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Space Technology
Published in Mohammad Razani, Information, Communication, and Space Technology, 2017
Managing traffic in space is a challenging task, especially when there are numerous satellite constellations in different orbits. Such challenges include collision avoidance, human zone, sun synchronous zoning, and geosynchronous maneuvers. In order to assure safe and secure traffic in space, a set of space traffic management (STM) rules should be in place and followed by those who are participating in space activities. These rules that are not focused on debris mitigations allow more efficient use of crowded orbits and give owner-operators the tools to protect their spacecraft.
Commercial Space Technologies
Published in Mohammad Razani, Commercial Space Technologies and Applications, 2018
Managing traffic in space is a challenging task, especially when there are numerous satellite constellations in different orbits. Such challenges include collision avoidance, human zone, sun synchronous zoning, and geosynchronous maneuvers. In order to assure safe and secure traffic in space, a set of space traffic management (STM) rules should be in place and followed by those who are participating in space activities. These rules that are not focused on debris mitigations allow more efficient use of crowded orbits and give owner-operators the tools to protect their spacecraft. STM provides standard data set, warnings, and recommendations of avoidance maneuvers to help owner-operators who might not have the tracking or analytical ability in-house. It also gives the owner-operators the flexibility of maneuvering based on internal cost–benefit analysis. These rules provide the spacecraft owner-operators with the information and tools to help make educated choices and to improve satellite safety. The human-rated zoning creates a protected zone for human traffic with minimal impact to current and future non-human-rated operators. STM rules also increase the efficiency of existing GEO slotting and operations and reduce energy costs. Following these rules will allow for more efficient planning for station-keeping maneuvers. Obstacles that might remain in the way of following and implementing such rules are the reluctance to share data due to privacy and competitive advantage concerns and the legitimacy of STM organizational body to implement and enforce rules. Brian Weeden and Ben-Baseley Walker34 outline the key steps for STM systems in three phases: Phase 1: Develop Rules, Phase 2: Build Consensus, and Phase 3: Implement the systems. The potential STM organizations are shown in Figure 2.3.
Signal fingerprint feature extraction and recognition method for communication satellite
Published in Connection Science, 2022
The communication mode of the current marine environment mainly relies on communication satellite terminals. Among them, the most widely used communication satellite terminal is the Iridium system. The system comprises a satellite constellation, system control station, and gateway station. Users can make voice calls worldwide through the equipped iridium satellite terminal. The satellite constellation of the Iridium system is composed of 66 low-orbit satellites operating in orbit at an altitude of 780 km, which can ensure that the Iridium satellites cover any location on the earth at any time. The iridium communication system mainly transmits the signal to the gateway station through the interstellar link, and the gateway station sends the signal to the ground telephone. This paper will simulate the iridium signal to carry out the fingerprint feature extraction and recognition experiment of communication satellite signals. The iridium star system adopts Quadrature Phase Shift Keying (QPSK) modulation method. QPSK is a digital modulation method. QPSK represents four binary combinations of 01, 00, 10, and 11 according to four initial phases. After the serial-to-parallel conversion of the data stream is performed according to the corresponding trigonometric function, it is divided into two channels, multiplied by cos and sin, respectively, and then superimposed to generate a QPSK signal. QPSK has high modulation efficiency, fast transmission rate, and strong anti-interference ability, so it is especially suitable for satellite channels with serious noise and attenuation.
Framework for extracting rails and setting-out railway line axis based on UAV photogrammetric measurements
Published in International Journal of Rail Transportation, 2022
Pawel Burdziakowski, Cezary Specht, Andrzej Stateczny, Mariusz Specht, Pawel S. Dabrowski, Oktawia Lewicka
Dynamic satellite measurement accuracies are variable and depend on momentary field barrier conditions and the satellite constellation geometry during the measurements. As a result, one can expect a measurement accuracy within the studied section to vary. Coordinate quality (CQ) coefficient time series in the horizontal plane (2D) and 3D, shown within the studied section, clearly indicates this property (Figure 8). A typical range of 2D and 3D accuracies in this range is 1–3 cm. The accuracy of the initial fragment of the measured track decreased to approximately 20 cm. In this section, the line passes near a high forest, where satellite visibility is significantly lower, resulting in a decrease in the dilution of precision (DOP) parameter for satellite measurements.
Investigating spatial relationship between vegetation cover and soil moisture using sentinel satellites: a case study of North Gondar Zone, Ethiopia
Published in Journal of Spatial Science, 2022
Worku Nega, Wondifraw Nigussie, Abel Balew
The Sentinel-1A and Sentinel-1B SAR satellites were launched in 2014 and 2016, respectively, as part of the Copernicus program for the observation and monitoring of the earth’s surface, and the development of operational applications for environmental monitoring (Bousbih et al. 2019). This dual-satellite constellation offers a six-day repeat frequency for all regions of the globe. The Sentinel-1 SAR images have 10 m spatial resolution with a C-band frequency of 5.4 GHz and have the Strip Map (SM), Interferometric Wide Swath (IW), Extra Wide Swath (EW), and Wave (WV) standard operating modes (Bousbih et al. 2017; https://scihub.copernicus.eu/dhus/#/home). The Sentinel-1 satellites are equipped with C-band SAR instruments, providing data in a dual or single polarization. They provide data with a temporal resolution of 12 days, in both Vertical transmit and Vertical receive (VV) and Vertical transmit and Horizontal receive (VH) polarizations. Many studies reported that Sentinel-1 with VV polarization is better than VH polarization for soil moisture estimation (Alexakis et al. 2017, Bai et al. 2017, Bousbih et al. 2017, Gao et al. 2017, Attarzadeh et al. 2018, Urban et al. 2018, Bousbih et al. 2019, Mirsoleimani et al. 2019, Ezzahar et al. 2020).