In the early morning on December 17, 2020 Beijing time, China's chang'E-5 probe successfully returned to the Earth with 1731 grams of lunar samples after completing drilling, shoveling, packaging of lunar soil and scientific exploration on lunar surface. It is the successful completion of the third phase of China's lunar exploration project, namely “circling, landing and returning to the moon”. The

Long sequences of ionograms from three European mid-latitude ionospheric stations (Athens, Nicosia, and Pruhonice) are examined, by applying the ‘height–time–intensity’ (HTI) technique along with Spectrum (Lomb periodogram) analysis with the aim to investigate the daily and seasonal variability of sporadic E (Es) and intermediate descending layers (IDLs). Es and IDL traces are observed over all three

Remote Sensing (RS) offers efficient tools for drought monitoring, especially in countries with a lack of reliable and consistent in-situ multi-temporal datasets. In this study, a novel RS-based Drought Index (RSDI) named Temperature-Vegetation-soil Moisture-Precipitation Drought Index (TVMPDI) was proposed. To the best of our knowledge, TVMPDI is the first RSDI using four different drought indicators

With the accessibility of Synthetic Aperture Radar (SAR) data and evolution of deep learning, several experiments have been performed in the recent years to actively monitor human activities at sea. Due to the flexible network configuration and complex nature, models based on Convolutional Neural Networks have been able to boost the performance of maritime target classification systems. The novel idea

Indo Gangetic flood plains are subjected to recurring floods due to large low-lying land areas adjacent to major Himalayan Rivers. Recent floods in the Ganga River during the late withdrawal phase of Indian summer monsoon rains in 2019 had reportedly caused the death of ∼200-500 people and damaged major infrastructures in different parts of Bihar, India. This paper presents a detailed analysis of the

With the deployment of the global BeiDou navigation satellite system (BDS-3) constellation completed, the positioning service performance is significantly improved relative to the regional system (BDS-2). As one of the key prerequisite products for precise point positioning (PPP), the combined BDS-2/BDS-3 real-time satellite clock estimation method is investigated in this study. Since the code hardware

The orbital dynamics in the gravitational environment of irregular asteroids is an important issue for space missions and a quite complex problem. In this paper we propose a methodological approach for computing periodic orbits around rotating, irregular-shaped asteroids. Our study starts from the families of periodic orbits of a triaxial ellipsoid model that can approximate the gravitational field

Detection of volcanic hazards are important for public health and aircraft safety. In this study, we investigate the ability to detect volcanic plume using a simple analytic approach based on Global Navigate Satellite System (GNSS) observations, numerical weather model (NWM) fields and ground-based automatic weather stations. The GNSS data obtained from the network located around the Sakurajima volcano

Diverse studies about equatorial plasma bubble structures and their relation with ionospheric scintillation have been performed in the last decades. Among many findings, the investigations usually reported dominant plasma bubble eastward velocity with a magnitude of few tens of m/s and larger amplitude scintillation for transionospheric signals aligned with these depleted structures. However, an uncommon

To reduce transportation costs for building a lunar base station, it is important to utilise in-situ resources like lunar regolith. Lunar regolith can be used to create a concrete-like material by means of geopolymerization. For application of geopolymerizing mixtures, the rheology of the slurry must be known in advance. This article investigates the rheology of mixtures of lunar dust simulants with

An on-board guidance generation approach for Mars pinpoint landing has been developed based on sequential convex programming. To optimize the flight time in the formulation, a discretized form of the landing problem was constructed under the conditions of linearized states, controls, and time increment between consecutive time steps. To implement this strategy in real time, on-board demonstrations

The evaluation of microvibrations effect is crucial for the success of remote sensing missions. The moving parts on the satellite such as reaction wheels can create microvibrations disturbances, which cause degradation of image quality. In our paper we present an experimental investigation methodology for on-ground quantification of wheel noise disturbance transmitted through the structure to the payload

Globally the land subsidence is a significant problem of the rapidly growing urban area. The factor responsible for the land subsidence caused by over-exploitation of the underground fluid such as water, petroleum, and gas respectively. In present study we present the result of detail investigation of active ground subsidance in New Delhi, National Capital Region (NCR). This area indicates a high rate

The relation between ionosonde critical frequency of ionospheric sporadic E-layer (foEs) and disturbed zonal wind is studied over Okinawa (26.68°N, 128.15°E), Rome (41.98°N, 12.49°E) and Townsville (19.63°S, 146.8°E) during different solar activity years, 1987 (moderate), 1996 (low) & 2001 (high) (Okinawa and Townsville) and 1987 (moderate), 1995 (low) & 2000 (high) (Rome). The variation of monthly

Central Yunnan Province is the political, economic, cultural, and transportation hub of Yunnan Province, China. Climate change has resulted in increased seasonality of global averaged precipitation, temperature, runoff, and evapotranspiration, thereby exacerbating extreme events such as drought and soil erosion. The simulation and mapping of drought and soil erosion within Central Yunnan Province is

NTCM is a relatively simple climatological ionosphere model. However, its weather ionosphere characteristic specification capability is limited. Also, its nowcasting and forecasting performance of the East-African equatorial ionosphere has not yet been tested. Therefore, this paper demonstrates techniques of changing NTCM to an ionospheric weather model that nowcasts and forecasts VTEC for East Africa

The Kototabang (0.20°S, 100.3° E, 10.36°S dip latitude) Equatorial Atmosphere Radar (EAR) observations of valley region field-aligned irregularities (FAI) reveal maximum percentage of occurrence (PO) of high signal to noise ratio (> 3 dB) type-B 150-km echoes during boreal summer (June-August) and winter (December-January) of solar moderate to minimum years 2016-2019. The PO is anomalously high in

Lithological maps derived from traditional pixel-based image analysis are widely established in remote sensing. Recent development of new segmentation-based approaches such as object-based image analysis (OBIA) has led to significant improvements of accuracy in land cover classifications. However, additional enhancements have been reported by coupling OBIA with machine learning (ML) techniques. ML

This study was done to investigate the effect of perturbations of both oblate massive primaries on the periodic orbit-attitude behavior of satellites at the three-body problem. Governing equations of the perturbed coupled orbit-attitude were derived using principles of the Lagrangian mechanics. As initial conditions of the coupled model play a key role in finding periodic responses of both orbit and

Investigations of the dynamics of the hot coronal plasma are crucial for understanding various space weather phenomena and making in-depth analyzes of the global heating of the solar corona. We present here numerical simulations of observations of siphon flows along loops (simple semi-circular flux ropes) to demonstrate the capabilities of the Solar Line Emission Dopplerometer (SLED), a new instrument

Based on the CORSIKA simulations of inclined extensive air sowers with proton and iron as primary particles, we have calculated the rise time (t1/2) of detected pulses in particle detectors. We performed the simulations for six different zenith angles between 20° and 53°. It is shown that the rise time has a strong dependence on the core location, zenith, and azimuth angle of a primary particle. Moreover

The BeiDou Navigation Satellite System with global coverage (BDS-3) was officially launched on July 31, 2020. In addition to the legacy B1I and B3I signals from the regional system (BDS-2), BDS-3 provides several new signals, i.e., B1C, B2a, B2b and B2a+b, with advanced technologies and global availability, which brings new opportunities for ground-based BDS multipath reflectometry (BDS-MR) altimetry

The present study provided the first-time comprehensive evaluation of 12 advanced statistical and machine learning (ML) algorithms for the Soil Moisture (SM) estimation from dual polarimetric Sentinel-1 radar backscatter. The ML algorithms namely support vector machine (SVM) with linear, polynomial, radial and sigmoid kernel, random forest (RF), multi-layer perceptron (MLP), radial basis function (RBF)

One of the major challenges in the Hayabusa2 sample-return mission was the second touchdown on the asteroid Ryugu, which was designed to collect subsurface materials near the artificial crater formed by a small carry-on impactor. Due to engineering and scientific requirements, a narrow area with a radius as small as 3.5 m was selected as the target landing site. To achieve pinpoint touchdown at the

This paper investigates the finite-time attitude stabilization of spacecraft under multiple uncertainties. Besides inertia uncertainties, external disturbances, and actuator faults, the measurement uncertainties are particularly considered. When including the measurement uncertainties, the spacecraft attitude control system becomes a mismatching system, which brings a great challenge to the control

In this paper, the far-distance nonplanar rapid cooperative rendezvous with multiple specific-direction thrusts is investigated. In the optimization process, the indirect method is adopted. The homotopy method is used to smooth the dynamical equations. The solutions of the initial co-state variables of the energy-optimal problem are obtained by the quantum-behaved particle swarm optimization (QPSO)

The ascending trajectory from the surface of Phobos to a resonant quasi-satellite orbit around Phobos is investigated with a newly proposed dynamical model based on the Elliptic Restricted Three-Body Problem. The proposed model incorporates the non-spherical gravity field and physical libration of Phobos as well. The trajectories from the surface of Phobos are classified into three types according

This study contains predictions for mass spectrometry and plasma instrument measurements during upcoming Venus flybys of BepiColombo and Solar Orbiter and discusses the possibility of a phosphine detection with mass spectrometry in Venus’ upper atmosphere. The results extend the ones published previously in Gruchola et al. (2019), where predictions for the proposed ESA mission EnVision and the Venus

Context Physical and dynamical characterisations of asteroids are used in different fields, such as Solar System formation modelling, Planetary Defence and Resources Prospecting. The vast majority of asteroids are not known in detail - have at best their orbit well defined - and the knowledge on the composition or internal structure is derived by models of reflectivity curves, with limited certainty

The continuously developing Global Navigation Satellite Systems (GNSS), in particular with the latest operational BDS and Galileo, provide good opportunities to enhance the performance of precise positioning. This study evaluates the performance of high-rate precise point positioning (PPP) applied for seismogeodesy with very recent BDS and Galileo. The static experiments with 20-Hz GNSS data show that

Satellite antenna phase center offsets (PCOs) is an important error source in global navigation satellite system (GNSS). With GNSS observations in a global network, the PCOs estimation strategy generally uses a dual-frequency (DF) ionospheric-free (IF) combination as the observation model. This model cannot derive the PCO values at each frequency, which results in the PCOs of the third frequency being

In the framework of the Coastal sea level project of the ESA Climate Change Initiative, a new coastal sea level product from the Jason-1, 2 and 3 missions over 2002–2018 has been made recently available. This product consists of along-track, high-resolution (20 Hz, i.e., ~350 m) sea level anomalies and coastal sea level trends derived from a complete reprocessing of the Jason altimetry data, including

Many predictors are considered in estimating the spatial distribution of air temperature. However, a key problem remains the optimal selection of predictors. In this study, genetic algorithm (GA) was used to select optimal regression variables among 17 predictors, and GA-selected predictors were applied to random forest (RF) regression models for mapping air temperature in eastern and central China

Remote sensing and aeromagnetic data analyses were conducted for the characterization of basement structural elements that influence iron ore deposits and other mineralization over kabba and its surroundings. Spectral analysis suggests depth to magnetic sources range from deep, intermediate, and shallow with depths (i.e., 2.8 km, 1.5 km, and 0.3 km respectively). Three lithological zones were revealed

The mixed function consisting of the harmonic and polynomial terms is used to model and study the characteristics of the GNSS satellite clock. The harmonic terms are obtained from the Fast Fourier Transform (FFT) results. The modeling results of the GNSS satellite clocks indicate that the RMS of GLONASS is the largest, and that of GPS Cs clocks is at the same level. The results also show that the RMS

Short-term investigations of atmospheric pollutants (PM10, PM2.5, SO2, NO2, O3, and CO) were performed during the Diwali festival over Varanasi for a period of six years from 2011 to 2016. Aerosol Optical Depth (AOD) observed for the corresponding days of Diwali was found to be considerably much higher and even its value reached 2.0 for some Diwali years, which is basically almost 3-folds than the

In this article, two popular linear empirical methods viz., log-ratio model (LRM) and log-linear model (LLM) are used to derive water depths in shallow nearshore waters from Sentinel-2 multi-spectral images. Based on these empirical models, a multi-scene ensemble and a non-linear Support Vector Regression (SVR) machine learning approaches are applied to improve the accuracies from these traditional

Monitoring earthquakes to rapidly forecast their consequences remains a challenging task, especially in areas far from seismic and geodetic networks. Large and shallow earthquakes induce disturbances in the ionospheric Total Electron Content (TEC). These disturbances are commonly detected using Global Navigation Satellite Systems (GNSS) stations that can sound the ionosphere at great distances. To

This work analyzes the geo-effectiveness of Coronal Mass Ejection- (CME-) induced storms by investigating the responses of ionospheric Vertical Total Electron Content (VTEC) and the Equatorial Ionization Anomaly (EIA) over the Indian sector to two storms. One of the storms occurred on February 19, 2014 (SYM-H: −120 nT), while the other occurred on June 23, 2015 (SYM-H: −204 nT). Both storms were driven

This paper studies the ionospheric response to a low-latitude annular solar eclipse event on 21 June 2020 at both eclipse and conjugate regions using a dense network of Global Navigation Satellite Systems receivers, Defense Meteorological Satellite Program and Swarm satellites data, as well as ionosonde measurements over the Asian-Oceania sector. The large scale ionospheric variation and small scale

By introducing the Kappa distribution function (κ) and considering the dimensionless variables and applying them to the Poisson equation, the Bohm sheath equation in a plasma is obtained. We know the above distribution function has two important factors: 1-the invariant kappa spectral index (κ0), 2-the number of degrees of freedom (de,Φ). In this regard, we considered soliton with positive and negative

Solar radio type II bursts serve as early indicators of incoming geo-effective space weather events such as coronal mass ejections (CMEs). In order to investigate the origin of high-frequency type II bursts (HF type II bursts), we have identified 51 of them (among 180 type II bursts from SWPC reports) that are observed by ground-based Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy

The paper presents a nonlinear dynamic model for DGMSCMGs, sometimes used as actuators to control the attitude of large satellites. The developed models describe the translation dynamics, the rotation dynamics of the Active Magnetic Bearing Rotor, as well as the rotation dynamics of the two mobile gimbals. Two control architectures are initially designed by using the dynamic inversion concept, pro

Safety of air transportation strongly depends on the performance of on-board positioning sensors. Positioning by data from navigational aids is considered by international aviation community as one of the main stand-by positioning approaches onboard of civil airplanes. However, only positioning by pair of distance measuring equipment (DME) meets requirements of Performance-Based Navigation. A DME service

One of the simplest and most popular methods to design a model-based controller for a nonlinear dynamic system is to apply linear control theories to the linearized model of the nonlinear system. For linearization, first-order Taylor series expansion is a straightforward and widely used method. Although the related linearization method is fairly simple, unfortunately, it causes an error in the linearized

Local measurement of ionospheric parameters such as electron density, electron neutral collision frequency, neutral density, and the background temperature has a great benefit to improve the empirical models and validate remote observations of the lower ionosphere. One of the well-established instruments that have been used on rocket payloads and satellites to study the dynamic and temporal evolution

In this paper, the China’s first global ocean Climate Data Records (CDRs) are used to analyze and predict the sea level changes in the Yellow Sea with obvious seasonal changes. Based on the singular spectrum analysis (SSA) method, the spatiotemporal and time series of sea level anomalies (SLAs) in the Yellow Sea are decomposed and de-noised. Then the long short-term memory (LSTM) neural network is

We analyze the time-variation of cosmic ray intensity during the periods when large and sudden disturbances occur and last for several days. We consider periods when there are sudden decreases of ≥ 5% in the galactic cosmic ray (GCR) intensity records. For the analysis, in addition to cosmic-ray intensity data, we utilize several solar wind plasma and field parameters. Time variation of changes in

The change in the phase, from quiescence to surge, may perturb the glacier’s dynamical behavior. To understand these changes through geospatial technique, the fastest moving tidewater Monacobreen Glacier, Svalbard, was studied for the year 2016 – 2019. It was elucidated that the surge had initiated during 2017 – 2018 before it the glacier was in quiescence since 2001. Initially, the glacier radar zones

AR (Ambiguity Resolution) is one of the critical issues in high-accuracy GNSS (Global Navigation Satellite System) applications. Commonly, the double-difference AR technique is employed in GNSS network data processing. With the demand of high-accuracy, low-latency and high-integrity GNSS orbit, the orbit estimation in sequential mode becomes a candidate of that in batch mode. Unlike orbit estimation

We report the estimation of the Maximum Usable Frequency of F2-layer for 3000 km circuit (MUF(3000)F2) using Earth-ionosphere geometry. The study is based on the assumption that h′F2 may replace hmF2 to estimate M(3000)F2. The monthly hourly medians of foF2,h′F2, and M(3000)F2 are extracted for Karachi (geog. coord. 24.9° N, 67.3° E) & Multan (30.2° N, 71.5° E) during 1996, 1992, & 1989 representing

Solar panel flexibility plays an important role in the attitude control of satellites. Therefore, traditionally the deformations of flexible solar panels are measured with a series of sensors along the panels itself. This paper presents a novel maiden attempt to simultaneously estimate the attitude and deformation of a flexible satellite using only 2 low-cost attitude sensors namely the sun sensor

The present study is aimed to investigate the variation in solar radiance, surface ozone, temperature, relative humidity and wind velocity during the most recent and one of the most significant annular solar eclipses of 21st June 2020. Effects of solar eclipse have been analyzed first time at eight different cities of India located nearly perpendicular to the eclipse axis having an eclipse magnitude

Currently, there are more than 130 available navigation satellites, a much larger scale low earth orbit (LEO) satellites will be deployed in the near future. However, limited by computational performance, capacity and receiver channels, a subset of all visible satellites is suggested to be selected with a with better geometric dilution of precision (GDOP). Since a reduced set of used satellite will

This investigation presents for the first time the seasonal and solar cycle variations of the daytime F-layer multiple stratifications (F3 and F4 layers) near the southern crest of the EIA in two different longitudinal sectors of South America. To perform the study, the ionograms recorded from 2007 to 2015 at Sao José dos Campos (23.2°S, 45.9°W), Brazil (eastern sector), and at Tucumán (26.9°S, 65

The GNSS tomography provides the opportunity to estimate atmospheric wet refractivity, which is important for precise positioning and navigation, as well as for constraining weather and climate models. The GNSS-derived water vapor is often estimated by implementing voxel-based inversions, but this technique is numerically unstable due to the high number of unknown parameters especially in networks

Soil Organic Carbon (SOC) is a measure of the total carbon content of the soil and is a vital soil health indicator. Over the decades, SOC has been estimated using sampling followed by rigorous laboratory-based testing methods. Spaceborne Microwave/Synthetic Aperture RADAR (SAR) remote sensing has proven to be a versatile tool for various soil study applications. However, there have been very few studies

Monitoring river water level is of great importance to understand hydrological and hydraulic processes and evaluate flood and landslide risk. This paper proposes a method for estimating river water levels under bridges using multi-temporal high-resolution synthetic aperture radar (SAR) intensity images. Due to the side-looking characteristics of SAR data acquisitions, bridges crossing over rivers usually

Increased focus on space debris push regulations by the UN and thereby the demand for debris removal systems to be implemented in future spacecraft. This research focuses on debris removal of post-mission satellites in LEO using drag augmented deorbit into the earth's atmosphere. By using gossamer sails (drag sails), aerodynamic breaking can effectively be achieved in LEO up to 700km. The presented

Lightning is a sudden release of electrostatic energy that plays a significant role in the ionospheric-magnetospheric coupling process. A short-term increase in the particle count rates (CR) in the Van Allen Radiation Belt (VAB) is known as the particle bursts. Due to lightning events, the increase in the number of high-energy particles in the inner region of the VAB (L<2) is a fascinating research