This paper proposes a novel description of the equations of motion for low-thrust trajectory design in the presence of a third-body perturbation. The framework is formulated using Gauss’ Variational Equations (GVE) with two distinct accelerations: the one produced by the electric engine and the disturbing term of the third-body effect, which is computed using the disturbing potential of the previously

Achieving a soft landing over the surface of small celestial bodies is an essential maneuver in space to advance the status of space exploration, sample collecting and in-situ resource utilization, among other on-orbit tasks. Landing on these bodies is challenging due to the reduced-gravity and airless environment. The correct planning of execution of the trajectory to land on the surface of the body

This paper is aimed at finding the best separation angle between spacecraft for the three-dimensional reconstruction of solar-wind inhomogeneous structures by the CORrelation-Aided Reconstruction(CORAR) method. The analysis is based on the dual-point heliospheric observations from the STEREO HI-1 cameras. We produced synthetic HI-1 white-light images containing artificial blob-like structures in different

Radio occultations are commonly used to determine vertical profiles of ionospheric electron density and neutral atmospheric density from measurements of frequency. Previous work has developed expressions for how uncertainties in electron density and neutral density depend on uncertainty in frequency. However, these expressions assume that the relevant density decreases exponentially with increasing

During the August 25, 2018 geomagnetic storm, the new borne CSES-01 satellite and the Swarm A satellite detected a really large equatorial plasma bubble (EPB) in the post-midnight sector over western Africa. We investigated the features of this deep ionospheric plasma depletion using data from the Langmuir probes on-board CSES-01 and Swarm A satellites, and data from the high-precision magnetometer

In a recent study, we developed ultralow-binder-content (UBC) structural materials based on lunar soil simulant and thermoset binders. In the current research, we investigated thermoplastic binders. Compared to thermosets, advanced thermoplastics could be more UV resistant, more durable, more robust, and recyclable. Our main technology is the compaction self-assembly (CSA). By using only ∼4 wt% polyetherketoneketone

Over land and inland waters satellite radar altimetry is being used in numerous applications including polar mass change, ice topography, river and lake heights and soil moisture. To achieve high accuracy altimetric range measurements, geophysical corrections are applied including the Zenith Total Delay (ZTD) which varies spatially, temporally and with altitude. Over oceans, the wet tropospheric component

The filtering procedure is usually mandatory for computing the mean dynamic topography (MDT) by combining the mean sea surface (MSS) and geoid due to the inconsistent spectral contents between them. Recently, a rigorous fusion method is proposed to solve this inconsistency problem through the least square method (Becker et al., 2012), where MDT is parameterized by the Lagrange basis functions (LBFs)

The error variance-covariance matrices of the monthly GRACE gravity field models are usually well-structured (e.g., order-leading) to contain the error information of the monthly gravity field models, and they are important information to further improve the accuracy of the estimated mass transportation by a post-processing scheme. Intensive studies have been performed to understand the impact of different

Eight proxy records of Northern Fennoscandian summer temperature variability were analyzed for the AD 1700–2000 period. Stable and statistically significant correlation between the summer temperature reconstructions and a quasi 22-year Hale solar cycle was found to be present through the entire study period. The revealed solar–climatic link is a result of the effect of a weak solar cycle signal on

The third phase BeiDou Navigation Satellite System (BDS-3) provides a BeiDou Global broadcast Ionospheric delay correction Model (BDGIM) for single-frequency navigation and positioning applications. According to the BDS Interface Control Document (ICD) Signal B1C (Version 1.0), the BDGIM contains nine parameters and was broadcast in December 2018. The BDGIM will gradually replace the BDS-2 ionospheric

Nonlinear propagation of purely stationary large amplitude electromagnetic (EM) solitary waves in a magnetized electron-positron (EP) plasma is studied using a fully relativistic two-fluid hydrodynamic model which accounts for physical regimes of both weakly relativistic (P≪nmc2) and ultrarelativistic (P≫nmc2) random thermal energies. Here, P is the thermal pressure, n the number density and m the

There are remarkable ionospheric discrepancies between space-borne (COSMIC) measurements and ground-based (ionosonde) observations, the discrepancies could decrease the accuracies of the ionospheric model developed by multi-source data seriously. To reduce the discrepancies between two observational systems, the peak frequency (foF2) and peak height (hmF2) derived from the COSMIC and ionosonde data

This paper proposes a fixed time disturbance observer (FTDO) based fixed time sliding mode control scheme for spacecraft proximity operations in the presence of parameter uncertainties and disturbances. The FTDO is designed to estimate the lumped disturbance which includes kinematic couplings, parameter uncertainties, and disturbances. Based on the observation of lumped disturbance, the fixed time

The Ionosphere PhotoMeter (IPM) is a far ultraviolet nadir-viewing photometer that flew aboard the second-generation, polar-orbiting Chinese meteorological satellite Feng-Yun 3D (FY-3D), which was launched on November 25th, 2017. By observing far ultraviolet night-time OI 135.6 nm emissions, which are produced by the recombination of O+ ions and electrons, the F2 layer peak electron density (NmF2)

The goal of this study is to examine the capability of the TRMM 3B42 product to detect spatial and temporal patterns in extreme precipitation events over southwestern Iran during the period of 1998-2016. A ground-based gridded precipitation dataset was created using a dense network of surface observations for the evaluation process. Various extreme precipitation indices in the three categories of fixed

Global navigation satellite systems (GNSSs) play an important role in both military and civilian industries, but most of the existing GNSS carriers are crowded in the L band. Although some modulations, such as binary-offset-carrier (BOC) and its modifications, can reduce the mutual interference of one GNSS signal to others, the exhausted L-band frequencies are still the bottleneck to improve GNSS performance

This paper investigates an optimal fuel station (FS) arrangement problem for multiple geosynchronous (GEO) spacecrafts with many-to-many (M2M) refueling, subject to the capacity of the servicing spacecraft (SSC) and the different fuel requirements of the targets. Several FSs with their reusable SSC are arranged on GEO, while the SSC commutes between fuel-deficient targets and FSs to refuel the multiple

A ground-based electro-optical (EO) array, deployed at the Jilin Space Tracking Base of Changchun Observatory, China, has been in operation since April 2017. The array has 8 small telescopes, each has an aperture of 15cm and a field of view of 14°x14°. On average, the array can collect angles data over 3∼4 thousand Very Short Arcs (VSAs) of Low Earth Orbit (LEO) space objects each night. Correlation

We present a detailed mechanical and thermal analysis of a stand-alone nanospacecraft that performs asteroid flybys in the main asteroid belt (2.75 AU) and one Earth flyby at the end of the mission to return the gathered data. A fleet of such nanospacecraft (<10 kg) has been proposed as part of the Multi-Asteroid Touring mission concept, a nearly propellantless mission where the electric solar wind

The lunar south pole is being targeted for exploration, in part, because it contains topographical high points with >50% illumination needed for solar power. Additionally, the south pole is being targeted because it contains permanently shadowed regions (PSRs), which may sequester resources in the form of volatile materials. Geologically, the pole lies on the rim of ~21 km diameter Shackleton crater

Low radio frequency experiments performed on Earth are contaminated by both ionospheric effects and radio frequency interference (RFI) from Earth-based sources. The lunar farside provides a unique environment above the ionosphere where RFI is heavily attenuated by the presence of the Moon. We present electrodynamics simulations of the propagation of radio waves around and through the Moon in order

High altitude Venus ionosphere is characterized by the presence of H+ and O+ ions as well as electrons. Because of these two positive ions, the ion-acoustic wave (IAW) was observed. Propagation properties of nonlinear IAWs in the Venusian ionosphere are investigated. Korteweg de-Vries (KdV) equation is derived for weakly nonlinear behavior of the IAWs, while Sagdeev pseudo-potential is obtained to

The accuracy of discrete element model has great influence on the DEM simulations of lunar soil, especially on the soil-tool interaction simulations. In this paper, the mechanical property of lunar soil is classified into three categories and the particularity of shear strength is newly explained as higher internal friction angle and lower cohesion with respect to Earth soil, and the plasticity performance

In this study, the double-differenced positioning bias of different frequency observations (PBDFO) in a code division multiple access (CDMA) signal system is analyzed based on real-time kinematic (RTK) positioning using raw observations at different frequencies. To test and verify the existence of the DD PBDFO, a set of ultra-short baseline (25 m) GNSS observation data were collected. The stations

The next-generation of satellite-based augmentation system (SBAS) will employ a dual-frequency multi-constellation (DFMC) service providing several advantages over the classical SBAS L1 service. In September 2017, a two-year SBAS test-bed was initiated by Australia and New Zealand in preparation for building an operational system. This system includes DFMC SBAS in addition to the legacy SBAS L1 service

China’s National Height Datum was determined by the mean sea level at the Qingdao tide gauge station. Research was conducted to study the long-term changes in China’s National Height Datum. The first step was to analyze the long-term changes in the Qingdao Huanghai mean sea level relative to the crust by analyzing the tide data from 1952 to 2011. The frequencies and amplitudes of main tides, including

Stone dust induced risk and vulnerability in the developing nations is very thought-provoking and therefore is necessary to address scientifically to manage it. Identifying vulnerable areas using the robust method is preliminary and essential steps. The present study has intended to delineate Human health vulnerability models (HHVMs) using machine learning algorithms and justify whether ensemble prediction

With the rapid change of urban areas in developing countries, construction areas are constantly appearing in different parts of cities. Those changed areas require timely monitoring to provide up-to-date information for of urban information systems. As a result, it is a challenge to develop an effective change analysis of different objects, especially buildings in cities. This paper presents an object-based

In order to cope up with the emerging demand of interpreting and detecting urban features from remotely sensed imagery, this study proposes an innovative unique yet practically easy approach to extract impervious surfaces and features using certain built-up indices (BUIs) that are developed from space-borne optical and SAR remotely sensed sensors. Resourcesat-2 LISS III and HH/HV dual polarized L-band

The hardware delay difference for different navigation signals in satellite or receiver channels is called Differential Code Bias (DCB). DCB is a major error of global navigation satellite system (GNSS), which may lead to tens of Total Electron Content unit (TECu) ionospheric delay errors or several-meter ranging errors. The basic system of BeiDou Navigation Satellite System has opened services and

Modern society replies on the ionosphere for technology such as radio navigation and telecommunications. However, this is not a static environment and its characteristics can be affected by solar phenomena such as coronal mass ejections (CMEs) and high-speed solar winds. In this paper we present a set of space weather parameters (e.g. type and velocity of CMEs, X-ray flux, the velocity of high-speed

This study investigates the response of equatorial and low latitude ionosphere during an intense geomagnetic storm of 26 August 2018 (Dst min = −206 nT) using the TEC observations from two chains of GPS stations along 80° E and 120° E longitudes in the Asian sector. These GPS networks include Waltair and four IGS stations (SGOC, IISC, HYDE and LCK4) along 80° E and five IGS stations (SHAO, TCMS, CKSV

This study investigates the quiet-time and storm-time variations of the African equatorial and low latitude ionosphere during 2009–2015. We obtained TEC observation data from four Global Navigation Satellite System (GNSS) stations over the African equatorial and low latitude, namely: Asab (ASAB, geographic coordinates 13.0°N, 42.65°E; geomagnetic coordinates 4.85°N, 114.34°E), Arba Minch University

In the on-orbit servicing missions, autonomous close proximity operations require knowledge of the target’s motion and inertial parameters in order to safely interact with the target. In particular, the motion and parameter estimation of an uncooperative target is a challenging task because of the lack of some prior information about the target in unfamiliar environments. In this paper, a novel method

The precise positioning of a lander is a key issue during in situ planetary exploration. This paper proposes an optimal weighting algorithm based on a Helmert-variance component estimation applied to VLBI phase delay data. We validated our algorithm on Chang’e 3 lander VLBI phase delay from the Chinese VLBI Network. We consider that the lander positioning accuracy achieved with our new algorithm is

High-energy atomic impacts represent one of the biggest threats to material performance in both the low earth orbit (LEO) and deep space environment. However, while significant test data exists for LEO atomic oxygen (AO) collisions, further research is needed on the effect of high-energy collisions that can potentially occur in deeper space. As such, this study investigated using the ReaxFF force field

This work describes the design and optimization of spacecraft swarm missions to meet spatial and temporal visual mapping requirements of missions to planetary moons, using resonant co-orbits. The algorithms described here are a part of Integrated Design Engineering and Automation of Swarms (IDEAS), a spacecraft swarm mission design software that automates the design trajectories, swarm, and spacecraft

Energetic particles interacting with interplanetary or interstellar plasmas experience transport along and across large scale magnetic fields. In particular the diffusion of particles in the perpendicular direction is difficult to understand theoretically. However, significant progress has been achieved due to the development of test-particle simulations, non-linear systematic theories, and heuristic

The problem of optimum solar proxy is important for long-term and/or climatological studies of ionospheric parameters. Here we focus on possibly different optimum solar proxies for different ionospheric parameters, as they are affected by partly different spectral ranges of solar ionizing radiation. We use yearly average values of foF2 and foE of four European stations with long (1976-2014) and high-quality

Turkey is located in a highly active earthquake zone. Many geodynamic and seismic activities occur during a day, such as earthquakes, landslides, sinkholes, and creep movements. In addition to seismicity, Turkey has unique physical features like being surrounded with seas on three sides, affected by different climate types. It is located on mid latitudes, which makes Turkey very suitable for atmospheric

PROBA-3 is a space mission of the European Space Agency that will test, and validate metrology and control systems for autonomous formation flying of two independent satellites. PROBA-3 will operate in a High Elliptic Orbit and when approaching the apogee at 6⋅104 Km, the two spacecraft will align to realize a giant externally occulted coronagraph named ASPIICS, with the telescope on one satellite

Navigation augmentation based on Low Earth Orbit (LEO) satellites has become a hot topic in recent years. The orbital design of LEO augmentation constellations and the analysis of their performance are essential issues for the development of LEO augmentation systems. In this paper, LEO constellations for navigation are designed with the constraint that they augment the BeiDou Navigation Satellite System

We analyzed astronomical data in the Tongmunhwigo, one of the history books containing diplomatic documents of the Joseon government (the last dynasty of Korea). This book contains predictions of solar and lunar eclipses for Seoul and Beijing with specific information such as magnitude and time, sent by the Qing government to the King of Joseon between 1721 to 1881. We analyzed the accuracy of the

This paper regards small/midsize square sails on which a field of wrinkles appears owing to the necessary sail-membrane operations before and during the deployment. We collected a large amount of data in our laboratory. Many ten thousands of measurements had been statistically processed for characterizing some sail’s sampled membranes consisting of aluminized-polyimide layers (2.5+0.1)μm thin, and

In this study we use the CHAMP wind observations from 2002 to 2004 to investigate features of mid-latitude thermospheric winds at low and high geomagnetic activity levels. The winds are observed between the geomagnetic latitudes 40o-50o north or south within an altitude range of 370 to 450 Km and averaged longitudinally. The low geomagnetic activity level wind generally leads eastward in both hemispheres

Thunderstorm is a complex of electrical, optical, and acoustical phenomena that occurs in the tropospheric layer and liberates a huge amount of energy, which diffuses the electric field, propagates atmospheric acoustic and gravity waves into the ionosphere, and changes the ionospheric parameters such as the electron density and ionospheric conductivity. In this paper, irregularities in the TEC, the

Cataclysmic Variables (CVs) are compact binaries with white dwarf (WD) primaries. CVs and other accreting WD binaries (AWBs) are useful laboratories for studying accretion flows, gas dynamics, outflows, transient outbursts, and explosive nuclear burning under different astrophysical plasma conditions. They have been studied over decades and are important for population studies of galactic X-ray sources

Cataclysmic Variables (CVs) are binaries in which a white dwarf accretes from a low-mass companion star. CVs are the best-suited laboratories to test our understanding of the evolution of compact, interacting binaries as they are numerous, relatively bright, and both stellar components are structurally simple. Nonetheless, while a large fraction (≃40-80%) of the present-day Galactic CV population is

This paper presents observations of the F2-layer critical frequency (foF2) and height (hmF2) obtained at Phu Thuy (21.03°N, 105.95°E) and Bac Lieu (9.28°N, 105.73°E) observatories in Vietnam. The data have been examined for all seasons, during high and low solar activities, and compared with the foF2 and hmF2 of the International Reference Ionosphere model (IRI-2012, IRI-2016 two options: AMTB, SHU)

Precise pointing of the satellite and its payload is essential in the accurate accomplishment of a space mission. In this study, the system of a satellite and its payload are considered as 4-DOF equations of motion. The time-varying payload can observe one direction of the Earth independently, and the satellite can point to the Earth station by its 3-DOF motions simultaneously. Sliding mode and LQR

Ionosphere plays crucial role in satellite communication as well as the modern space-based positioning, navigation and timing applications. Progressive exploitation of ground and space-based observations across the African region has relatively strengthened the understanding and modeling of spatiotemporal ionospheric variations over the territory. However, it is also equally important to understand

This paper reports the effects of interfacial heat transfer due to convection and radiation on thermocapillary convection in a liquid bridge of high-Prandtl-number fluids (i.e., Pr = 67) in weightlessness. A liquid bridge is placed inside a cylindrical chamber filled with argon gas, and the two-dimensional (i.e., axisymmetric) time-independent flow and temperature fields in the liquid bridge and in

Metallized thin films are commonly considered for solar sail membranes operating in the interplanetary space. A key characteristic of this environment is the solar wind, with its charged low energy <10 keV particles. Aluminum subjected to low energy protons undergoes recombination processes between protons and metal electrons, resulting in the formation of blisters on the surface. Blistering results

A torus-shaped sail consists of a reflective membrane attached to an inflatable torus-shaped rim. The sail’s deployment from its stowed configuration is initiated by introducing inflation pressure into the toroidal rim with an attached circular flat membrane coated by heat-sensitive materials that undergo thermal desorption (TD) from a solid to a gas phase. Our study of the deployment and acceleration

Managed forests, dynamic with activities of harvest and afforestation, have become an area of imminent research opportunity to understand the effects of these disturbances and regrowth dynamics. As low frequency polarized radar signals have the ability to penetrate forest canopies, the fully polarized Synthetic Aperture Radar (SAR) data gives an ideal representation of conditions in the forest. However

Radio occultation (RO) has proved to be a powerful tool for weather forecasting and ionospheric modelling. It is a truly global technique for the observation in the lower as well as in the upper atmosphere. With the evolution of radio occultation technique, the data inversion algorithms used to extract data from the raw RO measurements also evolved over the period of last two decades. In this work

The present study reports the variations in bottom-side thickness (B0) and shape (B1) parameters from ionospheric measurements of Digisonde Portable Sounder, DPS-4 installed at Multan (geog coord 30.18°N, 71.48°E, dip 47.4°) during the deep solar minimum between solar cycles 23/24 i.e., 2008-09 as a continuation to our previous work Ameen et al. (2018). We have found that B0 has peak values during

This paper presents a computation efficient Immersion and Invariance (I&I) adaptive control method for the tracking control problem of Euler-Lagrange mechanical systems with parametric uncertainties. By employing a generalized velocity observer, the proposed controller retains the basic advantages of the I&I design and requires much less extension on extra closed-loop system states when compared with

In a first paper, we presented an in-depth discussion and a computational method (free of the calendar problem) to reckon any kind of latitudinal insolation gradients, LIGs, throughout the Holocene and up to CE 3000. One of the main insights from this exact definition of LIGs is that, unlike what is argued in prior works, during the Holocene, a general classification of LIGs in terms of obliquity signal