Geodetic Sciences

Space geodetic techniques, e.g., global navigation satellite systems (GNSS), Very Long Baseline Interferometry (VLBI), satellite gravimetry and altimetry, and GNSS Reflectometry & Radio Occultation, are capable of measuring small changes of the Earth�s shape, rotation, and gravity field, as well as mass changes in the Earth system with an unprecedented accuracy. This book is devoted to presenting recent results and development in space geodetic techniques and sciences, including GNSS, VLBI, gravimetry, geoid, geodetic atmosphere, geodetic geophysics and geodetic mass transport associated with the ocean, hydrology, cryosphere and solid-Earth. This book provides a good reference for geodetic techniques, engineers, scientists as well as user community

Análisis e interpretación física del efecto de las irregularidades de plasma ionosférico en el posicionamiento

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física de la Tierra, Astronomía y Astrofísica I (Geofísica y Meteorología) (Astronomía y Geodesia), leída el 27/06/2016The ionosphere is one of the largest sources of error in the GNSS (Global Navigation Satellite System) positioning not only because the ionospheric refraction can induce errors of several meters in the satellite-receiver signals ranges but also due to the frequent occurrence of plasma density irregularities that lead to signal degradation when crosses them. The effect of the ionospheric irregularities on GNSS signals can be quantified by estimating the TEC (Total Electron Content) from dual frequency GNSS observations. At mid-latitudes it is expected that TEC values vary smoothly in the quiet periods whereas large electron density irregularities occurrence will be related to magnetic storms and other Space Weather phenomena. On the other hand, the physical characteristics of the ionosphere at low magnetic latitudes induce, among other phenomena, the appearance of a peculiar kind of irregularities known as equatorial plasma bubbles (EPBs) which are characterized by TEC depletions. The difference in the physics of the ionosphere at low-latitudes and mid-latitudes marks one of the fundamental guidelines of this Doctoral Thesis and the ROT (Rate of change of TEC) parameter is introduced to evaluate the changes in the electron content over time. In the case of positioning performed using dual-frequency receivers, the error introduced by the ionosphere can, in first approximation, be eliminated by the correction known as "ionospheric-free combination" (iono-free). However, significant errors in the height estimated by Precise Point Positioning (PPP) has been observed in the presence of strong variation in the ROT...La ionosfera constituye una de las mayores fuentes de error en el posicionamiento GNSS (Global Navigation Satellite System) no sólo debido al hecho de que la refracción ionosférica puede introducir errores de algunos metros en las medidas de distancia satélite-receptor, sino también a la frecuente aparición de irregularidades en la densidad de plasma que dan lugar a degradaciones de las señales electromagnéticas que las atraviesan. El efecto de las irregularidades ionosféricas sobre las señales GNSS se puede cuantificar por medio de la estimación del TEC (Total Electron Content) a partir de observaciones de señales en doble frecuencia. En latitudes medias se espera que los valores de TEC varíen de una forma suave en los periodos tranquilos mientras que la presencia de irregularidades importantes está relacionada con tormentas magnéticas y otros fenómenos significativos de la Meteorología Espacial. En cambio, las características físicas de la ionosfera a bajas latitudes magnéticas inducen, entre otros fenómenos, la aparición de un tipo peculiar de irregularidades conocidas como burbujas de plasma ecuatorial (EPBs) que se caracterizan por disminuciones bruscas del TEC. La diferencia en la física de la ionosfera para bajas y medias latitudes marca una de las pautas fundamentales de este trabajo en el que se utiliza el parámetro ROT (Rate Of change of TEC) para evaluar las variaciones del contenido electrónico con el tiempo. En el caso del posicionamiento realizado mediante receptores de doble frecuencia, el error introducido por la ionosfera puede ser eliminado en primera aproximación mediante la corrección conocida como “combinación libre de ionosfera”. Sin embargo, se ha observado la presencia de errores significativos en la altura obtenida mediante el Posicionamiento Puntual de Precisión (PPP) bajo condiciones de fuerte variación del ROT...Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEunpu

Imaging ionospheric irregularities by earth observation radar satellite

The sensitivity of Synthetic Aperture Radar (SAR) satellite signal in the L-band to ionospheric plasma density is used to obtain two-dimensional imaging of ionospheric density irregularities. As an application for equatorial ionosphere, we have recently reported first simultaneous observation of equatorial plasma bubble by the ALOS-2/PALSAR-2 satellite and a ground 630-nm airglow imager in northern Brazil. In this case, SAR ionospheric scintillation are represented as stripe-like signature of radar image over the terrain along the local magnetic field lines near an airglow depletion region. This so-called SAR scintillation stripes are discussed to be the signature of existing small-scale plasma irregularities with the scale size of hundreds of meters associated with equatorial plasma bubbles. We present the observational setup and the interpretation of SAR signal parameters to characterize the two-dimensional ionospheric density structures, and discuss future studies

National Astronomy Meeting 2019 Abstract Book

The National Astronomy Meeting 2019 Abstract Book. Abstracts accepted and presented, including both oral and poster presentations, at the Royal Astronomical Society's NAM2019 conference, held at Lancaster University between 30 June and 4 July 2019

Wave Propagation

A wave is one of the basic physics phenomena observed by mankind since ancient time. The wave is also one of the most-studied physics phenomena that can be well described by mathematics. The study may be the best illustration of what is “science”, which approximates the laws of nature by using human defined symbols, operators, and languages. Having a good understanding of waves and wave propagation can help us to improve the quality of life and provide a pathway for future explorations of the nature and universe. This book introduces some exciting applications and theories to those who have general interests in waves and wave propagations, and provides insights and references to those who are specialized in the areas presented in the book