Satellite Frame Research Articles

Study on Word Formation and Coding of French and Romanian Table Separated Event Verbs

This article invites 10 native French and 10 Romanian speakers to describe 24 videos, and then compares the verbs representing separation events to conduct empirical research on separation events in French and Romanian. In the verb expression of separation events, both French and Romanian verbs use corresponding verb prefixes, indicating tension from "receiving" to "opening". However, when encoding the same separation event, the encoding focus of the two languages is different. Romanian focuses on the movement of a certain component after separation, while French focuses on the action itself. However, overall, both languages can be classified as dual frame languages with both satellite frame language and verb frame language features.

La expresión de eventos de movimiento causativos mediante verbos de contacto por impacto en alemán y sus correspondencias en español

Abstract The subject of this article is the expression of causative movement events in German and Spanish. It is hypothesized that, being respectively a satellite frame language and a verbal frame language, it is likely that both differ in the syntactic order with which the semantic material of the aforementioned events is expressed, a question already studied for this pair of languages in the intransitive movement events. It is especially interesting to analyse this possible interlingual difference in statements with types of verbs that cannot necessarily be expected to develop the triargumental scheme of these causative events (agent subject, affected object and dynamic locative complement) due to their basic argument structure. This contribution specifically studies the possible development of these triargumental structures by the so-called verbs of contact by impact. To do this, a one-way contrastive analysis is carried out, from German to Spanish, of a corpus of pairs of statements extracted from the PaGeS corpus. The results certify the existence of the phenomenon in both languages, but also point to important interlingual differences in their productivity.

Successive Energy Conversion at a Stepwise Dipolarization Front

Dipolarization fronts (DFs), ion-scale magnetic structures characterized by sharp enhancement of northward magnetic field developed within plasma jets, have been suggested to play a crucial role in the energy transfer chain in the terrestrial magnetotail. Here we present the first observation of successive energy conversion driven by multiple current layers at a stepwise DF, using high-cadence measurements from NASA’s Magnetospheric Multiscale mission. The multiple current layers are adjacent and cause gradual variations of particles and electromagnetic fields, leading to an intense, successive increase of energy conversion rates at the DF in the satellite frame, with electromagnetic field energy being transformed into particle energy. The energy conversion is contributed by both ion and electron currents. The motional electric field drives the energy conversion, while the wave electric field fed by lower hybrid drift instability modulates the energy partition. These results provide new insights into understanding energy transfer in the terrestrial magnetotail.

Design and manufacturing of nano satellite frame

Currently, small spacecraft and their constellations are increasingly used in the rocket and space industry due to several their advantages. A version of a nano satellite frame made by a method of composite three-dimensional printing is presented in the research. A finite element analysis, a comparison of a designed structure with an aluminium analogue, and an economic substantiation of the proposed method for manufacturing the nano satellite frame have been carried out.

Casting and forming of nano hard aluminum oxide film on the modified 6061 Al alloys for NARSSCube satellite structure

This research focuses on metal additive manufacturing (MAM) and examines the impact of alloying materials on the anodized produced layer, placing particular emphasis on its use in the construction of the NARSSCube satellite's frame. To enhance the AA6061-T6 Al alloy's mechanical and physical qualities, Mg, Mn, Si, and Cr concentrations were changed. As a result, seven different alloys were cast, and their mechanical and physical characteristics were assessed. It is essential to anodize aluminum alloy AA6061-T6 in H2SO4 solution in order to produce an aluminum oxide film (AOF) that increases corrosion and wear resistance. This study looked into how the chemical composition of the AA6061-T6 aluminum alloy, particularly Mn, affected the production of the nano hard aluminum oxide film (NHAOF) at fixed anodization conditions of 4 °C and 20 V. Calculations were made on the thickness variation at various operating voltages throughout the anodizing process. The differences in NHAOF thickness were investigated using optical and scanning electron microscopes. Finally, anodizing the alloy with low Mn Wt.% (0.005 wt% S6) at 4 °C, 20 V, and a duration period of 120 min in a 10 % H2SO4 solution produced the oxide coating with the highest thickness (53 μm) and high-performance attributes. An increase in the hardness ratio, resistance to plastic indentation, and elastic recovery are all results of the surface's harder (5.86 Gpa) than the un-anodized sample's (1.18 Gpa) surface.

A Comparative Study on the Solar Radiation Pressure Modeling in GPS Precise Orbit Determination

For Global Positioning System (GPS) precise orbit determination (POD), the solar radiation pressure (SRP) is the dominant nongravitational perturbation force. Among the current SRP models, the ECOM and box-wing models are widely used in the International GNSS Service (IGS) community. However, the performance of different models varies over different GPS satellites. In this study, we investigate the performances of different SRP models, including the box-wing and adjustable box-wing as a priori models, and ECOM1 and ECOM2 as parameterization models, in the GPS POD solution from 2017 to 2019. Moreover, we pay special attention to the handling of the shadow factor in the SRP modeling for eclipsing satellites, which is critical to achieve high-precision POD solutions but has not yet been fully investigated. We demonstrate that, as an a priori SRP model, the adjustable box-wing has better performance than the box-wing model by up to 5 mm in the orbit day boundary discontinuity (DBD) statistics, with the largest improvement observed on the BLOCK IIR satellites using the ECOM1 as a parameterization SRP model. The box-wing model shows an insignificant orbit improvement serving as the a priori SRP model. For the eclipsing satellites, the three-dimensional (3D) root mean square (RMS) values of orbit DBD are improved when the shadow factor is applied only in the D direction (pointing toward to Sun) than that in the three directions (D, Y, and B) in the satellite frame. Different SRP models have comparable performance in terms of the Earth rotation parameter (ERP) agreement with the IERS EOP 14C04 product, whereas the magnitude of the length of day (LoD) annual signal is reduced when the shadow factor is applied in the D direction than in the three directions. This study clarifies how the shadow factor should be applied in the GPS POD solution and demonstrates that the a priori adjustable box-wing model combined with ECOM1 is more suitable for high-precision GPS POD solutions, which is useful for the further GNSS data analysis.

E‐POP Observations of Suprathermal Electron Bursts in the Ionospheric Alfvén Resonator

AbstractUtilizing the suprathermal electron imager onboard the e‐POP satellite, we performed a statistical study of groups of repetitive suprathermal electron bursts (STEBs) with 52 events (each with ≥3 STEBs) during 21 e‐POP orbits. The STEBs are observed on both the day side and night side, and within a wide range of geomagnetic latitudes, from 64° to 78°. We interpret these data as temporally varying signatures; we suggest the repetition is due to the ionospheric Alfvén resonator (IAR), since the statistical time separation of adjacent STEBs in the satellite frame is 0.5–1.5 s, which is consistent with the characteristic period of the IAR. Furthermore, the STEBs are associated with low‐frequency magnetic field perturbations. The statistical occurrence of repetitive STEBs shows a preference toward postnoon and midnight sectors at high magnetic latitudes. We also present one example event of four successive STEBs associated with auroral rays in conjugate imagery. The repetition period of STEBs is similar to the oscillation period of magnetic fields observed by Enhanced Polar Outflow Probe (e‐POP). One of the STEBs in an example event exhibits “normal” dispersion (high energy particles with field‐aligned pitch angle arriving first) and the adjacent STEB exhibits “inverse” dispersion (low energy particles with broad pitch angles arriving first). With a test particle simulation, we propose one possible explanation of inverse dispersion in terms of a suprathermal electron population and a downward‐propagating parallel electric field.

Algorithm and software for minimization of temperature errors of fiber-optic gyroscopes, mounted on artificial earth satellites

The description of the developed algorithms and programs, which are used for calibration of fiber-optic gyroscopes working in the conditions of heat varying during spacecraft’s motion in circumterrestrial orbit, is discussed. The mathematical statement for problem of non-stationary heat conduction for the satellite frame and on-board devices is presented.The method of numerical solution is based on the combination of Finite Element Method for boundary value problem and finite difference time integration method for initial one. The developed approach which allows use the parallel calculations in heat problems, is described. The information about developed software is presented by description of main functions written in C++ language. The temperature distribution in dependence on time in the satellite frame and directly in fiber-optic gyroscope’s shell is found by use of developed software. Found distribution makes an opportunity at first to justify demands for ground calibration of gyroscopes for obtaining the compensation models. Secondly, the use of similar models in the conditions of uncertain value of gyroscope’s temperature, which can be, for example, in the case of heat-sensing device’s failure, can be done. The mathematical model of fiber-optic gyroscope snap data is discussed. The hypothesis of the linear dependence of the drift motion from temperature is suggested. The description of calibration algorithm for temperature model of fiber-optic gyroscope is presented. It was concluded that the main influence on the errors of fiber-optic gyroscope measurements is caused by temperature gradient and influence of absolute temperature is not so significant. Thereby, the minimization of temperature error of devices, which are affiliated in orientation and navigation on-board systems, can be performed as well as fail safety of such systems can be increased by use of the presented methods and algorithms.

Motion in Toposa: is Toposa a verb frame or satellite frame language?

AbstractThe goal of this paper is to discuss motion events in Toposa, an Eastern Nilotic language of South Sudan in the light of

Modeling of current characteristics of segmented Langmuir probe on DEMETER

We model the current characteristics of the DEMETER Segmented Langmuir probe (SLP). The probe is used to measure electron density and temperature in the ionosphere at an altitude of approximately 700 km. It is also used to measure the plasma flow velocity in the satellite frame of reference. The probe is partitioned into seven collectors: six electrically insulated spherical segments and a guard electrode (the rest of the sphere and the small post). Comparisons are made between the predictions of the model and DEMETER measurements for actual ionospheric plasma conditions encountered along the satellite orbit. Segment characteristics are computed numerically with PTetra, a three-dimensional particle in cell simulation code. In PTetra, space is discretized with an unstructured tetrahedral mesh, thus, enabling a good representation of the probe geometry. The model also accounts for several physical effects of importance in the interaction of spacecraft with the space environment. These include satellite charging, photoelectron, and secondary electron emissions. The model is electrostatic, but it accounts for the presence of a uniform background magnetic field. PTetra simulation results show different characteristics for the different probe segments. The current collected by each segment depends on its orientation with respect to the ram direction, the plasma composition, the magnitude, and the orientation of the magnetic field. It is observed that the presence of light H+ ions leads to a significant increase in the ion current branch of the I-V curves of the negatively polarized SLP. The effect of the magnetic field is demonstrated by varying its magnitude and direction with respect to the reference magnetic field. It is found that the magnetic field appreciably affects the electron current branch of the I-V curves of certain segments on the SLP, whereas the ion current branch remains almost unaffected. PTetra simulations are validated by comparing the computed characteristics and their angular anisotropy with the DEMETER measurements, as simulation results are found to be in good agreement with the measurements.

Elliptic Rendezvous in the Chaser Satellite Frame

The analysis of satellite rendezvous in planetary orbits typically derives control laws in a frame rotating with the target satellite. However, because the control law is ultimately required in the chaser satellite’s frame, knowledge of the chaser satellite’s motion with respect to the planet may be required to correctly transform the control laws. The transformation may also result in suboptimal or infeasible control laws if control components have different relative weights. A new approach is described that poses the rendezvous problem in the chaser satellite’s frame directly. A nonlinear transformation between the chaser and target frames, in terms of relative position and velocity variables is derived. This transformation is used to formulate and solve the second-order nonlinear rendezvous problem using optimal power-limited propulsion analytically. Thus, a framework is developed that can be used to solve the orbital transfer problem. The efficacy of the derived control algorithm is demonstrated by means of an example.

ULF Waves Associated with Solar Wind Deceleration in the Earth's Foreshock

Characteristics of ULF waves associated with the solar wind deceleration in the Earth's foreshock on 6–7 April 2003 is studied using the wave telescope technique. In the satellite frame, the ULF waves are the left-handed polarized and quasi anti-parallel propagating mode, with a power peak at about 18.63 mHz. The wave vector in the GSE coordinates is estimated to be κ = (−4.29, 2.28, 1.21) × 10−4 km−1. In the solar wind frame, the frequency of waves becomes −9.39 mHz after the Doppler shift correction. The propagation direction of the waves is thus reversed and correspondingly the polarization of the waves becomes right-handed. The above-mentioned characteristics of the ULF waves in the solar wind frame indicate that the ULF waves associated with the solar wind deceleration are the Alfven-whistler waves, which have been frequently reported in both the observations and computer simulations.

Nonmigrating tidal signals in the upper thermospheric zonal wind at equatorial latitudes as observed by CHAMP

Abstract. The accelerometer onboard CHAMP enables us to derive the thermospheric zonal wind at orbit altitudes (~400 km). Numerous equatorial overflights (~45 250) are used to investigate the influence of nonmigrating tides on the thermospheric zonal wind. In a previous study a so called "wave-4" longitudinally signal observed in the satellite frame was identified in the zonal wind residuals during equinox. Using four years of data (2002–2005), we determine the annual variation of this prominent feature which is strongest during the months of July through October and has a smaller second maximum during March/April. Due to the large data set we were able to separate the observed wavenumbers into the tidal components. Thereby, we can identify the eastward propagating diurnal tide with zonal wavenumber s=3 (DE3) as the prime cause for the observed wave-4 pattern in the zonal wind. Analyzing the zonal wind along the geographic and the dip equator revealed that the largest amplitudes of DE3 are found along the dip equator. Besides DE3 we present the full spectrum of nonmigrating tides in the upper thermosphere.

Differential Charging of Satellite Surface Materials

High electrostatic potentials of satellite surfaces can result in electrostatic discharges (ESDs) that can damage or interfere with the satellite electronics. Measurements of the satellite conducting frame potential relative to the plasma environment are typically used to provide information on the statistical probability of charging. The frame potential is usually measured from the spectrum of the ions incident to the satellite or by voltage probes outside the satellite plasma sheath. However, ESD events are more directly related to the differential charging of various surface materials on the satellite. We will present satellite differential charging observations of several sample materials from the Satellite Surface Potential Monitor (SSPM) on the Spacecraft Charging at High Altitudes (SCATHA) mission. The SSPM data are compared statistically with measurements of the satellite frame potential and with the ESD events detected by the SCATHA discharge monitor. Local time and radial occurrence of frame and SSPM sample potentials are shown to be very similar. However, the functional relationship between the sample and frame potentials appears to differ widely from event to event.

HEO Satellite Frame and Differential Charging and SCATHA Low-Level Frame Charging

Significant amounts of satellite charging data have been taken at geosynchronous (GEO) and near-GEO orbit and in low-altitude orbits. There are only limited satellite charging measurements at intermediate altitudes or at middle to high latitudes at high altitudes. In this paper, results of spacecraft frame and differential potentials are shown that were measured over several years on a highly elliptical orbit (HEO2) satellite with an apogee of ~7.2 R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</sub> geocentric and ~63deg inclination. The HEO2 frame and differential charging data were obtained using a plasma spectrometer. Measurements of HEO2 charging levels les -30 V are summarized according to their occurrence in magnetic local time and L. The data show that the HEO2 satellite frame charged to potentials les -30 V, and that the occurrence of satellite frame charging at these high latitudes mimics the charging local time patterns observed by GEO satellites. In addition, the data show that such charging extends from at least a minimum L of les 4 R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</sub> to L > 10 R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</sub> . It was found that the differential charging potential usually exceeded the frame potential and could be estimated by V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</sub> ~ 74 + 1.384 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</sub> . Separately, we show the results of a one-year study of the Spacecraft Charging AT High Altitude (SCATHA) satellite frame potential in the near-GEO region. SCATHA's frame potential was positive les 15% of the time and was ges - 1 V ~ 95% of the time. Large negative frame potentials (< - 1 V) occurred ~ 5% of the time. The data also showed that the large negative frame potentials preferentially occurred on the nightside, as expected, and that they occurred less that 1% of the time on the dayside. These statistics may be used as a reference for estimating the relative attraction of ionized outgassed contaminants for a satellite.

Generation of kinetic Alfvén waves by velocity shear instability on auroral field lines

Ion beams observed in the plasma sheet boundary layer (PSBL), cusp, and on the auroral zone field lines are expected to have spatial gradients in their drift velocity. Generation of kinetic Alfvén waves by velocity shear of the ion beams is discussed. It is shown that a hot ion beam can excite both a resonant kinetic Alfvén wave instability and a non-resonant coupled Alfvén-ion acoustic instability. For typical parameters, observed on the auroral field lines in the altitude range of 5–7 R E (where R E is the Earth’s radius), the frequency of the velocity shear modes, in the satellite frame of reference, lie in the ultra-low frequency (ULF) range. The noise due to velocity shear driven Alfvén modes is electromagnetic in nature, and has a finite parallel electric field component.

A statistical analysis of longitudinal dependences of upper thermospheric zonal winds at dip equator latitudes derived from CHAMP

New observations, obtained by the accelerometer onboard the CHAMP satellite, reveal a detailed picture of the thermospheric zonal wind. Based on three years of data (2002–2004) we have studied the longitudinal dependence of the zonal delta wind (deviations from the zonal average) at the dip equator. The large number of passes ( ∼ 33 750) allows to consider several aspects of the wind characteristics at the same time. For this analysis we derived the longitudinal variation of the zonal delta wind at about 400 km altitude and investigated its dependence on solar flux, magnetic activity, and season. Major longitudinal dependences are confined to the morning hours, 03-09 local time (LT). The amplitude of the delta wind is approximately proportional to the latitudinal displacement of the magnetic dip equator from the geographic equator. The direction of the delta wind reverses sign between the June and December Solstices. During Equinox seasons these large scale features are almost absent. The flux level of solar EUV has no significant influence on the longitudinal variations. A dependence on magnetic activity could only be found during the post-sunset hours, 18-21 LT. Performing a Fourier transform of our delta wind velocities revealed a dominance of the wavenumber 4 in the Equinox data at some LT sectors. The wave-4 structure is a prevailing feature in the slowly precessing satellite frame, which has been recently reported, e.g. in nonmigrating tidal temperature measurements of the SABER instrument on the TIMED satellite in the Mesosphere Lower Thermosphere (MLT) region. Therefore, this statistical study of zonal wind longitudinal dependences provides new observational evidence for the coupling of the various atmospheric layers by nonmigrating tides.

Troposphere‐thermosphere tidal coupling as measured by the SABER instrument on TIMED during July–September 2002

Coupling between the troposphere and lower thermosphere due to upward propagating tides is investigated using temperatures measured from the SABER instrument on the TIMED satellite. The data analyzed here are confined to 20–120 km altitude and ±40° latitude during 20 July to 20 September 2002. Apart from the migrating (Sun‐synchronous) tidal components, the predominant feature seen (from the satellite frame) during this period is a wave‐4 structure in longitude with extrema of up to ±40–50 K at 110 km. Amplitudes and longitudes of maxima of this structure evolve as the satellite precesses in local time and as the wave(s) responsible for this structure vary with time. The primary wave responsible for the wave‐4 pattern is the eastward propagating diurnal tide with zonal wave number s = 3 (DE3). Its average amplitude distribution over the interval is quasi‐symmetric about the equator, similar to that of a Kelvin wave, with maximum of about 20 K at 5°S and 110 km. DE3 is primarily excited by latent heating due to deep tropical convection in the troposphere. It is demonstrated that existence of DE3 is intimately connected with the predominant wave‐4 longitude distribution of topography and land‐sea difference at low latitudes, and an analogy is drawn with the strong presence of DE1 in Mars atmosphere, the predominant wave‐2 topography on Mars, and the wave‐2 patterns that dominate density measurements from the Mars Global Surveyor (MGS) spacecraft near 130 km. Additional diurnal, semidiurnal, and terdiurnal nonmigrating tides are also revealed in the present study. These tidal components are most likely excited by nonlinear interactions between their migrating counterparts and the stationary planetary wave with s = 1 known to exist in the Southern Hemisphere during this period just prior to the austral midwinter stratospheric warming of 2002.

In-flight spacecraft magnetic field monitoring using scalar/vector gradiometry

Earth magnetic field mapping from planetary orbiting satellites requires a spacecraft magnetic field environment control program combined with the deployment of the magnetic sensors on a boom in order to reduce the measurement error caused by the local spacecraft field. Magnetic mapping missions (Magsat, Oersted, CHAMP, SAC-C MMP and the planned ESA Swarm project) carry a vector magnetometer and an absolute scalar magnetometer for in-flight calibration of the vector magnetometer scale values and for monitoring of the inter-axes angles and offsets over time intervals from months to years. This is done by comparing the two magnetometer outputs for several days and for as many different external field directions and amplitudes in the satellite frame as available. The vector and the scalar sensor may be placed of the order of 2 m apart and at the end of an about 10 m long boom counted from the spacecraft centre-of-gravity. In line with the classical dual vector sensors technique for monitoring the spacecraft magnetic field, this paper proposes and demonstrates that a similar combined scalar/vector gradiometry technique is feasible by using the measurements from the boom-mounted scalar and vector sensors onboard the Oersted satellite. For Oersted, a large difference between the pre-flight determined spacecraft magnetic field and the in-flight estimate exists causing some concern about the general applicability of the dual sensors technique.

Magnetic turbulent spectra in the magnetosheath: new insights

Abstract. The spectrum of the magnetic fluctuations measured by the Cluster satellites in the inner magnetosheath is investigated using the k-filtering technique. On a case study, it is shown first that the wave vectors calculated from the Flux Gate Magnetometer (FGM) data fit well with those determined from the Spatio-Temporal Analysis of Field Fluctuations (STAFF) data for their common range of frequency, which allows one to confirm that the high pass filter applied to STAFF data does not alter the spatial characteristics of its spectra. Both analyses confirm the dominance of the mirror mode for frequencies up to 1.4Hz. Furthermore, by comparing the experimental charateristics of the identified mirror mode to the prediction of the linear theory, it is shown that the predicted maximum growth rate is observed in the frequency range 0-0.15Hz, i.e. the FGM range. All the rest of the mirror mode, identified for higher frequencies is more likely to be a non linear extension of the most instable one. This cascade on the spatial scales is, in turn, observed in the satellite frame as a temporal spread due to Doppler shift. Further implications on the real nature of the observed spectrum are discussed.