Lake Vostok, der größte der über 70 subglazialen Seen in der Antarktis, ist derzeit einer der Forschungsschwerpunkte der geowissenschaftlichen Polarforschung. Der See erstreckt sich unter einer 4 000 m dicken Eisschicht auf über 250 km Länge mit einer Wassertiefe von bis zu 1 000 m. Ziel der hier vorliegenden Arbeit ist die Untersuchung des Einflusses der Gezeiten auf den Wasserstand des Sees, die eine bisher nicht betrachtete Komponente in der Zirkulation im See darstellen. Auf Grund seiner Ausdehnung ist das Gezeitenpotential an verschiedenen Punkten auf dem See nicht gleich, sondern weist differentielle Unterschiede auf. Unter der Annahme, dass sich die Seeoberfläche entlang einer Äquipotentialfläche ausrichtet, ergeben sich Gleichgewichtsgezeiten des Sees mit Amplituden von bis zu 4,6 mm für die größte ganztägige Tide K1 und 1,8 mm für die größte halbtägige Tide M2. Differenzen des Luftdruckes zwischen Nord- und Südteil des Sees rufen zusätzlich einen differentiellen inversen Barometer-Effekt hervor. Der inverse Barometer-Effekt besitzt im wesentlichen die spektralen Eigenschaften eines roten Rauschens. Die Variationen erreichen bis zu +/- 20 mm. Zum messtechnischen Nachweis derartiger Höhenänderungen an der Eisoberfläche über dem See wurden drei unterschiedliche Verfahren herangezogen. Differentielle GPS-Messungen zwischen einem Punkt auf aufliegendem Eis und einem zweiten in der südlichen Seemitte bestätigen die Modellvorstellungen und zeigen sowohl mit der Luftdruckdifferenz korrelierte Höhenänderungen als auch Höhenänderungen mit ganz- und halbtägigen Perioden. Die SAR-Interferometrie als flächenhaft arbeitende Methode zur Bestimmung von Höhenänderungen lässt den räumlichen Verlauf der Deformation erkennen. Dabei zeigt sich, dass sich die Aufsetzzone auf dem etwa 50 km breiten See bis in die Seemitte ersteckt. Erdgezeitenregistrierungen, die im Jahr 1969 in der Station Vostok durchgeführt wurden, zeigen zwar Auffälligkeiten wie etwa einen stark erhöhten Luftdruckregressionskoeffzienten und einen Phasenvorlauf der K1-Tide, diese können jedoch nicht eindeutig als Resultat von Höhenänderungen der Seeoberfläche identifiziert werden. Auf Grund der Lage der Station Vostok nahe dem Ufer des Sees ist die Deformation dort schon stark gedämpft. Die zu erwartenden Effekte liegen daher unterhalb der Auflösung der damaligen Messungen. Damit sind die theoretischen Grundvorstellungen über die Reaktion des subglazialen Sees auf Gezeiten- und Luftdruckanregungen herausgearbeitet, sowie diese Effekte mit zwei unabhängigen und komplementären Messverfahren nachgewiesen. / Lake Vostok, the largest of more than 70 subglacial lakes in the Antarctic, is one of the prominent topics of recent geoscientific polar research. The lake extends beneath the 4,000 m thick ice sheet to a length of more than 250 km with a water depth of up to 1,000 m. This thesis aims to investigate the influence of tides on the lake level which has not been considered so far in the discussion of water circulation within the lake. Due to the extent of the lake the tidal potential at different positions on its surface is not equal but exhibits a differential effect. Under the assumption of the lake level to be parallel to an equipotential surface the equilibrium tides of the lake yield amplitudes of up to 4.6 mm for the largest diurnal tidal constituent K1 and 1.8 mm for the largest semi-diurnal wave M2. In addition, differences in air pressure between the northern and the southern part of the lake result in a differential inverse barometric effect. This effect shows red noise characteristics with variations of up to +/- 20 mm. Three different types of measurements were used to verify corresponding height changes of the ice surface above the lake. Differential GPS measurements between one station on grounded ice and one in the southern centre of the lake confirm the concept and show height changes correlated to air pressure differences as well as changes with diurnal and semi-diurnal periods. SAR interferometry as a spatial method to determine height changes reveals the areal extent of the deformation with a grounding zone extending to the centre of the about 50 km wide lake. Gravimetric earth tide data recorded at Vostok Station in 1969 show pecularities such as an increased regression with air pressure and a phase lead of the K1 tide. However, these effects cannot be explicitly attributed to height changes of the lake surface. Due to the position of the station near the edge of the lake the effect is highly attenuated and below the noise level of these measurements. This work introduces the concept of the response of the subglacial lake to the tidal potential and to air pressure forcings and presents evidence for the effect by two different techniques proving the validity of the model.

The Brigham Young University (BYU) Radio Astronomy group, in collaboration with Cornell University, the University of Massachusetts, and the National Radio Astronomy Observatory (NRAO), have in recent years developed and deployed PAF systems that demonstrated the advantages of PAFs for astronomy. However, these systems lacked the necessary bandwidth and acquisition times to be scientifically viable. This thesis outlines the development of a 20-MHz bandwidth system that can acquire for much longer periods of time and across much larger bandwidths than previous BYU systems. A report of the deployment of this system on the 305-meter reflector at the Arecibo Observatory in Puerto Rico is also summarized.The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is currently constructing a PAF-equipped synthesis imaging array named the Australian Square Kilometre Array Pathfinder (ASKAP) that offers great promise for widening FOVs and enhancing RFI mitigation techniques. Previous work in RFI mitigation has demonstrated effective cancellation for synthesis imaging arrays under the assumption that the processing bandwidth is narrowband and correlator dump times are short. However, these assumptions do not necessarily reflect real-world instrument limitations. This thesis explores simulated adaptive array cancellation algorithm effectiveness as applied on the ASKAP instrument given realistic bandwidths and correlator dump times. The results demonstrate that active RFI mitigation performed across long baselines is largely ineffectual.

[pt] Nas últimas décadas, interações entre luz e matéria provaram ser uma ferramenta versátil para medir e controlar sistemas mecânicos, encontrando aplicações desde detecção de forças até resfriamento ao estado fundamental de nanoesferas. Nesta dissertação, nós apresentamos algumas das ferramentas teóricas necessárias para descrever interferômetros, pinças ópticas e cavidades ópticas, constituintes fundamentais da caixa de ferramentas optomecânica. No regime clássico, estudamos o campo eletromagnético circulante em interferômetros lineares e mostramos como encontrar o campo resultante transmitido, apresentando exemplos de cavidades ópticas com um número arbitrário de elementos dispersivos. Nós também estudamos as forças de pressão de radiação que feixes ópticos podem imprimir em partículas dielétricas e mostramos como o aprisionamento óptico 3D é possível em focos claros e escuros. A potencial aplicação para captura de organismos vivos é estudada. No regime quântico, nós estudamos como o campo ressonante de cavidades ópticas pode interagir de forma dispersiva com diferentes sistemas mecânicos, dando origem a uma dinâmica quântica fechada emaranhante. Ao considerar uma nuvem ultra resfriada de átomos interagindo com dois modos ópticos, mostramos o surgimento de emaranhamento óptico que evidencia a natureza não-clássica do conjunto atômico macroscópico. A viabilidade experimental deste experimento com tecnologia atual é estudada. Além disso, nós investigamos o cenário em que uma pinça óptica posiciona uma partícula levitada dentro de uma cavidade óptica de forma que os fótons da pinça espalhados pela partícula possam sobreviver dentro da cavidade. Já foi demonstrado que esta interação, chamada de espalhamento coerente, pode resfriar nanopartículas até números de fônons menores do que um, atingindo profundamente o regime quântico. Nós mostramos que esta interação também pode gerar emaranhamento mecânico entre muitas partículas levitadas, mesmo em um ambiente a temperatura de 300K. Um resumo sobre sistemas de variáveis contínuas e a caixa de ferramentas numérica customizada usada ao longo deste trabalho são apresentados. / [en] Over the last decades, light-matter interactions have proven to be a versatile tool to measure and control mechanical systems, finding application from force sensing to ground state cooling of nanospheres. In this dissertation, we present some of the theoretical tools that describe interferometers, optical tweezers and optical cavities, fundamental constituents of the optomechanical toolbox. In the classical regime, we study the circulating electromagnetic field within linear interferometers and show how one can find the resulting transmitted field, presenting examples of optical cavities with an arbitrary number of dispersive elements. Moreover, we also study the radiation-pressure forces that optical beams can imprint on dielectric particles and show how 3D optical trapping is possible in both bright and dark focuses. Potential application to trapping of living organisms is studied. In the quantum regime, we study how the resonant field of optical cavities can dispersivelly interact with different mechanical systems, giving rise to an entangling closed quantum dynamics. When considering an ultracold cloud of atoms interacting with two optical modes, we show the emergence of optical entanglement which evidences the nonclassical nature of the macroscopic atomic ensemble. The experimental feasibility of this experiment with current technology is studied. Furthermore, we investigate the scenario where a finely tuned optical tweezer places a trapped particle inside an optical cavity such that the tweezer s scattered photons can survive inside the cavity. This so-called coherent scattering interaction has been shown to cool nanoparticles to phonon numbers lower than one deep into the quantum regime. We show that it also can generate mechanical entanglement between many levitated particles even in a room temperature environment. An overview on continuous variable systems and the custom numerical toolbox used throughout this work are presented.

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Die satellitengestützte Radarinterferometrie liefert Informationen zu vertikalen Bodenbewegungen in hoher raum-zeitlicher Auflösung. Moderne Auswerteverfahren in Kombination mit hochauflösenden Sensoren ermöglichen die Anwendung dieser Monitoringmethode auf Tagebaukippen. Die damit verfügbare Datenbasis erlaubt eine flächenhafte Analyse des Setzungsverhaltens der Oberfläche der Tagebaukippe und erweitert damit die bisherige punktartige Betrachtung unter Nutzung von Höhenfestpunkten. Der vorliegende Beitrag demonstriert, wie aus den räumlich verteilten Zeitreihen eine flächenhafte Modellierung des Zeitsetzungsverhaltens von Tagebaukippen erfolgen kann. Dazu werden klassische Modelle des Zeitsetzungsverlaufes auf die Ergebnisse der satellitengestützten Radarinterferometrie angewandt. Im Ergebnis kann geschlussfolgert werden, dass das hier vorgestellte Verfahren eine nahezu rein datengetriebene Prognose von wichtigen Indikatoren, wie z. B. Zeit bis zum Abklingen der Setzung oder zu erwartende maximale Setzung, erlaubt. Weiterhin liefert das Verfahren eine reiche Datengrundlage zur detaillierten Untersuchung weitere Einflussfaktoren auf das Setzungsverhalten von Tagebaukippen.

LISA, the Laser Interferometry Space Antenna, is the 3rd large mission (L3) of the ESA program Cosmic Vision with a junior partnership from NASA planned to be launched around 2034. Space-based gravitational wave observatories such as LISA have been developed for observation of sources that produce gravitational wave (GW) signals with frequencies in the mHz regime. The frequency band is achievable by having a longer-baseline interferometer compared to ground-based detectors. In addition, the significant size of the LISA arms-length guarantees the detection of many astrophysical sources. The absence of Newtonian noise in space, which is the dominant source of noise below few hertz for ground-based detectors, allows LISA to be sensitive to lower frequency compared to the former. Thus, going to space allows studying different sources with respect to the ones of interest for ground-based detectors such as supermassive black holes. Although having very long baselines between the satellites generally increases the sensitivity to gravitational waves, it also implies many technical challenges, such that a balance must be found between scientific performance and technical feasibility.In the actual proposal LISA is designed to be a constellation of three identical spacecraft in a triangular formation with six active laser links connecting the three spacecraft, which are separated by 2.5 million km. To fulfil the observatory program every spacecraft has a minimum requirement of two free-falling test masses, two telescopes, and two lasers. The detector’s center-of-mass follows a circular, heliocentric trajectory, trailing 20 degrees behind the Earth and the plane of the detector is tilted by 60 degrees with respect to the ecliptic.The goal of LISA is to detect GWs which manifest themselves as a tiny fluctuation in the frequency of the laser beam measured at the phase-meter. Thus, to detect GW you need to compete with many sources of disturbance that simulate the effect of a GW frequency modulation. Laser noise is an example of those. Therefore, one key element in the LISA data production chain is the post-processing technique called Time Delay Interferometry aimed at suppressing the intense laser frequency noise that would completely cover the astrophysical signal. Data from the six independent inter-satellite links, connecting the three spacecraft, are properly time-shifted and combined to form the final scientific signal. This post-processing technique circumvents the impossibility of physically building in space an equal arm interferometer, which would intrinsically beat the frequency noise by comparing light generated at the same time.The following work is focused on revisiting the Time-Delay-Interferometry (TDI) for LISA and studying the usage of all the possible TDI combinations we can build for the LISA instrument characterisation and science extraction. Many possible TDI combinations that suppress the frequency noise have been identified in the past and this thesis revisits the TDI technique focusing on the physical interpretation of it, that is a virtual interference of photons that have been travelling through the constellation via different paths but performing the same total distance. We illustrate all possible TDI configurations that suppress the laser noise contribution to the level required by the mission to understand how TDI channels can be best used for the diagnostic of the instrument and LISA science. With this philosophy, we develop an algorithm to search for all possible combinations that suppress laser noise at the same level as the classical TDI X, Y, and Z combinations presented in the TDI literature. This algorithm finds new combinations that fulfill the noise suppression requirement as accurately as X, Y, and Z.The LISA mission has been also advertised to probe the early Universe by detecting a stochastic GW background. Once the laser frequency noise has been subtracted, the stochastic signal, both cosmological and astrophysical, is itself going to contribute to the noise curve. Therefore it is necessary to have a good estimate of the noise of the instrument to discriminate between the stochastic background signal and the LISA noise.The strategy that has been suggested in the literature is to use the TDI T, insensitive (up to a certain order) to GW signals to estimate the pure instrumental noise in order to distinguish between the LISA background noise and the GW stochastic signal. Following this idea, as instrument noise is expected to have multiple, independent sources, this thesis explores combinations that could allow discriminating among those sources of noise, and between them and the GW signal, with the purpose of understanding how we can characterise our instrument using TDI. We illustrate special TDI combination signals in LISA, in addition to TDI T, that we call null-channels, which are ideally insensitive to gravitational waves and only carry information about instrumental noise. Studying the noise properties that can be extracted by monitoring these interferometric signals, we state that individual acceleration noise parameters are not well constrained. All null-channels behave as an ideal Sagnac interferometer, sensitive just to a particular linear combination of the six test masses acceleration that resembles a rotational acceleration signal of the entire constellation. Moreover, all null-channels show approximately the same signal to noise ratio remarkably suppressed relative to that of the TDI X. In support and application of our theoretical studies, we also give an introduction on calibrating the LISA instrument by injecting spurious signals in a LISA link and see how these propagates through a TDI channel. Indeed, this will be useful to calibrate the instrument during operations and also to build the basis for the data analysis to discriminate spurious signals from gravitational waves. My contribution to the results we present in this thesis can be summarised as the following. I supported the studies and the realisation of the search TDI algorithm whose results are published in the article. In particular, I took care of cataloging the new TDI combinations and consolidating the results we found. I have updated the TDI combinations reported in the above-mentioned work, the final version of it is reported in this thesis. I worked on the characterisation of these combinations concerning secondary noises such as clock noise, readout noise, residual laser frequency noise, and acceleration noise. In particular, I studied how these noises are transferred through the various TDI and I derive the correspondent analytical models. I then realize a software with Wolfram Mathematica, design to load and combines phase data produced by an external simulator to build the final TDI outputs, besides I also did the noise models’ validation. The basis of this program was then used to implement these TDI combinations in LISANode. Finally, I developed the algorithm to study how disturbances in force, such as glitches, and simple GW signals, such as monochromatic GW binaries, propagate through TDI and null-channels. Moreover, I tested through simulations the validity of these TDI and null-channels to distinguish instrumental artefact from GW signals and to characterise the instrumental noise.

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