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N. Dunbar

Bio: N. Dunbar is an academic researcher from Airbus Defence and Space. The author has contributed to research in topics: Pathfinder & Gravitational-wave observatory. The author has an hindex of 5, co-authored 9 publications receiving 492 citations.

Papers
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Journal ArticleDOI
Michele Armano1, Heather Audley2, G. Auger3, J. Baird4, Massimo Bassan5, Pierre Binétruy3, M. Born2, Daniele Bortoluzzi6, N. Brandt7, M. Caleno1, L. Carbone6, Antonella Cavalleri8, A. Cesarini6, Giacomo Ciani6, G. Congedo6, A. M. Cruise9, Karsten Danzmann2, M. de Deus Silva1, R. De Rosa, M. Diaz-Aguilo10, L. Di Fiore, Ingo Diepholz2, G. Dixon9, Rita Dolesi6, N. Dunbar7, Luigi Ferraioli11, Valerio Ferroni6, Walter Fichter, E. D. Fitzsimons12, R. Flatscher7, M. Freschi1, A. F. García Marín2, C. García Marirrodriga1, R. Gerndt7, Lluis Gesa10, Ferran Gibert6, Domenico Giardini11, R. Giusteri6, F. Guzmán2, Aniello Grado13, Catia Grimani14, A. Grynagier, J. Grzymisch1, I. Harrison15, Gerhard Heinzel2, M. Hewitson2, Daniel Hollington4, D. Hoyland9, Mauro Hueller6, Henri Inchauspe3, Oliver Jennrich1, Ph. Jetzer16, Ulrich Johann7, B. Johlander1, Nikolaos Karnesis2, B. Kaune2, N. Korsakova2, Christian J. Killow17, J. A. Lobo10, Ivan Lloro10, L. Liu6, J. P. López-Zaragoza10, R. Maarschalkerweerd15, Davor Mance11, V. Martín10, L. Martin-Polo1, J. Martino3, F. Martin-Porqueras1, S. Madden1, Ignacio Mateos10, Paul McNamara1, José F. F. Mendes15, L. Mendes1, A. Monsky2, Daniele Nicolodi6, Miquel Nofrarías10, S. Paczkowski2, Michael Perreur-Lloyd17, Antoine Petiteau3, P. Pivato6, Eric Plagnol3, P. Prat3, U. Ragnit1, B. Rais3, Juan Ramos-Castro18, J. Reiche2, D. I. Robertson17, H. Rozemeijer1, F. Rivas10, G. Russano6, J Sanjuán10, P. Sarra, A. Schleicher7, D. Shaul4, Jacob Slutsky19, Carlos F. Sopuerta10, Ruggero Stanga20, F. Steier2, T. J. Sumner4, D. Texier1, James Ira Thorpe19, C. Trenkel7, Michael Tröbs2, H. B. Tu6, Daniele Vetrugno6, Stefano Vitale6, V Wand2, Gudrun Wanner2, H. Ward17, C. Warren7, Peter Wass4, D. Wealthy7, W. J. Weber6, L. Wissel2, A. Wittchen2, A. Zambotti6, C. Zanoni6, Tobias Ziegler7, Peter Zweifel11 
TL;DR: The first results of the LISA Pathfinder in-flight experiment demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density.
Abstract: We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2 +/- 0.1 fm s(exp -2)/square root of Hz, or (0.54 +/- 0.01) x 10(exp -15) g/square root of Hz, with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8 +/- 0.3) fm square root of Hz, about 2 orders of magnitude better than requirements. At f less than or equal to 0.5 mHz we observe a low-frequency tail that stays below 12 fm s(exp -2)/square root of Hz down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.

523 citations

Journal ArticleDOI
Michele Armano1, Heather Audley2, G. Auger3, J. Baird4, Pierre Binétruy3, M. Born2, Daniele Bortoluzzi5, N. Brandt6, A. Bursi, M. Caleno1, Antonella Cavalleri5, A. Cesarini5, M. Cruise7, Karsten Danzmann2, M. de Deus Silva1, Ingo Diepholz2, Rita Dolesi5, N. Dunbar6, Luigi Ferraioli8, Valerio Ferroni5, E. D. Fitzsimons9, R. Flatscher6, M. Freschi1, J. Gallegos1, C. García Marirrodriga1, R. Gerndt6, Lluis Gesa10, Ferran Gibert5, Domenico Giardini8, R. Giusteri5, Catia Grimani11, J. Grzymisch1, I. Harrison12, Gerhard Heinzel2, M. Hewitson2, Daniel Hollington4, Mauro Hueller5, J. Huesler1, Henri Inchauspe3, Oliver Jennrich1, Ph. Jetzer13, B. Johlander1, Nikolaos Karnesis2, B. Kaune2, Christian J. Killow14, N. Korsakova14, Ivan Lloro10, L. Liu5, J. P. López-Zaragoza10, R. Maarschalkerweerd12, S. Madden1, Davor Mance8, V. Martín10, L. Martin-Polo1, J. Martino3, F. Martin-Porqueras1, Ignacio Mateos10, Paul McNamara1, José F. F. Mendes12, L. Mendes1, A. Moroni, Miquel Nofrarías10, S. Paczkowski2, Michael Perreur-Lloyd14, Antoine Petiteau3, P. Pivato5, Eric Plagnol3, P. Prat3, U. Ragnit1, Juan Ramos-Castro15, J. Reiche2, J. A. Romera Perez1, D. I. Robertson14, H. Rozemeijer1, F. Rivas10, G. Russano5, P. Sarra, A. Schleicher6, Jacob Slutsky16, Carlos F. Sopuerta10, T. J. Sumner4, D. Texier1, James Ira Thorpe16, C. Trenkel6, Daniele Vetrugno5, S. Vitale5, Gudrun Wanner2, H. Ward14, Peter Wass4, D. Wealthy6, W. J. Weber5, A. Wittchen2, C. Zanoni5, Tobias Ziegler6, Peter Zweifel8 
TL;DR: Electrostatic measurements made on board the European Space Agency mission LISA Pathfinder are the first made in a relevant environment for a space-based gravitational wave detector and resolve the stochastic nature of the TM charge buildup due to interplanetary cosmic rays and theTM charge-to-force coupling through stray electric fields in the sensor.
Abstract: We report on electrostatic measurements made on board the European Space Agency mission LISA Pathfinder. Detailed measurements of the charge-induced electrostatic forces exerted on free-falling test masses (TMs) inside the capacitive gravitational reference sensor are the first made in a relevant environment for a space-based gravitational wave detector. Employing a combination of charge control and electric-field compensation, we show that the level of charge-induced acceleration noise on a single TM can be maintained at a level close to 1.0 fm s-2 Hz-1/2 across the 0.1–100 mHz frequency band that is crucial to an observatory such as the Laser Interferometer Space Antenna (LISA). Using dedicated measurements that detect these effects in the differential acceleration between the two test masses, we resolve the stochastic nature of the TM charge buildup due to interplanetary cosmic rays and the TM charge-to-force coupling through stray electric fields in the sensor. All our measurements are in good agreement with predictions based on a relatively simple electrostatic model of the LISA Pathfinder instrument.

73 citations

Journal ArticleDOI
Michele Armano1, Heather Audley2, G. Auger3, J. Baird4, Pierre Binétruy3, M. Born2, Daniele Bortoluzzi5, N. Brandt6, A. Bursi, M. Caleno1, Antonella Cavalleri7, A. Cesarini5, M. Cruise8, Karsten Danzmann2, M. de Deus Silva1, D. Desiderio, E. Piersanti, Ingo Diepholz2, Rita Dolesi5, N. Dunbar6, Luigi Ferraioli9, Valerio Ferroni5, Ewan Fitzsimons6, R. Flatscher6, M. Freschi1, J. Gallegos1, C. García Marirrodriga1, R. Gerndt6, Lluis Gesa10, Ferran Gibert5, Domenico Giardini9, R. Giusteri5, Catia Grimani11, J. Grzymisch1, I. Harrison12, Gerhard Heinzel2, M. Hewitson2, Daniel Hollington4, Mauro Hueller5, J. Huesler1, Henri Inchauspe3, Oliver Jennrich1, Philippe Jetzer13, B. Johlander1, Nikolaos Karnesis2, B. Kaune2, N. Korsakova2, Christian J. Killow14, Ivan Lloro10, L. Liu5, J. P. López-Zaragoza10, R. Maarschalkerweerd12, S. Madden1, Davor Mance9, V. Martín10, L. Martin-Polo1, J. Martino3, F. Martin-Porqueras1, Ignacio Mateos10, Paul McNamara1, José F. F. Mendes12, Luis Mendes1, A. Moroni, Miquel Nofrarías10, S. Paczkowski2, Michael Perreur-Lloyd14, Antoine Petiteau3, P. Pivato5, Eric Plagnol3, P. Prat3, U. Ragnit1, Juan Ramos-Castro15, J. Reiche2, J. A. Romera Perez1, D. I. Robertson14, H. Rozemeijer1, F. Rivas10, G. Russano5, P. Sarra, A. Schleicher6, Jacob Slutsky16, Carlos F. Sopuerta10, T. J. Sumner4, D. Texier1, James Ira Thorpe16, R. Tomlinson6, C. Trenkel6, Daniele Vetrugno5, Stefano Vitale5, Gudrun Wanner2, H. Ward14, C. Warren6, Peter Wass4, D. Wealthy6, W. J. Weber5, A. Wittchen2, C. Zanoni5, Tobias Ziegler6, Peter Zweifel9 
TL;DR: The LISA Pathfinder satellite was launched on 3 December 2015 toward the Sun Earth first Lagrangian point (L1) where the LISA Technology Package (LTP), which is the main science payload, will be tested.
Abstract: LISA Pathfinder satellite was launched on 3 December 2015 toward the Sun Earth first Lagrangian point (L1) where the LISA Technology Package (LTP), which is the main science payload, will be tested. LTP achieves measurements of differential acceleration of free-falling test masses (TMs) with sensitivity below 3 x 10(exp -14) m s(exp -2) Hz(exp - 1/2) within the 130 mHz frequency band in one dimension. The spacecraft itself is responsible for the dominant differential gravitational field acting on the two TMs. Such a force interaction could contribute a significant amount of noise and thus threaten the achievement of the targeted free-fall level. We prevented this by balancing the gravitational forces to the sub nm s(exp -2) level, guided by a protocol based on measurements of the position and the mass of all parts that constitute the satellite, via finite element calculation tool estimates. In this paper, we will introduce the gravitational balance requirements and design, and then discuss our predictions for the balance that will be achieved in flight.

19 citations

Journal ArticleDOI
James Ira Thorpe1, Jacob Slutsky1, John G. Baker1, Tyson Littenberg2, Sophie Hourihane3, Sophie Hourihane2, Sophie Hourihane1, Nicole Pagane1, Nicole Pagane4, Petr Pokorny5, Petr Pokorny1, Diego Janches1, Michele Armano6, Heather Audley7, G. Auger8, J. Baird9, Massimo Bassan10, Pierre Binétruy8, M. Born7, Daniele Bortoluzzi11, N. Brandt12, M. Caleno6, Antonella Cavalleri11, A. Cesarini11, A. M. Cruise13, Karsten Danzmann7, M. de Deus Silva6, R. De Rosa, L. Di Fiore14, Ingo Diepholz7, G. Dixon13, Rita Dolesi11, N. Dunbar12, Luigi Ferraioli15, Valerio Ferroni11, E. D. Fitzsimons16, R. Flatscher12, M. Freschi6, C. García Marirrodriga6, R. Gerndt12, Lluis Gesa17, Ferran Gibert11, Domenico Giardini15, R. Giusteri11, Aniello Grado18, Catia Grimani19, J. Grzymisch6, I. Harrison20, Gerhard Heinzel7, M. Hewitson7, Daniel Hollington9, D. Hoyland13, Mauro Hueller11, Henri Inchauspe8, Oliver Jennrich6, Ph. Jetzer21, B. Johlander6, Nikolaos Karnesis7, B. Kaune7, N. Korsakova7, Christian J. Killow22, J. A. Lobo17, Ivan Lloro17, L. Liu11, J. P. López-Zaragoza17, R. Maarschalkerweerd20, Davor Mance15, V. Martín17, L. Martin-Polo6, J. Martino8, F. Martin-Porqueras6, S. Madden6, Ignacio Mateos17, Paul McNamara6, José F. F. Mendes20, L. Mendes6, Miquel Nofrarías17, S. Paczkowski7, Michael Perreur-Lloyd22, Antoine Petiteau8, P. Pivato11, Eric Plagnol8, P. Prat8, U. Ragnit6, Juan Ramos-Castro23, J. Reiche7, D. I. Robertson22, H. Rozemeijer6, F. Rivas17, G. Russano11, P. Sarra, A. Schleicher12, D. Shaul9, Carlos F. Sopuerta17, Ruggero Stanga24, T. J. Sumner9, D. Texier6, C. Trenkel12, Michael Tröbs7, Daniele Vetrugno11, S. Vitale11, Gudrun Wanner7, H. Ward22, Peter Wass9, D. Wealthy12, W. J. Weber11, L. Wissel7, A. Wittchen7, A. Zambotti11, C. Zanoni11, Tobias Ziegler12, Peter Zweifel15, St Drs Operations Team, P. Barela25, Curt Cutler25, Nate Demmons, C. Dunn25, M. Girard25, O. Hsu1, S. Javidnia25, I. Li25, P. Maghami1, C. Marrese-Reading25, J. Mehta25, J. O’Donnell, Andrew Romero-Wolf25, John Ziemer25 
TL;DR: In this article, a new set of data obtained from direct measurements of momentum transfer to a spacecraft from individual particle impacts is presented, which can be used to detect impacts and measure properties such as the transferred momentum, direction of travel, and location of impact on the spacecraft.
Abstract: The zodiacal dust complex, a population of dust and small particles that pervades the solar system, provides important insight into the formation and dynamics of planets, comets, asteroids, and other bodies. We present a new set of data obtained from direct measurements of momentum transfer to a spacecraft from individual particle impacts. This technique is made possible by the extreme precision of the instruments flown on the LISA Pathfinder spacecraft, a technology demonstrator for a future space-based gravitational wave observatory. Pathfinder employed a technique known as drag-free control that achieved rejection of external disturbances, including particle impacts, using a micropropulsion system. Using a simple model of the impacts and knowledge of the control system, we show that it is possible to detect impacts and measure properties such as the transferred momentum, direction of travel, and location of impact on the spacecraft. In this paper, we present the results of a systematic search for impacts during 4348 hr of Pathfinder data. We report a total of 54 candidates with transferred momenta ranging from 0.2 to 230 μNs. We furthermore make a comparison of these candidates with models of micrometeoroid populations in the inner solar system, including those resulting from Jupiter-family comets (JFCs), Oort Cloud comets, Halley-type comets, and asteroids. We find that our measured population is consistent with a population dominated by JFCs, with some evidence for a smaller contribution from Halley-type comets, in agreement with consensus models of the zodiacal dust complex in the momentum range sampled by LISA Pathfinder.

14 citations

Journal ArticleDOI
01 Apr 2015
TL;DR: In this paper, the authors report on how these kind of thermal diagnostics experiments were simulated in the last LPF Simulation Campaign (November, 2013) involving all the LPF Data Analysis team and using an end-to-end simulator of the whole spacecraft.
Abstract: Thermal Diagnostics experiments to be carried out on board LISA Pathfinder (LPF) will yield a detailed characterisation of how temperature fluctuations affect the LTP (LISA Technology Package) instrument performance, a crucial information for future space based gravitational wave detectors as the proposed eLISA. Amongst them, the study of temperature gradient fluctuations around the test masses of the Inertial Sensors will provide as well information regarding the contribution of the Brownian noise, which is expected to limit the LTP sensitivity at frequencies close to 1 mHz during some LTP experiments. In this paper we report on how these kind of Thermal Diagnostics experiments were simulated in the last LPF Simulation Campaign (November, 2013) involving all the LPF Data Analysis team and using an end-to-end simulator of the whole spacecraft. Such simulation campaign was conducted under the framework of the preparation for LPF operations.

7 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the authors review early universe sources that can lead to cosmological backgrounds of GWs and discuss the basic characteristics of present and future GW detectors, including advanced LIGO, advanced Virgo, the Einstein telescope, KAGRA, and LISA.
Abstract: Gravitational waves (GWs) have a great potential to probe cosmology. We review early universe sources that can lead to cosmological backgrounds of GWs. We begin by presenting proper definitions of GWs in flat space-time and in a cosmological setting (section 2). Following, we discuss the reasons why early universe GW backgrounds are of a stochastic nature, and describe the general properties of a stochastic background (section 3). We recap current observational constraints on stochastic backgrounds, and discuss the basic characteristics of present and future GW detectors, including advanced LIGO, advanced Virgo, the Einstein telescope, KAGRA, and LISA (section 4). We then review in detail early universe GW generation mechanisms, as well as the properties of the GW backgrounds they give rise to. We classify the backgrounds in five categories: GWs from quantum vacuum fluctuations during standard slow-roll inflation (section 5), GWs from processes that operate within extensions of the standard inflationary paradigm (section 6), GWs from post-inflationary preheating and related non-perturbative phenomena (section 7), GWs from first order phase transitions related or not to the electroweak symmetry breaking (section 8), and GWs from general topological defects, and from cosmic strings in particular (section 9). The phenomenology of these early universe processes is extremely rich, and some of the GW backgrounds they generate can be within the reach of near-future GW detectors. A future detection of any of these backgrounds will provide crucial information on the underlying high energy theory describing the early universe, probing energy scales well beyond the reach of particle accelerators.

643 citations

Journal ArticleDOI
TL;DR: In this paper, the LISA space-based interferometer was used to detect the stochastic gravitational wave background produced from different mechanisms during inflation, focusing on well-motivated scenarios.
Abstract: We investigate the potential for the LISA space-based interferometer to detect the stochastic gravitational wave background produced from different mechanisms during inflation. Focusing on well-motivated scenarios, we study the resulting contributions from particle production during inflation, inflationary spectator fields with varying speed of sound, effective field theories of inflation with specific patterns of symmetry breaking and models leading to the formation of primordial black holes. The projected sensitivities of LISA are used in a model-independent way for various detector designs and configurations. We demonstrate that LISA is able to probe these well-motivated inflationary scenarios beyond the irreducible vacuum tensor modes expected from any inflationary background.

418 citations

Journal ArticleDOI
TL;DR: The MICROSCOPE satellite aims to test its validity at the 10^{-15} precision level, by measuring the force required to maintain two test masses exactly in the same orbit, by characterizing the relative difference in their free-fall accelerations.
Abstract: According to the weak equivalence principle, all bodies should fall at the same rate in a gravitational field. The MICROSCOPE satellite, launched in April 2016, aims to test its validity at the 10−15 precision level, by measuring the force required to maintain two test masses (of titanium and platinum alloys) exactly in the same orbit. A nonvanishing result would correspond to a violation of the equivalence principle, or to the discovery of a new long-range force. Analysis of the first data gives δ(Ti; Pt)=[-1+/-9(stat)+/-9(syst)] × 10−15 (1σ statistical uncertainty) for the titanium-platinum Eotvos parameter characterizing the relative difference in their free-fall accelerations.

321 citations

Journal ArticleDOI
TL;DR: The article considers both Bayesian and frequentist searches using ground-based and space-based laser interferometers, spacecraft Doppler tracking, and pulsar timing arrays; and it allows for anisotropy, non-Gaussianity, and non-standard polarization states.
Abstract: We review detection methods that are currently in use or have been proposed to search for a stochastic background of gravitational radiation. We consider both Bayesian and frequentist searches using ground-based and space-based laser interferometers, spacecraft Doppler tracking, and pulsar timing arrays; and we allow for anisotropy, non-Gaussianity, and non-standard polarization states. Our focus is on relevant data analysis issues, and not on the particular astrophysical or early Universe sources that might give rise to such backgrounds. We provide a unified treatment of these searches at the level of detector response functions, detection sensitivity curves, and, more generally, at the level of the likelihood function, since the choice of signal and noise models and prior probability distributions are actually what define the search. Pedagogical examples are given whenever possible to compare and contrast different approaches. We have tried to make the article as self-contained and comprehensive as possible, targeting graduate students and new researchers looking to enter this field.

306 citations

Journal ArticleDOI
TL;DR: In this paper, a space-based gravitational wave (GW) detector consisting of two spatially separated, drag-free satellites sharing ultrastable optical laser light over a single baseline is proposed.
Abstract: We propose a space-based gravitational wave (GW) detector consisting of two spatially separated, drag-free satellites sharing ultrastable optical laser light over a single baseline. Each satellite contains an optical lattice atomic clock, which serves as a sensitive, narrowband detector of the local frequency of the shared laser light. A synchronized two-clock comparison between the satellites will be sensitive to the effective Doppler shifts induced by incident GWs at a level competitive with other proposed space-based GW detectors, while providing complementary features. The detected signal is a differential frequency shift of the shared laser light due to the relative velocity of the satellites, and the detection window can be tuned through the control sequence applied to the atoms' internal states. This scheme enables the detection of GWs from continuous, spectrally narrow sources, such as compact binary inspirals, with frequencies ranging from $\ensuremath{\sim}3\text{ }\text{ }\mathrm{mHz}--10\text{ }\text{ }\mathrm{Hz}$ without loss of sensitivity, thereby bridging the detection gap between space-based and terrestrial optical interferometric GW detectors. Our proposed GW detector employs just two satellites, is compatible with integration with an optical interferometric detector, and requires only realistic improvements to existing ground-based clock and laser technologies.

301 citations