Calibrating and improving the sensitivity of the LIGO detectors

The Laser Interferometer Gravitational wave Observatory (LIGO) is network of three, power recycled Fabry-Perot Michelson interferometers built to detect gravitational waves from astrophysical sources at frequencies between 40 and 6000 Hz. For their fifth science run, from 2005 to 2007, the detectors observed at designed sensitivity, achieving equivalent strain amplitude noise of 3x10^−23 strain/rtHz at 100 Hz. To date, the observatory has not detected gravitational waves. However, even at such sensitivity, the expected detection rate for known astrophysical sources of gravitational waves is likely 0.02 yr^−1. The fundamental noise source of these ground-based detectors limiting the sensitivity below 40 Hz is seismic motion. They use multi-stage passive isolation platforms from which their test masses are suspended from piano wire as single pendula providing isolation from ground motion. The residual test mass motion is controlled by electromagnetic actuators on the suspension system in response to the output of the interferometers, keeping them at their operating point. In the first portion of this thesis, I discuss the absolute calibration of the first generation of LIGO interferometer\u27s gravitational wave readout during their fifth science run, the uncertainty of which is limited by the precision to which we can measure the control system above residual seismic noise. A second generation of detectors, called Advanced LIGO, is currently under construction which will completely replace the first generation. Scheduled to become operational in 2014, they are predicted to improve the sensitivity by ten-fold or more, and will likely improve the detection rate to as much as 40 yr^−1. To achieve this sensitivity at the lower limit of the band, the test masses will be suspended from from multiple cascading pendula. In addition, the multi-stage passive isolation platforms will be replaced with single- and double-stage suspended platforms with built-in active feedback control systems. Prototypes of single-stage active control systems have been in use for two years for a non-invasive upgrade of the LIGO interferometers. In the second portion of this thesis, I present results from these prototypes and demonstrate that their performance can meet the stringent requirement of the second generation of interferometers

Machine-learning nonstationary noise out of gravitational-wave detectors

Signal extraction out of background noise is a common challenge in high-precision physics experiments, where the measurement output is often a continuous data stream. To improve the signal-to-noise ratio of the detection, witness sensors are often used to independently measure background noises and subtract them from the main signal. If the noise coupling is linear and stationary, optimal techniques already exist and are routinely implemented in many experiments. However, when the noise coupling is nonstationary, linear techniques often fail or are suboptimal. Inspired by the properties of the background noise in gravitational wave detectors, this work develops a novel algorithm to efficiently characterize and remove nonstationary noise couplings, provided there exist witnesses of the noise source and of the modulation. In this work, the algorithm is described in its most general formulation, and its efficiency is demonstrated with examples from the data of the Advanced LIGO gravitational-wave observatory, where we could obtain an improvement of the detector gravitational-wave reach without introducing any bias on the source parameter estimation

Experiential Learning Framework for Smaller Computer Science Programs

Experiential learning (EL) permeates the Computer Science discipline. This work seeks to codify EL practices for computer science pedagogy into ve key pillars. These pillars have been successfully applied at a small to mid-sized college within the heavily competitive Boston area. This paper further describes how a computer science department may eectively implement the pillars in their own curriculum

Improving LIGO calibration accuracy by tracking and compensating for slow temporal variations

Calibration of the second-generation LIGO interferometric gravitational-wave detectors employs a method that uses injected periodic modulations to track and compensate for slow temporal variations in the differential length response of the instruments. These detectors utilize feedback control loops to maintain resonance conditions by suppressing differential arm length variations. We describe how the sensing and actuation functions of these servo loops are parameterized and how the slow variations in these parameters are quantified using the injected modulations. We report the results of applying this method to the LIGO detectors and show that it significantly reduces systematic errors in their calibrated outputs.Comment: 13 pages, 8 figures. This is an author-created, un-copyedited version of an article published in Classical and Quantum Gravity. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from i

A Distribution of Large Particles in the Coma of Comet 103P/Hartley 2

The coma of comet 103P/Hartley 2 has a significant population of large particles observed as point sources in images taken by the Deep Impact spacecraft. We measure their spatial and flux distributions, and attempt to constrain their composition. The flux distribution of these particles implies a very steep size distribution with power-law slopes ranging from -6.6 to -4.7. The radii of the particles extend up to 20 cm, and perhaps up to 2 m, but their exact sizes depend on their unknown light scattering properties. We consider two cases: bright icy material, and dark dusty material. The icy case better describes the particles if water sublimation from the particles causes a significant rocket force, which we propose as the best method to account for the observed spatial distribution. Solar radiation is a plausible alternative, but only if the particles are very low density aggregates. If we treat the particles as mini-nuclei, we estimate they account for <16-80% of the comet's total water production rate (within 20.6 km). Dark dusty particles, however, are not favored based on mass arguments. The water production rate from bright icy particles is constrained with an upper limit of 0.1 to 0.5% of the total water production rate of the comet. If indeed icy with a high albedo, these particles do not appear to account for the comet's large water production rate. production rate. Erratum: We have corrected the radii and masses of the large particles of comet 103P/Hartley 2 and present revised conclusions in the attached erratum.Comment: Original article: 46 pages, 17 figures, 5 tables, published in Icarus. Erratum: 5 pages, 1 table, accepted for publication in Icaru

University of Southern Indiana\u27s Solar Eclipse Experience

The University of Southern Indiana Eclipse Ballooning team\u27s experience from May 2016 to August 2017 is comprehensively reviewed. Experience gained during four rehearsal balloon flights is covered, including the need to coordinate with a pre-Senior Design class assisting in three of the flights. Challenges encountered were: learning ballooning techniques, reconfiguring the pod stack, adding new hardware, like a grounding rod and 3D printed standoff, losing tracking visibility due to server crashes at the Borealis hub, and making quick software turnarounds. The students found the networking afforded by the entire experience to be one of the highlights of the project

Optical properties of cometary particles collected by the COSIMA mass spectrometer on-board <i>Rosetta</i> during the rendezvous phase around comet 67P/Churyumov–Gerasimenko

40 000 collected cometary particles have been identified on the 21 targets exposed by the COSIMA experiment on-board Rosetta to the environment of comet 67P/Churyumov–Gerasimenko from 2014 August to 2016 September. The images of the targets where obtained by the COSIMA microscope (Cosiscope, 13.95 μm pixel−1) with near grazing incidence, which is optimal for the primary objective (detection of collected particles) but very challenging for photometry. However, more than 300 of the collected particles are larger than 100 μm which makes it possible to derive constraints on the optical properties from the distribution of light levels within the particles. Two types of particles collected by COSIMA (compact particles and cluster particles) have been identified in Langevin et al. The best estimate reflectance factors of compact particles range from 10 per cent to 23 per cent. For cluster particles (>90 per cent of large collected particles), the comparison of the signal profiles with illumination from two opposite directions shows that there is scattering within the particles, with a mean free path in the 20–25 μm range, which requires high porosity. The best estimate reflectance factors of cluster particles range from 3 per cent to 22 per cent. This range of reflectance factors overlaps with that obtained from observations of the cometary nucleus at macroscopic scales by OSIRIS and it is consistent with that measured for interplanetary dust particles collected in the stratosphere of the Earth

Effect of Visual Reminder on the TTR and MLU-W of Oral Hearing-Impaired Students During High/Scope Recall Sessions

Language samples of sixteen oral hearing-impaired students, aged 3.8 to 10.6 years with a mean SRT average of 27dB, were taken during High/Scope recall sessions under two conditions: with visual reminder (a videotape replay of their session work-time) or without visual reminder (no videotape replay of their work-time). These language samples, taken over a three month period, were analyzed with SALT (Systematic Analysis of Language Transcripts) for flexibility (using TTR) and structure (using MLU-W), and for five other SALT analyses. In each of the seven SALT analyses, improvement was shown for both groups with a trend for greater improvement shown in favor of the gorup with visual reminder

Experiential Learning in the Technology Disciplines February 2020

Learning-by-doing has long been a tradition in the technology disciplines. It is the hands-on work, combined with student reflection, feedback and assessment, that reinforces theory into practice. Over the past 40 years, experiential learning (EL) in higher education has grown beyond in-class assignments to include internships, cooperative education, team-based learning, project-based learning, community engagement, service learning, international and study-away experiences, capstone projects and research opportunities. This paper provides an overview of experiential education theory and practice in the undergraduate technology disciplines, and presents examples of how experiential learning practices have evolved over time at a medium-sized institution in the Northeast USA. In addition, this paper offers instructors theoretical strategies to improve the hands-on work that is likely already present in their courses

Low Frequency Tilt Seismology with a Precision Ground Rotation Sensor

We describe measurements of the rotational component of teleseismic surface waves using an inertial high-precision ground-rotation-sensor installed at the LIGO Hanford Observatory (LHO). The sensor has a noise floor of 0.4 nrad$/ \sqrt{\rm Hz}$ at 50 mHz and a translational coupling of less than 1 $\mu$rad/m enabling translation-free measurement of small rotations. We present observations of the rotational motion from Rayleigh waves of six teleseismic events from varied locations and with magnitudes ranging from M6.7 to M7.9. These events were used to estimate phase dispersion curves which shows agreement with a similar analysis done with an array of three STS-2 seismometers also located at LHO