 Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
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- Similarities and Differences in the Earth’s Water Variations Signal
Provided by Grace and AMSR-E Observations Using Maximum Covariance
Analysis at Various Land Cover Data Backgrounds
Abstract: ABSTRACTThe study presents a compatibility analysis of gravimetric observations with passive microwave observations. Monitoring the variability of soil water content is one of the essential issues in climate-related research. Total water storage changes (ΔTWS) observed by Gravity Recovery and Climate Experiment (GRACE), enables the creation of many applications in hydrological monitoring. Soil moisture (SM) is a critical variable in hydrological studies. Advanced Microwave Scanning Radiometer (AMSR-E) satellite products provided unique observations on this variable in near-daily time resolutions. The study used maximum covariance analysis (MCA) to extract principal components for ΔTWS and SM signals. The analysis was carried out for the global area, dividing the discussion into individual continents. The amplitudes of gravimetric and microwave signals were computed via the complex empirical orthogonal function (EOF) and the complex conjugate EOF* to determine the regions for detailed comparison. Similarities and differences in signal convergence results were compared with land cover data describing soil conditions, vegetation cover, urbanization status, and cultivated land. Convergence was determined using Pearson correlation coefficients and cross-correlation. In order to compare ΔTWS and SM in individual seasons, ΔTWS observations were normalized. Results show that naturally forested areas and large open spaces used for agriculture support the compatibility between GRACE and AMSRE observations and are characterized by a good Pearson correlation coefficient >0.8. Subpolar regions with permafrost present constraints for AMSR-E observations and have little convergence with GRACE observations.
PubDate: Tue, 18 Jul 2023 00:00:00 GMT
- Geodynamic Studies in the Pieniny Klippen Belt in 2004–2020
Abstract: ABSTRACTThe Pieniny Geodynamic Test Field is situated in the middle of the region between the Inner and Outer Carpathians. Geodynamic research conducted in the past in the Pieniny Klippen Belt (PKB) region were suggestive of neotectonic activity. The goal of the investigation was to determine whether the nearby structures, the Podhale Flysh (FP) and the Magura Nappe (MN), are affected by neotectonic activity in the PKB. The goal of the study was to ascertain the velocity and direction of motion of stations situated close to the Pieniny Geodynamic Test Field’s 3 main structures. Twelve GNSS stations, including 6 in the PKB, 3 in the MN, and 3 in the FP, make up the Pieniny Geodynamic Test Field. Three GNSS sites in the Tatra Mountains (TM) complete the entire geodynamic test field. The satellite observations made between 2004 and 2020 (excluding the year 2005 due to lack of observation) were investigated to identify the horizontal movements. Using the IGb14 reference system, the station’s positions and velocities were calculated. First, daily sessions were used to process the horizontal coordinates of the points for an average observation epoch in a given year. Sixteen measurement epochs were included in the long-time solution. Based on the horizontal velocity residues in the north–south and east–west directions, the station’s movement was calculated. The collected results were compared to information from the EUREF Permanent GNSS Network (EUREF) and to the findings of prior research on the tectonic activity of the PKB. The results of horizontal displacements calculated using GNSS measurements in the area of the PKB and nearby structures—the MN and the FP are presented and analyzed in this article.
PubDate: Tue, 18 Jul 2023 00:00:00 GMT
- Interstellar Probe: Science, Engineering, Logistic, Economic, and Social
Factors
Abstract: ABSTRACTIn this publication, we refer to a certain novelty introduced to the presentation at the AGU 2020 conference. This novelty consists of quoting the thoughts, remarks, and comments of six young people who declared their interest in space research after listening to a lecture on the Interstellar Probe journey, organized in June 2020 by the Polish Space Agency. Therefore, they were then asked to express their comments after reading two publications on the Interstellar Probe that were sent to them. As a result, this idea also became the topic of this article. Although the interstellar mission is primarily a research and science project, its engineering, logistics, business (economic), and social aspects, as well as a short commentary on our home in the universe, which is the heliosphere, have also been included in this article.
PubDate: Tue, 18 Jul 2023 00:00:00 GMT
- Study on Secular Change of the Earth’s Rotation Rate Based on Solar
Eclipse Observation Records on October 13, 443 BC
Abstract: ABSTRACTAn observation of a solar eclipse that occurred on October 13, 443 BC during the reign of the Duke Ligong of Qin was recorded in the Twenty-Four Histories (China’s dynastic histories from remote antiquity till the Ming Dynasty). With modern astronomical planetary ephemeris, the observation records were studied. The results showed that the eclipse probably occurred around sunset in Yongcheng, the capital of Qin, where the sunset time was exactly between the first contact stage (partial eclipse begins) and the fourth contact stage (partial eclipse ends) of the eclipse. Furthermore, secular change of the earth’s rotation rate at that time is investigated in this work.
PubDate: Tue, 18 Jul 2023 00:00:00 GMT
- Medium- and Long-Term Prediction of Polar Motion Using Weighted Least
Squares Extrapolation and Vector Autoregressive Modeling
Abstract: ABSTRACTThis article presents the application of weighted least squares (WLS) extrapolation and vector autoregressive (VAR) modeling in polar motion prediction. A piecewise weighting function is developed for the least squares (LS) adjustment in consideration of the effect of intervals between observation and prediction epochs on WLS extrapolation. Furthermore, the VAR technique is used to simultaneously model and predict the residuals of xp, yp pole coordinates for WLS misfit. The simultaneous predictions of xp, yp pole coordinates are subsequently computed by the combination of WLS extrapolation of harmonic models for the linear trend, Chandler and annual wobbles, and VAR stochastic prediction of the residuals (WLS+VAR). The 365-day-ahead xp, yp predictions are compared with those generated by LS extrapolation+univariate AR prediction and LS extrapolation+VAR modeling. It is shown that the xp, yp predictions based on WLS+VAR taking into consideration both the interval effect and correlation between xp and yp outperform those generated by two others. The accuracies of the xp predictions are 13.97 mas, 18.47 mas, and 20.52 mas, respectively for the 150-, 270-, and 365-day horizon in terms of the mean absolute error statistics, 36%, 24.8%, and 33.5% higher than LS+AR, respectively. For the yp predictions, the 150-, 270-, and 365-day accuracies are 15.41 mas, 21.17 mas, and 21.82 mas respectively, 27.4%, 11.9%, and 21.8% higher than LS+AR respectively. Moreover, the absolute differences of the WLS+VAR predictions and observations are smaller than the differences from LS+VAR and LS+AR, which is practically important to practical and scientific users, although the improvement in accuracies is no more than 10% relative to LS+VAR. The further comparison with the predictions submitted to the 1st Earth Orientation Parameters Prediction Comparison Campaign (1st EOP PCC) shows that while the accuracy of the predictions within 30 days is comparable with that by the most accurate prediction techniques including neural networks and LS+AR participating in the campaign for xp, yp pole coordinates, the accuracy of the predictions up to 365 days into the future are better than accuracies by the other techniques except best LS+AR used in the EOP PCC. It is therefore concluded that the medium- and long-term prediction accuracy of polar motion can be improved by modeling xp, yp pole coordinates together.
PubDate: Tue, 18 Jul 2023 00:00:00 GMT
- Periodic Orbits Around the Triangular Points with Prolate Primaries
Abstract: ABSTRACTPeriodic orbits play a fundamental role in the study and deep understanding of the behavior of dynamical systems. In the current work, we investigated the periodic orbits around the triangular libration points of the restricted three-body problem. The equations of motion of the restricted problem are presented when both primaries are prolate triaxial. Periodic orbits around the triangular points are obtained and then illustrated graphically for some selected initial conditions and for the entire domain of the mass ratio μ, as well. The eccentricities of the periodic orbits are obtained and then represented graphically. It is observed that the periodic orbits about the triangular stationary points are elliptical, and the frequencies of short and long orbits of the periodic motion are influenced by the shape of the primary bodies. Furthermore, we found that the perturbing forces influence the period, the orientation, and the eccentricities of the short and long periodic orbits.
PubDate: Sat, 15 Apr 2023 00:00:00 GMT
- Interstellar Probe — Where is the “Nose” of the
Heliosphere'
Abstract: ABSTRACTIn this paper are reviewed publications that were concerned about the discovery of the location of the heliopause “nose” by the Newtonian Approximation method and publications using the full three-dimensional magnetohydrodynamic simulations of the heliosphere that confirmed that discovery.Since we do not have a clear answer to the question of what the heliosphere looks like, in connection with the planned launch of the Interstellar Probe within this decade, there was a problem with deciding which direction to send it. The discovery of the movement of the “nose” of the heliopause depending on the direction of the interstellar magnetic field and the determination of the position of the “nose” is very important for this decision. Therefore, the purpose of the article is to answer the question of where is the “nose” of the heliopause.In the second part of the article, the possibility of changing the paradigm of scientific research projects related to interstellar missions (including those focused on the study of the heliosphere), among other things, by increasing the interdisciplinarity of research, is explored. As part of initiating such cooperation, the article develops social sciences themes related to the sustainable logistics of Interstellar Probe missions to increase public involvement in these projects.
PubDate: Sat, 15 Apr 2023 00:00:00 GMT
- ESMGFZ Products for Earth Rotation Prediction
Abstract: The Earth System Modelling Group of GeoForschungsZentrum Potsdam (ESMGFZ) provides geodetic products for gravity variations, Earth rotation excitations, and Earth surface deformations related to mass redistributions and mass loads in the atmosphere, ocean, and terrestrial water storage. Earth rotation excitation compiled as effective angular momentum (EAM) functions for each Earth subsystem (atmosphere, ocean, continental hydrology) are important for Earth rotation prediction. Especially the 6-day forecasts extending the model analysis runs offer essential information for the improvement of ultra-short-term Earth rotation predictions. In addition to the individual effective angular momentum function of each subsystem, ESMGFZ calculates a combined EAM prediction product. Adjusted to the official Earth orientation parameter (EOP) products IERS 14C04 and Bulletin A, this EAM prediction product allows to extrapolate the polar motion and Length-of-Day parameter time series for 90 days into the future via the Liouville equation. ESMGFZ submits such an EOP prediction to the 2nd EOPPCC campaign.
PubDate: Thu, 05 Jan 2023 00:00:00 GMT
- Improved Prediction of Polar Motions by Piecewise Parameterization
Abstract: On seanonal timescale, the variation of Earth rotation is mainly regulated by angular momentum exchanges between the solid Earth and the fluidal atmosphere, ocean and hydrosphere. In the 2nd EOP PCC, we developed Dill2019’s method for polar motion prediction, using piecewise autoagressive parameters. The maximum prediction errors within 90 days are 36 and 16 mas for polar motion x and y components, respectively. Compared with Bulletin A, the mean absolute error of polar motion y prediction is improved by 20% in all timescale, and with a maximum improvement of 49% on the 5th day. Whereas, for polar motion x, the performance is slightly better (2% - 8%) within 30 days but worse (−7%~ −19%) within 30~90 days. We found that the prediction accuracy is very sensitive to the quality of the angular momentum data. For example, on average, the prediction of polar motion y is around 2 times better than polar motion x. In addition, we found the accuracy of 30-90 days prediction is dramatically decreased in the year 2020. We suspect that such deterioration might be due to the pandemic of coronavirus COVID-19, which suppressed global airline activities by more than 60%, then result in a lose of air-borne meteorological data, which are important for weather forecast.
PubDate: Thu, 05 Jan 2023 00:00:00 GMT
- Earth Rotation Parameters Prediction and Climate Change Indicators in it
Abstract: As one of the participants in the Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC), we submitted two data files. One is 365 days’ predictions into the future for Earth orientation parameters (EOP) (the position parameters Px and Py, the time parameters UT1-UTC and length of day changes ΔLOD), processed by the traditional least-square and autoregressive (LS + AR) model. Another is 90 days’ predictions by the combined least-square and convolution method (LS + Convolution), with effective angular momentum (EAM) from Earth System Modelling GeoForschungsZentrum in Potsdam (ESMGFZ). Results showed that the LS + Convolution method performed better than the LS + AR model in short-term EOP predictions within 10 days, while the traditional LS + AR model presented higher accuracy in medium-term predictions over 10–90 days. Furthermore, based on the climate change information in Earth’s rotation (mainly in the interannual variations of LOD), the climate change indicators are investigated with ΔLOD observations and long-term predictions. After two intermediate La Nina events were detected in the climate-related ΔLOD observations during the period of 2020–2022, another stronger La Nina phenomenon is indicated in the climate-related ΔLOD long-term predictions.
PubDate: Thu, 05 Jan 2023 00:00:00 GMT
- Second Earth Orientation Parameters Prediction Comparison Campaign (2nd
EOP PCC): Overview
Abstract: Precise positioning and navigation on the Earth’s surface and in space require accurate earth orientation parameters (EOP) data and predictions. In the last few decades, EOP prediction has become a subject of increased attention within the international geodetic community, e.g., space agencies, satellite operators, researchers studying Earth rotation dynamics, and users of navigation systems. Due to this fact, many research centres from around the world have developed dedicated methods for the forecasting of EOP. An assessment of the various EOP prediction capabilities is currently being pursued in the frame of the Second Earth Orientation Parameters Prediction Comparison Campaign (2nd EOP PCC), which began in September 2021 and will be continued until the end of the year 2022. The new campaign was prepared by the EOP PCC Office run by Centrum Badań Kosmicznych Polskiej Akademii Nauk (CBK PAN) in Warsaw, Poland, in cooperation with GeoForschungsZentrum (GFZ) and under the auspices of the International Earth Rotation and Reference Systems Service (IERS). In this paper, we provide an overview of the 2nd EOP PCC five months after its start. We discuss the technical aspects and present statistics about the participants and valid prediction files received so far. Additionally, we present the results of preliminary comparisons of different reference solutions with respect to the official IERS 14 C04 EOP series. Root mean square values for different solutions for polar motion, length of day, and precession-nutation components show discrepancies at the level from 0.04 to 0.36 mas, from 0.01 to 0.10 ms, and from 0.01 to 0.18 mas, respectively.
PubDate: Thu, 05 Jan 2023 00:00:00 GMT
- Prediction of Earth Rotation Parameters with the Use of Rapid Products
from IGS, Code and GFZ Data Centres Using Arima and Kriging – A
Comparison
Abstract: Real-time prediction of Earth Orientation Parameters is necessary for many advanced geodetic and astronomical tasks including positioning and navigation on Earth and in space. Earth Rotation Parameters (ERP) are a subset of EOP, consisting of coordinates of the Earth’s pole (PMx, PMy) and UT1-UTC (or Length of Day – LOD). This paper presents the ultra-short-term (up to 15 days into the future) and short-term (up to 30 days into the future) ERP prediction using geostatistical method of ordinary kriging and autoregressive integrated moving average (ARIMA) model. This contribution uses rapid GNSS products EOP 14 12h from IGS, CODE and GFZ and also IERS final products – IERS EOP 14 C04 12h (IAU2000A). The results indicate that the accuracy of ARIMA prediction for each ERP is better for ultra-short prediction. The maximum differences between methods for first few days of 15-day predictions are around 0.32 mas (PMx), 0.23 mas (PMy) and 0.004 ms (LOD) in favour of ARIMA model. The maximum differences of Mean Absolute Prediction Errors (MAPEs) on the last few days of 30-day predictions are 1.91 mas (PMx), 0.30 mas (PMy) and 0.026 ms (LOD) with advantage to kriging method. For all ERPs the differences of MAPEs for time series from various analysis centres are not significant and vary up to maximum value of around 0.05 mas (PMx), 0.04 mas (PMy) and 0.005 ms (LOD).
PubDate: Thu, 05 Jan 2023 00:00:00 GMT
- Study of the Lightning Activity Over Poland for Different Solar Activity
Abstract: The question of the connection between solar and thunderstorm activity is not new. The discussion among scientists began before the cosmic era. The correlations of the ground-based registration of the cosmic ray flux and meteorological observations have been performed since the 50s of the 20th century. The discussed problem is related to the influence of cosmic rays on the creation of clouds, particularly thunderstorm clouds. The intensity of the galactic cosmic ray flux is controlled by the density and velocity of the solar wind. The increase in the solar wind flux during high solar activity leads to decreasing galactic cosmic ray flux, but on the other hand, the solar activity creates solar cosmic rays. Using data from the PERUN system and the DEMETER satellite, we tried to estimate the connection between the thunderstorm activity in Poland and solar activity during the period of the DEMETER operational activity (2004–2010). The influence of thunderstorms on the ionosphere and its dependence on solar activity is also discussed. However, due to the short time interval of the available data covering an insignificant part of the solar cycle, close to the minimum activity, our findings are not fully conclusive. No correlation was found between the cosmic ray flux and lightning activity given by the number of the discharges. However, some of the most energetic lightning discharges in the analyzed period occurred close to the minimum of the solar activity and their appearance is discussed.
PubDate: Thu, 29 Dec 2022 00:00:00 GMT
- Investigation of Signals of the Range 10–10 Hz Registered by Water-Tube
Tiltmeters in the Underground Geodynamic Laboratory in Książ (Sw Poland)
Abstract: The Geodynamic Laboratory in Książ includes investigations of various kinds of geodynamic signals. Among others, we registered harmonic signals of the range 10−3–10−4 Hz. These signals had been found in the measurement series of the long water-tube (WT) tiltmeters. The discovered signals consist of two classes of harmonics associated with various kinds of phenomena. The first class of these signals belongs to viscoelastic vibrations of the Earth’s solid body, while the second class is produced possibly by the extremely long atmospheric infrasound waves. The signals of the vibrations of the Earth had been well recognized by the characteristic frequencies of the Earth’s free vibrations’ resonance, which occur mainly after strong earthquakes. The atmospheric pressure microvibrations affected the water level in the hydrodynamic systems of the WTs as a result of an inverse barometric effect. We observed that signals from both classes blend in the harmonics of similar frequencies and jointly affect the hydrodynamic systems of the WTs. We found that the amplitude of the second-class signals strongly depends on the location of water-tube gauges inside the underground, while the amplitudes of the first-class signals are similar for all the gauges. These observations clearly indicate the atmospheric origin of the second class of registered signals.
PubDate: Thu, 29 Dec 2022 00:00:00 GMT
- Physical Augmentation Factor of Precision in Gnss
Abstract: The dilution of precision (DOP) in satellite navigation system provides a simple characterization of the user–satellite geometry and a quantitative assessment of the positioning constellation configuration. The essential idea of physical augmentation factor of precision (PAFP) proposed in this work, is that navigation signals are transmitted at multiple frequencies from each visible satellite in the positioning constellation, while users measure the corresponding multiple pseudoranges of satellites to achieve high precision code positioning. As the multiple pseudoranges of one satellite are measured independently by the corresponding navigation signals at different frequencies, it is reasonable to treat the measurement errors due to the satellite clock and ephemeris, the atmospheric propagation as uncorrelated, random, and identically distributed. The multipath effects and receiver noise are also processed with some empirical models. By measuring user–satellite code pseudoranges at different frequencies, the PAFP offers a scheme that produces the same effect as that of the redundant-overlapping constellation, thus equivalently improving the geometric DOP. It can effectively improve code positioning precision of satellite navigation system.
PubDate: Fri, 21 Oct 2022 00:00:00 GMT
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