atom. The interaction term between Ti3+, Y3+ cations and O2- ligands has been estimated. The refinement statistics obtained by means of the orbital method are compared with those obtained by the multipole model previously published.

Analysis of the functioning of the orientation device to the Earth of a telecommunications space satellite

This article presents the results of statistical observations of an operating communications spacecraft. The functioning of the orientation system to the Earth is considered. For ensure the reliability of communication between the satellite and ground stations, it is important to have a constant direction to the coverage area. For this, the spacecraft has an orientation system to the Earth. The orientation aims to create a reliable connection on the territory of the country of the spacecraft owner. The article examines the analysis of the operation of the satellite guidance system to the Earth using the example of a telecommunications communication satellite of the Republic of Kazakhstan. At the same time, the satellite orientation system to the Sun works in parallel to organize a stable and stable connection. The statistics of the operation of the orientation system to the Earth are presented. For this, the satellite has devices responsible for positioning – the orientation devices to the Earth. There are two given devices, namely, POZ-1 and POZ-2. The analysis of real statistics is given. The forecast of the system operation for the next nine years has been made.

A Theoretical Procedure Based on Classical Electrostatics and Density Functional Theory for Screening Non-Square-Shaped Mixed-Valence Complexes for Logic Gates in Molecular Quantum-Dot Cellular Automata

Abstract Understanding the requisite geometry of molecules and peripheral components is an essential step in endowing molecules with logical functions in quantum-dot cellular automata. To respond to the real problem of structural distortion from the ideal square cell configuration, a practical procedure is presented that simplifies the molecular shapes for device design with features that combine aspects of classical electrostatics and density functional theory calculations. By applying this method to a library of biferrocenium dimers with a three-input junction, it was demonstrated in theory that a covalently bonded parallelogram dimer responds precisely to six different patterns of nanoscale electric fields and works correctly as a device cell in both AND and OR logic gates. The counterintuitive usefulness of the non-square-shape is rationalized by four ferrocene-based orbital orientations and a functional group arrangement, equalizing the disadvantageous energy asymmetry between the states 0 and 1. The present procedure was applied to quasi-square tetrametallic Ru complexes and it was found that these complexes do not work as logic gates. This procedure expands the range of existing candidate molecules from squares to parallelograms and facilitates screening for implementation.

A Variable Sampling-Time Method for Elliptical Orbit Motion Prediction in Nanosatellites

Nanosatellite missions may contain payloads for high pointing accuracy such as laser communication systems for crosslinks or astronomical observations. Therefore, the satellite requires a precise orbital position and orientation determination in order to point the scientific instrument to the desired target. In this work, an elliptical rotation method based on quaternion representation is presented. The proposed method allows determining the future position of a satellite around its orbit. Furthermore, in Low Earth Orbits (LEO) with an eccentricity larger than zero, the distance between the satellite and the Earth is changing over the time, increasing the satellite velocity in the perigee region compared to the apogee, due to the gravity forces. The elliptical rotation method and the orbital current position are deduced, considering a variable sampling-time as a function of the eccentricity and the orbital current position. The proposed algorithm can increase the position accuracy four times compared to fixed sampling time along the satellite orbit.

Comparison of Gravitational and Light Frequency Shifts in Rubidium Atomic Clock

The article presents the results of an experimental study of the external magnetic field orientation and magnitude influence on the rubidium atomic clock, simulating the influence of the geomagnetic field on the onboard rubidium atomic clock of navigation satellites. The tensor component value of the atomic clock frequency light shift on the rubidium cell was obtained, and this value was ~2 Hz. The comparability of the relative light shift (~10−9) and the regular gravitational correction (4×10−10) to the frequency of the rubidium atomic clock was shown. The experimental results to determine the orientational shift influence on the rubidium atomic clock frequency were presented. A significant effect on the relative frequency instability of a rubidium atomic clock at a level of 10−12(10−13) for rotating external magnetic field amplitudes of 1.5 A/m and 3 A/m was demonstrated. This magnitude corresponds to the geomagnetic field in the orbit of navigation satellites. The necessity of taking into account various factors (satellite orbit parameters and atomic clock characteristics) is substantiated for correct comparison of corrections to the rubidium onboard atomic clock frequency associated with the Earth’s gravitational field action and the satellite orientation in the geomagnetic field.

LiMnO2 cathode stabilized by interfacial orbital ordering for sustainable lithium-ion batteries

Global lithium-ion battery deployments stand poised to grow substantially in the coming years, but it will be necessary to include sustainability considerations in the design of electrode materials. The current cathode chemistry relies heavily on cobalt, which, due to its scarcity and the environmental abuse and violation of human rights during its mining, must be replaced by abundant and environmentally friendly elements such as redox-active manganese. LiMnO2 is a strong contender for sustainable cathodes but cycles poorly because the Jahn–Teller distorted Mn3+ ions destabilize the lattice framework. Here, we report a LiMnO2 cathode design with interwoven spinel and layered domains. At the interface between these two domains, the Mn dz2 orbitals are oriented perpendicular to each other, giving rise to interfacial orbital ordering, which suppresses the otherwise cooperative Jahn–Teller distortion and Mn dissolution. As a result, the heterostructured cathode delivers enhanced structural and electrochemical cycling stability. This work provides a new strategy for interface engineering, possibly stimulating more research on Mn-rich cathode materials for sustainable lithium-ion batteries. The field of battery chemistry must embrace abundant elements such as Mn for improved sustainability. Here the authors engineer the orientation of Mn 3d orbitals, resulting in excellent performance in LiMnO2 cathodes.

Two-dimensional MOS2 for hydrogen evolution reaction catalysis: The electronic structure regulation

Molybdenum disulfide (MoS2) has been recognized as one of the most promising candidates to replace precious Pt for hydrogen evolution reaction (HER) catalysis, due to the natural abundance, low cost, tunable electronic properties, and excellent chemical stability. Although notable processes have been achieved in the past decades, their performance is still far less than that of Pt. Searching effective strategies to boosting their HER performance is still the primary goal. In this review, the recent process of the electronic regulation of MoS2 for HER is summarized, including band structure engineering, electronic state modulation, orbital orientation regulation, interface engineering. Last, the key challenges and opportunities in the development of MoS2-based materials for electrochemical HER are also discussed.

Hydrogenation engineering of bimetallic Ag–Cu-modified-titania photocatalysts for production of hydrogen

The efficacy of treatment with hydrogen and Ag-Cu co-deposition on TiO2 photocatalysts has been investigated computationally and experimentally. The hydrogenated Ag-Cu with co-loaded TiO2 (H:(Ag-Cu/TiO2)) achieved a photoactivity about 110 times that of pristine TiO2, which corresponds to a rate of 1.16 mmol h−1 g−1 for hydrogen generation. Soft X-ray spectra and quantum-chemical calculations indicate that the notable promotion of photoactivity on H:(Ag-Cu/TiO2) is ascribable to the synergy between new electronic states and a lattice distortion. The soft X-ray absorption spectra (XAS) indicated that the TiO6 octahedral symmetry and the Ti 3d- orbital orientation are significantly affected by the Ag-Cu decoration and the hydrogenation treatment. The mechanisms involved in this photocatalysis were studied with soft XAS in situ, which showed that the photoexcited electrons transfer from the bimetallic Ag-Cu to the TiO2 conduction band as the photoresponse of this composite photocatalyst. The strategy of coupling hydrogenation with bimetallic Ag-Cu onto TiO2-based photocatalysis provides a facile and promising solution to other environmental and energy applications.

Wave asymmetry and particle orbits in irregular wave models

Abstract

Understanding the Activity of Single-Atom Catalysis from Frontier Orbitals.

The d-band center and charge states are often used to analyze the catalytic activity of noble or transition metal surfaces and clusters, but their applicability for single-atom catalysts (SACs) is unsure. This work suggests that the spatial structure and orientation of frontier orbitals which are closest to the Fermi level of SACs play a vital role. Taking adsorption of several molecules and CO oxidization on C_{3}N-supported single-atom Au as examples, we demonstrate that adsorption and catalytic activities are well correlated with the characteristics of frontier orbitals. This work provides an effective guidance for understanding the performance of single-atom catalysts.

Orbital-regulated interfacial electronic coupling endows Ni3N with superior catalytic surface for hydrogen evolution reaction

The interstitial structure and weak Ni-N interaction of Ni3N lead to high unoccupied d orbital energy and unsuitable orbital orientation, which consequently results in weak orbital coupling with H2O and slow water dissociation kinetics for alkaline hydrogen evolution catalysis. Herein, we successfully lower the unoccupied d orbital energy of Ni3N to strengthen the interfacial electronic coupling by employing the strong electron pulling capability of oxygen dopants. The prepared O-Ni3N catalyst delivers an overpotential of 55 mV at 10 mA cm−2, very close to the commercial Pt/C. Refined structural characterization indicates the oxygen incorporation can decrease the electron densities around the Ni sites. Moreover, density functional theory calculation further proves the oxygen incorporation can create more unoccupied orbitals with lower energy and superior orientation for water adsorption and dissociation. The concept of orbital-regulated interfacial electronic coupling could offer a unique approach for the rational design of hydrogen evolution catalysts and beyond.

Analyzer-free linear dichroic ptychography

Linear dichroism is an important tool to characterize the transmission matrix and determine the crystal or orbital orientation in a material. In order to achieve high-resolution mapping of transmission properties, the linear-dichroism scattering model in ptychographic imaging is introduced, and an efficient two-stage reconstruction algorithm is developed. Using the proposed algorithm on a uniaxial material, the dichroic transmission matrix can be recovered without an analyzer by using ptychography measurements with as few as three different polarization angles, with the help of an empty region to remove phase ambiguities.

Solvent Cage Effects: A Comparison of Geminate and Nongeminate Radical Cage Pair Combination Efficiencies.

This study measured and compared the combination efficiencies (FcP) of geminate radical cage pairs to nongeminate (collisional) radical cage pairs (Fc'). For the [Cp'(CO)3Mo·, ·Mo(CO)3Cp'] radical cage pair, Fc' was found to be smaller than FcP in solutions having the same viscosity. It is proposed that the difference in FcP and Fc' arises because the radicals in the collisional cage pair are less likely to have the correct orbital orientation for radical-radical combination to occur, whereas photochemically generated geminate cage pairs are more likely to have the correct orbital orientation. As predicted, FcP and Fc' both increase when the microviscosity of a solution increases.

Young stellar cluster dilution near supermassive black holes: the impact of vector resonant relaxation on neighbour separation

ABSTRACT We investigate the rate of orbital orientation dilution of young stellar clusters in the vicinity of supermassive black holes. Within the framework of vector resonant relaxation, we predict the time evolution of the two-point correlation function of the stellar orbital plane orientations as a function of their initial angular separation and diversity in orbital parameters (semimajor axis, eccentricity). As expected, the larger the spread in initial orientations and orbital parameters, the more efficient the dilution of a given set of co-eval stars, with a characteristic time-scale set up by the coherence time of the background potential fluctuations. A Markovian prescription that matches numerical simulations allows us to efficiently probe the underlying kinematic properties of the unresolved nucleus when requesting consistency with a given dilution efficiency, imposed by the observed stellar disc within the 1 arcsec of Sgr A*. As a proof of concept, we compute maps of constant dilution times as a function of the semimajor axis cusp index and fraction of intermediate-mass black holes in the old background stellar cluster. This computation suggests that vector resonant relaxation should prove useful in this context since it impacts orientations on time-scales comparable to the stars’ age.

Vortex-induced vibrations of a flexible cylinder at subcritical Reynolds number

Abstract

Ab initio determination of the magnetic ground state of pyrochlore Y2Mn2O7

There are two discrepant experimental results on the magnetic ground state of Y$_{2}$Mn$_{2}$O$_{7}$, one study proposes a spin glass state, while another introduces the material as a ferromagnet. In this study, we attempt to resolve this issue by employing density functional theory and Monte Carlo simulations. We derive different spin models by varying the Hubbard $U$ parameter in ab initio GGA+$U$ calculations. For the most range of Hubbard $U$, We obtain that the leading terms in the spin Hamiltonian are bi-quadratic and the nearest neighbor Heisenberg exchange interactions. By comparing Monte Carlo simulations of these models with the experiments, we find a ferromagnetic ground state for Y$_{2}$Mn$_{2}$O$_{7}$ as the most compatible with experiments. We also consider Y$_{2}$Mo$_{2}$O$_{7}$ as a prototype of the defect-free pyrochlore system with spin-glass behavior and compare it with Y$_{2}$Mn$_{2}$O$_{7}$. The orbital degrees of freedom are considered as a leading factor in converting a defect-free pyrochlore such as Y$_{2}$Mn$_{2}$O$_{7}$ to a spin glass system. By changing the $d$ orbital occupations of Mo atoms, our GGA+$U$ calculations for Y$_{2}$Mo$_{2}$O$_{7}$ indicate many nearly degenerate states with different $d$ orbital orientations which reveals $d$ orbital degrees of freedom in this material. While for Y$_{2}$Mn$_{2}$O$_{7}$, we find a single ground state with a fixed orbital orientation. Consequently, all of our ab initio approaches confirm Y$_{2}$Mn$_{2}$O$_{7}$ as a ferromagnetic system.

Orbits and Structure of the Quadruple Systems GJ 225.1 and FIN 332

Only a handful of quadruple systems with two accurate inner visual orbits are known. Architecture of two such systems is studied here to determine period ratios, mutual orbit orientation, and other parameters; updated orbital elements and their errors are derived. Gliese 225.1 (HIP 28442) is composed of three K-type and one M-type dwarfs and has inner orbital periods of 67.2+-0.2 and 23.4+-0.5 yr. Its inner orbits have small mutual inclination and are likely coplanar with the outer orbit of ~2 kyr period. The quadruple system FIN 332 (HIP 92037) consists of four early A type stars with similar masses and magnitudes. Both its inner orbits with periods of 27.6+-0.2 and 39.8+-0.4 yr have large eccentricities (0.82 and 0.84). Their orientation in the sky is remarkably similar. In contrast, the outer orbit with a period of ~5 kyr has a large relative inclination to the inner orbits. Dynamics and formation of these quadruple systems are briefly discussed.

Electronic band structure phase diagram of 3D carbon allotropes from machine learning

The unique electronic configuration endows carbon with super-flexible bonding ability, displaying metallic, semi-conducting and insulating features with unprecedented applications. Inspired by the pressure–temperature phase diagram that clearly shows the phases (solid/liquid/gas) of a substance in different conditions, for the first time, we have derived the electronic ‘phase diagram’ using machine learning that can discover complex rules and invisible relationships among multi-variables. Based on SACADA database with 522 three-dimensional carbon allotropes, electronic band gap is studied by using support vector machine, decision tree and multiple-layer perception algorithms. It is identified that density and bond angle are two key factors in determining the electronic phase diagram for distinguishing metallic, semiconducting, and insulating carbon phases, where density relates to bond length and coordination number, while bond angle relates to orbital orientations, both together determine the overlap of wave functions between different orbitals.