Sergey A. Kaplev, M. Titov, Tamara Valentirova, Igor Mozharov, A. Bolkunov, Valeriy Yaremchuk
Abstract The revived interest of many countries and the growing number of ongoing and scheduled missions to the Moon increases the significance of supporting navigation system development. A number of publications are based on multi-Global Navigation Satellite System (GNSS) signal reception from the opposite side of the Earth using high-gain antennas and lunar augmentation constellations. While the accuracy of such systems could be sufficient, the positioning, navigation, and timing (PNT) service dependency on circumterestrial navigation sources prevents the use of advanced navigation technologies honed in circumlunar space for further Mars and other celestial body missions, which is one of the major goals of lunar exploration. Moreover, orbit determination and time synchronization (ODTS) method descriptions and estimations are usually skipped in the studies of lunar augmentations. An alternative concept of the Lunar Navigation Satellite System (LNSS) is proposed based on Earth-dependency reduction principal and on-board ODTS. The advantage of the proposed approach is that LNSS-like systems could be adapted for other celestial bodies taking into account aspects such as their shape, dynamics, perturbations, as well as exploration priority regions. The baseline LNSS constellation of three circular orbits with three satellites each has been chosen as the result of multicriterion analysis of orbital stability and geometry. Station keeping requires less than 15 m/s for 10 years without significant changes in navigation performance in the prioritized Polar Regions. The full cycle of LNSS operation from ODTS and signal generation to its reception, processing, and obtaining navigation solutions has been simulated to obtain positioning accuracy for different types of users. Positioning accuracy of space users in approach/departure phases, in near-lunar orbits, as well as static users on a lunar surface is confirmed on a level of a few tens of meters. The same accuracy is achievable by dynamic users on a lunar surface during route stops or also in motion in case of LNSS constellation expansion or deployment of ground-based augmentation beacons in on-site exploration zones.
{"title":"Lunar PNT system concept and simulation results","authors":"Sergey A. Kaplev, M. Titov, Tamara Valentirova, Igor Mozharov, A. Bolkunov, Valeriy Yaremchuk","doi":"10.1515/astro-2022-0014","DOIUrl":"https://doi.org/10.1515/astro-2022-0014","url":null,"abstract":"Abstract The revived interest of many countries and the growing number of ongoing and scheduled missions to the Moon increases the significance of supporting navigation system development. A number of publications are based on multi-Global Navigation Satellite System (GNSS) signal reception from the opposite side of the Earth using high-gain antennas and lunar augmentation constellations. While the accuracy of such systems could be sufficient, the positioning, navigation, and timing (PNT) service dependency on circumterestrial navigation sources prevents the use of advanced navigation technologies honed in circumlunar space for further Mars and other celestial body missions, which is one of the major goals of lunar exploration. Moreover, orbit determination and time synchronization (ODTS) method descriptions and estimations are usually skipped in the studies of lunar augmentations. An alternative concept of the Lunar Navigation Satellite System (LNSS) is proposed based on Earth-dependency reduction principal and on-board ODTS. The advantage of the proposed approach is that LNSS-like systems could be adapted for other celestial bodies taking into account aspects such as their shape, dynamics, perturbations, as well as exploration priority regions. The baseline LNSS constellation of three circular orbits with three satellites each has been chosen as the result of multicriterion analysis of orbital stability and geometry. Station keeping requires less than 15 m/s for 10 years without significant changes in navigation performance in the prioritized Polar Regions. The full cycle of LNSS operation from ODTS and signal generation to its reception, processing, and obtaining navigation solutions has been simulated to obtain positioning accuracy for different types of users. Positioning accuracy of space users in approach/departure phases, in near-lunar orbits, as well as static users on a lunar surface is confirmed on a level of a few tens of meters. The same accuracy is achievable by dynamic users on a lunar surface during route stops or also in motion in case of LNSS constellation expansion or deployment of ground-based augmentation beacons in on-site exploration zones.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"368 ","pages":"110 - 117"},"PeriodicalIF":0.7,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41280212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jun Zhu, Hengnian Li, Jie Li, Rengui Ruan, Min Zhai
Abstract The continuous full operation of the constellation of BeiDou navigation satellite system (BDS) provides favorable conditions for the performance evaluation of the BDS inter-satellite links (ISLs). The primary features of ISLs that affect the precision of precise orbit determination (POD) and time synchronization include (i) the spatiotemporal coverage or continuity of observations; (ii) the observational accuracy, such as observation noise and bias; and (iii) the observational geometry represented by dilution of precision. After comparing some technical features and the current status of the Global Navigation Satellite Systems ISLs, the measurement principle of dual one-way ISLs for BDS and its data processing methods are presented. The performance evaluation involving the above three aspects was carried out using 14 days of ISL data, with some typical indicators derived. POD based on data fusion of ISLs and ground-based L-band monitoring stations was conducted, with root-mean-square of posterior residuals of about 5.0 cm, and MEO radial accuracy better than 1.0 cm. The results show that ISLs offer crucial support for BDS to provide global high-precision services under regional monitoring network conditions.
{"title":"Performance of dual one-way measurements and precise orbit determination for BDS via inter-satellite link","authors":"Jun Zhu, Hengnian Li, Jie Li, Rengui Ruan, Min Zhai","doi":"10.1515/astro-2022-0034","DOIUrl":"https://doi.org/10.1515/astro-2022-0034","url":null,"abstract":"Abstract The continuous full operation of the constellation of BeiDou navigation satellite system (BDS) provides favorable conditions for the performance evaluation of the BDS inter-satellite links (ISLs). The primary features of ISLs that affect the precision of precise orbit determination (POD) and time synchronization include (i) the spatiotemporal coverage or continuity of observations; (ii) the observational accuracy, such as observation noise and bias; and (iii) the observational geometry represented by dilution of precision. After comparing some technical features and the current status of the Global Navigation Satellite Systems ISLs, the measurement principle of dual one-way ISLs for BDS and its data processing methods are presented. The performance evaluation involving the above three aspects was carried out using 14 days of ISL data, with some typical indicators derived. POD based on data fusion of ISLs and ground-based L-band monitoring stations was conducted, with root-mean-square of posterior residuals of about 5.0 cm, and MEO radial accuracy better than 1.0 cm. The results show that ISLs offer crucial support for BDS to provide global high-precision services under regional monitoring network conditions.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"31 1","pages":"276 - 286"},"PeriodicalIF":0.7,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44290297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Multiphase astrochemical modeling presents a numerical challenge especially for the simulation of objects with the wide range of physical parameters such as protoplanetary disks. We demonstrate an implementation of the analytical Jacobian for the numerical integration of the system of differential rate equations that govern chemical evolution in star-forming regions. The analytical Jacobian allowed us to greatly improve the stability of the code in protoplanetary disk conditions. We utilize the MONACO code to study the evolution of abundances of chemical species in protoplanetary disks. The chemical model includes 670 species and 6,015 reactions in the gas phase and on interstellar grains. The specific feature of the utilized chemical model is the inclusion of low-temperature chemical processes leading to the formation of complex organic molecules (COMs), included previously in the models of chemistry of COMs in prestellar clouds. To test the impact of analytical Jacobian on the stability of numerical simulations of chemical evolution in protoplanetary disks, we calculated the chemical composition of the disk using a two-phase model and four variants of the chemical reaction network, three values of the surface diffusion rates, and two types of the initial chemical composition. We also show a preliminary implementation of the analytical Jacobian to a three-phase model.
{"title":"A numerical approach to model chemistry of complex organic molecules in a protoplanetary disk","authors":"M. Kiskin, A. Vasyunin, V. Akimkin","doi":"10.1515/astro-2022-0009","DOIUrl":"https://doi.org/10.1515/astro-2022-0009","url":null,"abstract":"Abstract Multiphase astrochemical modeling presents a numerical challenge especially for the simulation of objects with the wide range of physical parameters such as protoplanetary disks. We demonstrate an implementation of the analytical Jacobian for the numerical integration of the system of differential rate equations that govern chemical evolution in star-forming regions. The analytical Jacobian allowed us to greatly improve the stability of the code in protoplanetary disk conditions. We utilize the MONACO code to study the evolution of abundances of chemical species in protoplanetary disks. The chemical model includes 670 species and 6,015 reactions in the gas phase and on interstellar grains. The specific feature of the utilized chemical model is the inclusion of low-temperature chemical processes leading to the formation of complex organic molecules (COMs), included previously in the models of chemistry of COMs in prestellar clouds. To test the impact of analytical Jacobian on the stability of numerical simulations of chemical evolution in protoplanetary disks, we calculated the chemical composition of the disk using a two-phase model and four variants of the chemical reaction network, three values of the surface diffusion rates, and two types of the initial chemical composition. We also show a preliminary implementation of the analytical Jacobian to a three-phase model.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"31 1","pages":"80 - 91"},"PeriodicalIF":0.7,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44684454","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The equilibrium cold dark matter halos show the almost universal inner r − 1 {r}^{-1} cusps, whose physical origin is still not completely clear. This work tries to further clarify this problem by the Landau–Ginzburg (LG) theory, which is often used to study the long-range correlation of the fluctuations in the critical phenomenon, and we will first introduce it in detail. The order parameter in this work is the density fluctuation, and the external perturbation is denoted by its gravitational effects on the particles. Then we discuss the availability of the aforementioned method for the cold dark matter halos and show that the universal r − 1 {r}^{-1} cusp may even form at the early age of the halo formation and can be expected for the dark matter halos with all the scales, which is also consistent with recent works. This article suggests that the r − 1 {r}^{-1} cusp may originate from the long-range correlations of the gravitating system. This correlation also exists in the short-range system near the critical point, and the difference is that the correlation length in the gravitating system is much longer than that of the short-range system.
{"title":"Explaining the cuspy dark matter halos by the Landau–Ginzburg theory","authors":"Dong-Biao Kang, Tong-Jie Zhang","doi":"10.1515/astro-2022-0024","DOIUrl":"https://doi.org/10.1515/astro-2022-0024","url":null,"abstract":"Abstract The equilibrium cold dark matter halos show the almost universal inner r − 1 {r}^{-1} cusps, whose physical origin is still not completely clear. This work tries to further clarify this problem by the Landau–Ginzburg (LG) theory, which is often used to study the long-range correlation of the fluctuations in the critical phenomenon, and we will first introduce it in detail. The order parameter in this work is the density fluctuation, and the external perturbation is denoted by its gravitational effects on the particles. Then we discuss the availability of the aforementioned method for the cold dark matter halos and show that the universal r − 1 {r}^{-1} cusp may even form at the early age of the halo formation and can be expected for the dark matter halos with all the scales, which is also consistent with recent works. This article suggests that the r − 1 {r}^{-1} cusp may originate from the long-range correlations of the gravitating system. This correlation also exists in the short-range system near the critical point, and the difference is that the correlation length in the gravitating system is much longer than that of the short-range system.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"31 1","pages":"181 - 187"},"PeriodicalIF":0.7,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67441182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Eismont, V. Zubko, A. Belyaev, L. Zasova, Dmitriy A. Gorinov, A. Simonov, R. Nazirov, K. Fedyaev
Abstract This study discusses the usage of Venus gravity assist in order to choose and reaching any point on Venusian surface. The launch of a spacecraft to Venus during the launch windows of 2029 to 2031 is considered for this purpose. The constraints for the method are the re-entry angle and the maximum possible overload. The primary basis of the proposed strategy is to use the gravitational field of Venus to transfer the spacecraft to an orbit resonant to the Venusian one – with the aim of expanding accessible landing areas. Results of the current research show that this strategy provides an essential increase in accessible landing areas and, moreover, may provide an access to any point on the surface of Venus with a small increase in ∆V required for launch from the Earth and in the flight duration. The comparison with the landing without using gravity assist near planet is also given.
{"title":"Gravity assists maneuver in the problem of extension accessible landing areas on the Venus surface","authors":"N. Eismont, V. Zubko, A. Belyaev, L. Zasova, Dmitriy A. Gorinov, A. Simonov, R. Nazirov, K. Fedyaev","doi":"10.1515/astro-2021-0013","DOIUrl":"https://doi.org/10.1515/astro-2021-0013","url":null,"abstract":"Abstract This study discusses the usage of Venus gravity assist in order to choose and reaching any point on Venusian surface. The launch of a spacecraft to Venus during the launch windows of 2029 to 2031 is considered for this purpose. The constraints for the method are the re-entry angle and the maximum possible overload. The primary basis of the proposed strategy is to use the gravitational field of Venus to transfer the spacecraft to an orbit resonant to the Venusian one – with the aim of expanding accessible landing areas. Results of the current research show that this strategy provides an essential increase in accessible landing areas and, moreover, may provide an access to any point on the surface of Venus with a small increase in ∆V required for launch from the Earth and in the flight duration. The comparison with the landing without using gravity assist near planet is also given.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"30 1","pages":"103 - 109"},"PeriodicalIF":0.7,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48196592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Kupryakov, K. Bychkov, O. M. Belova, A. Gorshkov, P. Heinzel, P. Kotrč
Abstract We present intensity curves of solar flares obtained in the Hα hydrogen line and CaII H, CaIR 8542Å lines using multichannel spectrographs of Ondřejov Observatory (Czech Republic) for the period 2000–2012. The general behavior of observed intensity curves is practically the same for all flares and is consistent with temporal variations of X-ray emission. However, our results differ significantly from those obtained by other authors for selected flare stars, for example, AD Leo; EV Lac; YZ CMi. We tried to explain the difference in the behavior of Ca II and Hα radiation flux by appearance of a shock wave during a flare and slow heating of the plasma.
{"title":"Analysis and modeling of the dynamics of the glow of calcium and hydrogen lines in solar and stellar flares","authors":"Y. Kupryakov, K. Bychkov, O. M. Belova, A. Gorshkov, P. Heinzel, P. Kotrč","doi":"10.1515/astro-2021-0011","DOIUrl":"https://doi.org/10.1515/astro-2021-0011","url":null,"abstract":"Abstract We present intensity curves of solar flares obtained in the Hα hydrogen line and CaII H, CaIR 8542Å lines using multichannel spectrographs of Ondřejov Observatory (Czech Republic) for the period 2000–2012. The general behavior of observed intensity curves is practically the same for all flares and is consistent with temporal variations of X-ray emission. However, our results differ significantly from those obtained by other authors for selected flare stars, for example, AD Leo; EV Lac; YZ CMi. We tried to explain the difference in the behavior of Ca II and Hα radiation flux by appearance of a shock wave during a flare and slow heating of the plasma.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"30 1","pages":"91 - 95"},"PeriodicalIF":0.7,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46453906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The analysis of the electron acceleration by the quasi-stationary sub-Dreiser electric fields in the lower solar atmosphere has been done. It has been shown that the Dreiser electric field turned out to be several orders of magnitude larger than coronal values due to the inelastic collisions between electrons and hydrogen atoms. The ionization of hydrogen atoms gives rise to the resulting secondary electrons, which become runaway under the action of sub-Dreiser electric fields. This causes an further avalanche-like ionization of the plasma and leads to the acceleration of the large number of fast electrons up to relativistic energies at small (≲ 100 km) distances.
{"title":"Flare energy release and avalanche ionization of plasma by runaway electrons in lower solar atmosphere","authors":"Y. Tsap, Y. Kopylova, M. Karlický","doi":"10.1515/astro-2021-0028","DOIUrl":"https://doi.org/10.1515/astro-2021-0028","url":null,"abstract":"Abstract The analysis of the electron acceleration by the quasi-stationary sub-Dreiser electric fields in the lower solar atmosphere has been done. It has been shown that the Dreiser electric field turned out to be several orders of magnitude larger than coronal values due to the inelastic collisions between electrons and hydrogen atoms. The ionization of hydrogen atoms gives rise to the resulting secondary electrons, which become runaway under the action of sub-Dreiser electric fields. This causes an further avalanche-like ionization of the plasma and leads to the acceleration of the large number of fast electrons up to relativistic energies at small (≲ 100 km) distances.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"30 1","pages":"216 - 218"},"PeriodicalIF":0.7,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44726180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract We introduce the application of the clustering algorithm to the preliminary compiled list of probable wide pairs of co-moving stars. The main aim of such development is a possibility of unsupervised blind search of coeval loose stellar structures over significant regions in space. Using Gaia EDR3 data, we investigated the application of the method to nearby region hosting recently discovered loose structures – tidal tails of Coma Ber star cluster and a nearby stellar group named Group X. We compare the results of straightforward clustering of stellar data with results of using our method with varying parameters. We then compare the results of our method to the recent results of the two groups of authors who independently discovered the discussed structures. We find parameters allowing the method to find the full scope of distributed stellar groups without preliminary knowledge of their characteristics. It decreases the risk of false positive clustering and improves the ability to discover loose stellar groups, in comparison with the application of clustering algorithm to the individual stars. Further we obtain a refined dataset of probable members of both stellar groups and independently obtain their ages (700 ± 70 Myr and 450 ± 100 Myr) and space velocities ((U,V,W) = (8.63 ± 0.13, 6.63 ± 0.20, 6.65 ± 0.95) km/s for Coma Ber star cluster, and (U,V,W) = (7.70 ± 0.12, 3.27 ± 0.45, 5.69 ± 0.80) km/s for Group X). Our results are in very good agreement with those of previous investigators.
{"title":"Application of clustering algorithm to wide stellar pairs for unsupervised search of parts of disrupting clusters","authors":"Sergei Sapozhnikov, D. Kovaleva","doi":"10.1515/astro-2021-0025","DOIUrl":"https://doi.org/10.1515/astro-2021-0025","url":null,"abstract":"Abstract We introduce the application of the clustering algorithm to the preliminary compiled list of probable wide pairs of co-moving stars. The main aim of such development is a possibility of unsupervised blind search of coeval loose stellar structures over significant regions in space. Using Gaia EDR3 data, we investigated the application of the method to nearby region hosting recently discovered loose structures – tidal tails of Coma Ber star cluster and a nearby stellar group named Group X. We compare the results of straightforward clustering of stellar data with results of using our method with varying parameters. We then compare the results of our method to the recent results of the two groups of authors who independently discovered the discussed structures. We find parameters allowing the method to find the full scope of distributed stellar groups without preliminary knowledge of their characteristics. It decreases the risk of false positive clustering and improves the ability to discover loose stellar groups, in comparison with the application of clustering algorithm to the individual stars. Further we obtain a refined dataset of probable members of both stellar groups and independently obtain their ages (700 ± 70 Myr and 450 ± 100 Myr) and space velocities ((U,V,W) = (8.63 ± 0.13, 6.63 ± 0.20, 6.65 ± 0.95) km/s for Coma Ber star cluster, and (U,V,W) = (7.70 ± 0.12, 3.27 ± 0.45, 5.69 ± 0.80) km/s for Group X). Our results are in very good agreement with those of previous investigators.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"30 1","pages":"191 - 202"},"PeriodicalIF":0.7,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44781270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract A new method of orbit determination (OD) is proposed: distribution regression. The paper focuses on the process of using sparse observation data to determine the orbit of the spacecraft without any prior information. The standard regression process is to learn a map from real numbers to real numbers, but the approach put forward in this paper is to map from probability distributions to real-valued responses. According to the new algorithm, the number of orbital elements can be predicted by embedding the probability distribution into the reproducing kernel Hilbert space. While making full use of the edge of big data, it also avoids the problem that the algorithm cannot converge due to improper initial values in precise OD. The simulation experiment proves the effectiveness, robustness, and rapidity of the algorithm in the presence of noise in the measurement data.
{"title":"An orbit determination method of spacecraft based on distribution regression","authors":"Chunsheng Jiang","doi":"10.1515/astro-2021-0021","DOIUrl":"https://doi.org/10.1515/astro-2021-0021","url":null,"abstract":"Abstract A new method of orbit determination (OD) is proposed: distribution regression. The paper focuses on the process of using sparse observation data to determine the orbit of the spacecraft without any prior information. The standard regression process is to learn a map from real numbers to real numbers, but the approach put forward in this paper is to map from probability distributions to real-valued responses. According to the new algorithm, the number of orbital elements can be predicted by embedding the probability distribution into the reproducing kernel Hilbert space. While making full use of the edge of big data, it also avoids the problem that the algorithm cannot converge due to improper initial values in precise OD. The simulation experiment proves the effectiveness, robustness, and rapidity of the algorithm in the presence of noise in the measurement data.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"30 1","pages":"159 - 167"},"PeriodicalIF":0.7,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41923311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Sunspot groups are often used as tracers to probe the differential rotation of the Sun. However, the results on the rotation rate variation obtained by different authors are not always in agreement. The reason for this might be a number of effects. In particular, faster decay of the following part of a sunspot group results in a false apparent shift of the area-weighted center of the group toward the leading part. In this work we analyze how significantly this effect may contribute to the derived rotation rate. For a set of 670 active regions, we compare the rotation rate derived from continuum intensity images to that derived from line-of-sight magnetograms. We found that the difference between the calculated rotation rates is 0.45° day−1 on average. This value is comparable to the difference between the rotation rate of the solar surface near the equator and at 30° latitude. We conclude that the accuracy of the rotation rate measurements using white-light images is not satisfactory. Magnetograms should be used in future research on the differential rotation of the Sun.
{"title":"Probing the rotation rate of solar active regions: the comparison of methods","authors":"A. Kutsenko, V. Abramenko","doi":"10.1515/astro-2021-0029","DOIUrl":"https://doi.org/10.1515/astro-2021-0029","url":null,"abstract":"Abstract Sunspot groups are often used as tracers to probe the differential rotation of the Sun. However, the results on the rotation rate variation obtained by different authors are not always in agreement. The reason for this might be a number of effects. In particular, faster decay of the following part of a sunspot group results in a false apparent shift of the area-weighted center of the group toward the leading part. In this work we analyze how significantly this effect may contribute to the derived rotation rate. For a set of 670 active regions, we compare the rotation rate derived from continuum intensity images to that derived from line-of-sight magnetograms. We found that the difference between the calculated rotation rates is 0.45° day−1 on average. This value is comparable to the difference between the rotation rate of the solar surface near the equator and at 30° latitude. We conclude that the accuracy of the rotation rate measurements using white-light images is not satisfactory. Magnetograms should be used in future research on the differential rotation of the Sun.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"30 1","pages":"219 - 224"},"PeriodicalIF":0.7,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47533018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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