The hardware delay difference for different frequencies of 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 error or several-meter ranging error. The basic system of BeiDou Navigation Satellite System has opened

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

Time is the fundamental measurement in satellite altimetry and the key parameter in building and keeping up a long-term, consistent, and reliable record for monitoring changes in sea level. Over the years, different time scales, although interconnected, have been used in altimetry and also in satellite positioning. This sometimes leads to inexplicit descriptions and ambiguous use of time and orbit

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

This paper proposes a solution for multiple-impulse orbital maneuvers near circular orbits for special cases where orbital observations are not globally available and the spacecraft is being observed through a limited window from a ground or a space-based station. The current study is particularly useful for small private launching companies with limited access to global observations around the Earth

Satellite Based Augmentation Systems (SBAS) broadcasts to users Grid Ionospheric Vertical Delays (GIVDs) and associated confidence bounds called Grid Ionospheric Vertical Errors (GIVEs) at Ionospheric Grid Points (IGPs). The correlation structure of ionosphere and undersampled threat should be taken into account in the generation of GIVE to meet the integrity requirement. In this contribution, the

Scientists can study the global ionospheric weather by manually or automatically scaling ionograms recorded by global ionosondes to obtain characteristic values of D, E, F regions in the ionosphere. Therefore, fast and accurate ionogram scaling is crucial to real-time space weather monitoring, which is closely related to performance of space-borne and ground-based technological systems as well as life

The development of fast and reliable optimization algorithms is required in order to obtain real-time optimal trajectory on-board spacecraft. In addition, the wide spread of small satellites, due to their low costs, is leading to a greater number of satellite formations in space. This paper presents an Improved version of the Magnetic Charged System Search (IMCSS) metaheuristic algorithm to compute

We present a first estimate of the triboelectric charging generated by a drill in Shackleton crater; a permanently shadowed region at the Moon’s south pole. The results depend upon the local plasma environment as well as material properties of the drill and lunar regolith. We show how in the dark plasma-poor regions, a high voltage can accumulate due to the negligible electrical grounding, leading

Attitude kinematics using a single axis was developed to establish the relationships among the axis trajectory, enclosed solid angle and the associated attitude transformation. An arbitrary transformation due to a sequence of finite rotations or due to propagation consisting of an infinite number of infinitesimal rotations is equivalent to the product of a slewing transformation along a great circle

Precise Point Positioning Velocity Estimation (PPPVE) and Doppler Velocity Estimation (DVE) are two commonly used methods for precise velocity estimation with a stand-alone GPS receiver. The accuracy of PPPVE is affected by the dynamic model and the dynamic conditions of the vehicle, while the motion state of the vehicle has little influence on DVE. Therefore, we propose an approach by combining PPPVE

Hydrodynamic (HD) modelling in data sparse region represents a challenge due to poor hydrological and topographic data availability. Recently, remote sensing techniques offer additional data that may help to improve the reliability and accuracy of such analysis. In this study, an attempt has been made to investigate the potential and added value of altimeter measurements for multi-site validation of

Landslide susceptibility mapping has become one of the most important tools for the management of landslide hazards. In this study, we proposed a novel approach to improve the performance of Credal Decision Tree (CDT) by using four ensemble frameworks: Bagging, Dagging, Decorate, and Rotation Forest (RF) for landslide susceptibility mapping. A total number of 180 past and present landslides data of

In the context of Deep Space Exploration as planned by the International Space Exploration Coordination Group (ISECG), the Moon represents a significant step to feed forward what could be done on Mars. Navigation is a key-technology to enable the cis-lunar and lunar volume discovery. The use of Earth Global Navigation Satellite System (GNSS) signals at Moon altitude has been extensively studied in

In the present study, rainfall estimates from TRMM (Tropical Rainfall Measuring Mission) and GPM (Global Precipitation Mission) constellation of satellites are analyzed in the context of rainfall induced landslide occurrences over Western Ghats (WG) of India along with the daily gridded rainfall data developed by the India Meteorological Department (IMD) and ARW- Weather Research and Forecasting (WRF)

The deformation of the solar-sail membrane is an important factor for causing inaccuracies in the solar-sail missions. This paper describes the solar sail under deformation by using a new modelling technique based on point cloud and triangular mesh generation. Two types of deformation, stemming from wrinkling and billowing, are modelled. The changes in the solar radiation pressure force and the moment

Because control moment gyroscopes (CMGs) can generate a large torque compared to reaction wheels, they are used as actuators for attitude control of large spacecraft. However, when the number of Single-Gimbal CMG (SGCMG) units is five or less, there can be internal singularities that cannot generate torque around the desired direction. To construct a system that has no internal singularities, six or

Naval transportations have grown exponentially in the past few years’ and the quantity of illegitimate oil discharges in the oceans has developed with the volume of traffic imposing a severe threat to marine lives and ecosystem. Oil spills dampen the capillary wave’s effect hence create a dark signature on satellite image which is often called a dark object/matter that can be easily detected by SAR

One of the important areas where satellite images can play a key role in the monitoring of the temporal changes is the vegetated cover regions. In particular, the conversion of natural vegetation cover types in human dominated areas is still changing on a global scale with a number of unknown consequences for the environment. In these difficult circumstances, vegetation growth monitoring technique

We report for validation of cloud fraction estimated from high-resolution (hourly) data from MERRA-2 and AIRS instrument aboard NASA’s Aqua satellite during its ascending and descending orbits with hourly ground-based visual observation taken at Indian Astronomical Observatory (IAO), Hanle during 1997-2018. The study reveals 70% useful nights, equivalent to 254 spectroscopic nights in a year. A comparative

This study detected, mapped and analysed lineaments from Landsat-8 satellite images of the coastal area of Kribi-Campo, Cameroon. Kribi, a fast-growing coastal city with a youthful population whose main industry is agriculture, is currently under great pressure due to the influx of internally displaced persons, victims of the current socio-political crisis in the western part of Cameroon. With the

The in-depth investigation of the parameters of the solar wind, the zonal geomagnetic indices and the interplanetary magnetic field (IMF) is the key to furthering space weather researches. The investigations got meaning through modeling various interplanetary parameters and geomagnetic indices. These models, built on the basis of the correlations between solar wind parameters and zonal geomagnetic

The real-time precise point positioning (RT PPP) with ambiguity resolution (AR) technique has attracted increasing attention due to its high accuracy and low cost. With the availability of RT precise orbits, clocks, and multi-frequency phase bias products for multi-GNSS constellations, which are provided freely by the Centre National d’Etudes Spatiales (CNES), it is possible now to investigate RT PPP

The main focus of this paper is the effect of surface distortions on the electromagnetic performance of a large and lightweight active membrane phased array antenna (AMPAA) in P-band. The ideal structural-electromagnetic (SE) model of AMPAA is established for analyzing the relationship between the structural displacement and the electromagnetic performance. Based on the SE model, the amplitude and

This paper proposes an analytical solution of removing end-of-life GEO satellites to the GEO graveyard region using solar radiation pressure (SRP) and impulsive thrusts. The dynamic model of a GEO satellite equipped with a solar sail is first built upon the magnitude comparisons of different accelerations exerted on the satellite. Then the dynamic system is constructed based on the Gauss’s Variation

With the development of the Global Navigation Satellite System (GNSS), the accuracy and reliability requirements on observations are constantly increasing. The effect of ionospheric disturbance is not negligible, especially for accurate GNSS applications. To reduce the influence of ionospheric delay and disturbance, this study uses the Ionospheric Continuity Equation (ICE) to establish a new model

Marine gravity anomalies are essential data for determining coastal geoid, investigating tectonics and crustal structures, and offshore explorations. The objective of this study is to present a methodology for estimating marine gravity anomalies from CryoSat-2 and Saral/AltiKa satellite altimeter data for the Gulf of Tonkin of Vietnam with a high-resolution 2'×2' grid. A total of 15665 sea surface

This paper presents the storm time comparative analysis of the performances of latest versions of global ionospheric models: International Reference Ionosphere (IRI) 2016, NeQuick 2 (NeQ) and the IRI extended to Plasmasphere (IRI-P) 2017 with respect to Navigation with Indian Constellation (NavIC) and Global Navigation Satellite System (GNSS) derived ionospheric Total Electron Content (TEC). The analysis

Solar Radiation Pressure (SRP) is one of the main perturbations that needs to be carefully considered for space missions requiring great precision in satellite’s orbit. The computation of SRP is related to both satellite’s geometry and surface material. SRP model is usually used in the estimation of satellite’s position in space. However, the quality of SRP model is not easy to be assessed in a straightforward

This work introduces the n-dimensional congruent lattices using necklaces, a general methodology to generate uniform distributions in multidimensional modular spaces. The formulation presented in this manuscript constitutes the mathematical foundation of the most used satellite constellation designs, including Walker Constellations, and Lattice and Necklace Flower Constellations. These constellation

Time series prediction of rain attenuation from rain rate measurement during rain is made by using Synthetic Storm Technique (SST) for Ka and Q band signal for a temperate location, Vigo, Spain. Rain rate and rain attenuation data for the three year measurement period from 2016 to 2018 have been used to test the validity of the SST model at the present location. As we move from the Ka band to the Q

The Global Positioning System (GPS) is a space-based radio positioning system which is capable of providing continuous position, velocity and time information to users anywhere on, or near, the surface of the Earth. The positional accuracy of GPS is limited by several sources of error, such as satellite and receiver clock offsets, signal propagation delays (due to the ionosphere and troposphere), multipath

Space debris detumbling technology can be an effective supplement to the direct capture capability of space robot for simplifying and completing the active debris removal mission. This paper focuses on the optimal contact control for space debris rotation eliminating and nutation damping. Firstly, the space debris attitude motion is analyzed. The space debris detumbling strategy is presented with a

This work discusses a variation of the Double Donut Schmidt Camera (DDSC), originally proposed for the EUSO-FF (EUSO on Free Flyer) project and devoted to the observation of UHECRs from space with a threshold of about 5*1019eV for a 600 km altitude. Increasing the entrance pupil area by a factor ∼3, and then lowering the energy threshold to about 8 EeV (assuming for the differential energy spectrum

The Yuncheng Basin (China)is affected by severe land subsidence and ground fissure hazards, which have caused serious land damage and economic losses to the local inhabitants. Due to the lack of long-term continuous monitoring in the region, the trend of land subsidence and fissure activities is unknown, which can not meet requirements for disaster reduction and disaster prevention. In this study,

A novel method using single station beacon Relative Slant Total Electron Content (RSTEC) measurements is proposed to estimate the location of Equatorial Ionization Anomaly Trough (EAT). The feasibility of this method is established based on simulations of RSTEC using (International Reference Ionosphere) IRI model electron densities. Using the RSTEC measured by the Coherent Radio Beacon Receiver at

The precision of numerical orbit integration is crucial in precise orbit determination and gravity field recovery, especially in the context of future satellite gravimetry missions where nanometer-level inter-satellite measurements are provided by laser ranging interferometer. In this paper, we propose a hybrid-precision arithmetic in both Cowell’s and Encke’s formulations for numerical orbit integration

In paleoclimatology, the concept of latitudinal insolation gradients (LIGs), reckoned in various ways, has received increasing attention regarding glacial/inter-glacial climatic transitions and oscillations. In particular, the Holocene, which permits the reconstruction of past climatic proxies with an increasingly finer spatial and temporal resolutions, has provided evidence that suggests that LIGs

Human activity in the polar regions is increasing, and as a result of this, the positioning performance of global navigation satellite systems (GNSSs) in these regions is attracting more attention. Since the constellation design of GNSS systems (such as GPS, GLONASS, Galileo, and BDS) only provides superior coverage for human activity in the middle and low latitudes, the elevation angles of GNSS satellites

The direction and magnitude of a solar sail acceleration are strongly related. For this reason, once the characteristic acceleration has been fixed, it is not possible to modulate the acceleration in a particular direction. In this work, a semi-analytical switching control law is derived, enabling a solar sail to emulate a smaller effective characteristic acceleration (without changes in geometry or

We present an update on the multi-GNSS orbit and clock solution (COM), the CODE analysis center provides to the International GNSS service (IGS) in the frame of the multi-GNSS extension (MGEX). In recent years substantial progress was achieved in the fields of orbit modelling (Earth albedo, transmit antenna thrust, thermal radiation, eclipse attitude law), receiver and transmitter antenna calibration

We present results on temporal and longitudinal modulations of semidiurnal tide amplitudes in the mesosphere and lower thermosphere winds. The wind data were obtained during October – December 2017 when six meteor radars operated simultaneously. The radar network covers latitudes from 51°N to 72°N and longitudes from 13°E to 178°E. The results show a clear tidal 8-9 day amplitude modulation, which

The integer characteristics of the undifferenced ambiguity can be recovered after the correction of fractional cycle biases (FCB), which can significantly shorten the initialization time of precise point positioning (PPP). In the former work, the ambiguity resolution model of the client end needs to be consistent with the FCB products server. However, the client may face the problem that inconsistent

The next-generation satellite-based augmentation system (SBAS) will follow the dual-frequency multi-constellation (DFMC) protocol and broadcast satellite clock-ephemeris corrections and integrity information via GPS L5-like signals to improve the accuracy and integrity for GNSS dual-frequency users. BeiDou Navigation Satellite System (BDS)-3 B1C/B2a dual-frequency users will obtain a higher positioning

The selection of optimal actual evapotranspiration (ET) dataset for hydro-meteorological applications requires a detailed accuracy assessment and uncertainty characterization. This evaluation study was conducted at the site scale to compare the accuracies of ET measurements extracted from four widely used satellite- and model-based ET datasets (MOD16, GLEAM, GLDAS, and AWRA-L). Site-scale ET values

Low Earth Orbit (LEO) enhanced Global Navigation Satellite System (LeGNSS) has been recognized as the promising positioning system in the near future where mega-constellations of LEO satellites are used for precise positioning. Fast Precise Point Positioning (PPP) convergence can be achieved if LEO constellations are employed into current GNSS due to the fast motion of LEO satellites. In order to fulfill

Tomography is an important technique for ionosphere investigation. For a voxel-based tomography method, the way the voxel model is constructed is crucial and may affect the quality of the reconstructed image. However, previous research has paid less attention to voxel model construction and how this may improve or reduce the quality of the produced tomography image. To mitigate this issue, a new method

This study evaluates the performance of Ionospheric and Solar proxy indices for the International Reference Ionosphere extended to the Plasmasphere (IRI-Plas 2017/SPIM) model in predicting the Total Electron Content (TEC) over the East African equatorial region during the high (2014) and low (2018) solar activity periods of solar cycle 24. TEC is derived from Global Positioning System (GPS) installed

The earlier developed alternative technique for calculating the ionospheric contribution into the full phase of the signal on the transionospheric paths of propagation, based on the perturbation theory in spherical co-ordinates with the spherically symmetric inhomogeneous zero-order approximation for the ionosphere, is further extended in order to apply it to the two-frequency mode of operation of

CubeSats has evolved from purely educational tools, to useful platforms for technology demonstration and many practical applications. This paper reviews a CubeSat constellation mission involving 3 CubeSats launched into orbit on Sep. 25th 2015, aiming to demonstrate the integrated application of low-cost CubeSat technologies with distributed payloads using a group of satellites, as well as to demonstrate

This study presents a detailed comparative analysis of the two widely used percentage of occurrence methodologies used to compute the statistics of ionospheric scintillation activity based on the data of a Global Positioning System (GPS) Ionospheric Scintillation and (TEC) Total Electron Content Monitor (GISTM) receiver located at the northern Equatorial Ionization Anomaly (EIA) crest region Agartala

Thanks to 25-years of radar altimetry measurements from TOPEX/POSEIDON, Jason 1, 2 and 3, ENVISAT and others, water level changes of major lakes and rivers can be measured regularly, remotely, with unprecedented precision, facilitating monitoring of continental water storage variations. In addition, the 18 laser altimeter measurement campaigns over 6 years by the Ice, Cloud and Land Elevation Satellite

This study presents a comparison of tropospheric parameters, namely zenith tropospheric delay and total refractivity calculated using meteorological measurements from a Meteodrone and Global Navigation Satellite Systems (GNSS) stations. A Meteodrone is a unique Unmanned Aerial Vehicle (UAV) originally designed for automatic measurements of meteorological parameters in vertical profiles (up to 3 km

This work proposes the use of 2D Lattice Flower Constellations (2D-LFCs) to facilitate the design of a Low Earth Orbit (LEO) slotting system to avoid collisions between compliant satellites and to optimize the available orbital volume. Specifically, this manuscript proposes the use of concentric orbital shells of admissible “slots” with stacked intersecting orbits that preserve a minimum separation

4D Lattice Flower Constellations is a new constellation design framework, based on the previous 2D and 3D Lattice theories of Flower Constellations, that focus on the generation of constellations whose satellites can have different semi-major axis and still present a constellation structure that is maintained during the dynamic of the system. This situation can arise when dealing with satellites with

Over recent times there has been a rise in the number of objects placed into Earth orbit. With various countries licensing a number of large constellations, the orbital population is set to increase dramatically. A significant number of technical advances have facilitated this and, in the UK and elsewhere, this has been matched by the updating of legislation and an increased policy focus on the need

This paper studies the attitude tracking control problem of the rigid spacecraft with parametric uncertainties and unknown bounded disturbances. Firstly, an ideal generalized predictive controller (GPC) containing unknown items is constructed, which can optimize the receding horizon performance index and ensure the optimal performance of the closed-loop system. Afterward, in an attempt to estimate

This paper shows morphological similarity between aggregates separated from the lunar regolith ultra-fine size fraction and interplanetary dust particles (IDPs) collected in Earth’s stratosphere. It also demonstrates morphological difference between mentioned above and cometary particles from comet Wild 2 collected in the “Stardust” project. Given the number of lunar meteorites found on Earth, the

Urban heat island (UHI) refers to the occurrence of very high temperature patches in urban areas with respect to surrounding rural areas. The behaviour of Land Surface Temperature (LST) with different land covers varies for day and night time in a given urban area. Therefore, an attempt has been made for the comparative analysis of the day and night LST in two semi-arid cities in India i.e. Ahmedabad

This paper studies the problem of attitude stabilization for a rigid spacecraft subject to external disturbances, time-varying inertia uncertainties, and input magnitude and rate constraints (MRCs). By analyzing the influence of inertia uncertainties, the reconstruction of lumped disturbances is accomplished to facilitate the controller design. Then, a disturbance observer is designed, based on which