Papers by Oliver Jennrich
Strahlungsdruckrauschen, thermisches Rauschen, Standard Quanten Limit der Interferometrie In mode... more Strahlungsdruckrauschen, thermisches Rauschen, Standard Quanten Limit der Interferometrie In modernen Experimenten zum interferometrischen Nachweis von Gravitationswellen ist die Frage nach den grundlegenden Grenzen einer interferometrischen Längenbestimmung von sehr großer Bedeutung. Die Ursache dieser Begrenzung ist zum einen das thermische Rauschen der optischen Komponenten im Interferometer, welches für den Fall sehr kleiner Temperaturen gegen das durch die HEISENBERGsche Unschärferelation gegebene Quantenrauschen geht. Eine weitere Grenze wird durch die Effekte der Photonenstatistik gegeben. Diese erzeugt einerseits durch das Rauschen des Nachweisprozesses eine scheinbare Längenänderung des Interferometers, andererseits überträgt sich die Photonenstatistik des Lichts durch den Impulsübertrag auf das Positionsrauschen der Spiegel. Da diese beiden Rauschprozesse in verschiedener Art von der Lichtleistung im Interferometer abhängen, existiert eine optimale Leistung für den Betrieb eines Interferometers. Dabei muß die Korrelation der beiden Rauschprozesse, die durch die Bewegung des Spiegels hervorgerufen wird, berücksichtigt werden. Zur theoretischen Betrachtung des Problems wurde eine alternative Formulierung des Standard Quanten Limits verwendet, die es erlaubt, die Orts-und Impulsunschärfen der optischen Komponenten spektral aufgelöst darzustellen. Im experimentellen Teil dieser Arbeit wurde ein Experiment zur Untersuchung des Strahlungsdruckrauschens und des thermischen Rauschens konzipiert und aufgebaut. Zentraler Bestandteil des Experimentes ist ein FABRY-PEROT-Resonator hoher Finesse, der aus zwei monolithisch aufgehängten Spiegeln besteht. Zur seismischen Isolation sind die Spiegel an einem System von Mehrfachpendeln und seismischen Vorisolatoren befestigt. Der Nachweis der Längenänderung des Resonators erfolgte über das POUND-DREVER-HALL-Verfahren. MIt Hilfe eines Simulationsprogrammes wurden die Parameter des Resonators, der Spiegel und der Aufhängung bezüglich der Empfindlichkeit des Experimentes auf Strahi
Classical and Quantum Gravity, 2012
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licenc... more Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Classical and Quantum Gravity, 2003
The interferometer of the LISA technology package (LTP) on SMART-2 is needed to verify the perfor... more The interferometer of the LISA technology package (LTP) on SMART-2 is needed to verify the performance of the gravitational sensors by monitoring the distance between two test masses with a noise level of 10 pm Hz −1/2 between 3 mHz and 30 mHz. It must continuously track the motion of the test mass distance while that distance changes by many µm with a speed of up to 20 µm s −1 , without losing track of the sign of the motion and without exerting any influence on the test masses that might lead to a motion above that level. As a result of a detailed comparison study, a heterodyne Mach-Zehnder interferometer was selected as the baseline for the SMART-2 mission. Its design and expected performance are described in this paper.
Classical and Quantum Gravity, 2011
Preparations for the LISA Pathfinder mission have reached an exciting stage. Tests of the enginee... more Preparations for the LISA Pathfinder mission have reached an exciting stage. Tests of the engineering model (EM) of the optical metrology system (OMS) have recently been completed at the Albert Einstein Institute, Hannover, and flight model (FM) tests are now underway. Significantly, they represent the first complete integration and testing of the space-qualified hardware and are the first tests on an optical system level. The results and test procedures of these campaigns will be utilised directly in the ground-based flight hardware tests, and subsequently during in-flight operations. In addition, they allow valuable testing of the data analysis methods using the MATLAB based LTP data analysis (LTPDA) toolbox. This paper presents an overview of the results from the EM test campaign that was successfully completed in December 2009.
Classical and Quantum Gravity, 2008
In the framework of the expected association between gamma-ray bursts and gravitational waves, we... more In the framework of the expected association between gamma-ray bursts and gravitational waves, we present results of an analysis aimed to search for a burst of gravitational waves in coincidence with gamma-ray burst 050915a. This was a long duration gamma-ray burst detected by Swift during September 2005, when the Virgo gravitational wave detector was engaged in a commissioning run during which the best sensitivity attained in 2005 was exhibited. This offered the opportunity for Virgo's first search for a gravitational wave signal in coincidence with a gamma-ray burst. The result of our study is a set of strain amplitude upper limits, based on the loudest event approach, for different but quite general types of burst signal waveforms. The best upper limit strain amplitudes we obtain are h rss = O(10 −20) Hz −1/2 around ∼200-1500 Hz. These upper limits allow us to evaluate the level up to which Virgo, when reaching nominal sensitivity, will be able to constrain the gravitational wave output associated with a long burst. Moreover, the analysis presented here plays the role of a prototype, crucial in defining a methodology for gamma-ray burst triggered searches with Virgo and opening the way for future joint analyses with LIGO.
Classical and Quantum Gravity, 2009
The data analysis of the LISA Technology Package (LTP) will comprise a series of discrete experim... more The data analysis of the LISA Technology Package (LTP) will comprise a series of discrete experiments, each focusing on a particular noise measurement or characterization of the instrument in various operating modes. Each of these
LISA Pathfinder is a mission planned by the European Space Agency (ESA) to test the key technolog... more LISA Pathfinder is a mission planned by the European Space Agency (ESA) to test the key technologies that will allow the detection of gravitational waves in space. The instrument on-board, the LISA Technology package, will undergo an exhaustive campaign of calibrations and noise characterisation campaigns in order to fully describe the noise model. Data analysis plays an important role in the mission and for that reason the data analysis team has been developing a toolbox which contains all the functionality required during operations. In this contribution we give an overview of recent activities, focusing on the improvements in the modelling of the instrument and in the data analysis campaigns performed both with real and simulated data.
Advances in Space Research, 2003
LISA is a spaceborne laser interferometer for the detection and observation of gravitational wave... more LISA is a spaceborne laser interferometer for the detection and observation of gravitational waves, currently under study by ESA. A brief introduction of the main features of this detector, concentrating on its oneyear orbital motion around the Sun is given. The amplitude as well as the phase of a gravitational wave is modulated due to that motion, allowing us to extract information from the signal. The detection of monochromatic gravitational waves based on the well-known signal detection theory is simulated, focusing on estimating the angular parameters of the source. The results of the semi-analytic calculations give the angular resolution of LISA.
arXiv: Instrumentation and Methods for Astrophysics, Aug 29, 2019
We propose a space-based interferometer surveying the gravitational wave (GW) sky in the milli-Hz... more We propose a space-based interferometer surveying the gravitational wave (GW) sky in the milli-Hz to µ-Hz frequency range. By the 2040s', the µ-Hz frequency band, bracketed in between the Laser Interferometer Space Antenna (LISA) and pulsar timing arrays, will constitute the largest gap in the coverage of the astrophysically relevant GW spectrum. Yet many outstanding questions related to astrophysics and cosmology are best answered by GW observations in this band. We show that a µ-Hz GW detector will be a truly overarching observatory for the scientific community at large, greatly extending the potential of LISA. Conceived to detect massive black hole binaries from their early inspiral with high signal-tonoise ratio, and low-frequency stellar binaries in the Galaxy, this instrument will be a cornerstone for multimessenger astronomy from the solar neighbourhood to the high-redshift Universe.
Experimental Astronomy, 2021
We propose a space-based interferometer surveying the gravitational wave (GW) sky in the milli-Hz... more We propose a space-based interferometer surveying the gravitational wave (GW) sky in the milli-Hz to μ-Hz frequency range. By the 2040s, the μ-Hz frequency band, bracketed in between the Laser Interferometer Space Antenna (LISA) and pulsar timing arrays, will constitute the largest gap in the coverage of the astrophysically relevant GW spectrum. Yet many outstanding questions related to astrophysics and cosmology are best answered by GW observations in this band. We show that a μ-Hz GW detector will be a truly overarching observatory for the scientific community at large, greatly extending the potential of LISA. Conceived to detect massive black hole binaries from their early inspiral with high signal-to-noise ratio, and low-frequency stellar binaries in the Galaxy, this instrument will be a cornerstone for multimessenger astronomy from the solar neighbourhood to the high-redshift Universe.
Review of Scientific Instruments, 2020
Analysis of the accuracy of actuation electronics in the laser interferometer space antenna pathf... more Analysis of the accuracy of actuation electronics in the laser interferometer space antenna pathfinder. Review of Scientific Instruments, 91(4), 045003. There may be differences between this version and the published version. You are advised to consult the publisher's version if you wish to cite from it.
The Astrophysical Journal, 2019
The zodiacal dust complex, a population of dust and small particles that pervades the solar syste... more 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
Physical Review D, 2018
LISA Pathfinder (LPF) was a European Space Agency mission with the aim to test key technologies f... more LISA Pathfinder (LPF) was a European Space Agency mission with the aim to test key technologies for future space-borne gravitational-wave observatories like LISA. The main scientific goal of LPF was to demonstrate measurements of differential acceleration between free-falling test masses at the sub-femto-g level, and to understand the residual acceleration in terms of a physical model of stray forces, and displacement readout noise. A key step towards reaching the LPF goals was the correct calibration of the dynamics of LPF, which was a three-body system composed by two testmasses enclosed in a single spacecraft, and subject to control laws for system stability. In this work, we report on the calibration procedures adopted to calculate the residual differential stray force per unit mass acting on the two test-masses in their nominal positions. The physical parameters of the adopted dynamical model are presented, together with their role on LPF performance. The analysis and results of these experiments show that the dynamics of the system was accurately modeled and the dynamical parameters were stationary throughout the mission. Finally, the impact and importance of calibrating system dynamics for future space-based gravitational wave observatories is discussed.
Physical Review D, 2019
The LISA Pathfinder mission has demonstrated the ability to limit and measure the fluctuations in... more The LISA Pathfinder mission has demonstrated the ability to limit and measure the fluctuations in acceleration between two free falling test masses down to sub-femto-g levels. One of the key elements to achieve such a level of residual acceleration is the drag free control. In this scheme the spacecraft is used as a shield against any external disturbances by adjusting its relative position to a reference test mass. The actuators used to move the spacecraft are cold gas micro-propulsion thrusters. In this paper, we report in-flight characterisation of these thrusters in term of noise and artefacts during science operations using all the metrology capabilities of LISA Pathfinder. Using the LISA Pathfinder test masses as an inertial reference frame, an average thruster noise of ∼ 0.17µN/ √ Hz is observed and decomposed into a common (coherent) and an uncorrelated component. The very low noise and stability of the onboard metrology system associated with the quietness of the space environment allowed the measurement of the thruster noise down to ∼ 20 µHz, more than an order of magnitude below any ground measurement. Spectral lines were observed around ∼ 1.5 mHz and its harmonics and around 55 and 70 mHz. They are associated with the cold gas system itself and possibly to a clock synchronisation issue. The thruster noise-floor exhibits an excess of ∼ 70% compared to characterisation that have been made on ground on a single unit and without the feeding system. However this small excess has no impact on the LPF mission performance and is compatible with the noise budget for the upcoming LISA gravitational wave observatory. Over the whole mission, nominal and extension, the thrusters showed remarkable stability for both the science operations and the different manoeuvres necessary to maintain LPF on its orbit around L1. It is therefore concluded that a similar cold gas system would be a viable propulsion system for the future LISA mission.
The Astrophysical Journal, 2018
Galactic cosmic-ray (GCR) energy spectra observed in the inner heliosphere are modulated by the s... more Galactic cosmic-ray (GCR) energy spectra observed in the inner heliosphere are modulated by the solar activity, the solar polarity and structures of solar and interplanetary origin. A high counting rate particle detector (PD) aboard LISA Pathfinder, meant for subsystems diagnostics, was devoted to the measurement of GCR and solar energetic particle integral fluxes above 70 MeV n −1 up to 6500 counts s −1. PD data were gathered with a sampling time of 15 s. Characteristics and energy dependence of GCR flux recurrent depressions and of a Forbush decrease dated 2016 August 2 are reported here. The capability of interplanetary missions, carrying PDs for instrument performance purposes, in monitoring the passage of interplanetary coronal mass ejections is also discussed.
Astroparticle Physics, 2018
Test mass charging caused by cosmic rays will be a significant source of acceleration noise for s... more Test mass charging caused by cosmic rays will be a significant source of acceleration noise for spacebased gravitational wave detectors like LISA. Operating between December 2015 and July 2017, the technology demonstration mission LISA Pathfinder included a bespoke monitor to help characterise the relationship between test mass charging and the local radiation environment. The radiation monitor made in situ measurements of the cosmic ray flux while also providing information about its energy spectrum. We describe the monitor and present measurements which show a gradual 40% increase in count rate coinciding with the declining phase of the solar cycle. Modulations of up to 10% were also observed with periods of 13 and 26 days that are associated with co-rotating interaction regions and heliospheric current sheet crossings. These variations in the flux above the monitor detection threshold (≈ 70 MeV) are shown to be coherent with measurements made by the IREM monitor on-board the Earth orbiting INTEGRAL spacecraft. Finally we use the measured deposited energy spectra, in combination with a GEANT4 model, to estimate the galactic cosmic ray differential energy spectrum over the course of the mission.
Journal of Physics: Conference Series, 2015
The cold gas micro-propulsion system that will be used during the LISA-Pathfinder mission will be... more The cold gas micro-propulsion system that will be used during the LISA-Pathfinder mission will be one of the most important component used to ensure the “free-fall” of the enclosed test masses. In this paper we present a possible strategy to characterize the effective direction and amplitude gain of each of the 6 thrusters of this system. A post-publication change was made to this article on 26 Jun 2020 to add an author.
Classical and Quantum Gravity, 2006
The LISA Technology Package uses a heterodyne Mach-Zehnder interferometer to monitor the relative... more The LISA Technology Package uses a heterodyne Mach-Zehnder interferometer to monitor the relative motion of the test masses with picometer accuracy. This paper discusses two classes of noise sources that were identified and investigated during the prototype experiments. Most troublesome are electrically induced sidebands on the light, which give rise to nonlinearities in the interferometer output. Even worse, if the differential pathlength between two optical fibres fluctuates, a noise term of milliradian amplitude appears and completely spoils the performance. We discuss the origin and mitigation of this process. Dissimilar beam shapes of the interfering beams produce another type of noise in conjunction with beam jitter and spatially inhomogeneous photodetectors. To study and minimize this effect, we have built a real-time high-resolution phasefront imaging system that will be used for the production of the flight model.
Classical and Quantum Gravity, 2011
This paper presents a quantitative assessment of the performance of the upcoming LISA Pathfinder ... more This paper presents a quantitative assessment of the performance of the upcoming LISA Pathfinder geodesic explorer mission. The findings are based on the results of extensive ground testing and simulation campaigns using flight hardware and flight control and operations algorithms. The results show that, for the central experiment of measuring the stray differential acceleration between the LISA test masses, LISA Pathfinder will be able to verify the overall acceleration noise to within a factor two of the LISA requirement at 1 mHz and within a factor 10 at 0.1 mHz. We also discuss the key elements of the physical model of disturbances, coming from LISA Pathfinder and ground measurement, that will guarantee the LISA performance.
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Papers by Oliver Jennrich