59 results on '"Maki Akioka"'
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2. Support activity using WINDS satellite link in the 2011 off the Pacific coast of Tohoku Earthquake.
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Norihiko Katayama, Takashi Takahashi, Maki Akioka, Takehiro Terada, Mitsugu Ohkawa, Toshio Asai, Akira Akaishi, Seiji Nagai, Naoko Yoshimura, Yoshihisa Takayama, and Ryutaro Suzuki
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- 2011
3. Small optical transponder for small satellites.
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Morio Toyoshima, Hideki Takenaka, Yozo Shoji, Yoshihisa Takayama, Yoshisada Koyama, and Maki Akioka
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- 2010
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4. Research and Development Issues of Satellite Communications Systems for Large Scale Disaster Relief.
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Naoto Kadowaki, Takashi Takahashi, Maki Akioka, Yoshiyuki Fujino, and Morio Toyoshima
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- 2012
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5. Performance Evaluation of Frequency Flexibility in High-Throughput Satellites: Application to Time-Varying Communication Traffic
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Mitsugu Okawa, Maki Akioka, Kazunori Okada, Morio Toyoshima, Yuma Abe, and Amane Miura
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Flexibility (engineering) ,High-throughput satellite ,Computer science ,Frequency assignment ,Real-time computing ,Communications satellite ,Throughput (business) - Published
- 2020
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6. Precise Control of Beam Formation for Mobile Communication Satellites Based on On-board Measurements of the Shape of the Large Reflector Surface
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Morio Toyoshima, Yoshiyuki Fujino, Teruaki Orikasa, Masaki Satoh, Hiroyuki Tsuji, Amane Miura, and Maki Akioka
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On board ,Surface (mathematics) ,Physics ,Optics ,business.industry ,Reflector (antenna) ,Mobile telephony ,business ,Beam (structure) - Published
- 2019
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7. High-Speed Transmission for Ka-Band Aeronautical Satellite Communications Using WINDS
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Toshio Asai, Takashi Takahashi, Kazuyoshi Kawasaki, Morio Toyoshima, Norihiko Katayama, Maki Akioka, and Tomoshige Kan
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Transmission (telecommunications) ,Communications satellite ,Environmental science ,Ka band ,Flight experiment ,Remote sensing - Published
- 2018
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8. Novel Satellite Antenna Pattern Compensation Method using Two Dimensional Least Square Method and Quadratic Function
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Masaki Satoh, Maki Akioka, Yoshiyuki Fujino, Teruaki Orikasa, and Amane Miura
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Control theory ,Satellite antennas ,Quadratic function ,Compensation (engineering) ,Mathematics - Published
- 2018
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9. APPLICATION OF VISION METROLOGY TO IN-ORBIT MEASUREMENT OF LARGE REFLECTOR ONBOARD COMMUNICATION SATELLITE FOR NEXT GENERATION MOBILE SATELLITE COMMUNICATION
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Maki Akioka, Hiroyuki Tsuji, Masaki Satoh, Yoshiyuki Fujino, Morio Toyoshima, Teruaki Orikasa, and Amane Miura
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lcsh:Applied optics. Photonics ,Beam waveguide antenna ,Engineering ,Cassegrain antenna ,lcsh:T ,business.industry ,Antenna measurement ,Astrophysics::Instrumentation and Methods for Astrophysics ,lcsh:TA1501-1820 ,Reflector (antenna) ,lcsh:Technology ,Radiation pattern ,Periscope antenna ,lcsh:TA1-2040 ,Electronic engineering ,Communications satellite ,Antenna (radio) ,lcsh:Engineering (General). Civil engineering (General) ,business - Abstract
Satellite for next generation mobile satellite communication service with small personal terminal requires onboard antenna with very large aperture reflector larger than twenty meters diameter because small personal terminal with lower power consumption in ground base requires the large onboard reflector with high antenna gain. But, large deployable antenna will deform in orbit because the antenna is not a solid dish but the flexible structure with fine cable and mesh supported by truss. Deformation of reflector shape deteriorate the antenna performance and quality and stability of communication service. However, in case of digital beam forming antenna with phased array can modify the antenna beam performance due to adjustment of excitation amplitude and excitation phase. If we can measure the reflector shape precisely in orbit, beam pattern and antenna performance can be compensated with the updated excitation amplitude and excitation phase parameters optimized for the reflector shape measured every moment. Softbank Corporation and National Institute of Information and Communications Technology has started the project "R&D on dynamic beam control technique for next generation mobile communication satellite" as a contracted research project sponsored by Ministry of Internal Affairs and Communication of Japan. In this topic, one of the problem in vision metrology application is a strong constraints on geometry for camera arrangement on satellite bus with very limited space. On satellite in orbit, we cannot take many images from many different directions as ordinary vision metrology measurement and the available area for camera positioning is quite limited. Feasibility of vision metrology application and general methodology to apply to future mobile satellite communication satellite is to be found. Our approach is as follows: 1) Development of prototyping simulator to evaluate the expected precision for network design in zero order and first order 2) Trial measurement for large structure with similar dimension with large deployable reflector to confirm the validity of the network design and instrumentation. In this report, the overview of this R&D project and the results of feasibility study of network design based on simulations on vision metrology and beam pattern compensation of antenna with very large reflector in orbit is discussed. The feasibility of assumed network design for vision metrology and satisfaction of accuracy requirements are discussed. The feasibility of beam pattern compensation by using accurately measured reflector shape is confirmed with antenna pattern simulation for deformed parabola reflector. If reflector surface of communication satellite can be measured routinely in orbit, the antenna pattern can be compensated and maintain the high performance every moment.
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- 2016
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10. On-orbit evaluation of satellite-ground laser communication experiment using small optical transponder (SOTA) equipment –Optical Antenna
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Maki Akioka, Yoshisada Koyama, Morio Toyoshima, Hiroo Kunimori, and Yasushi Munemasa
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Computer science ,business.industry ,Telecommunications link ,Bandwidth (signal processing) ,Electrical engineering ,Communications satellite ,Optical communication ,Satellite ,Radio frequency ,business ,Atmospheric optics ,Free-space optical communication - Abstract
Recently, the sensors ability of remote sensing satellites are offering much better resolution, higher quality, etc. [1] The gathered data size by the satellite has become larger. However, generally, downlink transfer capacity from the satellite to a ground station using RF (Radio Frequency) communication is limited, due to the internal balance of resources (power consumption, size capacity, mass, placement, etc.) in the satellite, and allocation of bandwidth by frequency regulation arrangement.
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- 2017
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11. Experimental results of satellite-to-ground laser communications link through atmospheric turbulence using SOTA
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Morio Toyoshima, Hideki Takenaka, Dimitar Kolev, Maki Akioka, Yoshisada Koyama, Hiroo Kunimori, and Yasushi Munemasa
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Scintillation ,business.industry ,Computer science ,Optical communication ,Communications satellite ,Satellite ,Radio frequency ,Aerospace engineering ,business ,Interference (wave propagation) ,Radio wave ,Remote sensing ,Free-space optical communication - Abstract
In recent years, the performance of observation equipment mounted on satellites has improved to such levels that it can obtain significant amount of data from a single observation [1]. Radio waves are used as a method for transmitting large volumes of data acquired by satellites to the ground. However, currently operational radio frequencies make it difficult to improve the communication speed, owing to interference problems and the carrier frequency. Space optical communication is expected to be a solution to this problem.
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- 2017
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12. Development of a breadboard model of space laser communication terminal for optical feeder links from Geo
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Yasushi Munemasa, Tetsuharu Fuse, Kenji Suzuki, Dimitar Kolev, Yoshisada Koyama, Toshihiro Kubooka, Maki Akioka, Hideki Takenaka, Hiroo Kunimori, and M. Toyoshima
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Geography ,Development (topology) ,Terminal (telecommunication) ,Information and Communications Technology ,business.industry ,Electronic engineering ,Optical communication ,Electrical engineering ,Communications satellite ,Space (commercial competition) ,Breadboard ,business ,Free-space optical communication - Abstract
National Institute of Information and Communications Technology (NICT) has a long history of the R&D of space laser communications.
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- 2017
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13. LEO-to-ground optical communications using SOTA (Small Optical TrAnsponder) - Payload verification results and experiments on space quantum communications
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Morio Toyoshima, Yasushi Munemasa, Hiroo Kunimori, Hideki Takenaka, Alberto Carrasco-Casado, Kenji Suzuki, Maki Akioka, Tetsuharu Fuse, Dimitar Kolev, Toshihiro Kubooka, and Yoshisada Koyama
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Engineering ,Physics - Instrumentation and Detectors ,Interoperability ,Optical communication ,Aerospace Engineering ,FOS: Physical sciences ,02 engineering and technology ,Quantum channel ,Space (commercial competition) ,01 natural sciences ,010309 optics ,Physics - Space Physics ,0103 physical sciences ,Transponder ,Quantum Physics ,Payload ,business.industry ,Electrical engineering ,Instrumentation and Detectors (physics.ins-det) ,021001 nanoscience & nanotechnology ,Space Physics (physics.space-ph) ,Transmission (telecommunications) ,Information and Communications Technology ,0210 nano-technology ,business ,Telecommunications ,Quantum Physics (quant-ph) - Abstract
Free-space optical communications have held the promise of revolutionizing space communications for a long time. The benefits of increasing the bitrate while reducing the volume, mass and energy of the space terminals have attracted the attention of many researchers for a long time. In the last few years, more and more technology demonstrations have been taking place with participants from both the public and the private sector. The National Institute of Information and Communications Technology (NICT) in Japan has a long experience in this field. SOTA (Small Optical TrAnsponder) was the last NICT space lasercom mission, designed to demonstrate the potential of this technology applied to microsatellites. Since the beginning of SOTA mission in 2014, NICT regularly established communication using the Optical Ground Stations (OGS) located in the Headquarters at Koganei (Tokyo) to receive the SOTA signals, with over one hundred successful links. All the goals of the SOTA mission were fulfilled, including up to 10-Mbit/s downlinks using two different wavelengths and apertures, coarse and fine tracking of the OGS beacon, space-to-ground transmission of the on-board-camera images, experiments with different error correcting codes, interoperability with other international OGS, and experiments on quantum communications. The SOTA mission ended on November 2016, more than doubling the designed lifetime of 1-year. In this paper, the SOTA characteristics and basic operation are explained, along with the most relevant technological demonstrations., Comment: 9 pages, 11 figures
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- 2017
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14. Performance Evaluation of Frequency Flexibility in High-Throughput Satellites: Application to Time-Varying Communication Traffic.
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Yuma ABE, Mitsugu OKAWA, Amane MIURA, Kazunori OKADA, Maki AKIOKA, and Morio TOYOSHIMA
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ARTIFICIAL satellites ,TELECOMMUNICATION satellites ,BANDWIDTHS - Abstract
In this study, we propose a frequency assignment method for high-throughput satellites (HTSs) with frequency flexibility. To meet the increase in communication traffic, next-generation HTSs will be equipped with digital channelizers and a frequency flexibility function, which can flexibly change the frequency assignment. Using this function, the bandwidth resources can be efficiently utilized. We propose a flexible channel assignment method to achieve higher throughput with fewer control actions, compared to conventional methods. This method divides the bandwidth into two types: one involves fixed assignment, whereas the other is utilized flexibly. The effectiveness of the proposed method is verified through numerical experiments, and the performance is compared with those of conventional methods. In these experiments, two different types of time-varying traffic, aircraft and disaster traffic, are assumed. It is established that the number of control actions in the proposed method is lesser than that in the conventional dynamic assignment method, with almost the same throughput as the conventional one. [ABSTRACT FROM AUTHOR]
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- 2020
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15. Economic effect of satellite communications based on the Great East Japan Earthquake
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Maki Akioka, Takashi Takahashi, Morio Toyoshima, Yoshiyuki Fujino, and Amane Miura
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geography ,geography.geographical_feature_category ,Meteorology ,Aerospace Engineering ,Magnitude (mathematics) ,Subsidence ,Communications system ,West (direction) ,Peninsula ,Communications satellite ,Objective evaluation ,Seismology ,Geology ,Submarine earthquake - Abstract
On 11 March 2011, an undersea earthquake of magnitude 9.0, the largest ever recorded in Japan, occurred off the Oshika Peninsula on the Pacific coast of the Tohoku region. The hypocentral region extended for 500 km in the north–south direction from Iwate Prefecture to Ibaraki Prefecture, and for 200 km in east–west direction. The earthquake generated a tsunami with a height of more than 10 m and a run-up height of up to 40.0 m in certain places, which inflicted devastating damage on the coastal areas of the Tohoku and Kanto regions. In addition to the tsunami, the earthquake caused shaking, liquefaction, subsidence, and the collapse of dams, causing major damage to vast areas in the Tohoku and Kanto regions and disrupting various types of infrastructure, including communication. In light of this unprecedented damage, satellite communications were important from various perspectives while terrestrial communications systems were damaged, and an objective evaluation of the role played by satellite communications is relevant to its future installation, adoption and use as a standalone or backup system. Furthermore, satellite communications can help reduce the extent of damage, particularly damage to communications systems, inflicted by strong earthquakes in the future. Accordingly, we report a preliminary quantitative evaluation of the role of satellite communications in the Great East Japan Earthquake, of the role of satellite communications if it becomes widespread, and of its expected role in future large-scale earthquakes in terms of the economic effect converted into cost.
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- 2013
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16. SOTA OPTICAL DOWNLINKS TO DLR’S OPTICAL GROUND STATIONS
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Christopher Schmidt, Yasushi Munemasa, Hideki Takenaka, Amita Shrestha, Morio Toyoshima, Maki Akioka, Martin Brechtelsbauer, Dimitar Kolev, Christian Fuchs, Fabian Rein, and Florian Moll
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Engineering ,German aerospace ,business.industry ,Optical communication ,Optical LEO downlinks ,Ground station ,Telecommunications link ,Communications satellite ,Satellite ,business ,Astronomical imaging ,Remote sensing ,Transponder ,Institut für Kommunikation und Navigation - Abstract
Optical Satellite Downlinks have gathered increasing attention in the last years. A number of experimental payloads have become available, and downlink experiments are conducted around the globe. One of these experimental systems is SOTA, the Small Optical Transponder, built by the National Institute of Information and Communications Technology (NICT). This paper describes the downlink experiments carried out from SOTA to the German Aerospace Center’s Optical Ground Stations located in Oberpfaffenhofen, Germany. Both the Transportable Optical Ground Station (TOGS) as well as the fixed Optical Ground Station Oberpfaffenhofen (OGS-OP) are used for the experiments. This paper will explain the preparatory work, the execution of the campaign, as well as show the first results of the measurements.
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- 2016
17. Measurement of Propagation characteristics for Ka-Band Aeronautical Satellite Communications Using WINDS
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Tomoshige Kan, Morio Toyoshima, Maki Akioka, Takashi Takahashi, Kazuyoshi Kawasaki, and Toshio Asai
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Engineering ,Thesaurus (information retrieval) ,business.industry ,0202 electrical engineering, electronic engineering, information engineering ,Communications satellite ,020206 networking & telecommunications ,Ka band ,02 engineering and technology ,Aerospace engineering ,business - Published
- 2016
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18. Dynamic Beam Pattern Control Based on Shape of Large Deployable Reflector Measured with Vision Metrology in Orbit
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Amane Miura, Morio Toyoshima, Masaki Satoh, Yoshiyuki Fujino, Teruaki Orikasa, Hiroyuki Tsuji, and Maki Akioka
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Beam pattern ,Physics ,Optics ,business.industry ,Reflector (antenna) ,Orbit (control theory) ,business ,Metrology - Published
- 2016
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19. LEO-to-ground polarization measurements aiming for space QKD using Small Optical TrAnsponder (SOTA)
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Dimitar Kolev, Yasushi Munemasa, Tetsuharu Fuse, Maki Akioka, Hideki Takenaka, Morio Toyoshima, Toshihiro Kubooka, Alberto Carrasco-Casado, Hiroo Kunimori, and Yoshisada Koyama
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Physics ,Quantum optics ,Quantum network ,Linear polarization ,business.industry ,Quantum channel ,Quantum key distribution ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,010309 optics ,Optics ,Quantum cryptography ,0103 physical sciences ,010306 general physics ,Quantum information science ,business ,Free-space optical communication - Abstract
Quantum communication, and more specifically Quantum Key Distribution (QKD), enables the transmission of information in a theoretically secure way, guaranteed by the laws of quantum physics. Although fiber-based QKD has been readily available since several years ago, a global quantum communication network will require the development of space links, which remains to be demonstrated. NICT launched a LEO satellite in 2014 carrying a lasercom terminal (SOTA), designed for in-orbit technological demonstrations. In this paper, we present the results of the campaign to measure the polarization characteristics of the SOTA laser sources after propagating from LEO to ground. The most-widely used property for encoding information in free-space QKD is the polarization, and especially the linear polarization. Therefore, studying its behavior in a realistic link is a fundamental step for proving the feasibility of space quantum communications. The results of the polarization preservation of two highly-polarized lasers are presented here, including the first-time measurement of a linearly-polarized source at λ = 976 nm and a circularly-polarized source at λ = 1549 nm from space using a realistic QKD-like receiver, installed in the Optical Ground Station at the NICT Headquarters, in Tokyo, Japan.
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- 2016
20. The NICT's New Optical Ground Station for Satellite Laser Communication and SOTA-SOCRATES Experiment
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Yoshisada Koyama, Hideki Takenaka, Takayuki Seki, Morio Toyoshima, Yoshihisa Takayama, and Maki Akioka
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SOCRATES ,Ground station ,Environmental science ,Satellite ,Free-space optical communication ,Remote sensing - Published
- 2016
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21. Telecom and scintillation first data analysis for DOMINO: laser communication between SOTA, onboard SOCRATES satellite, and MEO optical ground station
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Etienne Samain, Morio Toyoshima, H. Mariey, D. Albanesse, Naohiko Iwakiri, Jean-Luc Issler, Nicolas Maurice, Geraldine Artaud, M. Aimar, Duy-Ha Phung, Hideki Takenaka, Dimitar Kolev, G. M. Lagarde, Marie-Thérèse Velluet, Yasushi Munemasa, Nicolas Vedrenne, and Maki Akioka
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Physics ,020301 aerospace & aeronautics ,Scintillation ,Aperture ,business.industry ,Detector ,02 engineering and technology ,law.invention ,Telescope ,020210 optoelectronics & photonics ,Optics ,0203 mechanical engineering ,law ,Telecommunications link ,Computer Science::Networking and Internet Architecture ,0202 electrical engineering, electronic engineering, information engineering ,Communications satellite ,Satellite ,business ,Telecommunications ,Free-space optical communication ,Remote sensing - Abstract
In collaboration between CNES, NICT, Geoazur, the first successful lasercom link between the micro-satellite SOCRATES and an OGS in Europe has been established. This paper presents some results of telecom and scintillation first data analysis for 4 successful links in June & July 2015 between SOTA terminal and MEO optical ground station (OGS) at Caussols France. The telecom and scintillation data have been continuously recorded during the passes by using a detector developed at the laboratory. An irradiance of 190 nW/m2 and 430 nW/m2 has been detected for 1549 nm and 976 nm downlinks at 35° elevation. Spectrums of power fluctuation measured at OGS are analyzed at different elevation angles and at different diameters of telescope aperture to determine fluctuations caused by pointing error (due to satellite & OGS telescope vibrations) and caused by atmospheric turbulence. Downlink & Uplink budgets are analyzed, the theoretical estimation matches well to measured power levels. Telecom signal forms and bit error rates (BER) of 1549 nm and 976 nm downlink are also shown at different diameters of telescope aperture. BER is 'Error Free' with full-aperture 1.5m telescope, and almost in ‘good channel’ with 0.4 m sub-aperture of telescope. We also show the comparison between the expected and measured BER distributions.
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- 2016
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22. In-orbit verification of small optical transponder (SOTA): evaluation of satellite-to-ground laser communication links
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Dimitar Kolev, Eiji Okamoto, Maki Akioka, Hiroo Kunimori, Morio Toyoshima, Yasushi Munemasa, Hideki Takenaka, Naohiko Iwakiri, Alberto Carrasco-Casado, and Yoshisada Koyama
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010302 applied physics ,business.industry ,Computer science ,Electrical engineering ,Optical communication ,02 engineering and technology ,Orbital mechanics ,Laser ,Communications system ,01 natural sciences ,Transponder (aeronautics) ,law.invention ,Orbit ,020210 optoelectronics & photonics ,Link budget ,Low earth orbit ,law ,Physics::Space Physics ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Satellite ,business ,Telecommunications ,Transponder ,Free-space optical communication - Abstract
Research and development of space optical communications is conducted in the National Institute of Information and Communications Technology (NICT). The NICT developed the Small Optical TrAnsponder (SOTA), which was embarked on a 50kg-class satellite and launched into a low earth orbit (LEO). The space-to-ground laser communication experiments have been conducted with the SOTA. Atmospheric turbulence causes signal fadings and becomes an issue to be solved in satellite-to-ground laser communication links. Therefore, as error-correcting functions, a Reed-Solomon (RS) code and a Low-Density Generator Matrix (LDGM) code are implemented in the communication system onboard the SOTA. In this paper, we present the in-orbit verification results of SOTA including the characteristic of the functions, the communication performance with the LDGM code via satellite-to-ground atmospheric paths, and the link budget analysis and the comparison between theoretical and experimental results.
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- 2016
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23. Research and Development Issues of Satellite Communications Systems for Large Scale Disaster Relief
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Morio Toyoshima, Maki Akioka, Naoto Kadowaki, Takashi Takahashi, and Yoshiyuki Fujino
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Emergency management ,Computer Networks and Communications ,business.industry ,Computer science ,Scale (social sciences) ,Broadband ,Key (cryptography) ,Communications satellite ,Mobile telephony ,Electrical and Electronic Engineering ,business ,Telecommunications ,Software - Abstract
It is well known that satellite communications systems are effective and essential communication infrastructure for disaster relief. NICT sent researchers to Tsunami stricken area in March right after the Great East Japan Earthquake and provided broadband satellite communications link to support rescue activities. Through this experience, we learned many kinds of requirements of communications for such purposes. In this paper, we list up the requirements and report what kind of satellite communications technologies are needed, and research and development issues. key words: disaster relief, satellite communications, broadband, mobile communications, channelizer
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- 2012
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24. Small Optical Transponder for Small Satellite Data Transmission
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Yoshihisa Takayama, Yoshisada Koyama, Maki Akioka, and Morio Toyoshima
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Physics ,Transmission (telecommunications) ,Satellite data ,Transponder ,Remote sensing - Published
- 2015
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25. First free space optical communication in europe between SOTA and MeO optical ground station
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Dimitar Kolev, Morio Toyoshima, H. Mariey, Naohiko Iwakiri, G. M. Lagarde, Hideki Takenaka, Geraldine Artaud, Maki Akioka, D. Albanesse, M.-T. Velluet, M. Aimar, Yasushi Munemasa, Nicolas Vedrenne, J-L. Issler, Etienne Samain, Nicolas Maurice, and D-H. Phung
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Telescope ,Ground station ,Geography ,law ,Optical link ,Transmitter ,Satellite ,Laser ,Free-space optical communication ,law.invention ,Remote sensing ,Transponder - Abstract
A first free space optical communication campaign was established during June-October 2015 between the NICT SOTA [1], [2] (Small Optical TrAnsponder) instrument flying on the Low Earth Orbit satellite SOCRATES and the Optical Ground Station (OGS) MeO belonging to Observatoire de la Cote d’Azur (OCA) – GeoAzur. Several links at 10 Mbps have been done at 1549 and 976 nm. The main objectives of this experiment are the study of the laser beam propagation through the atmosphere and the design of all the sub-systems constituting the OGS. This experiment has been developed in the framework of an agreement signed between the Japan’s National Institute of Information and Communications Technology (NICT) and the French space agency (CNES). The development of the OGS and the measurement campaign were conducted in collaboration with NICT, CNES, ONERA and OCA. The OGS was specially designed for that optical link with SOTA from the existing MeO laser station (primary devoted to satellite and Moon laser ranging). We will first give a global presentation of the whole OGS with some details on the transmitter, the telescope, the receiver bench and the dedicated instrumentation used to monitor the link. We will then give an overview of some results obtained during that campaign.
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- 2015
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26. Telecom & scintillation first data analysis for DOMINO - laser communication between SOTA, onboard socrates satellite, and MEO OGS
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H. Mariey, M.-T. Velluet, Naohiko Iwakiri, Hideki Takenaka, M. Toyoshima, Jean-Luc Issler, D. Albanesse, Nicolas Maurice, Yasushi Munemasa, M. Aimar, Nicolas Vedrenne, Duy-Ha Phung, Maki Akioka, Dimitar Kolev, G. M. Lagarde, Etienne Samain, and Geraldine Artaud
- Subjects
Scintillation ,Aperture ,business.industry ,Detector ,Irradiance ,law.invention ,Telescope ,Optics ,Geography ,law ,Satellite ,Adaptive optics ,business ,Telecommunications ,Free-space optical communication ,Remote sensing - Abstract
In collaboration between CNES, NICT, Geoazur, the first successful lasercom link between the micro-satellite SOCRATES and a non-Japanese OGS has been established. This paper presents some results of telecom and scintillation first data analysis for 4 successful links in June & July 2015 between SOTA terminal and Meo optical ground station (OGS) at Caussols France. The telecom and scintillation data have been continuously recorded during the passes by using a detector developed at the laboratory. An irradiance of 190 nW/m2 and 430 nW/m2 has been detected for 1549 nm and 976 nm downlinks at 35° elevation. Spectrums of power fluctuation measured at OGS are analyzed at different elevation angles and at different diameters of telescope aperture to determine fluctuations caused by pointing error (due to satellite & OGS telescope vibrations) and caused by atmospheric turbulence. Telecom signal forms and bit error rates (BER) of 1549 nm and 976 nm downlink are also shown at different diameters of telescope aperture. BER is ‘Error Free’ with full-aperture 1.5m telescope, and almost in ‘good channel’ with 0.4 m sub-aperture of telescope.
- Published
- 2015
- Full Text
- View/download PDF
27. Overview of international experiment campaign with small optical transponder (SOTA)
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Maki Akioka, Yasushi Munemasa, Etienne Samain, Geraldine Artaud, R. Daddato, Duy-Ha Phung, Hiroo Kunimori, M. Toyoshima, J.-P. Aguttes, Jean-Luc Issler, Nicolas Maurice, Cl. Heese, D. Gratton, Dimitar Kolev, Hideki Takenaka, Naohiko Iwakiri, I. Zayer, Nicolas Vedrenne, Zoran Sodnik, Yoshisada Koyama, and A. Koujelev
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Geography ,Payload ,business.industry ,Optical communication ,Satellite broadcasting ,Integrated optics ,Satellite ,Telecommunications ,business ,Transponder ,Free-space optical communication - Abstract
NICT initiated R&D effort of Small Optical TrAnsponder (SOTA) for LEO satellites to demonstrate the laser communication via satellite-to-ground atmospheric path links. SOTA is the payload on a 50-kg class microsatellite called Space Optical Communication Research Advanced Technology Satellite (SOCRATES), launched on 24th of May, 2014. Several international partners were interested in joint collaboration and NICT has initiated the international experiment campaign using SOTA with other agencies to perform laser communication experiments between SOTA and different international Optical Ground Stations (OGSs). In this paper, we describe the interface and link establishment protocol that had to be considered in the different OGS and the preliminary results in the international experiment campaign using SOTA.
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- 2015
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28. Current status of research and development on space laser communications technologies and future plans in NICT
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Morio Toyoshima, Naohiko Iwakiri, Toshihiro Kubooka, Hideki Takenaka, Dimitar Kolev, Yasushi Munemasa, Yoshisada Koyama, Tetsuharu Fuse, Maki Akioka, Kenji Suzuki, and Hiroo Kunimori
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Geography ,Development (topology) ,Low earth orbit ,business.industry ,Information and Communications Technology ,Geostationary orbit ,Integrated optics ,Space (commercial competition) ,Telecommunications ,business ,Free-space optical communication ,Data transmission - Abstract
The National Institute of Information and Communications Technology (NICT) has successfully conducted several laser communication experiments between geostationary earth orbit (GEO) and low earth orbit (LEO) satellites and optical ground stations. To date other organizations have also conducted many space laser communication demonstrations worldwide and the time has come when space laser communications can be used as operational systems. The NICT has recently carried out the first-ever successful data transmission from a 50-kg class micro-satellite via laser communication links. This paper presents recent activities on space laser communications in the NICT including the organization’s future plans for next generation space laser communication research aiming to achieve 10 Gbps-class and 40 Gpbs-class laser communications at GEO and LEO distances.
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- 2015
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29. Adaptive optics results with SOTA
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Etienne Samain, Geraldine Artaud, Yasushi Munemasa, Maki Akioka, Cyril Petit, Jean-Luc Issler, Nicolas Vedrenne, Hideki Takenaka, Dimitar Kolev, Vincent Michau, Morio Toyoshima, and Naohiko Iwakiri
- Subjects
Wavefront ,Physics ,Optical fiber ,business.industry ,Bandwidth (signal processing) ,Single-mode optical fiber ,law.invention ,Telescope ,Optical path ,Optics ,law ,Telecommunications link ,Adaptive optics ,business - Abstract
Next generation satellite-to-ground laser link systems, either for telemetry or satcom will request very high data rate. This goal could be achieved with a manageable cost if the benefits from the fibered technologies are reaped. For downlink the wave therefore needs to be coupled into a single mode fiber. Due to atmospheric turbulence its spatial coherence is compromised. This causes strong coupling losses that result into deep fadings. To cope with this, adaptive optics (AO) is envisaged. Thanks to a real time compensation of atmospheric induced optical path differences, it might enable to reach average coupling efficiencies as high as 0,5 (3 dB average losses). AO is now a mature technology, mostly brought to market by astronomy or biomedical applications. Usual correction bandwidth and available flux to perform the wavefront measurement are rather small (typically 50 Hz bandwidth and tenth of photons per subaperture and per frame). The specificity of AO for LEO satellite to ground optical links resides into higher requested bandwidth, optimal operation for a wide variety of atmospheric conditions (daytime and nighttime) with potentially low elevations that might severely affect wavefront sensing due to scintillation. In addition to this the performance criterion of the correction is different from usual imaging applications, with appropriate constraints on coupling statistics and temporal characteristics. To address these specificities, AO dimensioning approach needs to be adapted and consolidated by in situ measurements. We report here the first AO results on a LEO microsatellite as far as we know. The AO bench located at Coude focus of the MeO telescope, designed for imaging applications, is used to correct for optical aberrations on a 976 nm laser beam provided by SOTA terminal. AO performances are investigated and confronted to state of the art performance evaluations for satellite to ground laser links.
- Published
- 2015
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30. On R&D Plan of Application of Vision Metrology to Large Reflector of Mobile Communication Satellite
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Hiroyuki Tsuji, Maki Akioka, Masaki Sato, Yoshiyuki Fujino, Teruaki Orikasa, and Amane Miura
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Geography ,business.industry ,Satellite ,Reflector (antenna) ,Mobile telephony ,Plan (drawing) ,business ,Metrology ,Remote sensing - Published
- 2015
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31. Development of Ka-band Aeronautical Earth Station for WINDS
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Shinichi Taira, Norihiko Katayama, Maki Akioka, and Takashi Takahashi
- Subjects
Meteorology ,Remote sensing (archaeology) ,Communications satellite ,Environmental science ,Ka band ,Satellite ,Wideband ,Antenna (radio) ,Interlock ,Internetworking - Abstract
Remoteley sensed images are useful for assessing damage caused by large-scale disasters. However, observation data recorded using aircraft are currently transmitted after the plane has landed using a terrestrial network, as inflight satellite communication links are inadequate. Therefore, the process of obtaining data is time-consuming. In this respect, the National Institute of Information and Communicaitons Technology (NICT) have developed an aeronautical earth station for the Wideband InterNetworking test and Demonstration Satellite (WINDS), wherein the remote sensing data observed from the aircraft can be transmitted via satellite links. NICT established the aeronautical earth station onboard an aircraft (Gulfstream II). A test flight was then conducted tomeasure the antenna teacking performance. Results confirmed that the tracking performance was good and that the interlock function worked when the drive angle was at limited values.
- Published
- 2015
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32. On R&D of footprint measurement system for satellite with onboard large antenna
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Morio Toyoshima, Masaki Sato, Teruaki Orikasa, Maki Akioka, Hiroyuki Tsuji, and Amane Miura
- Subjects
Footprint (electronics) ,Computer science ,System of measurement ,Satellite ,Antenna (radio) ,Remote sensing - Published
- 2015
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33. First results of Wavefront sensing on SOTA
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Hideki Takenaka, Marie-Thérèse Velluet, Dimitar Kolev, Aziz Ziad, Etienne Samain, Geraldine Artaud, Nicolas Vedrenne, Duy-Ha Phung, Morio Toyoshima, Naohiko Iwakiri, Julien Chabé, Yasushi Munemasa, Cyril Petit, Jean-Luc Issler, Nicolas Maurice, Vincent Michau, Maki Akioka, ONERA - The French Aerospace Lab [Châtillon], ONERA-Université Paris Saclay (COmUE), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Géoazur (GEOAZUR 7329), Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA), Centre National d'Études Spatiales [Toulouse] (CNES), and National Institute of Information and Communications Technology [Tokyo, Japan] (NICT)
- Subjects
TURBULENCE OPTIQUE ,Perturbation (astronomy) ,02 engineering and technology ,OPTIQUE ADAPTATIVE ,01 natural sciences ,law.invention ,010309 optics ,Telescope ,020210 optoelectronics & photonics ,Optics ,TELECOMMUNICATION OPTIQUE ,law ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Adaptive optics ,Remote sensing ,Wavefront ,Physics ,Scintillation ,business.industry ,Astrophysics::Instrumentation and Methods for Astrophysics ,ANALYSE FRONT ONDE ,Wavefront sensor ,Laser ,[SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic ,Satellite ,business - Abstract
International audience; For satellite to ground laser links, atmospheric turbulence is a major cause of impairments. The induced phase perturbations along the propagation path cause beam scintillation in the receiver plane and they can also severely compromise the coupling of the flux into a receiver of limited size. To address these impairments, dedicated mitigation strategies must be developed. This requires accurate understanding of the perturbation origin. Beam propagation models have demonstrated their ability to reproduce statistical characteristics of optical perturbations on a satellite to ground laser link for elevations as low as 20°. For smaller elevations, measurements performed on stars illustrated the limits of analytical approaches and the interest for end-to-end models. We report here the first propagation channel measurements performed on a LEO microsatellite with a Shack-Hartmann wavefront sensor (WFS). The laser beam at 976 nm provided by SOTA optical terminal have been analyzed with a Shack- Hartmann wavefront sensor located at Coudé focus of the French ground station (1,55 m MéO telescope) in July 2015. Wavefront characteristics and scintillation patterns recorded with the WFS are analyzed and compared to atmospheric turbulence perturbations model fed with in situ measurements of atmospheric parameters retrieved from GDIMM.; La turbulence atmosphérique est la principale cause de dégradation des liens laser sol satellite. Les perturbations de phase induites le long du cana de propagation conduisent à de la scintillation dans le plan du récepteur et peuvent sévèrement compromettre le couplage du flux dans un récepteur de petite dimension. Pour résoudre ces problèmes, différentes stratégies dédiées doivent être développées. Cela nécessite une compréhension précise de l'origine des perturbations. Les modèles de propagation de faisceau ont démontré leur capacité à reproduire les caractéristiques statistiques des perturbations optiques affectant un lien laser satellite sol pour des élévations descendant à 20°. Pour des élévations plus petites des mesures réalisées sur étoiles ont démontrées toutefois les limites de ces approches analytiques et l'intérêt de modèles de type Monte-Carlo. Nous faisons état ici des premières mesures sur un canal de propagation établi avec un microsatellite LEO grâce à un analyseur de Shack Hartmann. Le faisceau laser à 976nm est fourni par le terminal optique SOTA et analysé grâce à un Shack Hartmann situé au foyer coudé d'une station française (télescope MéO de 1.55m) en juillet 2015. Les caractéristiques du front d'onde et les structures de scintillation enregistrées avec l'analyseur sont analysées et comparées aux modèles de perturbation de la turbulence atmosphérique alimentés par les mesures in situ des paramètres atmosphériques tels que fournis par un GDIMM.
- Published
- 2015
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- View/download PDF
34. The L5 mission for space weather forecasting
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Tsutomu Nagatsuma, Maki Akioka, Kazuhiro Ohtaka, Katsuhide Marubashi, and Wataru Miyake
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Physics ,Atmospheric Science ,Zodiacal light ,Spacecraft ,Meteorology ,business.industry ,Aerospace Engineering ,Astronomy and Astrophysics ,Space weather ,Solar wind ,Geophysics ,Space and Planetary Science ,Physics::Space Physics ,Coronal mass ejection ,Astrophysics::Solar and Stellar Astrophysics ,General Earth and Planetary Sciences ,Point (geometry) ,Astrophysics::Earth and Planetary Astrophysics ,business ,Interplanetary spaceflight ,Remote sensing ,Space environment - Abstract
We have studied a number of interplanetary space mission scenarios for space weather research and operational forecasting experiments and concluded that a spacecraft should be deployed at the L5 point of the Sun–Earth system to enable remote sensing of the Sun and interplanetary space and in situ measurements of solar wind plasma and high energy solar particle events. The L5 point is an appropriate position for making side-view observations of geo-effective coronal mass ejections and interplanetary plasma clouds. Here, we describe briefly the mission plan and the ongoing BBM development of important subsystems such as the wide field coronal imager (WCI) and the mission processor. The WCI will have a large CCD array with 16-bit sampling, to achieve a dynamic range of several thousand in order to detect very small deviations due to plasma clouds under zodiacal light contaminations a hundred times brighter than the clouds. The L5 mission we propose will surely contribute to the construction of an international space weather observation network.
- Published
- 2005
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35. [Untitled]
- Author
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Yihua Yan, Yang Liu, Maki Akioka, and Fengsi Wei
- Subjects
Physics ,Field (physics) ,Field line ,Astrophysics::High Energy Astrophysical Phenomena ,Stellar magnetic field ,Astronomy and Astrophysics ,Coronal loop ,Computational physics ,law.invention ,L-shell ,Nanoflares ,Magnetic field ,Nuclear magnetic resonance ,Space and Planetary Science ,law ,Astrophysics::Solar and Stellar Astrophysics ,Flare - Abstract
In this paper, we reconstruct the finite energy force-free magnetic field of the active region NOAA 8100 on 4 November 1997 above the photosphere. In particular, the 3-D magnetic field structures before and after a 2B/X2 flare at 05:58 UT in this region are analyzed. The magnetic field lines were extrapolated in close coincidence with the Yohkoh soft X-ray (SXR) loops accordingly. It is found that the active region is composed of an emerging flux loop, a complex loop system with differential magnetic field shear, and large-scale, or open field lines. Similar magnetic connectivity has been obtained for both instants but apparent changes of the twisting situations of the calculated magnetic field lines can be observed that properly align with the corresponding SXR coronal loops. We conclude that this flare was triggered by the interaction of an emerging flux loop and a large loop system with differential magnetic field shear, as well as large-scale, or open field lines. The onset of the flare was at the common footpoints of several interacting magnetic loops and confined near the footpoints of the emerging flux loop. The sheared configuration remained even after the energetic flare, as demonstrated by calculated values of the twist for the loop system, which means that the active region was relaxed to a lower energy state but not completely to the minimum energy state (two days later another X-class flare occurred in this region).
- Published
- 2001
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- View/download PDF
36. 3D magnetic field structure and its relations with the flares in active region NOAA8100
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Yihua Yan, Yang Liu, and Maki Akioka
- Subjects
Physics ,Atmospheric Science ,Magnetic structure ,Aerospace Engineering ,Flux ,Astronomy ,Astronomy and Astrophysics ,Astrophysics ,Magnetic field ,law.invention ,Geophysics ,Space and Planetary Science ,law ,General Earth and Planetary Sciences ,Flare - Abstract
With the photospheric magnetograms, Hα, Hβ filtergrams, and Yohkoh/SXT data, we study an emerging flux region (EFR) and its associated flare activity in detail. This EFR appearred on 03 November 1997 in the active region NOAA8100 and was responsible for at least 3 M-class flares and 19 C-class and micro- flares. Overall magnetic structure in this region changed after emergence of this magnetic feature, and potential-like structure around the EFR site became highly sheared. Our research indicates that the EFR not only triggers flares but also, as an essential process and a major role in the following flare activity, enhances the degree of magnetic non-potentiality and builds up flare energy and flare-producing environment.
- Published
- 2000
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- View/download PDF
37. Flares and surges due to magnetic cancellation
- Author
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Maki Akioka, Y. Liu, and Yihua Yan
- Subjects
Physics ,Atmospheric Science ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,Phase (waves) ,Extrapolation ,Aerospace Engineering ,Astronomy and Astrophysics ,Astrophysics ,law.invention ,Loop (topology) ,Geophysics ,Optics ,Space and Planetary Science ,law ,Astrophysics::Solar and Stellar Astrophysics ,General Earth and Planetary Sciences ,skin and connective tissue diseases ,business ,human activities ,health care economics and organizations ,Flare - Abstract
A flare associated with magnetic cancellation and small pre-flare activity is analyzed. X-ray and H α emission was strongest at the canceling site and principal energy release occurred near the canceling site. However, small flare emission was observed also far from the canceling site and the overall structure of the active region was largely changed after the flare. Therefore, even this flare driven by small scale cancellation had an extension and influence over the active region. In the pre-flare phase, many small loop brightenings were observed at the canceling site. Associating with the brightening, expansion of the active region was observed and suggests a change of loop connectivity at the foot-point and contribution for energy build-up due to cancellation. 3D extrapolation with various alpha values shows that the bright loop near the canceling site was highly non-potential.
- Published
- 2000
- Full Text
- View/download PDF
38. Flare activity in NOAA8100 and its forecasting aspects
- Author
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Maki Akioka, Yihua Yan, and Y. Liu
- Subjects
Physics ,Atmospheric Science ,Sunspot ,Extrapolation ,Aerospace Engineering ,Astronomy and Astrophysics ,Astrophysics ,Coronal loop ,law.invention ,Magnetic field ,Geophysics ,Magnetogram ,Space and Planetary Science ,law ,Coronal plane ,General Earth and Planetary Sciences ,Forecasting aspects ,Flare - Abstract
The pre-flare build-up process of the X9.4/2B flare in NOAA8100 is examined using H α, white-light sunspot, vector magnetogram and soft X-ray images. A 3D extrapolation code is used to infer the coronal magnetic field from observed magnetic field. A magnetic interface of interacting bipoles is clearly identified, and its day by day change is tracked. Two X class flares occurred at the magnetic interface. Furthermore, we found that changes of overlying coronal loop structure and persistence of magnetic interface are strongly related to flare productivity. These results suggest that daily inspection of three dimensional structures of active regions should be useful for operational forecasting.
- Published
- 2000
- Full Text
- View/download PDF
39. On-orbit Evaluation of Satellite-ground Laser Communication Experiment using Small Optical TrAnsponder (SOTA) Equipment -Optical Antenna.
- Author
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Yasushi Munemasa, Maki Akioka, Yoshisada Koyama, Hiroo Kunimori, and Morio Toyoshima
- Published
- 2017
- Full Text
- View/download PDF
40. SOTA OPTICAL DOWNLINKS TO DLR'S OPTICAL GROUND STATIONS.
- Author
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Fuchs, Christian, Kolev, Dimitar, Moll, Florian, Shrestha, Amita, Brechtelsbauer, Martin, Rein, Fabian, Schmidt, Christopher, Maki Akioka, Yasushi Munemasa, Hideki Takenaka, and Morio Toyoshima
- Published
- 2017
- Full Text
- View/download PDF
41. EXPERIMENTAL RESULTS OF SATELLITE-TO-GROUND LASER COMMUNICATIONS LINK THROUGH ATMOSPHERIC TURBULENCE USING SOTA.
- Author
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Hideki Takenaka, Dimitar Kolev, Yoshisada Koyama, Maki Akioka, Yasushi Munemasa, Hiroo Kunimori, and Morio Toyoshima
- Published
- 2017
- Full Text
- View/download PDF
42. [Untitled]
- Author
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Yihua Yan, Maki Akioka, Yang Liu, and Guoxiang Ai
- Subjects
Physics ,Field (physics) ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,Extrapolation ,Astronomy and Astrophysics ,Astrophysics ,Magnetic field ,law.invention ,Divergence ,Atmosphere ,Telescope ,Optics ,Space and Planetary Science ,law ,Astrophysics::Solar and Stellar Astrophysics ,Boundary value problem ,business ,Flare - Abstract
Based on the photospheric vector magnetograms taken at Huairou Solar Observing Station (HSOS), Hα images taken at Hiraiso Solar Terrestrial Research Center of Communication Research Laboratory, soft X-ray images taken by Yohkoh and an extrapolation method, the magnetic field structures and some active phenomena of the active region AR 7321 around 04:12 UT on 27 October 1992 are analyzed in this paper. A divergence of the transverse magnetic field, located at a newly formed spot, was found. At least four highly sheared magnetic field systems separately spread from this divergence to four other sites around this divergence. Vertical current concentrations are upward in this region and downward in the other four sites, and the corresponding Hα bright patches and soft X-ray bright loops coincide with these structures, confirming the existence of these four systems. The extrapolated magnetic force lines reconstructed by the Boundary Element Method (BEM), force-free field assumption, and boundary condition of observed photospheric vector magnetic field, coincide in space with the Hα bright patches and soft X-ray bright loops, showing that this extrapolation method is very effective and suggesting that the Hα bright patches and soft X-ray bright loops in this case represent the magnetic field structures in the upper atmosphere of the Sun.
- Published
- 1998
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- View/download PDF
43. [Untitled]
- Author
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Yihua Yan, Jun Sato, Maki Akioka, and Yang Liu
- Subjects
Physics ,Coalescence (physics) ,Field line ,Astrophysics::High Energy Astrophysical Phenomena ,Astronomy and Astrophysics ,X-ray telescope ,Astrophysics ,Magnetic flux ,law.invention ,Magnetic field ,Computational physics ,Space and Planetary Science ,law ,Boundary value problem ,Boundary element method ,Flare - Abstract
A C6.0 GOES X-ray-class flare which occurred at 05:32 UT on 5 September 1994 in the active region NOAA 7773 is analyzed in this paper. We found that this flare was triggered by the interaction of a small loop and a large loop. The small loop connected a decaying magnetic flux, not an emergence of magnetic flux as usually shown. These two loops were matched well by the extrapolated force-free field lines based on the Boundary Element Method and the boundary condition of the observed photospheric vector magnetic field. Soft X-ray observation showed that these two loops gradually merged to become one, and the soft X-ray intensity increased during the merging process, agreeing with the simulated results of I-type coalescence derived by Fushiki and Sakai (1995) and Sakai and Fushiki (1995).
- Published
- 1998
- Full Text
- View/download PDF
44. Terrestrial Free-Space Optical Communications Network for Future Airborne and Satellite-Based Optical Communications Projects
- Author
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Hiroyuki Tsuji, Yoshisada Koyama, Yoshihisa Takayama, Shinich Yamamoto, Morio Toyoshima, Isao Nakazawa, Maki Akioka, Hideki Takenaka, Kenji Suzuki, Shinich Taira, Toshihiro Kubooka, and Hiroo Kunimori
- Subjects
Geography ,business.industry ,Information and Communications Technology ,Gigabit ,Site diversity ,Optical communication ,Usability ,Satellite ,Technology readiness level ,Free space ,business ,Telecommunications ,Simulation - Abstract
Increased performance of onboard sensors has greatly increased the amount of communications data from satellites. The data rates from Earth observation satellites are also increasing, but communication rates of several tens of gigabits per second will inevitably be required for data download. This cannot be achieved using radio communications, but is possible using optical communications. Many demonstrations have been conducted to verify the usability of sophisticated optical communications equipment in orbit. The technology readiness level for space-based optical communications has reached seven, so the time has come to develop spacebased optical communications for use in operational environments. However, the influence of terrestrial weather conditions remains as a problem to be solved. One potential solution is site diversity, where several ground stations are used. The National Institute of Information and Communications Technology (NICT), is investigating a terrestrial free-space optical communications network for future
- Published
- 2013
- Full Text
- View/download PDF
45. R&D status of satellite/terrestrial integrated mobile communication system
- Author
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Kazunori Okada, Maki Akioka, Hiroyuki Tsuji, Morio Toyoshima, Yoshiyuki Fujino, Teruaki Orikasa, and Amane Miura
- Subjects
biology ,Computer science ,Satellite (biology) ,Mobile communication systems ,biology.organism_classification ,Remote sensing - Published
- 2013
- Full Text
- View/download PDF
46. Novel Satellite Antenna Pattern Compensation Method using Two Dimensional Least Square Method and Quadratic Function.
- Author
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Yoshiyuki FUJINO, Masaki SATOH, Amane MIURA, Teruaki ORIKASA, and Maki AKIOKA
- Subjects
ANTENNAS (Electronics) ,LEAST squares ,GLOBAL Positioning System ,SIMULATION methods & models ,COMPUTER simulation - Abstract
In order to evaluate the accuracy of footprint measurement for a satellite large scale deployable antenna, we proposed a method of approximating antenna pattern shape with a quadratic function and determining its parameters by least squares method. Moreover, to obtain the required value of the measurement accuracy at the receiving station, the distribution of the boresight position when an error is added to the reception level was calculated. This method was applied to the experimental value of ETS-VIII. As a result, when the variation of each receiving station is within 0.5 dB, it is possible to estimate the boresight position within 1/10 of the beam width. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
47. H.ALPHA. Solar Telescope at Hiraiso and Its Initial Observations
- Author
-
Maki Akioka
- Subjects
Physics ,Data processing ,General Earth and Planetary Sciences ,High resolution ,Astronomy ,Center (algebra and category theory) ,Wavelength shift ,Lyot filter ,Research center ,General Environmental Science ,Solar telescope ,Space environment ,Remote sensing - Abstract
A new Hα solar telescope for the forecast of solar activity and the research on energetic phenomena of the sun has been constructed at Hiraiso Solar Terrestrial Research Center in Japan (Regional Warning Center of IUWDS). Its main features are (1) high resolution digital full-disk Hα images with a 2 K by 2 K CCD, (2) real-time data processing with an automatic frame-selection technique, (3) spectroscopic observation with an automatic wavelength shift of Hα Lyot filter. Because of these advanced features, continuous observations of the sun with this system will provide more reliable data for the forecast of solar activity and its influence on the space environment.
- Published
- 1996
- Full Text
- View/download PDF
48. Concept of Satellite Communication Facility for Disaster Support located in the Tohoku District
- Author
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Byeong-pyo Jeong, Akira Akaishi, Maki Akioka, Shinich Yamamoto, Yoshiyuki Fujino, Takashi Takahashi, Morio Toyoshima, and Naoto Kadowaki
- Subjects
Engineering ,Test facility ,Cover (telecommunications) ,business.industry ,Information and Communications Technology ,Fully automatic ,Communications satellite ,business ,Telecommunications ,Disaster response ,Remote sensing - Abstract
It is increasingly difficult to rely solely on terrestrial communications for use during disasters when the terrestrial communication infrastructure is extensively damaged in the affected area. After the Great East Japan Earthquake, fully automatic transportable earth stations were recognized as being among the most important aspects of disaster response. The National Institute of Information and Communications Technology (NICT) commenced the development of fully automatic earth stations and a test facility in the Tohoku district. A satellite communication network can be easily deployed using these automatic earth stations to cover the affected areas, and the communication links can be steadily re-established. We also recognized that the drastic increase in traffic during such disasters significantly affected the limited communication
- Published
- 2012
- Full Text
- View/download PDF
49. Current development status of Small Optical TrAnsponder (SOTA) for satellite-ground laser communications
- Author
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Maki Akioka, Koichi Shiratama, Morio Toyoshima, Yoshihisa Takayama, Hideki Takenaka, Yoshisada Koyama, Osamu Kawamoto, and Ichiro Mase
- Subjects
Physics ,Angular error ,Satellite ,Current (fluid) ,Breadboard ,Tracking (particle physics) ,Beam (structure) ,Transponder ,Free-space optical communication ,Remote sensing - Abstract
Current development status of the small optical transponder (SOTA) to be installed into a small satellite is described, where the breadboard model, the engineering model and the protoflight model are respectively introduced. The tracking performance is estimated to show that the angular error is low enough in comparison to the divergence angle of the transmitted beam.
- Published
- 2012
- Full Text
- View/download PDF
50. First Simultaneous Observation of H-alpha Moreton Wave, EUV Wave, and Filament/Prominence Oscillations
- Author
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Ayumi Asai, Takako T. Ishii, Hiroaki Isobe, Reizaburo Kitai, Kiyoshi Ichimoto, Satoru UeNo, Shin'ichi Nagata, Satoshi Morita, Keisuke Nishida, Daikou Shiota, Akihito Oi, Maki Akioka, and Kazunari Shibata
- Subjects
Sun: flares ,Physics ,Sun: corona ,Extreme ultraviolet lithography ,FOS: Physical sciences ,Astronomy and Astrophysics ,shock waves ,Astrophysics ,Sun: filaments, prominences ,magnetohydrodynamics (MHD) ,law.invention ,Protein filament ,Telescope ,Moreton wave ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,law ,Observatory ,Physics::Space Physics ,Astrophysics::Solar and Stellar Astrophysics ,H-alpha ,Astrophysics::Earth and Planetary Astrophysics ,Magnetohydrodynamics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Flare - Abstract
We report on the first simultaneous observation of an H-alpha Moreton wave, the corresponding EUV fast coronal waves, and a slow and bright EUV wave (typical EIT wave). Associated with an X6.9 flare that occurred on 2011 August 9 at the active region NOAA 11263, we observed a Moreton wave in the H-alpha images taken by the Solar Magnetic Activity Research Telescope (SMART) at Hida Observatory of Kyoto University. In the EUV images obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) we found not only the corresponding EUV fast "bright" coronal wave, but also the EUV fast "faint" wave that is not associated with the H-alpha Moreton wave. We also found a slow EUV wave, which corresponds to a typical EIT wave. Furthermore, we observed, for the first time, the oscillations of a prominence and a filament, simultaneously, both in the H-alpha and EUV images. To trigger the oscillations by the flare-associated coronal disturbance, we expect a coronal wave as fast as the fast-mode MHD wave with the velocity of about 570 - 800 km/s. These velocities are consistent with those of the observed Moreton wave and the EUV fast coronal wave., 15 pages, 5 figures, accepted for publication in ApJL
- Published
- 2011
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