Space-based Navigation Systems Research Articles

A Model of Android - Dependent Vehicle Monitoring System

From a global perspective, the number of cars using our roads around-the-clock has increased dramatically, and this has tremendously amplified the insecurity on our roads. This has become a key subject, especially in Nigeria. Consequently, automobile trailing schemes are gradually becoming evident amongst common users in the transport sector in most major metropolises. This paper aims to showcase a developed Android-based application system for vehicle trailing schemes that integrates Google Maps real-time features, the “Global Positioning System (GPS), and employs the Global System for Mobile Communication (GSM)” technology. The GPS component is a space-based navigation system that runs on location and time data at all times, irrespective of place and time on the globe, provided there is a line of sight to any of the four or more GPS satellites. The time and location are displayed, utilising Google Maps, which serves as an interface with the application so that the user will be able to constantly monitor moving vehicles via the smartphone. Presented here are the designed model and the experimental outcome of the automobile trailing system that verifies the possibility of the system trailing the movement of vehicles from one location to another at any given time, as well as an interactive Graphical User Interface (GUI) for the Smartphone application.

Ionospheric TEC Forecasting over an Indian Low Latitude Location Using Long Short-Term Memory (LSTM) Deep Learning Network

The forecasting of ionospheric electron density has been of great interest to the research scientists and engineers’ community as it significantly influences satellite-based navigation, positioning, and communication applications under the influence of space weather. Hence, the present paper adopts a long short-term memory (LSTM) deep learning network model to forecast the ionospheric total electron content (TEC) by exploiting global positioning system (GPS) observables, at a low latitude Indian location in Bangalore (IISC; Geographic 13.03° N and 77.57° E), during the 24th solar cycle. The proposed model uses about eight years of GPS-TEC data (from 2009 to 2017) for training and validation, whereas the data for 2018 was used for independent testing and forecasting of TEC. Apart from the input TEC parameters, the model considers sequential data of solar and geophysical indices to realize the effects. The performance of the model is evaluated by comparing the forecasted TEC values with the observed and global empirical ionosphere model (international reference ionosphere; IRI-2016) through a set of validation metrics. The analysis of the results during the test period showed that LSTM output closely followed the observed GPS-TEC data with a relatively minimal root mean square error (RMSE) of 1.6149 and the highest correlation coefficient (CC) of 0.992, as compared to IRI-2016. Furthermore, the day-to-day performance of LSTM was validated during the year 2018, inferring that the proposed model outcomes are significantly better than IRI-2016 at the considered location. Implementation of the model at other latitudinal locations of the region is suggested for an efficient regional forecast of TEC across the Indian region. The present work complements efforts towards establishing an efficient regional forecasting system for indices of ionospheric delays and irregularities, which are responsible for degrading static, as well as dynamic, space-based navigation system performances.

Analysis of Plasma Bubble Signatures in Total Electron Content Maps of the Low-Latitude Ionosphere: A Simplified Methodology

The ionosphere over the Brazilian region has particular characteristics due to the large geomagnetic declination angle over most of the territory. Furthermore, the equatorial ionization anomaly southern crest is located over the Brazilian territory. In this region, plasma irregularities may arise in the post-sunset hours. These ionospheric irregularities develop in the form of magnetic field-aligned plasma depletions, known as equatorial plasma bubbles, which may seriously affect radio signals that propagate through them. These irregularity structures can cause amplitude and phase scintillation of the propagating signals, thereby compromising the availability, performance, and integrity of satellite-based communication and navigation systems. Additionally, the total electron content (TEC) introduces propagation delays that can contribute to range measurement errors for global positioning system (GPS) users. The ionospheric characteristics change significantly according to the time of day, season, as well as the solar and geomagnetic activities, among other factors. Indeed, the ionosphere is one of the most significant sources of errors in the positioning and navigation systems based on the GPS satellites. Due to these features, there is a strong interest by the scientific community in better understanding and characterizing the ionospheric behavior. In this context, the TEC analysis has wide applicability for space plasma studies and is a well-established tool for investigating the ionospheric behavior and its potential impact on space-based navigation systems. One of the goals of these studies is the generation of TEC maps for a geographic region based on GPS observations. In the present work, some electrodynamic processes of the low-latitude ionosphere are reviewed and the TEC estimation based on GPS measurements is revisited in detail. A methodology aimed at creating the TEC maps is presented and validated by comparison with results from other geophysical instruments, such as all-sky imagers and ionosondes. Finally, examples of the ionospheric behavior displayed by TEC maps during equatorial plasma bubble events and a geomagnetic storm are fully described and discussed.

The Space Weather through a Multidisciplinary Scientific Approach

AbstractSpace weather encompasses understanding how the near-space environment responds to forces from lower-atmosphere weather systems as well as conditions on the Sun. Although the specific effects of space weather (including power grid failures, communication outages, and navigation errors when using space-based navigation systems such as GPS) are local in nature, understanding and predicting their occurrence requires a global view of the environment. Here we initiated a first attempt to link one solar event which occurred on 2014 February 25, and affected the Earth’s upper atmosphere.

Design of Deep Space Autonomous Navigation System Based on Spacecraft Networking

In order to reduce the heavy burden on the ground-based network,as well as increasing navigation efficiency for deep space explorers,a method of autonomous navigation based on Spacecraft Networking is proposed in this article. The network comprises two types of spacecraft,namely,basis spacecraft and customer spacecraft. The basis spacecraft implement autonomous navigation by observing X-ray pulsar,inter-ranging,etc. The basis spacecraft provides the standard basis for the whole network,and a customer spacecraft determines its position by communicating with the basis spacecraft or with the other customer spacecraft. The specific scheme of Spacecraft Networking is illustrated by an example of Earth to Moon transfer mission. The configuration scheme and the navigation method of the basis spacecraft are analyzed in this paper,and the navigation method for single and multi-tiered customer spacecraft is presented in this paper. Simulations demonstrate that by measuring X-ray pulsar and inter-ranging links,the basis spacecraft can reach the accuracy of 20 m. When observing the basis spacecraft,the customer spacecraft in Earth to Moon transfer orbit can reach the accuracy of better than 30 m. Autonomous navigation based on Spacecraft Networking is feasible and can significantly benefit China's Space-based navigation system.

Indoor Global Positioning System with Centimeter Accuracy Using Wi-Fi [Applications Corner

The global positioning system (GPS) is a space-based navigation system that can provide location and time information whenever there is an unobstructed line of sight (LOS) to four or more GPS satellites [1]. Such a system provides critical capabilities to military, civil, and commercial applications around world. On other hand, considering fact that people today spend more than 80% of their time in indoor environments, accurate indoor localization is highly desirable and has a great potential impact on many applications. Unfortunately, use of GPS satellites to enable indoor localization is a nonstarter due to a variety of reasons including poor signal strength, multipath effect, and limited on-device computation and communication power [2]. Therefore, over past two decades, research community has been urgently seeking new technologies that can enable high-accuracy indoor localization. However, results are still mostly unsatisfactory. Microsoft hosted Indoor Localization Competitions in recent years and concluded that the indoor location problem is not solved [3].

Technology, security, and policy implications of future transatlantic partnerships in space: Lessons from Galileo

Policy makers seek to identify an institutional framework that facilitates the commercialization of publicly funded R&D, while simultaneously addressing innovation market failure. In the space industry, the formation of such a framework is complicated by national security considerations and the fact that numerous sovereign nations are often included in the commercialization process. This paper analyses how multi-public partnerships with industry can promote commercially viable space programs, resolve market failures, and address transatlantic security concerns. The benefits and policy implications of the formation of such transatlantic multi-public–private partnerships (TMP 3) are illustrated based on a case study of the design of a major European public–private project in the space industry: the Galileo space-based navigation system.

Space Weather and the Global Positioning System

Space Weather and the Global Positioning System

The Application of NAVSTAR Differential GPS in the Civilian Community*

The NAVSTAR Global Positioning System (GPS), currently being developed for the Department of Defense, is a space based navigation system that will provide the user with precise position, velocity and time information on a 24-hour basis and in all weather conditions at any point on the globe. The potential unauthorized use of this source of very precise navigation information has prompted the DOD to intentionally contaminate the signals and to provide only authorized users with the necessary information to recover the original signals. The high probability of the implementation of these techniques, known as Selective Availability, indicated the need for a variation of the baseline GPS, so as to allow for an assured, uninterrupted level of accuracy, if the system was to be used effectively in the civilian sector. Differential GPS provides such a capability. This paper presents the current thinking in the implementation of Selective Availability and its impact on the civilian use of GPS. Further, different possible implementations of differential GPS are presented and their performance compared with the baseline system, with or without the use of Selective Availability. Finally, the support in the civilian community for the development of differential GPS and the potential market size are assessed.