The LISA Pathfinder mission was flown to test some key technologies for the in-flight detection of gravitational waves. The mechanism developed to initialise the science phase, releasing the test mass into a geodesic trajectory, produced unexpected test mass states, requiring dedicated in-flight and on-ground test campaigns. Due to the limited information available from the telemetry, the analysis

In this work, the Global Ionospheric Maps (GIMs) are used to analyze the behavior of the mid-latitude ionospheric trough (MIT) during the solar cycle 24 (2008-2019). This analysis is performed for the Northern and Southern Hemispheres at different local times: 00, 02 and 04 LT. We study the MIT position dependence on the phase of the solar cycle , seasonal, and geomagnetic activity during the post-midnight

The assumption of spherical uniformity while the retrieval of electron density profiles from the Global Navigation Satellite Systems-Radio Occultation (GNSS-RO) observations is often violated and introduces significant errors in the retrieved electron density profile data. This paper presents an improved Abel-inversion technique by incorporating the horizontal gradients in the ionosphere, which are

The extensive arch-shaped features, solar prominences, are observed subtending high into the solar corona. Considering the prominences to be unbound, homogeneous and isothermal, invoking the background flow, in presence of the Newtonian radiation and turbulent viscosity, to investigate the spatial damping of compressional MHD waves, we derived a dispersion relation and solved it numerically for both

We present a comparison of the ionosphere and plasmasphere total electron content over nearly geomagnetic conjugate locations Pruhonice (50.0∘N, 14.6∘E; 45.7∘N geomagnetic), Czech Republic and Hermanus (34.4∘S, 19.2∘E; 42.3∘S geomagnetic), South Africa during the low solar activity period of 2009-2010. The bottomside ionosphere, topside ionosphere and plasmaspheric contributions to the total electron

For directly linking the dynamical reference frame of satellite orbits to the quasi-inertial reference frame of extra-galactic radio sources, observations of satellites with the Very Long Baseline Interferometry (VLBI) technique are the only conceivable method. Hence, the satellite observations should be embedded in VLBI network sessions during which also natural radio sources are observed. For this

Low-latitude auroras are extremely rare. In this work, we study the low-latitude aurora observed on November 14 and 15, 1789. Before this one, several auroras had been studied in the world but no one of low-latitude. As far as we know, this was the first to be studied observationally, physically and mathematically: two explanations were proposed, aurora’s height and overhead were measured, one aurora

We study the local-time, seasonal and solar cycle variations of Nitric Oxide (NO) infrared radiative emission, as observed by Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the NASA’s Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) satellite, over Indian longitude sector. It covers nineteen (January 2002-December 2020) years of NO radiative

Known for unique ultrahigh spatial resolution and timing accuracy, the VLBI global observing system (VGOS) time transfer of ultralong baselines can achieve better long-term stability compared to other techniques. Because of the 1 mm positioning accuracy of the VGOS, comparing high-performance atomic clocks with VGOS time transfer can be used to accurately determine the geopotential difference between

Nowadays, there are many dryness indices based on vegetation indices (VIs)-land surface temperature (Ts) feature space. Which dryness index should we use in dryness monitoring? The differences and capabilities for dryness monitoring among seven indices were evaluated in this study. These dryness indices were based on VIs-Ts or Albedo feature space. For instance, Temperature Vegetation Dryness Index

WorldView-3 (WV-3) is the first high spatial resolution and super-spectral commercial satellite which has the capability in improvement of geological mapping. The VNIR-SWIR data of this satellite are evaluated in this study for mapping the lithological units of a metamorphic-igneous terrain in Chadormalu area, Central Iran, by the use of support vector machine (SVM) classification method. Applying

The rocket exhaust, as a source of the disturbance, provides a way to examine physical and chemical phenomena in the ionosphere. Since the disturbance morphological characteristics are closely related to rocket orbit, the ionospheric perturbation produced by the rocket exhaust considering the trajectory effect is simulated. The three-stage booster rocket trajectory is calculated, considering multi-stage

The orientation of GNSS satellites in space is a key quantity in GNSS data processing. It is required to correctly apply several force models and observation corrections. Incorrect or insufficient modeling of satellite attitude can lead to inconsistencies both among providers of GNSS products and between providers and users, which negatively affects the quality of combined products and positioning

Humans are once again preparing to leave Earth and land on the surface of another planetary body. The two objects high on the list for permanent bases are the Moon and Mars. Both have been at the center of attention of many recent spaceflight activities, albeit these have so far been uncrewed. If humans indeed land on either one of them, science can potentially benefit tremendously. In the past, most

The Center for Orbit Determination in Europe (CODE) is contributing to the most recent reprocessing effort of the International GNSS Service (IGS) with a triple-system solution including GPS (since 1994), GLONASS (since 2002) and Galileo (since 2013). Several model improvements with respect to the operational processing scheme have been implemented and applied for the reprocessing effort: The first

Lunar Laser Ranging (LLR) measures the distance between observatories on Earth and retro-reflectors on Moon since 1970. In this paper, we study the effect of non-tidal station loading (NTSL) in the analysis of LLR data. We add the non-tidal loading effect provided by three data centres: the German Research Centre for Geosciences (GFZ), the International Mass Loading Service (IMLS) and EOST loading

Drought is an important natural disaster that causes devastating impacts on the ecosystem, livestock, environment, and society. So far, various remote-sensing methods have been developed to estimate drought conditions, each of which has advantages and restrictions. This study aims to monitor the real-time drought indices at the field scales via the integration of various earth observations. Our proposed

Single-frequency precise point positioning (SF-PPP) has attracted increasing attention due to its high precision and cost effectiveness. With various strategies to handle the dominant error, i.e., ionosphere delay, the ionosphere-float (IF), ionosphere-free-half (IFH), ionosphere-corrected (IC), and ionosphere-weighted (IW) SF-PPP models are certain to possess different characteristics and performance

The BeiDou global navigation satellite system (BDS-3) has established the Ka-band inter-satellite link (ISL) to realize a two-way ranging function between satellites, which provides a new observation technology for the orbit determination of BDS-3 satellites. Therefore, this study presents a BDS satellite orbit determination model based on ground tracking station (GTS) observations and ISL ranging

In road transport, continuous high-accuracy positioning is required in real time. To ensure the proper functioning and safety of vehicular applications, integrity monitoring (IM) is needed to protect from the positioning errors under a certain alert limit (AL) with a pre-defined probability of misleading information (MI). In this study, a detailed threat model is developed for real-time kinematic (RTK)

Some second order rain attenuation statistics such as fade duration and fade slope are investigated on the basis of experimental measurements of received signals using the GSAT-14 satellite beacon signal at 20.2 GHz for three years (2014–2016) over the tropical location Ahmedabad (23.02 0E, 72.510N), India with an Elevation angle of 630. Existing models of fade duration are compared with experimental

A method is proposed for reconstructing the electron density profiles N(h) of the IRI model from ionograms of topside satellite sounding of the ionosphere. An ionograms feature is the presence of traces of signal reflection from the Earth's surface. The profile reconstruction is carried out in two stages. At the first stage, the N(h) –profile is calculated from the lower boundary of the ionosphere

The existence of a “dense” lunar ionosphere has been controversial for decades. Positive ions produced from the lunar surface and exosphere are inferred to have densities that are ≲106 – 107 m−3 near the surface and smaller at higher altitudes, yet electron densities derived from radio occultation measurements occasionally exceed these values by orders of magnitude. For example, about 4% of the single-spacecraft

Wave observations are as yet an important technique to resolve fine structures in the plasma that cannot be identified by different instruments. In this way, we proposed the generation of electrostatic solitary waves during the interaction between the solar wind particles and Venus’s atmosphere at high altitude. The plasma system is treated as a multicomponent unmagnetized plasma consists of background

The emergence of private space actors may soon enable the growth of the novel market segments of space research and exploration, space resources utilization, and human access to space. The interdisciplinary field of Planetary Protection has to keep up with these advances. Planetary Protection is defined as a set of guidelines that aim to prevent the forward contamination of celestial bodies with biological

The Miniaturised Asteroid Remote Geophysical Observer (M-ARGO) is planned to be the first standalone deep-space CubeSat mission to rendezvous with and characterise a near-Earth asteroid. To this aim, it is essential to assess the attainable set of target asteroids. This work presents the initial results of the mission analysis and design of M-ARGO. In particular, the original procedure developed to

Interstellar dust grains are illuminated in the reflection nebulae. Under conditions of the PAH size and the intensity of the interstellar radiation field, we follow their impact on the PAH aromatic infrared bands using the numerical DustEM code. For a dust model consisting of PAH, amorphous C and amorphous silicate, the PAH size varies in a range from 0.31 to 4.9 nm while the radiation intensity varies

This paper reports disturbance in the mid-latitude sub-ionospheric VLF radio signals due to the super geomagnetic storm which began on 17 March 2015. Narrow-band signals from the NAA transmitter are studied for the storm period recorded at eight mid-latitude receiving stations spread over the Europe and USA. Daytime signals amplitude at all places showed a disturbing pattern after 17 March. Fluctuation

A passive neutron-bubble dosimeter, developed by Bubble Technology Industries, has been used for space applications. This study provides a means to characterize the response of these detectors to various particle types in support of bubble-detector measurements made on aboard the International Space Station (ISS) in Low Earth Orbit. An analysis of the radiation environment onboard the ISS in the Service

Nanosatellites have become an integral part of space research in recent years, especially for universities and non-profit organizations. Attitude estimation is a key function that is playing a leading role in the success of their missions. Despite various research and several implemented algorithms, it is difficult to find comprehensive analyses on the attitude filtering algorithms used for nanosatellite

The convergence period is of critical significance in Precise Point Positioning (PPP) applications. Current criterion for determining PPP convergence period is by comparing the positioning error to the ground truth. This experiment-based criterion can be influenced by many factors like the accuracy of ephemeris and the test area. One can hardly get a consistent result of the convergence period without

This paper discusses the estimation of zonal geomagnetic indices of two super geomagnetic activities of 2015 in the 24th solar cycle. It estimates the zonal geomagnetic indices (Dst, ap, AE) of 17 March and 22 June 2015 super storms with an artificial neural network model. The activities that happened in March and June are considered on the solar wind parameters (Bz, E, P, N, v, T) and zonal geomagnetic

Accessibility and precise modelling of tropospheric delay play a significant role in the precise Global Navigation satellite system (GNSS) positioning applications as well as meteorological studies and weather forecasting. However, if in the event that a GNSS Continuously Operating Reference Station (CORS) is inaccessible due to power outages, poor internet connectivity, equipment failure, and firmware

In Global Navigation Satellite (GNSS)-based positioning, a user within a region covered by a network of reference stations can take advantage of the network-estimated parameters. The use of State Space Representation (SSR) parameters as GNSS-augmentation is valuable for Network-Real Time Kinematic (N-RTK) positioning and enables the ambiguity resolution for Precise Point Positioning (PPP) in the so-called

In the framework of circular restricted three-body problem, the libration point orbits form the families of periodic and quasi-periodic solutions. In the paper, the mapping of initial conditions is utilized to describe and study the structure and properties of these families. A new numerical method for orbit generation, which is applicable both for the periodic and quasi-periodic orbits, is provided

Solar-terrestrial environment is manifested primarily by the physical conditions of the solar interior, solar atmosphere and eruptive solar plasma. Each parameter gives unique information about the Sun and its activity according to its defined characteristics. Hence the variability of solar parameters is of interest from the point of view of plasma dynamics on the Sun and into the interplanetary space

Commercial proposals for large constellations of satellites present a major problem in the field of Space Situational Awareness (SSA). Space traffic management systems must produce accurate and timely predictions of potential collisions for operators to perform evasive maneuvers. This requires precise orbit determination solutions, but limitations on sensor resources can impair tracker performance

This paper proposes a novel sequence-to-sequence recurrent neural network model to predict re-entry trajectories of uncontrolled space objects. The epoch and altitude information of the objects from two-line element data were interpolated to equally spaced data and were used as inputs to the model. More than 200 datasets from five different objects with already known re-entry times were used as the

Several studies have been showing that cosmic ray intensity variations observed at the Earth surface can be a useful tool to analyze and predict space weather and climate phenomena. However, before reach the ground level, the cosmic ray particles interact with different atmospheric atoms. This results in the generation of different secondary particles that are differently affected by atmospheric effects

The tethered-net is one of the most promising flexible space debris cleaning technologies to be developed in recent years. Momentum and geometric analysis were used to select four characteristic parameters of the tethered-net ejection system—the radius of the circumcircle of the net, the ratio of the bullet mass to the net mass, the ejection velocity of the bullet, and the ejection angle—to establish

Based on the very high frequency (VHF) radar data during 2014.03-2019.02 from Fuke station, we presented a statistical analysis of the presunset bottom-type scattering layers (BSLs) on geomagnetic quiet days at low latitudes and preliminarily discussed the relationship between geomagnetic activities and presunset BSLs. It is found that when the seasonally mean F10.7 index is less than 120 during the

Based on the known fault distribution in Sichuan-Yunnan region (SYR), a rigid Euler rotation model is constructed by using GPS velocities (1998∼2016) after excluding the stations near the fault boundaries and simultaneously a translation-rotation-strain model is constructed by using almost all GPS velocities to calculate three periods strain rate fields (2008.6∼2010.4, 2010.5∼2013.4 and 2013.5∼2016

This paper presents the development, testing, and early operation of a space-borne instrument that can measure and identify charged particles and neutrals in the energy range of 20 keV to 400 keV with a 6.25 keV energy resolution. The instrument generates electric fields perpendicular to its entrance aperture, which allows it to identify electrons, ions, and neutrals by deflecting the trajectories

In this study, we have analyzed several geometrical aspects of the concept of nonlocal-in-time kinetic energy by deriving the extended geodesic and geodesic deviation equations which are the basic stone for analyzing tidal and lunar gravitational forces. We have used these equations to study nonlocal tidal effects of the moon. It was observed that nonlocality-in-time generates higher-order corrections

It is known that the electrodynamic coupling of plasma flows with a magnetic field and background plasma leads to the generation of field-aligned currents that cause many effects in the auroral regions of the Earth during magnetic storms and sub-storms. Much less is known about the influence of field-aligned currents on the dynamics and evolution of plasma flows themselves. The study of this effect

The quality of real-time satellite clock offsets products is one of the key elements for real-time satellite clock performance monitoring and real-time precise point positioning (PPP). However, impacted by the station location, environment, communication equipment, receiver performance, network delay, temporary modem failure or other reasons, the observation data of clock offset datum receiver occasionally

Exploration of small body systems poses the problem of designing path planning strategies for possibly uncharted environments. Traditional methods aimed at developing rigorous trajectory baselines may suffer inefficiencies, or turn infeasible when confronted with unknown dynamics. In strongly non-linear dynamics, mapping point design solutions from one dynamical regime to another may be hindered by

MICROSCOPE is a space mission launched in 2016 that aims to test the validity of the Equivalence Principle (EP), the main postulate of General Relativity (GR), with a precision never reached before (TOUBOUL20011271). EP states that two bodies of different compositions and masses fall with the same acceleration in the same gravitational field. In order to achieve this goal, MICROSCOPE’s instrument is

Electrostatic solitary waves (ESWs) have been observed in the reconnection jet region in the Earth’s magnetotail by the Magnetospheric Multiscale spacecraft (MMS). A mechanism for the reconnection jet ESWs is proposed in term of slow and fast ion-acoustic solitons. At the time of occurrence of ESWs, no hot plasmasheet ions were observed. Based on the observations, the reconnection jet plasma is modeled

Radio occultations are commonly used to determine vertical profiles of ionospheric electron density from measurements of frequency. “Frequency residuals” are important intermediate data products in radio occultation experiments. Frequency residuals are defined as the difference between observed and predicted values of the received frequency, where the predicted frequency includes all effects except

Sand-dominated rivers undergo a temporal change in surface water extent and in the supply of the water during the year. These rivers are mainly recharged through precipitation, which showcases their vulnerability to climate-change-induced aridification. Accurately detecting the surface water spread of the river is very significant for understanding and preserving the ecosystem dependent on the river

With the expansion of GNSS applications, Global Navigation Satellite System Reflectometry (GNSS-R) technology has become an essential means for sea level monitoring. The development and improvement of multi-GNSS have brought new opportunities for ground-based GNSS-R sea level inversion research. More than 100 satellites in orbit are expected to improve the time resolution and the reliability of inversion

The present study is focused to understand the geomagnetic storm effects on the short- and long-term variations of ionospheric Total Electron Content (TEC) over the equatorial and low latitude sectors. GPS-TEC observations over a near equatorial station Bangalore and low latitude stations Waltair and Hyderabad during the declining phase of the 24th solar cycle (2015 to 2019) is analysed. The TEC variations

Trans-ionospheric signals such as the Global Positioning System (GPS) signals propagating through irregular ionospheric plasma structures may experience phase variation and amplitude fades causing degradation in system performance. This paper investigates the latitudinal structure of equatorial F-region irregularities (EFI) in the African region at different seasons using a GPS-based proxy index (rate

Rain is one of the most dominant factors for satellite communication systems link performance at frequencies above 10 GHz, increasing rapidly at higher frequencies. The prediction of time dynamics of the rain attenuation is required to improve the efficiency of various fade mitigation techniques (FMTs) to reduce signal fading. Fade duration and fade slope statistics are used to describe the dynamic

In a recent paper we had discussed possibility of DM at high redshifts forming primordial planets composed entirely of DM to be one of the reasons for not detecting DM (as the flux of ambient DM particles would be consequently reduced). In this paper we discuss the evolution of these DM objects as the Universe expands. As Universe expands there will be accretion of DM, helium and hydrogen layers (discussed

Spatially distributed information of actual Evapotranspiration (ET) is essentially required for various applications in agriculture, as well as studies related to water balance. An Energy Balance model that uses optical and thermal remote sensing datasets is appropriate for the spatially distributed estimation of ET, which is primarily controlled by local environmental conditions. In this study, we

The capability of IRI-2016 in reproducing the hemispheric asymmetry, the winter and semiannual anomalies has been assessed over the equatorial ionization anomaly (EIA) during quiet periods of years 2013-2014. The EIA reconstructed using Total Electron Content (TEC) derived from Global Navigation Satellite System was compared with that computed using IRI-2016 along longitude 25o - 40oE. These were analyzed

The aim of this paper is to study the properties of the materials for spacecraft surfaces under the effects of simulated low Earth orbit (LEO) plasma environment to understand the effects of charging and discharging phenomena, which are known to take place when spacecraft is moving through space plasma in LEO. Anodized aluminum Al2O3 samples were prepared using electrochemical techniques with different

Recent observations have detected significant escape of ions from the Venusian ionosphere. The measurements indicate that the composition of the escaping mix of ions may reach a critical ratio of H+: O+≈2:1, suggesting that it originated in water molecules, in line with the observed dryness of the planet. In this work, we suggest an additional mechanism that can explain the escape of ions from Venus