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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
Showing 1 - 30 of 30 Journals sorted alphabetically
Acta Astronautica     Hybrid Journal   (Followers: 220)
Advances in Aerospace Engineering     Open Access   (Followers: 74)
Advances in Aerospace Science and Technology     Open Access   (Followers: 14)
Advances in Astronautics Science and Technology     Hybrid Journal   (Followers: 2)
Advances in Space Research     Hybrid Journal   (Followers: 295)
Aeronautical Journal, The     Hybrid Journal   (Followers: 9)
Aerospace     Open Access   (Followers: 64)
Aerospace Medicine and Human Performance     Full-text available via subscription   (Followers: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 306)
Aerospace Systems     Hybrid Journal   (Followers: 10)
Aerospace technic and technology     Open Access   (Followers: 7)
Aerotecnica Missili & Spazio : Journal of Aerospace Science, Technologies & Systems     Hybrid Journal   (Followers: 6)
AIAA Journal     Hybrid Journal   (Followers: 1002)
Air Medical Journal     Hybrid Journal   (Followers: 6)
Aircraft Engineering and Aerospace Technology     Hybrid Journal   (Followers: 139)
Artificial Satellites     Open Access   (Followers: 21)
ASTRA Proceedings     Open Access   (Followers: 3)
Astrodynamics     Hybrid Journal   (Followers: 4)
Aviation     Open Access   (Followers: 12)
Aviation in Focus - Journal of Aeronautical Sciences     Open Access   (Followers: 7)
Aviation Psychology and Applied Human Factors     Hybrid Journal   (Followers: 23)
Aviation Week     Full-text available via subscription   (Followers: 411)
Canadian Aeronautics and Space Journal     Full-text available via subscription   (Followers: 31)
CEAS Aeronautical Journal     Hybrid Journal   (Followers: 30)
Chinese Journal of Aeronautics     Open Access   (Followers: 19)
Ciencia y Poder Aéreo     Open Access   (Followers: 3)
Civil Aviation High Technologies     Open Access   (Followers: 6)
Control Systems     Hybrid Journal   (Followers: 235)
Cosmic Research     Hybrid Journal   (Followers: 5)
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 25)
Fatigue of Aircraft Structures     Open Access   (Followers: 21)
Frontiers in Aerospace Engineering     Open Access   (Followers: 20)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 15)
Gyroscopy and Navigation     Hybrid Journal   (Followers: 177)
IEEE Aerospace and Electronic Systems Magazine     Full-text available via subscription   (Followers: 251)
IEEE Journal on Miniaturization for Air and Space Systems     Hybrid Journal   (Followers: 2)
IEEE Transactions on Aerospace and Electronic Systems     Hybrid Journal   (Followers: 281)
IEEE Transactions on Circuits and Systems I: Regular Papers     Hybrid Journal   (Followers: 43)
International Journal of Aeroacoustics     Hybrid Journal   (Followers: 37)
International Journal of Aerodynamics     Hybrid Journal   (Followers: 46)
International Journal of Aeronautical and Space Sciences     Hybrid Journal   (Followers: 4)
International Journal of Aerospace Engineering     Open Access   (Followers: 86)
International Journal of Aerospace Innovations     Full-text available via subscription   (Followers: 23)
International Journal of Aerospace Psychology     Hybrid Journal   (Followers: 22)
International Journal of Aerospace Sciences     Open Access   (Followers: 36)
International Journal of Applied Geospatial Research     Hybrid Journal   (Followers: 7)
International Journal of Aviation Management     Hybrid Journal   (Followers: 5)
International Journal of Aviation Technology, Engineering and Management     Full-text available via subscription   (Followers: 8)
International Journal of Aviation, Aeronautics, and Aerospace     Open Access   (Followers: 9)
International Journal of Crashworthiness     Hybrid Journal   (Followers: 10)
International Journal of Micro Air Vehicles     Open Access   (Followers: 11)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 15)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 13)
International Journal of Space Structures     Full-text available via subscription   (Followers: 19)
International Journal of Space Technology Management and Innovation     Full-text available via subscription   (Followers: 11)
International Journal of Sustainable Aviation     Hybrid Journal   (Followers: 5)
Investigación Pecuaria     Open Access   (Followers: 1)
Journal of Aerodynamics     Open Access   (Followers: 27)
Journal of Aeronautical Materials     Open Access   (Followers: 10)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 66)
Journal of Aerospace Engineering & Technology     Full-text available via subscription   (Followers: 22)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 27)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 57)
Journal of Aerospace Technology and Management     Open Access   (Followers: 10)
Journal of Aircraft     Hybrid Journal   (Followers: 263)
Journal of Aircraft and Spacecraft Technology     Open Access   (Followers: 15)
Journal of Airline and Airport Management     Open Access   (Followers: 11)
Journal of Astrobiology & Outreach     Open Access   (Followers: 5)
Journal of Aviation Technology and Engineering     Open Access   (Followers: 10)
Journal of Aviation/Aerospace Education & Research     Open Access   (Followers: 2)
Journal of Engineering and Technological Sciences     Open Access   (Followers: 2)
Journal of Guidance, Control, and Dynamics     Hybrid Journal   (Followers: 165)
Journal of KONBiN     Open Access   (Followers: 4)
Journal of Navigation     Hybrid Journal   (Followers: 176)
Journal of Propulsion and Power     Hybrid Journal   (Followers: 569)
Journal of Space Safety Engineering     Hybrid Journal   (Followers: 8)
Journal of Space Weather and Space Climate     Open Access   (Followers: 30)
Journal of Spacecraft and Rockets     Hybrid Journal   (Followers: 702)
Journal of Spatial Science     Hybrid Journal   (Followers: 4)
Journal of the American Helicopter Society     Full-text available via subscription   (Followers: 9)
Journal of the Astronautical Sciences     Hybrid Journal   (Followers: 11)
Journal of the Australasian Society of Aerospace Medicine     Open Access   (Followers: 3)
Journal of Wind Engineering and Industrial Aerodynamics     Hybrid Journal   (Followers: 21)
Life Sciences in Space Research     Hybrid Journal   (Followers: 5)
MAD - Magazine of Aviation Development     Open Access   (Followers: 3)
Mekanika : Jurnal Teknik Mesin i     Open Access  
Microgravity Science and Technology     Hybrid Journal   (Followers: 3)
New Space     Hybrid Journal   (Followers: 6)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
npj Microgravity     Open Access   (Followers: 3)
Open Aerospace Engineering Journal     Open Access   (Followers: 4)
Perspectives of Earth and Space Scientists i     Open Access   (Followers: 1)
Population Space and Place     Hybrid Journal   (Followers: 10)
Problemy Mechatroniki. Uzbrojenie, lotnictwo, inżynieria bezpieczeństwa / Problems of Mechatronics. Armament, Aviation, Safety Engineering     Open Access   (Followers: 3)
Proceedings of the Human Factors and Ergonomics Society Annual Meeting     Hybrid Journal   (Followers: 16)
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (Followers: 42)
Progress in Aerospace Sciences     Full-text available via subscription   (Followers: 82)
Propulsion and Power Research     Open Access   (Followers: 89)
REACH - Reviews in Human Space Exploration     Full-text available via subscription   (Followers: 5)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 20)
RocketSTEM     Free   (Followers: 5)
Russian Aeronautics (Iz VUZ)     Hybrid Journal   (Followers: 23)
Science and Education : Scientific Publication of BMSTU     Open Access   (Followers: 1)
Space and Polity     Hybrid Journal   (Followers: 6)
Space Policy     Hybrid Journal   (Followers: 30)
Space Research Today     Full-text available via subscription   (Followers: 43)
Space Safety Magazine     Free   (Followers: 50)
Space Science International     Open Access   (Followers: 117)
Space Science Reviews     Hybrid Journal   (Followers: 92)
SpaceNews     Free   (Followers: 779)
Spatial Information Research     Hybrid Journal   (Followers: 1)
Transactions on Aerospace Research     Open Access   (Followers: 1)
Transport and Aerospace Engineering     Open Access   (Followers: 4)
Transportmetrica A : Transport Science     Hybrid Journal   (Followers: 7)
Unmanned Systems     Hybrid Journal   (Followers: 4)
Xibei Gongye Daxue Xuebao / Journal of Northwestern Polytechnical University     Open Access  
Вісник Національного Авіаційного Університету     Open Access   (Followers: 1)

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Journal Cover
Artificial Satellites
Journal Prestige (SJR): 0.302
Citation Impact (citeScore): 1
Number of Followers: 21  

  This is an Open Access Journal Open Access journal
ISSN (Print) 0208-841X - ISSN (Online) 2083-6104
Published by Sciendo Homepage  [370 journals]
  • QHY-174M-GPS Camera as the Device for Photometry of Artificial Satellites

    • Abstract: In this paper, we make an attempt to use the QHY174M-GPS camera for the photometry research of fast-rotating artificial objects including debris, satellites and rocket bodies. This device is useful for imaging occultations, eclipses, meteors, and so on due to a highly precise recording of the time (GPS-based) and location of the observation on every frame and fast readout of the CMOS detector. The precision of time registration by the QHY174M-GPS camera is at the level of microseconds. All light curves obtained by studied camera during observations of artificial satellites in this work were carried out at Derenivka Observatory of Uzhhorod National University, Ukraine. The created photometric system with QHY174M-GPS camera as the detector and reflector telescope with parameters D=120mm, F=114mm, FOV=2.82°1.76° was calibrated. For target observations, SharpCap software was used. For the purposes of photometry processing, ccd_phot software was developed using Python 3.8 programming language with astropy and photutils packages. Photometry observations of artificial satellites of the Earth and standard stars were carried out. Over 80 lightcurves of artificial satellites were obtained. Comparing synchronous observations from two sites, separated 15 km from each other, we can conclude that photometry on the QHY174M-GPS camera gave us the same shape of lightcurve and additional advantages, such as time of exposure or simplicity of usage.
      PubDate: Fri, 22 Apr 2022 00:00:00 GMT
  • Geodetic Precession of the Sun, Solar System Planets, and their Satellites

    • Abstract: The effect of the geodetic precession is the most significant relativistic effect in the rotation of celestial bodies. In this article, the new geodetic precession values for the Sun, the Moon, and the Solar System planets have been improved over the previous version by using more accurate rotational element values. For the first time, the relativistic effect of the geodetic precession for some planetary satellites (J1–J4, S1–S6, S8–S18, U1–U15, N1, and N3–N8) with known quantities of the rotational elements was studied in this research. The calculations of the values of this relativistic effect were carried out by the method for studying any bodies of the Solar System with long-time ephemeris. As a result, the values of the geodetic precession were first determined for the Sun, planets in their rotational elements, and for the planetary satellites in the Euler angles relative to their proper coordinate systems and in their rotational elements. In this study, with respect to the previous version, additional and corrected values of the relativistic influence of Martian satellites (M1 and M2) on Mars were calculated. The largest values of the geodetic rotation of bodies in the Solar System were found in Jovian satellite system. Further, in decreasing order, these values were found in the satellite systems of Saturn, Neptune, Uranus, and Mars, for Mercury, for Venus, for the Moon, for the Earth, for Mars, for Jupiter, for Saturn, for Uranus, for Neptune, and for the Sun. First of all, these are the inner satellites of Jupiter: Metis (J16), Adrastea (J15), Amalthea (J5), and Thebe (J14) and the satellites of Saturn: Pan (S18), Atlas (S15), Prometheus (S16), Pandora (S17), Epimetheus (S11), Janus (S10), and Mimas (S1), whose values of geodetic precession are comparable to the values of their precession. The obtained numerical values for the geodetic precession for the Sun, all the Solar System planets, and their satellites (E1, M1, M2, J1–J5, J14–J16, S1–S6, S8–S18, U1–U15, N1, and N3–N8) can be used to numerically study their rotation in the relativistic approximation and can also be used to estimate the influence of relativistic effects on the orbital–rotational dynamics of bodies of exoplanetary systems.
      PubDate: Fri, 22 Apr 2022 00:00:00 GMT
  • Efficient Cost-Effective Static-PPP Using Mixed GPS/Glonass
           Single-Frequency Observations (KSA)

    • Abstract: Precise point positioning (PPP) is a GNSS positioning technique that saves cost and has an acceptable accuracy for enormous applications. PPP proved its efficiency through two decades comparing with traditional differential positioning technique. PPP uses one receiver collecting observations at an unknown station without the need for a reference station with known coordinates. PPP-collected observations must undergo extensive mitigation of different GNSS errors. Static-PPP accuracy depends mainly on the observations type (dual or single frequency), used systems (GPS or GLONASS or mixed GPS/GLONASS), satellites geometry, and observations duration. Static-PPP using dual-frequency observations gives optimum accuracy with a high cost. Static-PPP using single-frequency observations gives acceptable accuracy with a low cost. Since the end of 2012, PPP users are able to depend on GLONASS system as an alternative. This research investigates singe-frequency/static-PPP accuracy variation on KSA based on different factors: the system used (GPS or GLONASS or GPS/GLONASS), satellites geometry, observations duration, and ionosphere activity state. Observations from 2 days reflecting different ionospheric activity states were used for this research from three CORS stations (KSA-CORS network) operated by KSA-General Authority for Survey and Geospatial Information (KSA-GASGI). It can be concluded that precision (0.05 m lat., 0.12 m long., and 0.13 m height) under quiet ionosphere and precision (0.09 m lat., 0.20 m long., and 0.23 m height) under active ionosphere could be attained using 24 h mixed GPS/GLONASS single-frequency observations. Static-PPP using 24 h mixed GPS/GLONASS single-frequency observations’ accuracies are 0.01 m lat., 0.01 m long., and 0.03 m height (quiet ionosphere) and 0.01 m lat., 0.06 m long., and 0.06 m height (active ionosphere) compared to true station coordinates.
      PubDate: Fri, 22 Apr 2022 00:00:00 GMT
  • Integration of Artificial Neural Network and the Optimal GNSS
           Satellites’ Configuration for Improving GNSS Positioning Techniques (A
           Case Study in Egypt)

    • Abstract: Nowadays, theglobal navigation satellite system (GNSS) positioning techniques based on the International GNSS Service (IGS) products are extensively used for various precise applications. However, specific conditions such as the dual-frequency observations and the final IGS products are required. Consequently, the absence of the final IGS data and using single-frequency observations will degrade these techniques’ accuracy. In this paper, two algorithms through two separated stages are formulated for improving the single-frequency GNSS observations by using one GNSS receiver based on the broadcast ephemerides in real time or close to real time. The first algorithm represents the preparation stage for the second one. It classifies the observations by separating the optimal values of position dilution of precision (PDOP) and the number of satellites (NOS), as well as the corresponding values of coordinates. The second stage includes an algorithm based on the artificial neural network (ANN) approach, which is set at the ANN variables that produce the best precision through the applied tests at the present study. Binary numbers, log sigmoid-Purelin, cascade forward net, and one hidden layer with a size of 10 neurons are the optimal variables of ANN inputs format, transfer functions constellations, feedforward net type, and the number of hidden layers (NHL) and its size, respectively. The simulation results show that the designed algorithms produce a significant improvement in the horizontal and vertical components. Lastly, an evaluation stage is performed in the case of dual-frequency observations by using broadcast ephemerides. The simulation outputs indicate that the precision at applying the proposed integration is completely enhanced compared with the outputs of IGS final data.
      PubDate: Fri, 22 Apr 2022 00:00:00 GMT
  • Reliability of CSRS-PPP for Validating the Egyptian Geodetic Cors Networks

    • Abstract: The development, utilization, and maintenance of continuously operating reference stations (CORS) network are vital in many areas of surveying and geodesy, such as controllinggeodetic networks, developinglocal ionospheric models, and estimating the tectonic plate movements. Accordingly, the Egyptian Surveying Authority (ESA) established a CORS network consisting of 40 stations covering the Nile valley and its delta in 2011. CORS collect global navigation satellite system (GNSS) data. Recently, Egypt has witnessed rapid growth in many infrastructure projects and the development of new cities on a national scale. Therefore, there is an urgent need to investigate the ESA-CORS accuracy; the quality of data from the ESA-CORS must be considered for monitoring continuous tectonic motion, coordinating changes, and for Egypt’s development plan. Contemporary research worldwide identified considerable benefits of the precise point positioning (PPP) solution of dual- or single-frequency GNSS data. This study investigates the reliability of using the CSRS-PPP service for three consecutive observation days of 32 ESA-CORS networks in Egypt and the surrounding six international GNSS services (IGS)-CORS. For ESA-CORS, the PPP solution showed a root mean square error (RMSE) value of 6 mm (standard deviation [SD] = 3–4 mm) in east and north; for the height direction, the solution indicated an RMSE value of 22 mm (SD was about 14 mm). At a confidence level of 95%, this study revealed that SD95% was 2 mm in east and north directions and 6–7 mm for the height direction. This study shows that the PPP solution shown from the ESA-CORS stations is associated with two times better for horizontal and four times for the height direction than the delivered form ESA-CORS stations.
      PubDate: Fri, 22 Apr 2022 00:00:00 GMT
  • Measurements to Space Debris in 2016–2020 by Laser Sensor at
           Borowiec Poland

    • Abstract: In 2014, a significant upgrade was made to the Borowiec (BORL 7811) laser-ranging system, which is the part of Space Research Centre of the Polish Academy of Sciences (SRC PAS). Two high-energy lasers modules were installed. First is the EKSPLA PL-2250, used for tracking objects equipped with retroreflectors. Second is the Continuum Surelite III, dedicated to the tracking of space debris without retroreflectors. In 2016, the BORL station joined the space debris tracking laser group and, since then, is tracking systematically inactive/defunct satellites and typical rocket bodies from LEO regime. Today, the BORL is tracking regularly about 80 different space debris objects. The paper presents the activity of the BORL laser station in observations of space debris. The results presented are from years 2016 to 2020. The sum of all passes from this period is almost 2 000, giving over 23 000 normal points. Average root mean square error (RMS) of objects with satellite laser ranging-dedicated (SLR-dedicated) retroreflectors ranges 1.5 cm–14 cm and of objects without SLR-dedicated retroreflectors ranges 8 cm–222 cm.
      PubDate: Tue, 18 Jan 2022 00:00:00 GMT
  • Distance Between Two Keplerian Orbits

    • Abstract: In this paper, constrained minimization for the point of closest approach of two conic sections is developed. For this development, we considered the nine cases of possible conics, namely, (elliptic–elliptic), (elliptic–parabolic), (elliptic–hyperbolic), (parabolic–elliptic), (parabolic–parabolic), (parabolic–hyperbolic), (hyperbolic–elliptic), (hyperbolic–parabolic), and (hyperbolic–hyperbolic). The developments are considered from two points of view, namely, analytical and computational. For the analytical developments, the literal expression of the minimum distance equation (S) and the constraint equation (G), including the first and second derivatives for each case, are established. For the computational developments, we construct an efficient algorithm for calculating the minimum distance by using the Lagrange multiplier method under the constraint on time. Finally, we compute the closest distance S between two conics for some orbits. The accuracy of the solutions was checked under the conditions that L solution ≤ ɛ1; G solution ≤ ɛ2, where ɛ1,2 < 10−10. For the cases of (parabolic–parabolic), (parabolic–hyperbolic), and (hyperbolic–hyperbolic), we studied thousands of comets, but the condition of the closest approach was not met.
      PubDate: Fri, 08 Oct 2021 00:00:00 GMT
  • First Results of Time Series Analysis of the Permanent GNSS Observations
           at Polish EPN Stations Using GipsyX Software

    • Abstract: The aim of this work is to explore, for the first time in Poland, the possibility of determining Earth’s crust movements from permanent observations at selected permanent stations using the GipsyX software for a period of 8 years (2011–2018) in the ITRF2014 reference frame. The data used in this work are from 15 Aktywna Sieć Geodezyjna (ASG)-EUPOS stations from 2011 to 2018, which are also European Permanent Network (EPN) stations. The stations Borowa Góra, Borowiec, Józefosław, Lamkówko, and Wroclaw are also International Global Navigation Satellite Systems (GNSS) Service (IGS) stations. Daily data, rinex files, for these stations have been made available for this work by the Main Office of Surveying and Cartography. The calculations were made using the GipsyX software in the ITRF14 reference frame. The tests performed have shown that daily solutions from 8-year-long time series give secular trends with an accuracy of 0.01 mm/yr. Our results suggest that there are small differences in horizontal and vertical velocities and in the accuracy estimated between our and EPN solutions. At some stations, for example, Łódź, the differences are much larger. The impact of additional GNSS observations on the accuracy of determination of horizontal and vertical movements of the Earth’s crust shows a submillimeter accuracy in computed coordinates of stations even at a relatively small time interval. It means that multi-GNSS Precise Point Positioning (PPP) processing can be used in the future for the estimation of geodynamic processes.
      PubDate: Fri, 08 Oct 2021 00:00:00 GMT
  • Evaluation of GGMs Based on the Terrestrial Gravity Data of Gravity
           Disturbance and Moho Depthin Afar, Ethiopia

    • Abstract: To estimate Moho depth, geoid, gravity anomaly, and other geopotential functionals, gravity data is needed. But, gravity survey was not collected in equal distribution in Ethiopia, as the data forming part of the survey were mainly collected on accessible roads. To determine accurate Moho depth using Global Gravity Models (GGMs) for the study area, evaluation of GGMs is needed based on the available terrestrial gravity data. Moho depth lies between 28 km and 32 km in Afar. Gravity disturbances (GDs) were calculated for the terrestrial gravity data and the recent GGMs for the study area. The model-based GDs were compared with the corresponding GD obtained from the terrestrial gravity data and their differences in terms of statistical comparison parameters for determining the best fit GGM at a local scale in Afar. The largest standard deviation (SD) (36.10 mGal) and root mean square error (RMSE) (39.00 mGal) for residual GD and the lowest correlation with the terrestrial gravity (0.61 mGal) were obtained by the satellite-only model (GO_CONS_GCF_2_DIR_R6). The next largest SD (21.27 mGal) and RMSE (25.65 mGal) for residual GD were obtained by the combined gravity model (XGM2019e_2159), which indicates that it is not the best fit model for the study area as compared with the other two GGMs. In general, the result showed that the combined models are more useful tools for modeling the gravity field in Afar than the satellite-only GGMs. But, the study clearly revealed that for the study area, the best model in comparison with the others is the EGM2008, while the second best model is the EIGEN6C4.
      PubDate: Fri, 08 Oct 2021 00:00:00 GMT
  • Performance Assessment of Real-Time Multiconstellation GNSS PPP Using a
           Low-Cost Dual-Frequency GNSS Module

    • Abstract: The release of low-cost dual-frequency (DF) global navigation satellite system (GNSS) modules provides an opportunity for low-cost precise positioning to support autonomous vehicle applications. The new GNSS modules support the US global positioning system (GPS) L1C/L2C or L5 civilian signals, the Russian GNSS Globalnaya Navigazionnaya Sputnikovaya Sistema (GLONASS) L1/L2, Europe’s GNSS Galileo E1/E5b, and Chinese GNSS BeiDou B1/B2 signals. The availability of the DF measurements allows for removal of the ionospheric delay, enhancing the obtained positioning accuracy. Unfortunately, however, the L2C signals are only transmitted by modernized GPS satellites. This means that fewer GPS DF measurements are available. This, in turn, might affect the accuracy and the convergence of the GPS-only precise point positioning (PPP) solution. Multi-constellation GNSS PPP has the potential to improve the positioning accuracy and solution convergence due to the high redundancy of GNSS measurements. This paper aims to assess the performance of real-time quad-constellation GNSS PPP using the low-cost u-blox Z9D-F9P module. The assessment is carried out for both open-sky and challenging environment scenarios. Static, simulated-kinematic, and actual field-kinematic trials have been carried out to evaluate real-time PPP performance. Pre-saved real-time precise orbit and clock products from the Centre National d’Etudes Spatiales are used to simulate the real-time scenario. It is shown that the quad-constellation GNSS PPP using the low-cost u-blox Z9D-F9P module achieves decimeter-level positioning accuracy in both the static and simulated-kinematic modes. In addition, the PPP solution convergence is improved compared to the dual- and triple-constellation GNSS PPP counterparts. For the actual kinematic trial, decimeter-level horizontal positioning accuracy is achieved through the GPS + GLONASS + Galileo PPP compared with submeter-level positioning accuracy for the GPS + GLONASS and GPS + Galileo PPP counterparts. Additionally, submeter-level vertical positioning accuracy is achieved through the GPS + GLONASS + Galileo PPP compared with meter-level positioning accuracy for GPS + GLONASS and GPS + Galileo PPP counterparts.
      PubDate: Fri, 08 Oct 2021 00:00:00 GMT
  • Quasi-1500-Year-Cycle Signal in Length-of-Day Change

    • Abstract: Length-of-day (LOD) change, i.e., variations in Earth’s rotation rate, includes the long-term slowdown trend, as well as periodic and irregular fluctuations. The current continuous sequence of the LOD change covers a time span of <400 years. Using astronomical records in ancient historical documents, combined with a modern astronomical ephemeris, it is possible to obtain ancient LOD change. Some scholars have given a discontinuous LOD data series for the past 4000 years. In this paper, the author uses the Lomb–Scargle periodogram to study the LOD series and finds a significant quasi-1500-year-cycle signal. Furthermore, with weighted wavelet Z-transform, time-varying characteristics of the cycle in the LOD change are obtained.
      PubDate: Fri, 13 Aug 2021 00:00:00 GMT
  • In Memoriam: Dr. Eng. Leszek Jaworski (1961–2021)

    • PubDate: Fri, 13 Aug 2021 00:00:00 GMT
  • Performance Assessment of PPP-AR Positioning and Zenith Total Delay
           Estimation with Modernized CSRS-PPP

    • Abstract: The precise point positioning (PPP) method has become more popular due to powerful online global navigation satellite system (GNSS) data processing services, such as the Canadian Spatial Reference System-PPP (CSRS-PPP). At the end of 2020, the CSRS-PPP service launched the ambiguity resolution (AR) feature for global positioning system (GPS) satellites. More reliable results are obtained with AR compared to the results with traditional ambiguity-float PPP. In this study, the performance of the modernized CSRS-PPP was comparatively assessed in terms of static positioning and zenith total delay (ZTD) estimation. Data for 1 month in the year 2019 obtained from 47 international GNSS service (IGS) stations were processed before and after modernization of the CSRS-PPP. The processes were conducted for GPS and GPS + GLONASS (GLObalnaya NAvigatsionnaya Sputnikovaya Sistema) satellite combinations. Besides, the results were analyzed in terms of accuracy and convergence time. According to the solutions, the AR feature of the CSRS-PPP improved the accuracy by about 50% in the east component for GPS + GLONASS configuration. The root-mean-square error (RMSE) of the ZTD difference between modernized CSRS-PPP service and IGS final troposphere product is 5.8 mm for the GPS-only case.
      PubDate: Fri, 13 Aug 2021 00:00:00 GMT
  • Effect of the Gravitational Aberration on the Earth Gravity Field

    • Abstract: Discussing the problem of the external gravitational potential of the rotating Earth, we have to consider the fundamental postulate of the finite speed of the propagation of gravitation. This can be done using the expressions for the gravitational aberration compared to the Liénard–Wiechert solution of the retarded potentials. The term gravitational counter-aberration or co-aberration is introduced to describe the pattern of the propagation of the gravitational signal emitted by the rotating Earth. It is proved that in the first approximation, the classic theory of the aberration of light can be applied to calculate this effect. Some effects of the gravitational aberration on the external gravity field of the rotating Earth may influence the orbit determination of the Earth artificial satellites.
      PubDate: Sun, 18 Apr 2021 00:00:00 GMT
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