To see the other types of publications on this topic, follow the link: Optical radar.

Journal articles on the topic 'Optical radar'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 journal articles for your research on the topic 'Optical radar.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.

1

Avrutov, Vadym, Sergii Rupich, and Vyacheslav Tsisarzh. "TRENDS OF THE MICROWAVE PHOTONIC RADARS." Bulletin of Kyiv Polytechnic Institute. Series Instrument Making, no. 67(1) (June 30, 2024): 5–12. http://dx.doi.org/10.20535/1970.67(1).2024.306719.

Full text
Abstract:
Today, the world's leading countries are intensively working on the development of new generation radars - microwave photonic radars. Microwave photonic radars make it possible to significantly reduce the mass and size characteristics of radar stations, to increase the information capability and range of target detection due to the reduction of losses in long communication lines when using optical fiber, to ensure high immunity due to the significantly lower sensitivity of optical-electronic equipment and fiber-optic lines of communication connection to external electromagnetic influences. Microwave photonics provides wide bandwidth, flat response, low loss transmission, multi-dimensional multiplexing, ultra-fast analog signal processing and immunity to electromagnetic interference. Radar implementation in the optical domain can provide better resolution, coverage, and speed performance, which would be difficult to implement with traditional electronics. The review article examines the state of development and system architectures of such photonic radars as optoelectronic hybrid radars, all-optical radars, multifunctional microwave photonic radar systems, distributed microwave photonic radars, software-defined radars, and cognitive radars. New technologies in this field and possible future directions of research are discussed. As an example, a broadband microwave photon radar reproduced on the basis of a microcircuit is considered. The broadband signal generator and receiver are built into the silicon crystal on the insulator. A high-precision distance measurement with a resolution of 2.7 cm and an error of less than 2.75 mm was obtained. Visualization of multiple targets with complex profiles has been implemented. But the performance of most integrated microwave photonic chips is not yet satisfactory for practical radar applications. Monolithic integration of key microwave photonic subsystems is also not mature enough for practical applications, so hybrid integration of devices fabricated on their optimal integration platforms is of practical interest. At present, indium phosphide, silicon nitride and silicon on insulator are the three leading platforms for photonic integration
APA, Harvard, Vancouver, ISO, and other styles
2

Brosch, N., D. Polishook, R. Helled, S. Schijvarg, and M. Rosenkrantz. "Radar and optical leonids." Atmospheric Chemistry and Physics Discussions 4, no. 2 (March 9, 2004): 1425–47. http://dx.doi.org/10.5194/acpd-4-1425-2004.

Full text
Abstract:
Abstract. We present joint optical-radar observations of meteors collected near the peak of the leonid activity in 2002. We show four examples of joint detections with a large, phased array L-band radar and with intensified video cameras. The general characteristic of the radar-detected optical meteors is that they show the radar detection below the termination of the optical meteor. Therefore, at least some radar events associated with meteor activity are neither head echoes nor trail echoes, but probably indicate the formation of "charged clouds" after the visual meteor is extinguished.
APA, Harvard, Vancouver, ISO, and other styles
3

Brosch, N., D. Polishook, R. Helled, S. Schijvarg, and M. Rosenkrantz. "Radar and optical leonids." Atmospheric Chemistry and Physics 4, no. 4 (July 6, 2004): 1063–69. http://dx.doi.org/10.5194/acp-4-1063-2004.

Full text
Abstract:
Abstract. We present joint optical-radar observations of meteors collected near the peak of the Leonid activity in 2002. We show four examples of joint detections with a large, phased array L-band radar and with intensified video cameras. The general characteristic of the radar-detected optical meteors is that they show the radar detection below the termination of the optical meteor. Therefore, at least some radar events associated with meteor activity are neither head echoes nor trail echoes, but probably indicate the formation of "charged clouds" after the visual meteor is extinguished.
APA, Harvard, Vancouver, ISO, and other styles
4

Mann, Ingrid, Asta Pellinen-Wannberg, and Anders Tjulin. "Meteor studies applying incoherent scatter radar instruments." Proceedings of the International Astronomical Union 10, H16 (August 2012): 181. http://dx.doi.org/10.1017/s1743921314005353.

Full text
Abstract:
AbstractOne of the interesting aspects of optical meteor studies is that the spectral composition of the brightness reveals information about the element composition of the solid particles that enter Earthfs atmosphere from interplanetary space. Deriving composition from optical spectra requires understanding the entry process during which the entering solid interacts with atmospheric species. This is especially so, because most meteors are observed at altitudes where the mean free path changes from tens of meters to millimeters, that is in the 120 km to 80 km altitude range within the atmosphere. The ionization that causes optical emission also reflects radio waves, so that meteors are observed with different kinds of radar instruments. Incoherent scatter radar facilities are in particular designed to study the upper atmosphere by using the backscattering from free electrons and are basically High Power Large Aperture radars. During the past 15 years they have been increasingly used for meteor studies. The phased-array incoherent scatter radars that are currently under development, such as the planned EISCAT-3Dsystem in northern Scandinavia, will further improve the spatial and time resolution of radar observations and will allow simultaneous measurements of the meteors and of the parameters of the surrounding ionosphere. Radar backscattering is also sensitive to objects that are smaller than those detected optically, so that the observations also permit studying the extension of the meteoroid size distribution to smaller sizes. In this presentation we consider the possibilities for measurements with the future EISCAT-3D as a new path of studying the physics of meteor phenomena with high accuracy.
APA, Harvard, Vancouver, ISO, and other styles
5

Djordjevic, Ivan B. "On Entanglement-Assisted Multistatic Radar Techniques." Entropy 24, no. 7 (July 17, 2022): 990. http://dx.doi.org/10.3390/e24070990.

Full text
Abstract:
Entanglement-based quantum sensors have much better sensitivity than corresponding classical sensors in a noisy and lossy regime. In our recent paper, we showed that the entanglement-assisted (EA) joint monostatic–bistatic quantum radar performs much better than conventional radars. Here, we propose an entanglement-assisted (EA) multistatic radar that significantly outperforms EA bistatic, coherent state-based quantum, and classical radars. The proposed EA multistatic radar employs multiple entangled transmitters performing transmit-side optical phase conjugation, multiple coherent detection-based receivers serving as EA detectors, and a joint detector.
APA, Harvard, Vancouver, ISO, and other styles
6

Ilovitsh, Asaf, Shlomo Zach, and Zeev Zalevsky. "Optical synthetic aperture radar." Journal of Modern Optics 60, no. 10 (June 2013): 803–7. http://dx.doi.org/10.1080/09500340.2013.814817.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Kakimoto, Yukiteru. "Optical fiber imaging laser radar." Optical Engineering 44, no. 1 (January 1, 2005): 016201. http://dx.doi.org/10.1117/1.1828092.

Full text
APA, Harvard, Vancouver, ISO, and other styles
8

Ogawa, T. "Radar observations of ionospheric irregularities at Syowa Station, Antarctica: a brief overview." Annales Geophysicae 14, no. 12 (December 31, 1996): 1454–61. http://dx.doi.org/10.1007/s00585-996-1454-z.

Full text
Abstract:
Abstract. We briefly overview the radar observations that have been made for 30 years at Syowa Station, Antarctica for studying small-scale electron-density irregularities in the southern high-latitude E- and F-region ionosphere. Some observational results (i.e., long-term variations of radio aurora, Doppler spectra with narrow spectral widths and low Doppler velocities, and simultaneous observations of radar and optical auroras) from VHF radars capable of detecting 1.3- to 3-m scale irregularities are presented. A new 50-MHz radar system equipped with phased-antenna arrays began operation in February 1995 to observe two-dimensional behaviours of E-region irregularities. An HF radar experiment also began in February 1995 to explore decameter-scale E- and F-region irregularities in the auroral zone and polar cap. These two radars will contribute to a better understanding of the ionospheric irregularities and ionospheric physics at southern high latitudes.
APA, Harvard, Vancouver, ISO, and other styles
9

Milan, S. E., M. Lester, N. Sato, H. Takizawa, and J. P. Villain. "Investigation of the relationship between optical auroral forms and HF radar E region backscatter." Annales Geophysicae 18, no. 6 (June 30, 2000): 608–17. http://dx.doi.org/10.1007/s00585-000-0608-7.

Full text
Abstract:
Abstract. The SuperDARN HF radars have been employed in the past to investigate the spectral characteristics of coherent backscatter from L-shell aligned features in the auroral E region. The present study employs all-sky camera observations of the aurora from Husafell, Iceland, and the two SuperDARN radars located on Iceland, Þykkvibær and Stokkseyri, to determine the optical signature of such backscatter features. It is shown that, especially during quiet geomagnetic conditions, the backscatter region is closely associated with east-west aligned diffuse auroral features, and that the two move in tandem with each other. This association between optical and radar aurora has repercussions for the instability mechanisms responsible for generating the E region irregularities from which radars scatter. This is discussed and compared with previous studies investigating the relationship between optical and VHF radar aurora. In addition, although it is known that E region backscatter is commonly observed by SuperDARN radars, the present study demonstrates for the first time that multiple radars can observe the same feature to extend over at least 3 h of magnetic local time, allowing precipitation features to be mapped over large portions of the auroral zone.Key words: Ionosphere (particle precipitation; plasma waves and instabilities)
APA, Harvard, Vancouver, ISO, and other styles
10

Nhemaphuki, David, Kiran Thapa Chetri, and Sanjeevan Shrestha. "Fusion of Radar and Optical Data for Land Cover Classification Using Machine Learning Approach." Journal on Geoinformatics, Nepal 20, no. 1 (December 1, 2020): 39–45. http://dx.doi.org/10.3126/njg.v20i1.39476.

Full text
Abstract:
This study evaluates the advantages of combining traditional space borne optical data with longer wavelengths of radar for land cover mapping. Land cover classification was carried out using Optical, radar data and combination of both for the Bardiya district using Random Forest algorithm. The fusion of optical and radar shows better land cover discrimination with 96.98% overall accuracy in compared to using radar data and optical data separately with overall accuracy of 69.2% and 95.89% respectively. Additionally, the qualitative result demonstrates that the combined utilization of optical and radar imagery yields useful land cover information over those obtained using either type of image on its own.
APA, Harvard, Vancouver, ISO, and other styles
11

Mathur, Manisha, Jaynendra Kumar Rai, and Nilakantan Sridhar. "Microwave photonic network for active electronically scanned array radar." International Journal of Microwave and Wireless Technologies 9, no. 3 (March 3, 2016): 543–50. http://dx.doi.org/10.1017/s1759078716000295.

Full text
Abstract:
Active electronically scanned array (AESA) radar has large number oftransmit/Receive (T/R) modules which require multiple microwave and digital signals. Distribution of these signals through conventional method such as coaxial cable, twisted pair, etc. not only introduces engineering complexities and signal loss but also have limitation of bandwidth, data rate, transmission distance, etc. This paper addresses design and implementation of microwave photonic network for distribution of microwave and digital signals over single optical fiber using wavelength division multiplexing for AESA radars. The design challenge is to limit the variation in output radio frequency power within ±1 dB over full operational band of radar from 2 to 4 GHz and functionality under hostile military environment. Optical amplifiers have been used in all channels to stabilize optical output independent of wavelength with automatic light control. The optical signal is split into 64 identical parts to feed multiplexed signal into different digital receivers physically spread across the antenna array. It is an additional challenge to normalize performance as all 64 receivers show variation in output in spite of identical electronic circuitry. Experimental results validate the feasibility of microwave photonic network for wide branching distribution of multiple microwave and digital signals for AESA radar.
APA, Harvard, Vancouver, ISO, and other styles
12

Emdin, V. S. "Optical strobing of the range in optical radar systems." Journal of Optical Technology 66, no. 8 (August 1, 1999): 766. http://dx.doi.org/10.1364/jot.66.000766.

Full text
APA, Harvard, Vancouver, ISO, and other styles
13

R, Giridhar. "Design and Demonstration of Optical Radar." International Journal for Research in Applied Science and Engineering Technology 9, no. 4 (April 30, 2021): 182–87. http://dx.doi.org/10.22214/ijraset.2021.33579.

Full text
APA, Harvard, Vancouver, ISO, and other styles
14

Tonda-Goldstein, S., D. Dolfi, A. Monsterleet, S. Formont, J. Chazelas, and Jean-Pierre Huignard. "Optical signal processing in Radar systems." IEEE Transactions on Microwave Theory and Techniques 54, no. 2 (February 2006): 847–53. http://dx.doi.org/10.1109/tmtt.2005.863059.

Full text
APA, Harvard, Vancouver, ISO, and other styles
15

Sekar, R., D. Chakrabarty, R. Narayanan, S. Sripathi, A. K. Patra, and K. S. V. Subbarao. "Characterization of VHF radar observations associated with equatorial Spread F by narrow-band optical measurements." Annales Geophysicae 22, no. 9 (September 23, 2004): 3129–36. http://dx.doi.org/10.5194/angeo-22-3129-2004.

Full text
Abstract:
Abstract. The VHF radars have been extensively used to investigate the structures and dynamics of equatorial Spread F (ESF) irregularities. However, unambiguous identification of the nature of the structures in terms of plasma depletion or enhancement requires another technique, as the return echo measured by VHF radar is proportional to the square of the electron density fluctuations. In order to address this issue, co-ordinated radar backscatter and thermospheric airglow intensity measurements were carried out during March 2003 from the MST radar site at Gadanki. Temporal variations of 630.0-nm and 777.4-nm emission intensities reveal small-scale ("micro") and large-scale ("macro") variations during the period of observation. The micro variations are absent on non-ESF nights while the macro variations are present on both ESF and non-ESF nights. In addition to the well-known anti-correlation between the base height of the F-region and the nocturnal variation of thermospheric airglow intensities, the variation of the base height of the F-layer, on occasion, is found to manifest as a bottomside wave-like structure, as seen by VHF radar on an ESF night. The micro variations in the airglow intensities are associated with large-scale irregular plasma structures and found to be in correspondence with the "plume" structures obtained by VHF radar. In addition to the commonly observed depletions with upward movement, the observation unequivocally reveals the presence of plasma enhancements which move downwards. The observation of enhancement in 777.4-nm airglow intensity, which is characterized as plasma enhancement, provides an experimental verification of the earlier prediction based on numerical modeling studies.
APA, Harvard, Vancouver, ISO, and other styles
16

Potapov, A. A., V. A. Kuznetsov, and E. A. Alikulov. "Methods for Complexing Images Formed by Multi-Band Synthetic Aperture Radars." Journal of the Russian Universities. Radioelectronics 24, no. 3 (June 24, 2021): 6–21. http://dx.doi.org/10.32603/1993-8985-2021-24-3-6-21.

Full text
Abstract:
Introduction. Synthetic aperture radars (SAR) are important components of aviation-based systems for remote sensing of the Earth. The current level of such systems allows simultaneous radar surveys in several frequency ranges. Such surveys require complexing of the images formed in each of the frequency channels, which task is yet to be resolved.Aim. To review the formation principles and methods for joint processing of images using space and aviation-based multi-band synthetic aperture radar systems.Materials and methods. The methodology of systems analysis, involving the integral stages of decomposition, analysis and synthesis, was used. Decomposition of integrating multi-band radar images was performed considering the effect of various factors on the characteristics of radar images in different frequency ranges. Such factors include the principles of radar imaging, issues of radar images of multi-band synthetic aperture radars with real characteristics, and complexing levels.Results. According to the classical systems approach, the results of review and analysis are corresponded by appropriate conclusions on the shortcomings of each decomposition element and the synthesis of a proposal for achieving the goal. It was shown that joint processing of multi-band radar images can be carried out at the levels of signals, pixels, features and solutions, as well as their aggregates. Each approach is characterised by its shortcomings, which impede implementation of full integration of multi-band radar images without loss of information, which is due to the absence of information redundancy of radar images, compared to, e.g., optical images.Conclusion. Recommendations on the application of a particular method and the synthesis of a system for radar complexing images based on the texture-fractal approach were formulated. Directions for further work meeting all the requirements for completeness, reliability and information content of remote sensing of the Earth were outlined.
APA, Harvard, Vancouver, ISO, and other styles
17

Aja, Daniel, Michael K. Miyittah, and Donatus Bapentire Angnuureng. "Quantifying Mangrove Extent Using a Combination of Optical and Radar Images in a Wetland Complex, Western Region, Ghana." Sustainability 14, no. 24 (December 13, 2022): 16687. http://dx.doi.org/10.3390/su142416687.

Full text
Abstract:
The classification of mangrove forests in tropical coastal zones, based only on passive remote sensing methods, is hampered by mangrove complexities, topographical considerations, and cloud cover effects, among others. This paper reports on a study that combines optical and radar data to address the challenges of distinguishing mangrove stands in cloud-prone regions. The Google Earth Engine geospatial processing platform was used to extract multiple scenes of Landsat surface reflectance Tier 1 and synthetic aperture radar (C-band and L-band). The images were enhanced by creating a feature that removes clouds from the optical data and using speckle filters to remove noise from the radar data. The random forest algorithm proved to be a robust and accurate machine learning approach for mangrove classification and assessment. Classification was evaluated using three scenarios: classification of optical data only, classification of radar data only, and combination of optical and radar data. Our results revealed that the scenario that combines optical and radar data performed better. Further analysis showed that about 16.9% and 21% of mangrove and other vegetation/wetland cover were lost between 2009 and 2019. Whereas water body and bare land/built-up areas increased by 7% and 45%, respectively. Accuracy was evaluated based on the three scenarios. The overall accuracy of the 2019 classification was 98.9% (kappa coefficient = 0.979), 84.6% (kappa coefficient = 0.718), and 99.1% (kappa coefficient = 0.984), for classification of optical data only, classification of radar data only, and combination of optical and radar data, respectively. This study has revealed the potential to map mangroves correctly, enabling on-site conservation practices in the climate change environment.
APA, Harvard, Vancouver, ISO, and other styles
18

Takewaka, Satoshi. "Visibility of River Plume Fronts with an X-Band Radar." Journal of Sensors 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/6594847.

Full text
Abstract:
A land-based X-band radar was employed to observe river plume fronts at the mouth of the Tenryu River, Japan. Time-averaged radar images captured fronts extending offshore from the river’s mouth as bright streaks. Comparisons between satellite optical images and radar images confirm that streaky features in the radar image represent color river plume fronts. Further corroboration comes from field observations of water temperature, salinity, and turbidity conducted simultaneously with the radar measurements. When a survey ship crossed the front, the measured properties varied discontinuously, suggesting that water from the river and sea converged there and also that a downwards current was present. Variation of visibility of the fronts was assessed and compared with the rate of variation of water level and the wind speed and direction. The radar is able to image fronts when the water level is decreasing during ebb tide and the wind speed is over 3 m/s along shore. Surface ripple waves are generated by the local wind, and if they propagate across the front, wave heights increase, causing higher backscatter of the emitted radar beam. This observation gives further evidence on the imaging mechanism of river plume fronts with X-band radars in relation to wind direction.
APA, Harvard, Vancouver, ISO, and other styles
19

Friedt, Jean-Michel, Éric Bernard, and Madeleine Griselin. "Ground-Based Oblique-View Photogrammetry and Sentinel-1 Spaceborne RADAR Reflectivity Snow Melt Processes Assessment on an Arctic Glacier." Remote Sensing 15, no. 7 (March 30, 2023): 1858. http://dx.doi.org/10.3390/rs15071858.

Full text
Abstract:
The snowpack evolution during the melt season on an Arctic glacier is assessed using ground-based oblique-view cameras, spaceborne imaging and spaceborne RADAR. The repeated and systematic Synthetic Aperture RADAR (SAR) imaging by the European Space Agency’s Sentinel-1 spaceborne RADARs allows for all-weather, all-illumination condition monitoring of the snow-covered fraction of the glacier and hence assessing its water production potential. A comparison of the RADAR reflectivity with optical and multispectral imaging highlights the difference between the observed quantities—water content in the former, albedo in the latter—and the complementarity for understanding the snow melt processes. This work highlights the temporal inertia between the visible spring melting of the snowpack and the snow metamorphism. It was found that the snowpack exhibits that approximately 30 days before it starts to fade.
APA, Harvard, Vancouver, ISO, and other styles
20

Zhang, Zhen, and Xue Wu Cheng. "The High Speed Optoelectronic Isolator Design in Laser Radar." Applied Mechanics and Materials 241-244 (December 2012): 2196–99. http://dx.doi.org/10.4028/www.scientific.net/amm.241-244.2196.

Full text
Abstract:
Laser radar is a kind of active modern optical equipment, It’s the extension of traditional radio or microwave radar to optical frequency. Because the probe beam wavelength shortening and directional strengthen, so that the laser radar has very strong space, time resolution and high detection sensitivity and other advantages, Laser radar has been widely applied in the atmosphere, ocean, land and in other target detection. Optoelectronic isolator is usually used in electronic circuit device, but the ns order of magnitude of the high-speed triggering and synchronization is more difficult, while the synchronization of laser radar and laser communication is in the order of ns. In order to solve this problem, this paper presents a high speed optical trigger, which can realize the high speed synchronization of emission laser and receiving circuit in laser radar, and delay time is within 150ns, that can provide protection to obtain synchronous valid data.
APA, Harvard, Vancouver, ISO, and other styles
21

Shuygina, N. V., and E. I. Yagudina. "The FK5 equinox and equator from combined radar and optical data of the near-earth asteroids." Symposium - International Astronomical Union 172 (1996): 469–74. http://dx.doi.org/10.1017/s0074180900127895.

Full text
Abstract:
Minor planets optical observations have long been used for the purpose of establishing a Celestial reference frame. Being in existence since the early 1960s modern high-accuracy radar measurements of the so-called near-Earth asteroids (NEAs) have been widely extended to the orbit determination process and predicting of the next apparition of the asteroid. Even few radar measurements, when added to optical ones, significantly improve asteroid's ephemeris and reduce standard deviations of the orbital elements (Yeomans et al., 1987). The idea to connect optical and radar data in the problem of the catalogue zero-point determination has been stated by several scientists (Boiko, 1975). And even the first attempt of the authors (Krivova et al., 1994) with actual optical and radar observations of two NEAs: (4179) Toutatis and (1862) Apollo appears to have considerable promise. It was demonstrated the possibility of obtaining standard deviations of catalogue orientation parameters 1.5–2 times better with radar data included.
APA, Harvard, Vancouver, ISO, and other styles
22

Djordjevic, Ivan B. "Entanglement-Assisted Joint Monostatic-Bistatic Radars." Entropy 24, no. 6 (May 26, 2022): 756. http://dx.doi.org/10.3390/e24060756.

Full text
Abstract:
With the help of entanglement, we can build quantum sensors with sensitivity better than that of classical sensors. In this paper we propose an entanglement assisted (EA) joint monostatic-bistatic quantum radar scheme, which significantly outperforms corresponding conventional radars. The proposed joint monostatic-bistatic quantum radar is composed of two radars, one having both wideband entangled source and EA detector, and the second one with only an EA detector. The optical phase conjugation (OPC) is applied on the transmitter side, while classical coherent detection schemes are applied in both receivers. The joint monostatic-bistatic integrated EA transmitter is proposed suitable for implementation in LiNbO3 technology. The detection probability of the proposed EA joint target detection scheme outperforms significantly corresponding classical, coherent states-based quantum detection, and EA monostatic detection schemes. The proposed EA joint target detection scheme is evaluated by modelling the direct radar return and forward scattering channels as both lossy and noisy Bosonic channels, and assuming that the distribution of entanglement over idler channels is not perfect.
APA, Harvard, Vancouver, ISO, and other styles
23

Rustamov, Asad, Yashar Kerimov, Ahmed Mammedov, Mehman Binnatov, and Vusal Katekhliyev. "ACOUSTO-OPTICAL RECEIVER OF AN OBSTRUCTION PASSIVE RADAR SYSTEM." Advanced Information Systems 7, no. 4 (December 3, 2023): 65–69. http://dx.doi.org/10.20998/2522-9052.2023.4.08.

Full text
Abstract:
The subject of research in the article is the passive radar system of a warship. The purpose of the work was to review the characteristics use of the acousto-optical receiver in the new passive radar system of the warship, to investigate the peculiarities of acoustooptic effect and the relevant synthesis of methods and tools for measuring the photodetector photoelectric characteristics and, in addition, to investigate the energy-and-geometric parameters of laser radiation Justification. It is shown that the transition, impulse and frequency characteristics are taken as the main means to determine the operating and technical parameters of the acousto-optical delay line. It is not possible to unambiguously extrapolate these characteristics to the known models of the characteristics of the acousto-optic radar receiver created on AODL. Research results. In the context of this postulate, mathematical models of the main characteristics of AODL were developed. On the basis of the synchronous compensation pulse obstacles applied to the passive radar acousto-optic receiver on military ships, the full compensation of the obstacles is determined for the effective reception of signals from the acousto-optic receiver. In radar stations (radar), the main attention is focused on the statistical properties of the useful signal and passive obstacles, the speed (frequency) of the signal passing through the passive obstacle and the space-time differences. The recommendations. These features are recommended to be used only in special cases where the target is outside the reflectors for informational duration, amplitude and differences between passive obstacles, obstacle silencing and signal separation. Conclusion. Applying the full attenuation of the band filter and synphase barrier organizers, whose frequency characteristics do not depend on the tuning frequency, it is possible to provide full compensation of obstacles during the effective reception of signals by the acousto-optic receiver in the passive radar system of warships based on the proposed method for high resistance to obstacles, pulse obstacle compensation.
APA, Harvard, Vancouver, ISO, and other styles
24

Armellin, Roberto, and Pierluigi Di Lizia. "Probabilistic Optical and Radar Initial Orbit Determination." Journal of Guidance, Control, and Dynamics 41, no. 1 (January 2018): 101–18. http://dx.doi.org/10.2514/1.g002217.

Full text
APA, Harvard, Vancouver, ISO, and other styles
25

Alping, A., P. Andersson, and S. T. Eng. "Picosecond semiconductor laser radar with optical amplifier." Electronics Letters 21, no. 4 (1985): 126. http://dx.doi.org/10.1049/el:19850089.

Full text
APA, Harvard, Vancouver, ISO, and other styles
26

Bamford, K., J. James, H. Barr, and R. P. Tatam. "Optical Radar Detection of Precancerous Bronchial Tissue." Lasers in Medical Science 15, no. 3 (September 2000): 188–94. http://dx.doi.org/10.1007/pl00011316.

Full text
APA, Harvard, Vancouver, ISO, and other styles
27

Ohsawa, Ryou, Akira Hirota, Kohei Morita, Shinsuke Abe, Daniel Kastinen, Johan Kero, Csilla Szasz, et al. "Relationship between radar cross section and optical magnitude based on radar and optical simultaneous observations of faint meteors." Planetary and Space Science 194 (December 2020): 105011. http://dx.doi.org/10.1016/j.pss.2020.105011.

Full text
APA, Harvard, Vancouver, ISO, and other styles
28

Zhyrnov, V., and S. Solonska. "Intelligent model of radar object images for surveillance radars." Radiotekhnika, no. 212 (March 28, 2023): 148–54. http://dx.doi.org/10.30837/rt.2023.1.212.14.

Full text
Abstract:
The results of developing an intelligent model of radar object images for surveillance radars are presented. The relevance of this work deals with the development of algorithm for automatic processing images of radar objects that provide effective detection of weak true signals due to the accumulation of signal and logical information in the analyzed cell and in its surroundings under interferences. The improvement of air safety tools and the automation of air traffic management processes require effective procedures to process signal information. The issues of more complete use and qualitative improvement of the information-processing capabilities of control systems are also topical, especially in difficult conditions of interfering signals. The basis of this study is the idea of using an intellectual model of radar object images for automatic decision-making on detection and recognition of radar objects, built on the space of semantic features. The main result is optical object recognition, similar to how an expert can easily recognize aerial objects and their types when viewing radar object images. Based on semantic features intelligent model of radar object images has been developed, which makes it possible to effectively detect and classify aerial objects. It is worth noting that the characteristic description of intelligent model of radar object images for point, extended, moving and stationary radar objects is the mathematical description of procedures and relationships at perception and analysis of signals in the form of distinguishing features or properties. As a result, various virtual images of radar object are generated in the form of spatial-semantic and spectral-semantic models. The main features and structural elements of the model are given. It is shown that the advantages of this model are related to the possibility of characteristic description of the radar object images using the algebra of finite predicates.
APA, Harvard, Vancouver, ISO, and other styles
29

Sarzynski, Thuan, Xingli Giam, Luis Carrasco, and Janice Ser Huay Lee. "Combining Radar and Optical Imagery to Map Oil Palm Plantations in Sumatra, Indonesia, Using the Google Earth Engine." Remote Sensing 12, no. 7 (April 10, 2020): 1220. http://dx.doi.org/10.3390/rs12071220.

Full text
Abstract:
Monitoring the expansion of commodity crops in the tropics is crucial to safeguard forests for biodiversity and ecosystem services. Oil palm (Elaeis guineensis) is one such crop that is a major driver of deforestation in Southeast Asia. We evaluated the use of a semi-automated approach with random forest as a classifier and combined optical and radar datasets to classify oil palm land-cover in 2015 in Sumatra, Indonesia, using Google Earth Engine. We compared our map with two existing remotely-sensed oil palm land-cover products that utilized visual and semi-automated approaches for the same year. We evaluated the accuracy of oil palm land-cover classification from optical (Landsat), radar (synthetic aperture radar (SAR)), and combined optical and radar satellite imagery (Combined). Combining Landsat and SAR data resulted in the highest overall classification accuracy (84%) and highest producer’s and user’s accuracy for oil palm classification (84% and 90%, respectively). The amount of oil palm land-cover in our Combined map was closer to official government statistics than the two existing land-cover products that used visual interpretation techniques. Our analysis of the extents of disagreement in oil palm land-cover indicated that our map had comparable accuracy to one of them and higher accuracy than the other. Our results demonstrate that a combination of optical and radar data outperforms the use of optical-only or radar-only datasets for oil palm classification and that our technique of preprocessing and classifying combined optical and radar data in the Google Earth Engine can be applied to accurately monitor oil-palm land-cover in Southeast Asia.
APA, Harvard, Vancouver, ISO, and other styles
30

Kopenkov, V. N. "Combined usage of the optical and radar remote sensing data in territory monitoring tasks." Information Technology and Nanotechnology, no. 2391 (2019): 334–41. http://dx.doi.org/10.18287/1613-0073-2019-2391-334-341.

Full text
Abstract:
At the present time, a lot of problems in a sphere of fundamental sciences as well as technical and applied tasks can be solved only with the use of satellite images, since their usage reduces material, financial and time costs significantly in comparison with traditional methods. One of the modern integrated approach remote sensing processing is to join the measurements obtained from the various sources, such as optical and radar sensors, allowing to achieve a gain in comparison with independent processing due to the extension of the information volume and the opportunities of data acquisition (weather conditions, spectral ranges, etc.). However, methods of digital processing and interpretation of radar data, as well as qualitative and proven methods and algorithms for joint processing of optical and radar satellite images, has not sufficiently been well developed yet. Therefore, the development of new methods and information technology of joint analysis and interpretation of optical and radar data which are a major issue of the current paper, are certainly relevant. The paper presents an information technology for joint processing of optical and radar satellite imagery, based on training the processing procedure based on the reference values of data from sensors of the one type (optical data), followed by applying to both data types: optical and SAR data.
APA, Harvard, Vancouver, ISO, and other styles
31

Pellinen-Wannberg, A., A. Westman, G. Wannberg, and K. Kaila. "Meteor fluxes and visual magnitudes from EISCAT radar event rates: a comparison with cross-section based magnitude estimates and optical data." Annales Geophysicae 16, no. 11 (November 30, 1998): 1475–85. http://dx.doi.org/10.1007/s00585-998-1475-x.

Full text
Abstract:
Abstract. Incoherent scatter radars (ISR) are versatile instruments for continuous monitoring of ionisation processes in the Earth's atmosphere. EISCAT, The European Incoherent Scatter facility has proven effective also in meteor studies. The time resolution of the radar can be reduced to a few milliseconds, sufficient to resolve the passage of individual meteors through the narrow ISR beam. Methods for group and phase velocity determination of the meteoroids and the discrepancy between the results related to the target behaviour are presented. The radar cross sections of echoes associated with moving meteoroids ("meteor head echoes") are very small and increase with decreasing wavelength. The parent meteoroids are found to have visual magnitudes far below the detection limit of most optical observations. The equivalent visual magnitude limit of the smallest objects observed by EISCAT in the current experiments has been estimated by two different methods, both from the cross-section measurements and from the measured event rates. Both methods give a limit value of +10 for the smallest objects while the upper limit is +4. The lower limit of the visual magnitude for the collocated optical measurement system is +4. Thus the two detection systems observe two different meteor size ranges, with the radar almost reaching micrometeorite population. Meteor fluxes estimated from the event rates and the radar system parameters agree well with previous extrapolated values for this size range.Key words. Ionosphere (ionization mechanisms). Radio science (ionospheric physics). Space plasma physics (ionization processes)
APA, Harvard, Vancouver, ISO, and other styles
32

Paim Gonçalves, André, Felipe Streitenberger Ivo, Olympio Lucchini Coutinho, Felipe Araújo Marins, and Heitor Albuquerque. "Radar Receiver with Intrinsic Power Limiter Assisted by Microwave Photonics." Aplicações Operacionais em Áreas de Defesa 24, no. 1 (September 22, 2023): 40–43. http://dx.doi.org/10.55972/spectrum.v24i1.397.

Full text
Abstract:
This article presents an approach of a radar receiver that has an intrinsic power limitation based on photodetector power saturation. The radar signal power detection is implemented using optical self-homodyne detection. The proposed architecture uses a phase modulator (PM) to modulate the optical carrier and a fiber Bragg grating (FBG) to filter the spectrum and convert the phase to intensity modulation. The self-homodyne technique eliminates the optical carrier influence. It enables to reduce of shot noise influence and increases the photodetected optic power to improve the conversion gain. Moreover, the photodetection is performed at the radar pulse baseband, allowing to obtain transimpedance gain. An experimental demonstration is performed. A dynamic range of 56 dB is achieved for a pulsed radar operating at 20 GHz.
APA, Harvard, Vancouver, ISO, and other styles
33

Choi, Eun-Jung, Sungki Cho, Jung Hyun Jo, Jang-Hyun Park, Taejin Chung, Jaewoo Park, Hocheol Jeon, Ami Yun, and Yonghui Lee. "Performance Analysis of Sensor Systems for Space Situational Awareness." Journal of Astronomy and Space Sciences 34, no. 4 (December 2017): 303–13. http://dx.doi.org/10.5140/jass.2017.34.4.303.

Full text
Abstract:
With increased human activity in space, the risk of re-entry and collision between space objects is constantly increasing. Hence, the need for space situational awareness (SSA) programs has been acknowledged by many experienced space agencies. Optical and radar sensors, which enable the surveillance and tracking of space objects, are the most important technical components of SSA systems. In particular, combinations of radar systems and optical sensor networks play an outstanding role in SSA programs. At present, Korea operates the optical wide field patrol network (OWL-Net), the only optical system for tracking space objects. However, due to their dependence on weather conditions and observation time, it is not reasonable to use optical systems alone for SSA initiatives, as they have limited operational availability. Therefore, the strategies for developing radar systems should be considered for an efficient SSA system using currently available technology. The purpose of this paper is to analyze the performance of a radar system in detecting and tracking space objects. With the radar system investigated, the minimum sensitivity is defined as detection of a 1-m2 radar cross section (RCS) at an altitude of 2,000 km, with operating frequencies in the L, S, C, X or Ku-band. The results of power budget analysis showed that the maximum detection range of 2,000 km, which includes the low earth orbit (LEO) environment, can be achieved with a transmission power of 900 kW, transmit and receive antenna gains of 40 dB and 43 dB, respectively, a pulse width of 2 ms, and a signal processing gain of 13.3 dB, at a frequency of 1.3 GHz. We defined the key parameters of the radar following a performance analysis of the system. This research can thus provide guidelines for the conceptual design of radar systems for national SSA initiatives.
APA, Harvard, Vancouver, ISO, and other styles
34

Muhetaer, Nuerbiye, Ilyas Nurmemet, Adilai Abulaiti, Sentian Xiao, and Jing Zhao. "An Efficient Approach for Inverting the Soil Salinity in Keriya Oasis, Northwestern China, Based on the Optical-Radar Feature-Space Model." Sensors 22, no. 19 (September 23, 2022): 7226. http://dx.doi.org/10.3390/s22197226.

Full text
Abstract:
Soil salinity has been a major factor affecting agricultural production in the Keriya Oasis. It has a destructive effect on soil fertility and could destroy the soil structure of local land. Therefore, the timely monitoring of salt-affected areas is crucial to prevent land degradation and sustainable soil management. In this study, a typical salinized area in the Keriya Oasis was selected as a study area. Using Landsat 8 OLI optical data and ALOS PALSAR-2 SAR data, the optical remote sensing indexes NDVI, SAVI, NDSI, SI, were combined with the optimal radar polarized target decomposition feature component (VanZyl_vol_g) on the basis of feature space theory in order to construct an optical-radar two-dimensional feature space. The optical-radar salinity detection index (ORSDI) model was constructed to inverse the distribution of soil salinity in Keriya Oasis. The prediction ability of the ORSDI model was validated by a test on 40 measured salinity values. The test results show that the ORSDI model is highly correlated with soil surface salinity. The index ORSDI3 (R2 = 0.656) shows the highest correlation, and it is followed by indexes ORSDI1 (R2 = 0.642), ORSDI4 (R2 = 0.628), and ORSDI2 (R2 = 0.631). The results demonstrated the potential of the ORSDI model in the inversion of soil salinization in arid and semi-arid areas.
APA, Harvard, Vancouver, ISO, and other styles
35

Atlas, David, and Zhien Wang. "Contrails of Small and Very Large Optical Depth." Journal of the Atmospheric Sciences 67, no. 9 (September 1, 2010): 3065–73. http://dx.doi.org/10.1175/2010jas3403.1.

Full text
Abstract:
Abstract This work deals with two kinds of contrails. The first comprises a large number of optically thin contrails near the tropopause. They are mapped geographically using a lidar to obtain their height and a camera to obtain azimuth and elevation. These high-resolution maps provide the local contrail geometry and the amount of optically clear atmosphere. The second kind is a single trail of unprecedentedly large optical thickness that occurs at a lower height. The latter was observed fortuitously when an aircraft moving along the wind direction passed over the lidar, thus providing measurements for more than 3 h and an equivalent distance of 620 km. It was also observed by Geostationary Operational Environmental Satellite (GOES) sensors. The lidar measured an optical depth of 2.3. The corresponding extinction coefficient of 0.023 km−1 and ice water content of 0.063 g m−3 are close to the maximum values found for midlatitude cirrus. The associated large radar reflectivity compares to that measured by ultrasensitive radar, thus providing support for the reality of the large optical depth.
APA, Harvard, Vancouver, ISO, and other styles
36

Wang, Yibo, Xusheng Li, Xiankun Yang, Wenchao Qi, Donghui Zhang, and Jinnian Wang. "Estimation of Picea Schrenkiana Canopy Density at Sub-Compartment Scale by Integration of Optical and Radar Satellite Images." Forests 15, no. 7 (July 1, 2024): 1145. http://dx.doi.org/10.3390/f15071145.

Full text
Abstract:
This study proposes a novel approach to estimate canopy density in Picea Schrenkiana var. Tianschanica forest sub-compartments by integrating optical and radar satellite data. This effort is aimed at enhancing methodologies for forest resource surveys and monitoring, particularly vital for the sustainable development of semi-arid mountainous areas with fragile ecological environments. The study area is the West Tianshan Mountain Nature Reserve in Xinjiang, which is characterized by its unique dominant tree species, Picea Schrenkiana. A total of 411 characteristic factors were extracted from Gaofen-2 (GF-2) sub-meter optical satellite imagery, Gaofen-3 (GF-3) multi-polarization synthetic aperture radar satellite imagery, and digital elevation model (DEM) data. Consequently, 17 characteristic parameters were selected based on their correlation with canopy density data to construct an estimation model. Three distinct models were developed, including a multiple stepwise regression model (a linear approach), a Back Propagation (BP) neural network model (a neural network-based method), and a Cubist model (a decision tree-based technique). The results indicate that combining optical and radar image characteristics significantly enhances accuracy, with an Average Absolute Percentage Precision (AAPP) value improvement in estimation accuracy from 76.50% (with optical image) and 78.50% (with radar image) to 78.66% (with both). Of the three models, the BP neural network model achieved the highest overall accuracy (79.19%). At the sub-component scale, the BP neural network model demonstrated superior accuracy in low canopy density estimation (75.37%), whereas the Cubist model, leveraging radar image characteristics, excelled in medium density estimations (87.46%). Notably, the integrated Cubist model combining optical and radar data achieved the highest accuracy for high canopy density estimation (89.17%). This study highlights the effectiveness of integrating optical and radar data for precise canopy density assessment, contributing significantly to ecological resource monitoring methodologies and environmental assessments.
APA, Harvard, Vancouver, ISO, and other styles
37

Del Valle, Héctor, Walter Fabián Sione, and Pablo Gilberto Aceñolaza. "Wetland Fire Assessment and Monitoring in the Paraná River Delta, Using Radar and Optical Data for Burnt Area Mapping." Fire 5, no. 6 (November 12, 2022): 190. http://dx.doi.org/10.3390/fire5060190.

Full text
Abstract:
In the past decades, important research has been carried out to map the natural disturbances in the Paraná River Delta. The benefits of the combined use optical and radar data are also known. The main objective of this paper is to assess the wetland fire cartography through a synergetic use of radar and optical data. We focus on integrating radar (SAOCOM) and Sentinel 1, as well as Sentinel 2 optical data, concerning the fires impact analyses in the wetland areas. The generation of water masks through the radar images can contribute to improve the burned wetland area estimations. The relationship between landforms, vegetation cover, and the spatial/temporal resolution imposed by the flood pulse, play a vital role in the results. Burnt areas represent a total of 2439.57 sq km, which is more than 85% of the wetland, during the winter and spring (Q3 and Q4) periods. Understanding the wetland heterogeneity and its recovery pattern after a fire, is crucial to improve the cartography of the burned areas; for this, biweekly or monthly image compositions periodicity are of crucial importance. The inclusion of different indexes, for optical and radar images, improve the precision for the final classification. The results obtained here are promising for post-flood and post-fire evaluation, even applying radar and optical data integration into the evaluation and the monitoring of wetland fires is far from being a uniform standardized process.
APA, Harvard, Vancouver, ISO, and other styles
38

Narula, Lakshay, Peter Iannucci, and Todd Humphreys. "All-Weather, sub-50-cm, Radar-Inertial Positioning." Field Robotics 2, no. 1 (March 10, 2022): 525–56. http://dx.doi.org/10.55417/fr.2022019.

Full text
Abstract:
Deploying automated ground vehicles beyond the confines of sunny and dry climes will require sub-lane-level positioning techniques that use radio waves, rather than near-visible light radiation. Like human sight, LiDAR and optical cameras perform poorly in low-visibility conditions. We present and demonstrate a novel technique for robust, sub-50-cm, urban ground vehicle positioning based on all-weather sensors. The technique incorporates a computationally-efficient, globally-optimal radar scan registration algorithm within a larger estimation pipeline that fuses data from commercially-available, low-cost, automotive radars, low-cost inertial sensors, vehicle motion constraints, and, when available, precise GNSS measurements. We evaluate the performance of the presented technique on an extensive and realistic urban dataset derived from all-weather sensors. Comparison against ground truth shows that during 60 min of GNSS-denied driving in the urban center of Austin, TX, the technique maintains 95th-percentile errors below 50 cm in horizontal position and 0.5 in heading.
APA, Harvard, Vancouver, ISO, and other styles
39

Leblon, Brigitte. "Mapping forest clearcuts using radar digital imagery: A review of the Canadian experience." Forestry Chronicle 75, no. 4 (August 1, 1999): 675–84. http://dx.doi.org/10.5558/tfc75675-4.

Full text
Abstract:
Annual clearcut mapping is currently done in Canada mainly from photo-interpretation of aerial photographs. An advantageous alternative would use digital imagery. Optical imagery acquisition depends on weather and illumination conditions, but not radar images. This paper documents the state of practice in Canada in the use of radar digital images for clearcut mapping, with regards to the type of images used, to the influence of environmental conditions, the band, polarization, time of the year, and incidence angles, as well as to the mapping accuracy. Synergism between optical and radar images is also discussed. Finally, a few experimental automated mapping systems using radar imageries are presented. Key words: remote sensing, forest inventory updating, clearcut mapping, synthetic aperture radar, microwave, digital imagery
APA, Harvard, Vancouver, ISO, and other styles
40

Cline, Don, Simon Yueh, Bruce Chapman, Boba Stankov, Al Gasiewski, Dallas Masters, Kelly Elder, et al. "NASA Cold Land Processes Experiment (CLPX 2002/03): Airborne Remote Sensing." Journal of Hydrometeorology 10, no. 1 (February 1, 2009): 338–46. http://dx.doi.org/10.1175/2008jhm883.1.

Full text
Abstract:
Abstract This paper describes the airborne data collected during the 2002 and 2003 Cold Land Processes Experiment (CLPX). These data include gamma radiation observations, multi- and hyperspectral optical imaging, optical altimetry, and passive and active microwave observations of the test areas. The gamma observations were collected with the NOAA/National Weather Service Gamma Radiation Detection System (GAMMA). The CLPX multispectral optical data consist of very high-resolution color-infrared orthoimagery of the intensive study areas (ISAs) by TerrainVision. The airborne hyperspectral optical data consist of observations from the NASA Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). Optical altimetry measurements were collected using airborne light detection and ranging (lidar) by TerrainVision. The active microwave data include radar observations from the NASA Airborne Synthetic Aperture Radar (AIRSAR), the Jet Propulsion Laboratory’s Polarimetric Ku-band Scatterometer (POLSCAT), and airborne GPS bistatic radar data collected with the NASA GPS radar delay mapping receiver (DMR). The passive microwave data consist of observations collected with the NOAA Polarimetric Scanning Radiometer (PSR). All of the airborne datasets described here and more information describing data collection and processing are available online.
APA, Harvard, Vancouver, ISO, and other styles
41

Surek, György, and Gizella Nádor. "Monitoring of Damage in Sunflower and Maize Parcels Using Radar and Optical Time Series Data." Journal of Sensors 2015 (2015): 1–25. http://dx.doi.org/10.1155/2015/548506.

Full text
Abstract:
The objective of this paper is to monitor the temporal behaviour of geometrical structural change of cropland affected by four different types of damage: weed infection, Western Corn Rootworm (WCR), storm damage, and drought by time series of different type of optical and quad-pol RADARSAT2 data. Based on our results it is established that ragweed infection in sunflower can be well identified by evaluation of radar (mid-June) and optical (mid-August) satellite images. Effect of drought in sunflower is well recognizable by spectral indices derived from optical as well as “I”-component of Shannon entropy (SEI) from radar satellite images acquired during the first decade of July. Evaluation of radar and optical satellite images acquired between the last decade of July and mid-August proven to be the most efficient for detecting damages in maize fields caused by either by WCR or storm. Components of Shannon entropy are proven to have significant role in identification. Our project demonstrates the potential in integrated usage of polarimetric radar and optical satellite images for monitoring several types of agricultural damage.
APA, Harvard, Vancouver, ISO, and other styles
42

Bondur, V. G., L. N. Zakharova, and A. I. Zakharov. "Monitoring of the landslide area state on Bureya river in 2018-2019 according to radar and optical satellite images." Исследования Земли из Космоса, no. 6 (December 21, 2019): 26–35. http://dx.doi.org/10.31857/s0205-96142019626-35.

Full text
Abstract:
The monitoring results of the current state of landslide area on the Bureya River in 20182019 are given using images from synthetic aperture radars and optical sensors of Sentinel multi-satellite system. Differential radar interferometry technique allowed to reveal the stability of the landslide surface in the first four months after the landslide and since the end of July 2019. Small-scale dynamics of the surface within the landslide circus was detected. It is shown that the interferometric technique is inapplicable for the observation of the large-scale modifications of the shoreline unlike the optical images where the effects of the collapse of the shoreline fragments and shoreline flooding were clearly observed compared also with radar amplitude images. The ongoing landslide activity within the landslide circus and the coastline collapse area was detected using satellite images. It requires the establishment of continuous monitoring of this and other dangerous landslide zones on Bureya River.
APA, Harvard, Vancouver, ISO, and other styles
43

Zambrano-Marin, Luisa Fernanda, Ellen S. Howell, Patrick A. Taylor, Sean E. Marshall, Maxime Devogèle, Anne K. Virkki, Dylan C. Hickson, Edgard G. Rivera-Valentín, Flaviane C. F. Venditti, and Jon D. Giorgini. "Radar and Optical Characterization of Near-Earth Asteroid 2019 OK." Planetary Science Journal 3, no. 6 (June 1, 2022): 138. http://dx.doi.org/10.3847/psj/ac63cd.

Full text
Abstract:
Abstract We conducted radar observations of near-Earth asteroid 2019 OK on 2019 July 25 using the Arecibo Observatory S-band (2380 MHz, 12.6 cm) planetary radar system. Based on Arecibo and optical observations the apparent diameter is between 70 and 130 m. Combined with an absolute magnitude of H = 23.3 ± 0.3, the optical albedo of 2019 OK is likely between 0.05 and 0.17. Our measured radar circular polarization ratio of μ C = 0.33 ± 0.03 indicates 2019 OK is likely not a V- or E-type asteroid and is most likely a C- or S-type. The measured radar echo bandwidth of 39 ± 2 Hz restricts the apparent rotation period to be approximately between 3 minutes (0.049 hr, D = 70 m) and 5 minutes (0.091 h, D = 130 m). Together, the apparent diameter and rotation period suggest that 2019 OK is likely not a rubble-pile body bound only by gravity. 2019 OK is one of a growing number of fast-rotating near-Earth asteroids that require some internal strength to keep them from breaking apart.
APA, Harvard, Vancouver, ISO, and other styles
44

Guliyev, A. Sh, and T. A. Khlebnikova. "Methods of joint processing of complex radar interferograms and multispectral optical images under temporal decorrelation." Interexpo GEO-Siberia 4 (May 18, 2022): 3–9. http://dx.doi.org/10.33764/2618-981x-2022-4-3-9.

Full text
Abstract:
This article substantiates the relevance of the study, the characteristics of the joint use of optical multispectral survey, radar interferometry and partial polarimetry, identifies the scope of interpretation of the radar-optical composite built by optical and radar data, and provides a mathematical model for image processing of the water surface area. The quantitative assessment of these automated or semi-automated methods is not inferior to the accuracy of traditional methods for assessing the state of the offshore marine environment. It was shown that the most efficient approach is the direct use of the ResNet-10 deep learning algorithm on scenes when combined with complex (amplitude and phase) centimeter-range radar images and multispectral optical images of Sentinel platforms. This approach made it possible to detect 86.72% of all spots in the scenes and had an average accuracy of 75.35%. The approach has also showed a significantly reduced ability to detect patches when the local wind speed was below 2 m/s or above 12 m/s.
APA, Harvard, Vancouver, ISO, and other styles
45

Su, Aifang, Han Li, Liman Cui, and Yungang Chen. "A Convection Nowcasting Method Based on Machine Learning." Advances in Meteorology 2020 (January 27, 2020): 1–13. http://dx.doi.org/10.1155/2020/5124274.

Full text
Abstract:
In this study, a convection nowcasting method based on machine learning was proposed. First, the historical data were back-calculated using the pyramid optical flow method. Next, the generated optical flow field information of each pixel and the Red-Green-Blue (RGB) image information were input into the Convolutional Long Short-Term Memory (ConvLSTM) algorithm for training purposes. During the extrapolation process, dynamic characteristics such as the rotation, convergence, and divergence in the optical flow field were also used as predictors to form an optimal nowcasting model. The test analysis demonstrated that the algorithm combined the image feature extraction ability of the convolutional neural network (CNN) and the sequential learning ability of the long short-term memory network (LSTM) model to establish an end-to-end deep learning network, which could deeply extract high-order features of radar echoes such as structural texture, spatial correlation, and temporal evolution compared with the traditional algorithm. Based on learning through the above features, this algorithm can forecast the generation and dissipation trends of convective cells to some extent. The addition of the optical flow information can more accurately simulate nonlinear trends such as the rotation, or merging, or separation of radar echoes. The trajectories of radar echoes obtained through nowcasting are closer to their actual movements, which prolongs the valid forecasting period and improves forecast accuracy.
APA, Harvard, Vancouver, ISO, and other styles
46

Javhar, Aminov, Xi Chen, Anming Bao, Aminov Jamshed, Mamadjanov Yunus, Aminov Jovid, and Tuerhanjiang Latipa. "Comparison of Multi-Resolution Optical Landsat-8, Sentinel-2 and Radar Sentinel-1 Data for Automatic Lineament Extraction: A Case Study of Alichur Area, SE Pamir." Remote Sensing 11, no. 7 (April 1, 2019): 778. http://dx.doi.org/10.3390/rs11070778.

Full text
Abstract:
Lineament mapping, which is an important part of any structural geological investigation, is made more efficient and easier by the availability of optical as well as radar remote sensing data, such as Landsat and Sentinel with medium and high spatial resolutions. However, the results from these multi-resolution data vary due to their difference in spatial resolution and sensitivity to soil occupation. The accuracy and quality of extracted lineaments depend strongly on the spatial resolution of the imagery. Therefore, the aim of this study was to compare the optical Landsat-8, Sentinel-2A, and radar Sentinel-1A satellite data for automatic lineament extraction. The framework of automatic approach includes defining the optimal parameters for automatic lineament extraction with a combination of edge detection and line-linking algorithms and determining suitable bands from optical data suited for lineament mapping in the study area. For the result validation, the extracted lineaments are compared against the manually obtained lineaments through the application of directional filtering and edge enhancement as well as to the lineaments digitized from the existing geological maps of the study area. In addition, a digital elevation model (DEM) has been utilized for an accuracy assessment followed by the field verification. The obtained results show that the best correlation between automatically extracted lineaments, manual interpretation, and the preexisting lineament map is achieved from the radar Sentinel-1A images. The tests indicate that the radar data used in this study, with 5872 and 5865 lineaments extracted from VH and VV polarizations respectively, is more efficient for structural lineament mapping than the Landsat-8 and Sentinel-2A optical imagery, from which 2338 and 4745 lineaments were extracted respectively.
APA, Harvard, Vancouver, ISO, and other styles
47

Balling, Johannes, Jan Verbesselt, Veronique De Sy, Martin Herold, and Johannes Reiche. "Exploring Archetypes of Tropical Fire-Related Forest Disturbances Based on Dense Optical and Radar Satellite Data and Active Fire Alerts." Forests 12, no. 4 (April 9, 2021): 456. http://dx.doi.org/10.3390/f12040456.

Full text
Abstract:
Tropical forest disturbances linked to fire usage cause large amounts of greenhouse gas (GHG) emissions and environmental damages. Supporting precise GHG estimations and counteracting illegal fire usages in the tropics require timely and thematically detailed large-scale information on fire-related forest disturbances. Multi-sensor optical and radar detection and ranging (radar) remote sensing data combined with active fire alerts shows the potential for a more in-depth characterization of fire-related forest disturbances. We utilized dense optical (Landsat-7, Landsat-8 and Sentinel-2) and radar (Sentinel-1) time series to individually map forest disturbances in the province of Riau (Indonesia) for 2018–2019. We combined the sensor-specific optical and radar forest disturbance maps with daily active fire alerts and classified their temporal relationship (predating, coinciding, postdating) into seven so-called archetypes of fire-related forest disturbances. The archetypes reflect sensor-specific sensitives of optical (e.g., changes in tree foliage) and radar (e.g., changes in tree structure) data to detect varying types of forest disturbances, ranging from either a loss of tree foliage and/or structure predating, coinciding or postdating fires. These can be related to different magnitudes of fire-related forest disturbances and burn severities and can be associated with specific land management practices, such as slash-and-burn agriculture and salvage logging. This can support policy development, local and regional forest management and law enforcement to reduce illegal fire usage in the tropics. Results suggest that a delayed or opposing forest disturbance detection in the optical and radar signal is not only caused by environmental influences or different observation densities but, in some cases, such as fire-related forest disturbances, can be related to their different sensitives to detect changes in tree foliage and structure. Multi-sensor-based forest monitoring approaches should, therefore, not simply combine optical and radar time series on a data level, as it bears the risk of introducing artefacts.
APA, Harvard, Vancouver, ISO, and other styles
48

Peña-Luque, Santiago, Sylvain Ferrant, Mauricio C. R. Cordeiro, Thomas Ledauphin, Jerome Maxant, and Jean-Michel Martinez. "Sentinel-1&2 Multitemporal Water Surface Detection Accuracies, Evaluated at Regional and Reservoirs Level." Remote Sensing 13, no. 16 (August 19, 2021): 3279. http://dx.doi.org/10.3390/rs13163279.

Full text
Abstract:
Water stock monitoring is a major issue for society on a local and global scale. Sentinel-1&2 satellites provide frequent acquisitions to track water surface dynamics, proxy variables to enable water surface volume monitoring. How do we combine such observations along time for each sensor? What advantages and disadvantages of single-date, monthly or time-windowed estimations? In this context, we analysed the impact of merging information through different types and lengths of time-windows. Satellite observations were processed separately on optical (Sentinel-2) and radar (Sentinel-1) water detectors at 10 m resolution. The analysis has been applied at two scales. First, validating with 26 large scenes (110 × 110 km) in different climatic zones in France, time-windows yielded an improvement on radar detection (F1-score improved from 0.72 to 0.8 for 30 days on average logic) while optical performances remained stable (F1-score 0.89). Second, validating reservoir area estimations with 29 instrumented reservoirs (20–1250 ha), time-windows presented in all cases an improvement on both optical and radar error for any window length (5–30 days). The mean relative absolute error in optical area detection improved from 16.9% on single measurements to 12.9% using 15 days time-windows, and from 22.15% to 15.1% in radar detection). Regarding reservoir filling rates, we identified an increased negative bias for both sensors when the reservoir is nearly full. This work helped to compare accuracies of separate optical and radar capabilities, where optical statistically outperforms radar at both local and large scale to the detriment of less frequent measurements. Furthermore, we propose a geomorphological indicator of reservoirs to predict the quality of radar area monitoring (R2 = 0.58). In conclusion, we suggest the use of time-windows on operational water mapping or reservoir monitoring systems, using 10–20 days time-windows with average logic, providing more frequent and faster information to water managers in periods of crisis (e.g., water shortage) compared to monthly estimations.
APA, Harvard, Vancouver, ISO, and other styles
49

Huyan, Zongbo, Yu Jiang, Hengnian Li, Pengbin Ma, and Dapeng Zhang. "Bistatic Radar Observations Correlation of LEO Satellites Considering J2 Perturbation." Mathematics 10, no. 13 (June 23, 2022): 2197. http://dx.doi.org/10.3390/math10132197.

Full text
Abstract:
Space debris near Earth severely interferes with the development of space, and cataloging space objects is increasingly important. Since optical telescopes and radars used to detect space debris only provide short-arc observations, mathematical algorithms are needed to solve problems in the correlation of observations. In this work, an efficient mathematical algorithm based on J2 analytic solutions is put forward. Initial orbit determination (IOD) serves as the starter and orbit determination (OD) with the weighted least-squares method (WLSM) is used to improve the accuracy of the estimated orbit. Meanwhile, the effect of the weight of different observation types is analyzed. The correlation criteria for bistatic radar observations are accordingly developed. Lastly, the variation in and evolution of the error of bistatic radar ranging are discussed.
APA, Harvard, Vancouver, ISO, and other styles
50

Michell, R. G. "Simultaneous optical and radar measurements of meteors using the Poker Flat Incoherent Scatter Radar." Journal of Atmospheric and Solar-Terrestrial Physics 72, no. 16 (October 2010): 1212–20. http://dx.doi.org/10.1016/j.jastp.2010.08.001.

Full text
APA, Harvard, Vancouver, ISO, and other styles
We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!

To the bibliography