A Review on Precise Orbit Determination of Various LEO Satellites

The need for precise orbit determination (POD) has grown significantly due to the increased amount of space-based activities appearing at an accelerating pace. POD has a positive contribution in achieving the requirements of Low-Earth Orbit (LEO) satellite mission which includes improved reliability and continuity. In this paper, we will review the POD approaches of various LEO satellites and discuss the accuracy levels obtained as well as the methods and algorithms used to achieve the POD of LEO satellites. With recent advancements in miniature space technology, a greater number of smaller low-cost satellites are launched into the LEO for various purposes. Furthermore, development in the Global Navigation Satellite Systems (GNSS) and chipsets played a vital role in revolutionizing the GNSS receiver technology. Lower-cost, smaller size but yet high performing GNSS receivers need to be implemented also in CubeSats in addition to the various terrestrial applications. POD using onboard GNSS receiver data will benefit the development of several upcoming space applications in the field of navigation systems, telecommunication, remote sensing, and earth observation. In the future, it is anticipated that LEO-based satellites enabled by POD can also offer positioning capabilities that will enhance GNSS and create vast opportunities for users with new features and possibilities to the navigation field.© 2021 Copyright for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0). CEUR Workshop Proceedings (CEUR-WS.org)fi=vertaisarvioitu|en=peerReviewed

Techniques and challenges in the assimilation of atmospheric water observations for numerical weather prediction towards convective scales

While contemporary Numerical Weather Prediction models represent the large-scale structure of moist atmospheric processes reasonably well, they often struggle to maintain accurate forecasts of small-scale features such as convective rainfall. Even though high-resolution models resolve more of the flow, and are therefore arguably more accurate, moist convective flow becomes increasingly nonlinear and dynamically unstable. Importantly, the models’ initial conditions are typically sub-optimal, leaving scope to improve the accuracy of forecasts with improved data assimilation. To address issues regarding the use of atmospheric water-related observations – especially at convective scales (also known as storm scales) – this paper discusses the observation and assimilation of water- related quantities. Special emphasis is placed on background error statistics for variational and hybrid methods which need special attention for water variables. The challenges of convective-scale data assimilation of atmospheric water information are discussed, which are more difficult to tackle than at larger scales. Some of the most important challenges include the greater degree of inhomogeneity and lower degree of smoothness of the flow, the high volume of water-related observations (e.g. from radar, microwave, and infrared instruments), the need to analyse a range of hydrometeors, the increasing importance of position errors in forecasts, the greater sophistication of forward models to allow use of indirect observations (e.g. cloud and precipitation affected observations), the need to account for the flow-dependent multivariate ‘balance’ between atmospheric water and both dynamical and mass fields, and the inherent non-Gaussian nature of atmospheric water variables

Precise orbit determination of LEO satellites : a systematic review

The need for precise orbit determination (POD) has grown significantly due to the increased amount of space-based activities taking place at an accelerating pace. Accurate POD positively contributes to achieving the requirements of Low-Earth Orbit (LEO) satellite missions, including improved tracking, reliability and continuity. This research aims to systematically analyze the LEO–POD in four aspects: (i) data sources used; (ii) POD technique implemented; (iii) validation method applied; (iv) accuracy level obtained. We also present the most used GNSS systems, satellite missions, processing procedures and ephemeris. The review includes studies on LEO–POD algorithms/methods and software published in the last two decades (2000–2021). To this end, 137 primary studies relevant to achieving the objective of this research were identified. After the investigation of these primary studies, it was found that several types of POD techniques have been employed in the POD of LEO satellites, with a clear trend observed for techniques using reduced-dynamic model, least-squares solvers, dual-frequency signals with undifferenced phase and code observations in post-processing mode. This review provides an understanding of the various POD techniques, dataset utilized, validation techniques, and accuracy level of LEO satellites, which have interest to developers of small satellites, new researchers and practitioners.© The Author(s) 2023. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.fi=vertaisarvioitu|en=peerReviewed

UK Monetary Policy Reaction Functions, 1992-2014: A Cointegration Approach Using Taylor Rules.

For more than two decades, monetary policy of countries around the world has undergone significant transformation. The long-term stabilization and lowering of inflation is the primary target of central banks founded on the principles of transparency and credibility. The achievement of inflation targeting and control is ultimately judged by the public’s expectations about future inflation. This objective has focused central bank policy making on modern monetary principles and the adoption of one of its core principles, the monetary policy rule. The central bank of the United Kingdom officially adopted an explicit inflating targeting monetary policy in October 1992 following its operational independence in May 1997. In this study, we attempt to investigate the behaviour of the Central Bank of England under an inflation targeting framework. In other words, whether Taylor-type policy rules can be used to describe the behaviour of the Central Bank of England. We specifically attempt to shed light on the question does Taylor's rule (Taylor, 1993) adequately describes central bank behaviour? And whether the existence of formal targets has induced nonlinearity in this behaviour, beginning in October 1992 until December 2014. The study uses time series estimations of Taylor-type reactions functions to characterise monetary policy conduct in the UK, we use time series data, because all the other studies in this area are using the time series method and recommended it, Osterholm (2005), Nelson (2000), Adam et al (2003), Clarida et al (2000) amongst others. In addition, this study uses a long database which is useful for time series analysis. The analysis uses a modified cointegration and error correction model that is robust to the stationary properties of the data as well as vector autoregression techniques; therefore, our methodology in this study employed three types of econometric tests namely: unit root tests, cointegration tests and error correction models. We used monthly data for the UK over the period October 1992 to December 2014, and we estimate Taylor-type policy rules for the UK in order to find answers to these questions. Our results indicate that the Central Bank of England has not been following the Taylor rule. In other words, the regression results clearly indicated that the Central Bank of England did not follow the Taylor rule in the period 1992-2014. This is because all coefficients of inflation gap and the output gap were statistically insignificant. In addition, we conclude these results link with the New Consensus Macroeconomics, criticism of inflation targeting and endogenous money theory. The main contribution in this study is an up-to-date analysis, and evidence that Bank of England policy does not work with Taylor rules. In addition, on the methodological level most previous studies reviewed in the literature have measured the interest rate, inflation and the output gap using one dependent variable, to measure the behaviour of the Central Bank of England, to assess whether the Taylor rule is effective or not. However, this study fills this gap by using two measure for interest rate, three measure for inflation and two variables to measure the output gap, using The Hodrick-Prescott (HP) filter and moving averages, to assess whether the Taylor rule is effective or not effective by using more than one dependent variable

Jean Epstein

Filmmaker and theoretician Jean Epstein profoundly influenced film practice, criticism and reception in France during the 1920s and well beyond. His work not only forms the crux of the debates of his time, but also remains key to understanding later developments in film practice and theory. Epstein' s film criticism is among the most wide-ranging, provocative and poetic writing about cinema and his often breathtaking films offer insights into cinema and the experience of modernity. This collection - the first comprehensive study in English of Epstein's far-reaching influence - arrives as several of the concerns most central to Epstein' s work are being reexamined, including theories of perception, realism, and the relationship between cinema and other arts. The volume also includes new translations from every major theoretical work Epstein published, presenting the widest possible historical and contextual range of Epstein' s work, from his beginnings as a biology student and literary critic to his late film projects and posthumously published writings.Filmmaker en -theoreticus Jean Epstein beïnvloedde sterk de filmpraktijk, -kritiek en -receptie in Frankrijk en ver daarbuiten tijdens de jaren twintig van de vorige eeuw. Zijn werk vormde niet alleen de kern van de debatten in die tijd, maar is ook een sleutel voor het begrijpen van latere ontwikkelingen in de filmpraktijk en -theorie. Epsteins filmkritieken zijn uiteenlopende, uitdagende en poëtisch geschreven teksten, en zijn vaak adembenemende films bieden belangrijke en moderne inzichten in de cinema. Dit boek verschijnt op het moment dat een aantal van de thema' s die centraal staan in het werk van Epstein opnieuw wordt onderzocht, met inbegrip van de theorie van de waarneming, realisme en de relatie tussen cinema en de andere kunsten. De kritische essays vormen een waardevolle inleiding tot het creatieve oeuvre van Epstein

Bibliography of Lewis Research Center technical publications announced in 1986

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1986. All the publications were announced in the 1986 issues of Scientific and Technical Aerospace Reports (STAR) and/or International Aerospace Abstracts (IAA). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Globalance towards a new world order : ethics matters and motivates : handbook with 250 graphs

2nd enlarged edition. Prefaces Mariana Bozesan, Liu Baocheng, Ernst Ulrich von Weizsäcker.First published 2020 under the title: Globalance : ethics handbook for a balanced world post-covid

Jean Epstein

Filmmaker and theoretician Jean Epstein profoundly influenced film practice, criticism and reception in France during the 1920s and well beyond. His work not only forms the crux of the debates of his time, but also remains key to understanding later developments in film practice and theory. Epstein' s film criticism is among the most wide-ranging, provocative and poetic writing about cinema and his often breathtaking films offer insights into cinema and the experience of modernity. This collection - the first comprehensive study in English of Epstein's far-reaching influence - arrives as several of the concerns most central to Epstein' s work are being reexamined, including theories of perception, realism, and the relationship between cinema and other arts. The volume also includes new translations from every major theoretical work Epstein published, presenting the widest possible historical and contextual range of Epstein' s work, from his beginnings as a biology student and literary critic to his late film projects and posthumously published writings