Will be available with at least 20% of his time to support the study activities throughout the st... more Will be available with at least 20% of his time to support the study activities throughout the study.
ABSTRACT We investigated the cathode region of free-burning argon arcs at atmospheric pressure an... more ABSTRACT We investigated the cathode region of free-burning argon arcs at atmospheric pressure and at currents from 0.3 A up to 25 A. Apart from the well known diffuse mode of operation we also found a more constricted form which we call the blue-core mode. Different diagnostic methods are simultaneously applied to these modes of operation, that is: emission spectroscopy in conjunction with a partial LTE model for the density and temperature measurements; Thomson scattering for the electron temperature and electron density determination; and Rayleigh scattering for a determination of the gas temperature. The large differences in appearance, densities, temperatures or current formation between the discharge modes are well defined by the measurements.
An elegant breadboard model of the LISA phasemeter is currently under development by a Danish-Ger... more An elegant breadboard model of the LISA phasemeter is currently under development by a Danish-German consortium. The breadboard is build in the frame of an ESA technology development activity to demonstrate the feasibility and readiness of the LISA metrology baseline architecture. This article gives an overview about the breadboard design and its components, including the distribution of key functionalities.
The Laser Ranging Interferometer (LRI) instrument on the Gravity Recovery and Climate Experiment ... more The Laser Ranging Interferometer (LRI) instrument on the Gravity Recovery and Climate Experiment (GRACE) Follow-On mission has provided the first laser interferometric range measurements between remote spacecraft, separated by approximately 220 km. Autonomous controls that lock the laser frequency to a cavity reference and establish the 5 degree of freedom two-way laser link between remote spacecraft succeeded on the first attempt. Active beam pointing based on differential wavefront sensing compensates spacecraft attitude fluctuations. The LRI has operated continuously without breaks in phase tracking for more than 50 days, and has shown biased range measurements similar to the primary ranging instrument based on microwaves, but with much less noise at a level of 1 nm/√( Hz) at Fourier frequencies above 100 mHz.
Will be available with at least 20% of his time to support the study activities throughout the st... more Will be available with at least 20% of his time to support the study activities throughout the study.
An elegant breadboard model of the LISA phasemeter is currently under development by a Danish-Ger... more An elegant breadboard model of the LISA phasemeter is currently under development by a Danish-German consortium. The breadboard is build in the frame of an ESA technology development activity to demonstrate the feasibility and readiness of the LISA metrology baseline architecture. This article gives an overview about the breadboard design and its components, including the distribution of key functionalities.
The LISA mission has been studied in great detail in Europe and the US for more than two decades ... more The LISA mission has been studied in great detail in Europe and the US for more than two decades in order to observe the Gravitational Universe at low frequencies. Following the selection of the LISA proposal by ESA in June 2017, and the successful in-flight technology demonstration of LISA Pathfinder, the LISA mission is currently in the first planning stages. This contribution presents an overview of the design for the Phase Metrology System (PMS), with special focus on instrument and performance testing. References [1] K. Danzmann et al., Response to ESA L3 mission call (2017)
Following the selection of The Gravitational Universe by ESA, and the successful flight of LISA P... more Following the selection of The Gravitational Universe by ESA, and the successful flight of LISA Pathfinder, the LISA Consortium now proposes a 4 year mission in response to ESA's call for missions for L3. The observatory will be based on three arms with six active laser links, between three identical spacecraft in a triangular formation separated by 2.5 million km. LISA is an all-sky monitor and will offer a wide view of a dynamic cosmos using Gravitational Waves as new and unique messengers to unveil The Gravitational Universe. It provides the closest ever view of the infant Universe at TeV energy scales, has known sources in the form of verification binaries in the Milky Way, and can probe the entire Universe, from its smallest scales near the horizons of black holes, all the way to cosmological scales. The LISA mission will scan the entire sky as it follows behind the Earth in its orbit, obtaining both polarisations of the Gravitational Waves simultaneously, and will measure ...
During the On-Station Thermal Test campaign of the LISA Pathfinder the Diagnostics Subsystem was ... more During the On-Station Thermal Test campaign of the LISA Pathfinder the Diagnostics Subsystem was tested in nearly space conditions for the first time after integration in the satellite. The results showed the compliance of the temperature measurement system, obtaining temperature noise around 10 −4 K Hz −1/2 in the frequency band of 1 − 30 mHz. In addition, controlled injection of heat signals to the suspension struts anchoring the LISA Technology Package (LTP) Core Assembly to the satellite structure allowed to experimentally estimate for the first time the phase noise contribution through thermo-elastic distortion of the LTP interferometer, the satellite's main instrument. Such contribution was found to be at 10 −12 m Hz −1/2 , a factor of 30 below the measured noise at the lower end of the measurement bandwidth (1 mHz).
LISA Pathfinder (formerly known as SMART-2) is an ESA mission designed to pave the way for the jo... more LISA Pathfinder (formerly known as SMART-2) is an ESA mission designed to pave the way for the joint ESA/NASA Laser Interferometer Space Antenna (LISA) mission by testing in flight the critical technologies required for space-borne gravitational wave detection; it will put two test masses in a near-perfect gravitational free-fall and control and measure their motion with unprecedented accuracy. This is
LISA is a proposed space-based laser interferometer detecting gravitational waves by measuring di... more LISA is a proposed space-based laser interferometer detecting gravitational waves by measuring distances between free-floating test masses housed in three satellites in a triangular constellation with laser links in-between. Each satellite contains two optical benches that are articulated by moving optical subassemblies for compensating the breathing angle in the constellation. The phase reference distribution system, also known as backlink, forms an optical bi-directional path between the intra-satellite benches. In this work we discuss phase reference implementations with a target non-reciprocity of at most 2π μrad √ Hz −1 , equivalent to 1 pm √ Hz −1 for a wavelength of 1064 nm in the frequency band from 0.1 mHz to 1 Hz. One phase reference uses a steered free beam connection, the other one a fiber together with additional laser frequencies. The noise characteristics of these implementations will be compared in a single interferometric setup with a Original 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.
Will be available with at least 20% of his time to support the study activities throughout the st... more Will be available with at least 20% of his time to support the study activities throughout the study.
ABSTRACT We investigated the cathode region of free-burning argon arcs at atmospheric pressure an... more ABSTRACT We investigated the cathode region of free-burning argon arcs at atmospheric pressure and at currents from 0.3 A up to 25 A. Apart from the well known diffuse mode of operation we also found a more constricted form which we call the blue-core mode. Different diagnostic methods are simultaneously applied to these modes of operation, that is: emission spectroscopy in conjunction with a partial LTE model for the density and temperature measurements; Thomson scattering for the electron temperature and electron density determination; and Rayleigh scattering for a determination of the gas temperature. The large differences in appearance, densities, temperatures or current formation between the discharge modes are well defined by the measurements.
An elegant breadboard model of the LISA phasemeter is currently under development by a Danish-Ger... more An elegant breadboard model of the LISA phasemeter is currently under development by a Danish-German consortium. The breadboard is build in the frame of an ESA technology development activity to demonstrate the feasibility and readiness of the LISA metrology baseline architecture. This article gives an overview about the breadboard design and its components, including the distribution of key functionalities.
The Laser Ranging Interferometer (LRI) instrument on the Gravity Recovery and Climate Experiment ... more The Laser Ranging Interferometer (LRI) instrument on the Gravity Recovery and Climate Experiment (GRACE) Follow-On mission has provided the first laser interferometric range measurements between remote spacecraft, separated by approximately 220 km. Autonomous controls that lock the laser frequency to a cavity reference and establish the 5 degree of freedom two-way laser link between remote spacecraft succeeded on the first attempt. Active beam pointing based on differential wavefront sensing compensates spacecraft attitude fluctuations. The LRI has operated continuously without breaks in phase tracking for more than 50 days, and has shown biased range measurements similar to the primary ranging instrument based on microwaves, but with much less noise at a level of 1 nm/√( Hz) at Fourier frequencies above 100 mHz.
Will be available with at least 20% of his time to support the study activities throughout the st... more Will be available with at least 20% of his time to support the study activities throughout the study.
An elegant breadboard model of the LISA phasemeter is currently under development by a Danish-Ger... more An elegant breadboard model of the LISA phasemeter is currently under development by a Danish-German consortium. The breadboard is build in the frame of an ESA technology development activity to demonstrate the feasibility and readiness of the LISA metrology baseline architecture. This article gives an overview about the breadboard design and its components, including the distribution of key functionalities.
The LISA mission has been studied in great detail in Europe and the US for more than two decades ... more The LISA mission has been studied in great detail in Europe and the US for more than two decades in order to observe the Gravitational Universe at low frequencies. Following the selection of the LISA proposal by ESA in June 2017, and the successful in-flight technology demonstration of LISA Pathfinder, the LISA mission is currently in the first planning stages. This contribution presents an overview of the design for the Phase Metrology System (PMS), with special focus on instrument and performance testing. References [1] K. Danzmann et al., Response to ESA L3 mission call (2017)
Following the selection of The Gravitational Universe by ESA, and the successful flight of LISA P... more Following the selection of The Gravitational Universe by ESA, and the successful flight of LISA Pathfinder, the LISA Consortium now proposes a 4 year mission in response to ESA's call for missions for L3. The observatory will be based on three arms with six active laser links, between three identical spacecraft in a triangular formation separated by 2.5 million km. LISA is an all-sky monitor and will offer a wide view of a dynamic cosmos using Gravitational Waves as new and unique messengers to unveil The Gravitational Universe. It provides the closest ever view of the infant Universe at TeV energy scales, has known sources in the form of verification binaries in the Milky Way, and can probe the entire Universe, from its smallest scales near the horizons of black holes, all the way to cosmological scales. The LISA mission will scan the entire sky as it follows behind the Earth in its orbit, obtaining both polarisations of the Gravitational Waves simultaneously, and will measure ...
During the On-Station Thermal Test campaign of the LISA Pathfinder the Diagnostics Subsystem was ... more During the On-Station Thermal Test campaign of the LISA Pathfinder the Diagnostics Subsystem was tested in nearly space conditions for the first time after integration in the satellite. The results showed the compliance of the temperature measurement system, obtaining temperature noise around 10 −4 K Hz −1/2 in the frequency band of 1 − 30 mHz. In addition, controlled injection of heat signals to the suspension struts anchoring the LISA Technology Package (LTP) Core Assembly to the satellite structure allowed to experimentally estimate for the first time the phase noise contribution through thermo-elastic distortion of the LTP interferometer, the satellite's main instrument. Such contribution was found to be at 10 −12 m Hz −1/2 , a factor of 30 below the measured noise at the lower end of the measurement bandwidth (1 mHz).
LISA Pathfinder (formerly known as SMART-2) is an ESA mission designed to pave the way for the jo... more LISA Pathfinder (formerly known as SMART-2) is an ESA mission designed to pave the way for the joint ESA/NASA Laser Interferometer Space Antenna (LISA) mission by testing in flight the critical technologies required for space-borne gravitational wave detection; it will put two test masses in a near-perfect gravitational free-fall and control and measure their motion with unprecedented accuracy. This is
LISA is a proposed space-based laser interferometer detecting gravitational waves by measuring di... more LISA is a proposed space-based laser interferometer detecting gravitational waves by measuring distances between free-floating test masses housed in three satellites in a triangular constellation with laser links in-between. Each satellite contains two optical benches that are articulated by moving optical subassemblies for compensating the breathing angle in the constellation. The phase reference distribution system, also known as backlink, forms an optical bi-directional path between the intra-satellite benches. In this work we discuss phase reference implementations with a target non-reciprocity of at most 2π μrad √ Hz −1 , equivalent to 1 pm √ Hz −1 for a wavelength of 1064 nm in the frequency band from 0.1 mHz to 1 Hz. One phase reference uses a steered free beam connection, the other one a fiber together with additional laser frequencies. The noise characteristics of these implementations will be compared in a single interferometric setup with a Original 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.
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