Pub Date : 2023-12-01DOI: 10.5140/jass.2023.40.4.225
Dong-Guk Kim, Sung-Woo Park, Jong-Pil Kim, Hwa-Young Jung, Yura Lee, Eung-Noh You, Hee Keun Cho, Jin Hyo An, Goo-Hwan Shin
This paper presents the structural design of a planar synthetic aperture radar (SAR) antenna applied to a microsatellite. For micro-satellite applications, the SAR antenna structure must be lightweight, flat, and designed to withstand the launch environment. To satisfy these conditions, our novel antenna structure was designed using aluminium (AL) alloy. Structural analysis was performed for quasi-static load, random vibration, and shock load to verify its robustness in the launch environment, and the results are presented here.
{"title":"Structural Design of Planar Synthetic Aperture Radar (SAR) Antenna for Microsatellites","authors":"Dong-Guk Kim, Sung-Woo Park, Jong-Pil Kim, Hwa-Young Jung, Yura Lee, Eung-Noh You, Hee Keun Cho, Jin Hyo An, Goo-Hwan Shin","doi":"10.5140/jass.2023.40.4.225","DOIUrl":"https://doi.org/10.5140/jass.2023.40.4.225","url":null,"abstract":"This paper presents the structural design of a planar synthetic aperture radar (SAR) antenna applied to a microsatellite. For micro-satellite applications, the SAR antenna structure must be lightweight, flat, and designed to withstand the launch environment. To satisfy these conditions, our novel antenna structure was designed using aluminium (AL) alloy. Structural analysis was performed for quasi-static load, random vibration, and shock load to verify its robustness in the launch environment, and the results are presented here.","PeriodicalId":44366,"journal":{"name":"Journal of Astronomy and Space Sciences","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139188239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.5140/jass.2023.40.4.259
Kihong Park, Kyungho Kim, Alexei Sytov, K. Cho
The Standard Model (SM) does not provide an information for 26% of dark matter of the universe. In the dark sector, dark matter is supposed to be linked with the hypothetical particles called dark photons that have similar role to photons in electromagnetic interaction in the SM. Besides astronomical observation, there are studies to find dark matter candidates using accelerators. In this paper, we searched for dark photons using future electron-positron colliders, including Circular Electron Positron Collider (CEPC)/CEPC, Future Circular Collider (FCC-ee)/Innovative Detector for Electron-positron Accelerator (IDEA), and International Linear Collider (ILC)/International Large Detector (ILD). Using the parameterized response of the detector simulation of Delphes, we studied the sensitivity of a double dark photon mode at each accelerator/detector. The signal mode is double dark photon decay channel, e+e− → A’A’, where A’ (dark photon with spin 1) decaying into a muon pair. We used MadGraph5 to generate Monte Carlo (MC) events by means of a Simplified Model. We found the dark photon mass at which the cross-sections were the highest for each accelerator to obtain the maximum number of events. In this paper we show the expected number of dark photon signal events and the detector efficiency of each accelerator. The results of this study can facilitate in the dark photon search by future electron-positron accelerators.
{"title":"Search for Dark Photon in e+e− → A′A′ Using Future Collider Experiments","authors":"Kihong Park, Kyungho Kim, Alexei Sytov, K. Cho","doi":"10.5140/jass.2023.40.4.259","DOIUrl":"https://doi.org/10.5140/jass.2023.40.4.259","url":null,"abstract":"The Standard Model (SM) does not provide an information for 26% of dark matter of the universe. In the dark sector, dark matter is supposed to be linked with the hypothetical particles called dark photons that have similar role to photons in electromagnetic interaction in the SM. Besides astronomical observation, there are studies to find dark matter candidates using accelerators. In this paper, we searched for dark photons using future electron-positron colliders, including Circular Electron Positron Collider (CEPC)/CEPC, Future Circular Collider (FCC-ee)/Innovative Detector for Electron-positron Accelerator (IDEA), and International Linear Collider (ILC)/International Large Detector (ILD). Using the parameterized response of the detector simulation of Delphes, we studied the sensitivity of a double dark photon mode at each accelerator/detector. The signal mode is double dark photon decay channel, e+e− → A’A’, where A’ (dark photon with spin 1) decaying into a muon pair. We used MadGraph5 to generate Monte Carlo (MC) events by means of a Simplified Model. We found the dark photon mass at which the cross-sections were the highest for each accelerator to obtain the maximum number of events. In this paper we show the expected number of dark photon signal events and the detector efficiency of each accelerator. The results of this study can facilitate in the dark photon search by future electron-positron accelerators.","PeriodicalId":44366,"journal":{"name":"Journal of Astronomy and Space Sciences","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139189357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.5140/jass.2023.40.4.131
P. Mahanti, M. S. Robinson, D. Humm, R. Wagner, Nick Estes, Jean-Pierre Williams
Lunar permanently shadowed regions (PSRs) never see direct sunlight and are illuminated only by secondary illumination - light reflected from nearby topography. The ShadowCam imaging experiment onboard the Korea Pathfinder Lunar Orbiter is acquiring images of these PSRs. We characterize and discuss the nature of secondary illumination for the Shackleton PSR from ShadowCam radiance-calibrated images. We also use modeling to understand the magnitude and direction of the secondary illumination. Results from our analysis highlight the non-homogeneous, dynamic, and complex nature of PSR secondary lighting. Knowledge of the direction of the secondary illumination is crucial for reli-able interpretation of contrasts observed in ShadowCam images. This preliminary analysis of the floor of Shackleton crater from images acquired over multiple secondary illumination conditions does not reveal indications of exposed surface ice, even though temperatures are constantly below 110K.
月球永久阴影区（PSRs）从来没有阳光直射，只能靠二次照明--附近地形反射的光线--来照明。韩国探路者月球轨道器上的ShadowCam成像实验正在获取这些PSR的图像。我们通过 ShadowCam 辐射校准图像来描述和讨论沙克尔顿 PSR 的二次光照性质。我们还利用建模来了解二次光照的大小和方向。我们的分析结果凸显了 PSR 二次光照的非均质性、动态性和复杂性。 了解二次光照的方向对于可靠解释 ShadowCam 图像中观察到的对比度至关重要。根据在多种二次光照条件下获取的图像对沙克尔顿陨石坑底部进行的初步分析，并未发现表面有裸露冰层的迹象，尽管温度一直低于 110K。
{"title":"Preliminary Characterization of Secondary Illumination at Shackleton Crater Permanently Shadowed Region from ShadowCam Observations and Modeling","authors":"P. Mahanti, M. S. Robinson, D. Humm, R. Wagner, Nick Estes, Jean-Pierre Williams","doi":"10.5140/jass.2023.40.4.131","DOIUrl":"https://doi.org/10.5140/jass.2023.40.4.131","url":null,"abstract":"Lunar permanently shadowed regions (PSRs) never see direct sunlight and are illuminated only by secondary illumination - light reflected from nearby topography. The ShadowCam imaging experiment onboard the Korea Pathfinder Lunar Orbiter is acquiring images of these PSRs. We characterize and discuss the nature of secondary illumination for the Shackleton PSR from ShadowCam radiance-calibrated images. We also use modeling to understand the magnitude and direction of the secondary illumination. Results from our analysis highlight the non-homogeneous, dynamic, and complex nature of PSR secondary lighting. Knowledge of the direction of the secondary illumination is crucial for reli-able interpretation of contrasts observed in ShadowCam images. This preliminary analysis of the floor of Shackleton crater from images acquired over multiple secondary illumination conditions does not reveal indications of exposed surface ice, even though temperatures are constantly below 110K.","PeriodicalId":44366,"journal":{"name":"Journal of Astronomy and Space Sciences","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139188890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.5140/jass.2023.40.4.149
M. S. Robinson, S. Brylow, M. Caplinger, Lynn M. Carter, Mattew John Clark, B. Denevi, Nick Estes, D. Humm, P. Mahanti, Douglas Arden Peckham, M. Ravine, Jacob Andrieu Schaffner, E. Speyerer, R. Wagner
ShadowCam is a National Aeronautics and Space Administration Advanced Exploration Systems funded instrument hosted onboard the Korea Aerospace Research Institute (KARI) Korea Pathfinder Lunar Orbiter (KPLO) satellite. By collecting high-resolution images of permanently shadowed regions (PSRs), ShadowCam will provide critical information about the distribution and accessibility of water ice and other volatiles at spatial scales (1.7 m/pixel) required to mitigate risks and maximize the results of future exploration activities. The PSRs never see direct sunlight and are illuminated only by light reflected from nearby topographic highs. Since secondary illumination is very dim, ShadowCam was designed to be over 200 times more sensitive than previous imagers like the Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC). ShadowCam images thus allow for unprecedented views into the shadows, but saturate while imaging sunlit terrain.
{"title":"ShadowCam Instrument and Investigation Overview","authors":"M. S. Robinson, S. Brylow, M. Caplinger, Lynn M. Carter, Mattew John Clark, B. Denevi, Nick Estes, D. Humm, P. Mahanti, Douglas Arden Peckham, M. Ravine, Jacob Andrieu Schaffner, E. Speyerer, R. Wagner","doi":"10.5140/jass.2023.40.4.149","DOIUrl":"https://doi.org/10.5140/jass.2023.40.4.149","url":null,"abstract":"ShadowCam is a National Aeronautics and Space Administration Advanced Exploration Systems funded instrument hosted onboard the Korea Aerospace Research Institute (KARI) Korea Pathfinder Lunar Orbiter (KPLO) satellite. By collecting high-resolution images of permanently shadowed regions (PSRs), ShadowCam will provide critical information about the distribution and accessibility of water ice and other volatiles at spatial scales (1.7 m/pixel) required to mitigate risks and maximize the results of future exploration activities. The PSRs never see direct sunlight and are illuminated only by light reflected from nearby topographic highs. Since secondary illumination is very dim, ShadowCam was designed to be over 200 times more sensitive than previous imagers like the Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC). ShadowCam images thus allow for unprecedented views into the shadows, but saturate while imaging sunlit terrain.","PeriodicalId":44366,"journal":{"name":"Journal of Astronomy and Space Sciences","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139190169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.5140/jass.2023.40.4.199
Wooin Jo, Ho Jin, Hye-Ock Park, Yunho Jang, Seongwhan Lee, Khan-Hyuk Kim, I. Garrick‐Bethell, Jehyuck Shin, S. Baek, Junhyun Lee, Derac Son, Eunhyeuk Kim
The Korea Pathfinder Lunar Orbiter (KPLO), the first South Korea lunar exploration probe, successfully arrived at the Moon on December, 2022 (UTC), following a 4.5-month ballistic lunar transfer (BLT) trajectory. Since the launch (4 August, 2022), the KPLO magnetometer (KMAG) has carried out various observations during the trans-lunar cruise phase and a 100 km altitude lunar polar orbit. KMAG consists of three fluxgate magnetometers capable of measuring magnetic fields within a ± 1,000 nT range with a resolution of 0.2 nT. The sampling rate is 10 Hz. During the originally planned lifetime of one year, KMAG has been operating successfully while performing observations of lunar crustal magnetic fields, magnetic fields induced in the lunar interior, and various solar wind events. The calibration and offset processes were performed during the TLC phase. In addition, reliabilities of the KMAG lunar magnetic field observations have been verified by comparing them with the surface vector mapping (SVM) data. If the KPLO’s mission orbit during the extended mission phase is close enough to the lunar surface, KMAG will contribute to updating the lunar surface magnetic field map and will provide insights into the lunar interior structure and lunar space environment.
{"title":"Korea Pathfinder Lunar Orbiter Magnetometer Instrument and Initial Data Processing","authors":"Wooin Jo, Ho Jin, Hye-Ock Park, Yunho Jang, Seongwhan Lee, Khan-Hyuk Kim, I. Garrick‐Bethell, Jehyuck Shin, S. Baek, Junhyun Lee, Derac Son, Eunhyeuk Kim","doi":"10.5140/jass.2023.40.4.199","DOIUrl":"https://doi.org/10.5140/jass.2023.40.4.199","url":null,"abstract":"The Korea Pathfinder Lunar Orbiter (KPLO), the first South Korea lunar exploration probe, successfully arrived at the Moon on December, 2022 (UTC), following a 4.5-month ballistic lunar transfer (BLT) trajectory. Since the launch (4 August, 2022), the KPLO magnetometer (KMAG) has carried out various observations during the trans-lunar cruise phase and a 100 km altitude lunar polar orbit. KMAG consists of three fluxgate magnetometers capable of measuring magnetic fields within a ± 1,000 nT range with a resolution of 0.2 nT. The sampling rate is 10 Hz. During the originally planned lifetime of one year, KMAG has been operating successfully while performing observations of lunar crustal magnetic fields, magnetic fields induced in the lunar interior, and various solar wind events. The calibration and offset processes were performed during the TLC phase. In addition, reliabilities of the KMAG lunar magnetic field observations have been verified by comparing them with the surface vector mapping (SVM) data. If the KPLO’s mission orbit during the extended mission phase is close enough to the lunar surface, KMAG will contribute to updating the lunar surface magnetic field map and will provide insights into the lunar interior structure and lunar space environment.","PeriodicalId":44366,"journal":{"name":"Journal of Astronomy and Space Sciences","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139194872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.5140/jass.2023.40.4.173
D. Humm, M. Kinczyk, S. Brylow, R. Wagner, E. Speyerer, Nick Estes, P. Mahanti, Aaron Kyle Boyd, M. S. Robinson
ShadowCam is a high-sensitivity, high-resolution imager provided by NASA for the Danuri (KPLO) lunar mission. ShadowCam calibration shows that it is well suited for its purpose, to image permanently shadowed regions (PSRs) that occur near the lunar poles. It is 205 times as sensitive as the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC). The signal to noise ratio (SNR) is greater than 100 over a large part of the dynamic range, and the top of the dynamic range is high enough to accommodate most brighter PSR pixels. The optical performance is good enough to take full advantage of the 1.7 meter/pixel image scale, and calibrated images have uniform response. We describe some instrument artifacts that are amenable to future corrections, making it possible to improve performance further. Stray light control is very challenging for this mission. In many cases, ShadowCam can image shadowed areas with directly illuminated terrain in or near the field of view (FOV). We include thorough qualitative descriptions of circumstances under which lunar brightness levels far higher than the top of the dynamic range cause detector or stray light artifacts and the size and extent of the artifact signal under those circumstances.
ShadowCam 是 NASA 为 Danuri（KPLO）月球任务提供的高灵敏度、高分辨率成像仪。ShadowCam 校准结果表明，它非常适合拍摄月球两极附近的永久阴影区（PSR）。它的灵敏度是月球勘测轨道器照相机（LROC）窄角照相机（NAC）的 205 倍。在很大一部分动态范围内，信噪比（SNR）大于 100，动态范围的顶端足以容纳大多数较亮的 PSR 像素。光学性能良好，可以充分利用 1.7 米/像素的图像比例，校准后的图像具有均匀的响应。我们描述了仪器的一些伪影，这些伪影可以在未来进行修正，从而进一步提高性能。对于这次任务来说，杂散光控制非常具有挑战性。在许多情况下，ShadowCam 可以在视场（FOV）内或附近对有直接照明地形的阴影区域进行成像。我们对月球亮度水平远高于动态范围顶端导致探测器或杂散光伪影的情况，以及在这些情况下伪影信号的大小和范围进行了全面的定性描述。
{"title":"Calibration of ShadowCam","authors":"D. Humm, M. Kinczyk, S. Brylow, R. Wagner, E. Speyerer, Nick Estes, P. Mahanti, Aaron Kyle Boyd, M. S. Robinson","doi":"10.5140/jass.2023.40.4.173","DOIUrl":"https://doi.org/10.5140/jass.2023.40.4.173","url":null,"abstract":"ShadowCam is a high-sensitivity, high-resolution imager provided by NASA for the Danuri (KPLO) lunar mission. ShadowCam calibration shows that it is well suited for its purpose, to image permanently shadowed regions (PSRs) that occur near the lunar poles. It is 205 times as sensitive as the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC). The signal to noise ratio (SNR) is greater than 100 over a large part of the dynamic range, and the top of the dynamic range is high enough to accommodate most brighter PSR pixels. The optical performance is good enough to take full advantage of the 1.7 meter/pixel image scale, and calibrated images have uniform response. We describe some instrument artifacts that are amenable to future corrections, making it possible to improve performance further. Stray light control is very challenging for this mission. In many cases, ShadowCam can image shadowed areas with directly illuminated terrain in or near the field of view (FOV). We include thorough qualitative descriptions of circumstances under which lunar brightness levels far higher than the top of the dynamic range cause detector or stray light artifacts and the size and extent of the artifact signal under those circumstances.","PeriodicalId":44366,"journal":{"name":"Journal of Astronomy and Space Sciences","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139195262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.5140/jass.2023.40.4.217
Jun Bang, Seung-Su Hong, Jonghee Bae, Young-Joo Song, Donghun Lee
The Korea Pathfinder Lunar Orbiter (KPLO), also known as Danuri, successfully entered its mission orbit on December 27, 2022 (UTC), and is currently performing its mission smoothly. To mitigate potential contingencies during the flight and to navigate the spacecraft into the desired lunar orbit, the KPLO flight dynamics (FD) team analyzed major trajectory-related contingencies that could lead to the violation of mission requirements and prepared operational procedures from the perspective of trajectory and FD. This paper presents the process of preparing contingency trajectory operations for the KPLO, including the identification of trajectory contingencies, prioritization results, and the development of recovery plans and operational procedures. The prepared plans were successfully applied to address minor contingencies encountered during actual operations. The results of this study will provide valuable insights to FD engineers preparing for space exploration mission operations.
{"title":"Preparation of Contingency Trajectory Operation for the Korea Pathfinder Lunar Orbiter","authors":"Jun Bang, Seung-Su Hong, Jonghee Bae, Young-Joo Song, Donghun Lee","doi":"10.5140/jass.2023.40.4.217","DOIUrl":"https://doi.org/10.5140/jass.2023.40.4.217","url":null,"abstract":"The Korea Pathfinder Lunar Orbiter (KPLO), also known as Danuri, successfully entered its mission orbit on December 27, 2022 (UTC), and is currently performing its mission smoothly. To mitigate potential contingencies during the flight and to navigate the spacecraft into the desired lunar orbit, the KPLO flight dynamics (FD) team analyzed major trajectory-related contingencies that could lead to the violation of mission requirements and prepared operational procedures from the perspective of trajectory and FD. This paper presents the process of preparing contingency trajectory operations for the KPLO, including the identification of trajectory contingencies, prioritization results, and the development of recovery plans and operational procedures. The prepared plans were successfully applied to address minor contingencies encountered during actual operations. The results of this study will provide valuable insights to FD engineers preparing for space exploration mission operations.","PeriodicalId":44366,"journal":{"name":"Journal of Astronomy and Space Sciences","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139189402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.5140/jass.2023.40.4.237
Seok-Min Song, Hyung-Chul Lim, Mansoo Choi, Yu Yi
Laser communication has been considered as a novel method for earth observation satellites with generation of high data volume. It offers faster data transmission speeds compared to conventional radio frequency (RF) communication due to the short wavelength and narrow beam divergence. However, laser beams are refracted due to atmospheric turbulence between the ground and the satellite. Refracted laser beams, upon reaching the receiver, result in angle-of-arrival (AoA) fluctuation, inducing image dancing and wavefront distortion. These phenomena hinder signal acquisition and lead to signal loss in the course of laser communication. So, precise alignment between the transmitter and receiver is essential to guarantee effective and reliable laser communication, which is achieved by pointing, acquisition, and tracking (PAT) system. In this study, we simulate the effectiveness of tip/tilt compensation for more efficient laser communication in the satellite-ground downlink. By compensating for low-order terms using tip/tilt mirror, we verify the alleviation of AoA fluctuations under both weak and strong atmospheric turbulence conditions. And the performance of tip/tilt correction is analyzed in terms of the AoA fluctuation and collected power on the detector.
{"title":"Analysis of Tip/Tilt Compensation of Beam Wandering for Space Laser Communication","authors":"Seok-Min Song, Hyung-Chul Lim, Mansoo Choi, Yu Yi","doi":"10.5140/jass.2023.40.4.237","DOIUrl":"https://doi.org/10.5140/jass.2023.40.4.237","url":null,"abstract":"Laser communication has been considered as a novel method for earth observation satellites with generation of high data volume. It offers faster data transmission speeds compared to conventional radio frequency (RF) communication due to the short wavelength and narrow beam divergence. However, laser beams are refracted due to atmospheric turbulence between the ground and the satellite. Refracted laser beams, upon reaching the receiver, result in angle-of-arrival (AoA) fluctuation, inducing image dancing and wavefront distortion. These phenomena hinder signal acquisition and lead to signal loss in the course of laser communication. So, precise alignment between the transmitter and receiver is essential to guarantee effective and reliable laser communication, which is achieved by pointing, acquisition, and tracking (PAT) system. In this study, we simulate the effectiveness of tip/tilt compensation for more efficient laser communication in the satellite-ground downlink. By compensating for low-order terms using tip/tilt mirror, we verify the alleviation of AoA fluctuations under both weak and strong atmospheric turbulence conditions. And the performance of tip/tilt correction is analyzed in terms of the AoA fluctuation and collected power on the detector.","PeriodicalId":44366,"journal":{"name":"Journal of Astronomy and Space Sciences","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139191845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.5140/jass.2023.40.4.247
Hongsu Kim, Uicheol Jang
Studying the accretion phenomena provides a window into understanding most heavenly bodies, from the birth of stars to active galactic nuclei (AGN). We would adopt the effect of the radiation pressure, which reduces accretion rates ( M ˙ ), on the accretion phenomena. The Shakura-Sunyaev α-disk model of disk accretion is a good candidate theory of advection dominated accretion flow (ADAF). Reduction in the angular velocity leads to the suppression the disk luminosity and surface temperature, essentially indicating the transition of the standard accretion disk model from convection dominated accretion flow (CDAF) to ADAF.
{"title":"Effect of Radiation Pressure Formed at the Inner Region of the Accretion Disk on the Accretion Flow in the Outer Region","authors":"Hongsu Kim, Uicheol Jang","doi":"10.5140/jass.2023.40.4.247","DOIUrl":"https://doi.org/10.5140/jass.2023.40.4.247","url":null,"abstract":"Studying the accretion phenomena provides a window into understanding most heavenly bodies, from the birth of stars to active galactic nuclei (AGN). We would adopt the effect of the radiation pressure, which reduces accretion rates ( M ˙ ), on the accretion phenomena. The Shakura-Sunyaev α-disk model of disk accretion is a good candidate theory of advection dominated accretion flow (ADAF). Reduction in the angular velocity leads to the suppression the disk luminosity and surface temperature, essentially indicating the transition of the standard accretion disk model from convection dominated accretion flow (CDAF) to ADAF.","PeriodicalId":44366,"journal":{"name":"Journal of Astronomy and Space Sciences","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139190323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-01DOI: 10.5140/jass.2023.40.3.113
Shimaa Farouk, Mahmoud El-Nokrashy, Ahmed Abd-Elhay, Nasr Saba
Although the Relative Global Navigation Satellite System (GNSS) positioning technique provides high accuracy, it has several drawbacks. The scarcity of control points, the long baselines, and using of ultra-rabid and rabid products increased position errors. This study has designed a New MATLAB Program that helps users automatically select suitable IGS stations related to the baseline lengths and the azimuth between GNSS points and IGS stations. This study presented criteria for the length of the baselines used in Egypt and an advanced estimated accuracy before starting the project. The experimental test studies the performance of the position accuracy related to the relation between three factors: observation session, final, rabid, and ultra-rabid products, and the baseline lengths. Ground control point mediates Egypt was selected as a test point. Nine surrounding IGS stations were selected as reference stations, and the coordinates of the tested point were calculated based on them. Baselines between the tested point and the IGS stations were classified regarding proposal criteria. The coordinates of the tested point were obtained in different observation sessions (0.5, 1, 2, 4, 5, 6, 7, 7.5 h). The results indicated that the lengths of the baseline in Egypt were classified short (less than 600 km), medium (600–1,200 km), and long (greater than 1,200 km) and required a minimum observation time of 4, 5, and 7 h to obtain accuracy 10, 19, 48 mm sequentially. The position accuracy was superior for the rapid and the final than the ultra-rapid products by 16%. A short baseline was at the best case; there was a performance in position accuracy with a 57% deduction in observation time compared with the long baseline.
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