In this paper we describe the architecture and the performances of a hybrid modular acquisition and control system prototype developed for the implementation of distributed monitoring and control ...systems. The system, an alternative to the VME-UDP/IP based system, is based on a dual-channel 18-bit low noise ADC and 16-bit DAC module at 800 kHz, managed by an ALTERA FPGA. Experimental tests have demonstrated that this architecture allows the implementation of distributed control systems with delay time t < 30μs, on single channel, using a standard laptop PC for the real-time computation. The system was used for the longitudinal control of the end mirror of a suspended Michelson Interferometer, performed through an electrostatic actuators, giving effective performances. The preliminary results are also reported.
We perform a statistical standard siren analysis of GW170817. Our analysis does not utilize knowledge of NGC 4993 as the unique host galaxy of the optical counterpart to GW170817. Instead, we ...consider each galaxy within the GW170817 localization region as a potential host; combining the redshift from each galaxy with the distance estimate from GW170817 provides an estimate of the Hubble constant, \(H_0\). We then combine the \(H_0\) values from all the galaxies to provide a final measurement of \(H_0\). We explore the dependence of our results on the thresholds by which galaxies are included in our sample, as well as the impact of weighting the galaxies by stellar mass and star-formation rate. Considering all galaxies brighter than \(0.01 L^\star_B\) as equally likely to host a BNS merger, we find \(H_0= 76^{+48}_{-23}\) km s\(^{-1}\) Mpc\(^{-1}\) (maximum a posteriori and 68.3% highest density posterior interval; assuming a flat \(H_0\) prior in the range \(\left 10, 220 \right\) km s\(^{-1}\) Mpc\(^{-1}\)). Restricting only to galaxies brighter than \(0.626 L^\star_B\) tightens the measurement to \(H_0= 77^{+37}_{-18}\) km s\(^{-1}\) Mpc\(^{-1}\). We show that weighting the host galaxies by stellar mass or star-formation rate provides entirely consistent results with potentially tighter constraints. While these statistical estimates are inferior to the value from the counterpart standard siren measurement utilizing NGC 4993 as the unique host, \(H_0=76^{+19}_{-13}\) km s\(^{-1}\) Mpc\(^{-1}\) (determined from the same publicly available data), our analysis is a proof-of-principle demonstration of the statistical approach first proposed by Bernard Schutz over 30 years ago.
In August 2017, Advanced Virgo joined Advanced LIGO for the end of the O2 run, leading to the first gravitational waves detections with the three-detector network. This paper describes the Advanced ...Virgo calibration and the gravitational wave strain h(t) reconstruction during O2. The methods are the same as the ones developed for the initial Virgo detector and have already been described in previous publications, this paper summarizes the differences and emphasis is put on estimating systematic uncertainties. Three versions of the h(t) signal have been computed for the Virgo O2 run, an online version and two post-run reprocessed versions with improved detector calibration and reconstruction algorithm. A photon calibrator has been used to establish the sign of h(t) and to make an independent partial cross-check of the systematic uncertainties. The uncertainties reached for the latest h(t) version are 5.1% in amplitude, 40 mrad in phase and 20 microseconds in timing.
The upcoming European design study `Einstein gravitational-wave Telescope' represents the first step towards a substantial, international effort for the design of a third-generation interferometric ...gravitational wave detector. It is generally believed that third-generation instruments might not be installed into existing infrastructures but will provoke a new search for optimal detector sites. Consequently, the detector design could be subject to fewer constraints than the on-going design of the second generation instruments. In particular, it will be prudent to investigate alternatives to the traditional L-shaped Michelson interferometer. In this article, we review an old proposal to use three Michelson interferometers in a triangular configuration. We use this example of a triple Michelson interferometer to clarify the terminology and will put this idea into the context of more recent research on interferometer technologies. Furthermore the benefits of a triangular detector will be used to motivate this design as a good starting point for a more detailed research effort towards a third-generation gravitational wave detector.
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 6 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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