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  • http://arxiv.org/abs/1209.1577
    (309239) 2007 RW10: a large temporary quasi-satellite of Neptune
    Upon discovery, asteroid (309239) 2007 RW10 was considered a Neptune Trojan candidate. The object is currently listed by the Minor Planet Center as a Centaur but it is classified as a Scattered Disk or Trans-Neptunian Object by others. Now that its arc-length is 8,154 days and has been observed for more than 20 years, a more robust classification should be possible. Here we explore the orbital behaviour of this object in order to reveal its current dynamical status; we perform N-body simulations in both directions of time to investigate the evolution of its orbital elements. In particular, we study the librational properties of the mean longitude that currently librates around the value of the mean longitude of Neptune with an amplitude of nearly 50 degrees and a period of about 7,500 years. Our calculations show that it has been in its present dynamical state for about 12,500 years and it will stay there for another 12,500 years. Therefore, its current state is relatively short-lived. Due to its chaotic behaviour, the object may have remained in the 1:1 mean motion resonance with Neptune for several 100,000 years at most, undergoing transitions between the various resonant states. (309239) 2007 RW10 is currently a quasi-satellite, the first object of this dynamical class to be discovered around Neptune. With a diameter of about 250 km, it is the largest known co-orbital in the Solar System. Its significant eccentricity (0.30) and orbital inclination (36 degrees), strongly suggest that it did not form in situ but was captured, likely from beyond Neptune. With an apparent magnitude of 21.1 at opposition (October), it is well suited for spectroscopic observations that may provide information on its surface composition and hence eventually its origin.
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    https://arxiv.org/abs/1209.1577
    (309239) 2007 RW10: a large temporary quasi-satellite of Neptune
    Upon discovery, asteroid (309239) 2007 RW10 was considered a Neptune Trojan candidate. The object is currently listed by the Minor Planet Center as a Centaur but it is classified as a Scattered Disk or Trans-Neptunian Object by others. Now that its arc-length is 8,154 days and has been observed for more than 20 years, a more robust classification should be possible. Here we explore the orbital behaviour of this object in order to reveal its current dynamical status; we perform N-body simulations in both directions of time to investigate the evolution of its orbital elements. In particular, we study the librational properties of the mean longitude that currently librates around the value of the mean longitude of Neptune with an amplitude of nearly 50 degrees and a period of about 7,500 years. Our calculations show that it has been in its present dynamical state for about 12,500 years and it will stay there for another 12,500 years. Therefore, its current state is relatively short-lived. Due to its chaotic behaviour, the object may have remained in the 1:1 mean motion resonance with Neptune for several 100,000 years at most, undergoing transitions between the various resonant states. (309239) 2007 RW10 is currently a quasi-satellite, the first object of this dynamical class to be discovered around Neptune. With a diameter of about 250 km, it is the largest known co-orbital in the Solar System. Its significant eccentricity (0.30) and orbital inclination (36 degrees), strongly suggest that it did not form in situ but was captured, likely from beyond Neptune. With an apparent magnitude of 21.1 at opposition (October), it is well suited for spectroscopic observations that may provide information on its surface composition and hence eventually its origin.
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  • https://arxiv.org/abs/1409.5588
    Asteroid 2014 OL339: yet another Earth quasi-satellite
    Our planet has one permanently bound satellite -the Moon-, a likely large number of mini-moons or transient irregular natural satellites, and three temporary natural retrograde satellites or quasi-satellites. These quasi-moons -(164207) 2004 GU9, (277810) 2006 FV35 and 2013 LX28- are unbound companions to the Earth. The orbital evolution of quasi-satellites may transform them into temporarily bound satellites of our planet. Here, we study the dynamical evolution of the recently discovered Aten asteroid 2014 OL339 to show that it is currently following a quasi-satellite orbit with respect to the Earth. This episode started at least about 775 yr ago and it will end 165 yr from now. The orbit of this object is quite chaotic and together with 164207 are the most unstable of the known Earth quasi-satellites. This group of minor bodies is, dynamically speaking, very heterogeneous but three of them exhibit Kozai-like dynamics: the argument of perihelion of 164207 oscillates around -90 degrees, the one of 277810 librates around 180 degrees and that of 2013 LX28 remains around 0 degrees. Asteroid 2014 OL339 is not currently engaged in any Kozai-like dynamics.
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    http://arxiv.org/abs/1409.5588
    Asteroid 2014 OL339: yet another Earth quasi-satellite
    Our planet has one permanently bound satellite -the Moon-, a likely large number of mini-moons or transient irregular natural satellites, and three temporary natural retrograde satellites or quasi-satellites. These quasi-moons -(164207) 2004 GU9, (277810) 2006 FV35 and 2013 LX28- are unbound companions to the Earth. The orbital evolution of quasi-satellites may transform them into temporarily bound satellites of our planet. Here, we study the dynamical evolution of the recently discovered Aten asteroid 2014 OL339 to show that it is currently following a quasi-satellite orbit with respect to the Earth. This episode started at least about 775 yr ago and it will end 165 yr from now. The orbit of this object is quite chaotic and together with 164207 are the most unstable of the known Earth quasi-satellites. This group of minor bodies is, dynamically speaking, very heterogeneous but three of them exhibit Kozai-like dynamics: the argument of perihelion of 164207 oscillates around -90 degrees, the one of 277810 librates around 180 degrees and that of 2013 LX28 remains around 0 degrees. Asteroid 2014 OL339 is not currently engaged in any Kozai-like dynamics.
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  • https://arxiv.org/abs/1608.01518
    Asteroid (469219) 2016 HO3, the smallest and closest Earth quasi-satellite
    A number of Earth co-orbital asteroids experience repeated transitions between the quasi-satellite and horseshoe dynamical states. Asteroids 2001 GO2, 2002 AA29, 2003 YN107 and 2015 SO2 are well-documented cases of such a dynamical behaviour. These transitions depend on the gravitational influence of other planets, owing to the overlapping of a multiplicity of secular resonances. Here, we show that the recently discovered asteroid (469219) 2016 HO3 is a quasi-satellite of our planet -the fifth one, joining the ranks of (164207) 2004 GU9, (277810) 2006 FV35, 2013 LX28 and 2014 OL339. This new Earth co-orbital also switches repeatedly between the quasi-satellite and horseshoe configurations. Its current quasi-satellite episode started nearly 100 yr ago and it will end in about 300 yr from now. The orbital solution currently available for this object is very robust and our full N-body calculations show that it may be a long-term companion (time-scale of Myr) to our planet. Among the known Earth quasi-satellites, it is the closest to our planet and as such, a potentially accessible target for future in situ study. Due to its presumably lengthy dynamical relationship with the Earth and given the fact that at present and for many decades this transient object remains well positioned with respect to our planet, the results of spectroscopic studies of this small body, 26-115 m, may be particularly useful to improve our understanding of the origins -local or captured- of Earth's co-orbital asteroid population. The non-negligible effect of the uncertainty in the value of the mass of Jupiter on the stability of this type of co-orbitals is also briefly explored.
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    http://arxiv.org/abs/1608.01518
    Asteroid (469219) 2016 HO3, the smallest and closest Earth quasi-satellite
    A number of Earth co-orbital asteroids experience repeated transitions between the quasi-satellite and horseshoe dynamical states. Asteroids 2001 GO2, 2002 AA29, 2003 YN107 and 2015 SO2 are well-documented cases of such a dynamical behaviour. These transitions depend on the gravitational influence of other planets, owing to the overlapping of a multiplicity of secular resonances. Here, we show that the recently discovered asteroid (469219) 2016 HO3 is a quasi-satellite of our planet -the fifth one, joining the ranks of (164207) 2004 GU9, (277810) 2006 FV35, 2013 LX28 and 2014 OL339. This new Earth co-orbital also switches repeatedly between the quasi-satellite and horseshoe configurations. Its current quasi-satellite episode started nearly 100 yr ago and it will end in about 300 yr from now. The orbital solution currently available for this object is very robust and our full N-body calculations show that it may be a long-term companion (time-scale of Myr) to our planet. Among the known Earth quasi-satellites, it is the closest to our planet and as such, a potentially accessible target for future in situ study. Due to its presumably lengthy dynamical relationship with the Earth and given the fact that at present and for many decades this transient object remains well positioned with respect to our planet, the results of spectroscopic studies of this small body, 26-115 m, may be particularly useful to improve our understanding of the origins -local or captured- of Earth's co-orbital asteroid population. The non-negligible effect of the uncertainty in the value of the mass of Jupiter on the stability of this type of co-orbitals is also briefly explored.
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  • https://arxiv.org/abs/1209.3116
    Plutino 15810 (1994 JR1), an accidental quasi-satellite of Pluto
    In the solar system, quasi-satellites move in a 1:1 mean motion resonance going around their host body like a retrograde satellite but their mutual separation is well beyond the Hill radius and the trajectory is not closed as they orbit the Sun not the host body. So far, minor bodies temporarily trapped in the quasi-satellite dynamical state have been identified around Venus, Earth, the dwarf planet (1) Ceres, the large asteroid (4) Vesta, Jupiter, Saturn and Neptune. Using computer simulations, Tiscareno and Malhotra have predicted the existence of a small but significant population of minor bodies moving in a 1:1 mean motion resonance with Pluto. Here we show using N-body calculations that the Plutino 15810 (1994 JR1) is currently an accidental quasi-satellite of Pluto and it will remain as such for nearly 350,000 yr. By accidental we mean that the quasi-satellite phase is triggered (or terminated) not by a direct gravitational influence in the form of a discrete close encounter but as a result of a resonance. The relative mean longitude of the Plutino circulates with a superimposed libration resulting from the oscillation of the orbital period induced by the 2:3 mean motion resonance with Neptune. These quasi-satellite episodes are recurrent with a periodicity of nearly 2 Myr. This makes 15810 the first minor body moving in a 1:1 mean motion resonance with Pluto. It also makes Pluto the second dwarf planet, besides Ceres, to host a quasi-satellite. Our finding confirms that the quasi-satellite resonant phase is not restricted to small bodies orbiting major planets but is possible for dwarf planets/asteroids too. Moreover, 15810 could be considered as a possible secondary target for NASA's Pluto-Kuiper Belt Mission New Horizons after the main Pluto flyby in 2015.
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  • https://www.upi.com/Science_News/2024/11/11/SpaceX-first-stage-booster-KoreaSat/6411731338735/
    SpaceX launches Koreasat-6A satellite with workhorse first-stage booster - UPI.com
    SpaceX successful launched a South Korean communication satellite from Kennedy Space Center in Florida on Monday afternoon.
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  • http://arxiv.org/abs/1511.08360
    From horseshoe to quasi-satellite and back again: the curious dynamics of Earth co-orbital asteroid 2015 SO2
    Earth co-orbitals of the horseshoe type are interesting objects to study for practical reasons. They are relatively easy to access from our planet and that makes them attractive targets for sample return missions. Here, we show that near-Earth asteroid (NEA) 2015 SO2 is a transient co-orbital to the Earth that experiences a rather peculiar orbital evolution characterised by recurrent, alternating horseshoe and quasi-satellite episodes. It is currently following a horseshoe trajectory, the ninth asteroid known to do so. Besides moving inside the 1:1 mean motion resonance with the Earth, it is subjected to a Kozai resonance with the value of the argument of perihelion librating around 270 degrees. Contrary to other NEAs, asteroid 2015 SO2 may have remained in the vicinity of Earth's co-orbital region for a few hundreds of thousands of years.
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  • https://en.wikipedia.org/wiki/Submillimeter_Wave_Astronomy_Satellite
    Submillimeter Wave Astronomy Satellite
    Submillimeter Wave Astronomy Satellite (SWAS, also Explorer 74 and SMEX-3) is a NASA submillimetre astronomy satellite, and is the fourth spacecraft in the Small Explorer program (SMEX). It was launched on 6 December 1998, at 00:57:54 UTC, from Vandenberg Air Force Base aboard a Pegasus XL launch vehicle. The telescope was designed by the Smithsonian Astrophysical Observatory (SAO) and integrated by Ball Aerospace, while the spacecraft was built by NASA's Goddard Space Flight Center (GSFC). The mission's principal investigator is Gary J. Melnick. History The Submillimeter Wave Astronomy Satellite mission was approved on 1 April 1989. The project began with the Mission Definition Phase, officially starting on 29 September 1989, and running through 31 January 1992. During this time, the mission underwent a conceptual design review on 8 June 1990, and a demonstration of the Schottky receivers and acousto-optical spectrometer concept was performed on 8 November 1991. Development The mission's Development Phase ran from February 1992, through...
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  • .

    \begin{figure*}[t]
    \centering
    \includegraphics[width=0.9\textwidth]{figures/satellite_example.pdf}
    \caption{\label{fig:satellite_example} Example of a satellite image from the ISPRS 2D Semantic Labeling dataset \cite{rottensteiner2012isprs}. The ground truth labels are shown in the rightmost panel.}
    \end{figure*}

    In this work, we focus on semantic segmentation, which is the task of assigning a class label to each pixel in an image. This task is important for many applications such as autonomous driving, medical imaging and remote sensing \cite{chen2018deeplab}. In particular, we focus on semantic segmentation of satellite images, which is a challenging problem due to the large variation in appearance between different classes and the small size of objects in satellite images (see Figure~\ref{fig:satellite_example}).

    In this paper, we propose a novel approach for semantic segmentation of satellite images based on deep learning. Specifically, our approach consists of two components: 1) an encoder-decoder architecture for feature extraction and pixel-wise classification and 2) an attention mechanism for improved feature learning. The encoder-decoder architecture consists of a convolutional neural network (CNN) encoder that extracts features from the input image and a decoder that uses these features to classify each pixel in the image. The attention mechanism is used to improve feature learning by focusing on relevant regions in the input image. We evaluate our approach on two publicly available datasets for semantic segmentation of satellite images and show that it achieves state-of-the-art performance.






















    % \section{Related Work} \label{sec:related_work}
    % Semantic segmentation has been studied extensively in recent years with deep learning approaches being particularly successful \cite{long2015fully}. In particular, fully convolutional networks (FCNs) \cite{long2015fully}, which are based on CNNs with upsampling layers added at the end of the network, have achieved state-of-the-art results for many applications such as medical imaging \cite{ronneberger2015u}, autonomous driving \cite{chen2018deeplab}, and remote sensing \cite{marmanis2016semantic}. FCNs are well suited for semantic segmentation tasks since they can be used to directly produce pixel-wise classifications without requiring additional postprocessing steps.
    % % FCNs have been used successfully for many applications such as medical imaging \cite{ronneberger2015u}, autonomous driving \cite{chen2018deeplab}, and remote sensing \cite{marmanis2016semantic}.
    % % FCNs are well suited for semantic segmentation tasks since they can be used to directly produce pixel-wise classifications without requiring additional postprocessing steps.
    % % FCNs have been used successfully for many applications such as medical imaging [], autonomous driving [], and remote sensing [].
    % % FCNs are well suited for semantic segmentation tasks since they can be used to directly produce pixel-wise classifications without requiring additional postprocessing steps.
    % % For example, Ronneberger et al. [] proposed U-Net [] which is an FCN based model designed specifically for biomedical image segmentation tasks. U-Net has achieved state-of-the art results on several datasets including ISBI cell tracking challenge [] and Kaggle data science bowl [] among others [].
    % % Chen et al.[] proposed DeepLab [] which is an FCN based model designed specifically for object boundary detection tasks such as autonomous driving []. DeepLab has achieved state-of-the art results on several datasets including Cityscapes [] and PASCAL VOC 2012 [] among others [].
    % % Marmanis et al.[] proposed SegNet [] which is an FCN based model designed specifically for semantic segmentation tasks such as remote sensing []. SegNet has achieved state-of-the art results on several datasets including ISPRS Vaihingen dataset [] among others [].

    By: ChatGPT AI
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