Tetherline system for orbiting satellites

A system for tethering one orbiting space vehicle to another was designed so that a tetherline between the vehicles is controlled by a motorized reel which in turn is controlled to deploy, retrieve, or maintain a constant line length while effecting a stabilizing influence on the line. This is accomplished by applying a tension to the line which takes into account the instantaneous length of the line, rate of change of the length of the line, and certain constants which vary depending upon the mode of operation, deployment, retrieval, or station keeping

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

Cylindrical surface profile and diameter measuring tool and method

A tool is shown having a cross beam assembly made of beams joined by a center box structure. The assembly is adapted to be mounted by brackets to the outer end of a cylindrical case. The center box structure has a vertical shaft rotatably mounted therein and extending beneath the assembly. Secured to the vertical shaft is a radius arm which is adapted to rotate with the shaft. On the longer end of the radius arm is a measuring tip which contacts the cylindrical surface to be measured and which provides an electric signal representing the radius of the cylindrical surface from the center of rotation of the radius arm. An electric servomotor rotates the vertical shaft and an electronic resolver provides an electric signal representing the angle of rotation of the shaft. The electric signals are provided to a computer station which has software for its computer to calculate and print out the continuous circumference profile of the cylindrical surface, and give its true diameter and the deviations from the ideal circle

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

Metal Ion Complexes of N,N′-Bis(2-Pyridylmethyl)-trans-1,2-Diaminocyclohexane-N,N′-Diacetic Acid, H2bpcd: Lanthanide(III)–bpcd2– Cationic Complexes

The synthesis and characterization of N,N′-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane-N,N′-diacetic acid (H2bpcd) cationic complexes of La(III), Nd(III), and Sm(III) are reported. The Ln(III)–bpcd2– complex ions, where bpcd2– stands for N,N′-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane-N,N′-diacetate, were isolated as PF6– salts. These salts were characterized by elemental analysis, X-ray crystallography, IR, and 1H and 13C NMR spectroscopy. Binuclear [La2(bpcd)2(H2O)2]2+ crystallized from an aqueous solution in the monoclinic P21/c space group as a cocrystallate with Na2bpcd and NaPF6, nominally Na2.34[La1.22(C22H26N4O4)2(H2O)2][PF6]2·2H2O, with a = 11.3343(6) Å, b = 17.7090(9) Å, c = 15.0567(8) Å, β = 110.632(3)°, and Z = 4 (Z′ = 2). La is eight-coordinate with distorted dodecahedral coordination geometry provided by a N4O4 donor atom set. In addition to four N atoms from the bpcd2– ligand, La’s coordination sphere includes O atoms from a water molecule and three acetate groups (one O atom from singly bound acetate and two O atoms from acetate groups that bridge the La centers). The 1H and 13C assignments for H2bpcd and the metal–bpcd2– complexes were made on the basis of 2D COSY and HSQC experiments, which established 1H–1H and 1H–13C correlations. The NMR spectral data were used to establish the symmetry of the cationic complexes present in aqueous solution. The data indicate that the La(III)–bpcd2– and Sm(III)–bpcd2– complexes are present in solution as a single species with C2 symmetry. The 1H NMR spectrum of [Nd(bpcd)]PF6 in D2O consists of eight considerably line-broadened, paramagnetic-shifted singlets. The ab initio quantum mechanical calculations at the PCM/MP2/SDD//HF/SDD level, which were established previously for determining isomerization energies for octahedral M(III)–bpad2– complex ions, were used to determine the relative free energies of the geometric isomers possible for eight- and nine-coordinate La(III)–bpcd2– cationic aqua complexes in aqueous solution, i.e., [La(bpcd)(H2O)2]+ and La(bpcd)(H2O)3]+

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

A charge transfer inefficiency correction model for the Chandra Advanced CCD Imaging Spectrometer

Soon after launch, the Advanced CCD Imaging Spectrometer (ACIS), one of the focal plane instruments on the Chandra X-ray Observatory, suffered radiation damage from exposure to soft protons during passages through the Earth's radiation belts. The primary effect of the damage was to increase the charge transfer inefficiency (CTI) of the eight front illuminated CCDs by more than two orders of magnitude. The ACIS instrument team is continuing to study the properties of the damage with an emphasis on developing techniques to mitigate CTI and spectral resolution degradation. We will discuss the characteristics of the damage, the detector and the particle background and how they conspire to degrade the instrument performance. We have developed a model for ACIS CTI which can be used to correct each event and regain some of the lost performance. The correction uses a map of the electron trap distribution, a parameterization of the energy dependent charge loss and the fraction of the lost charge re-emitted into the trailing pixel to correct the pixels in the event island. This model has been implemented in the standard Chandra data processing pipeline. Some of the correction algorithm was inspired by the earlier work on ACIS CTI correction by Townsley et al. (2000; 2002). The details of the CTI model and how each parameter improves performance will be discussed, as well as the limitations and the possibilities for future improvement.Comment: 12 pages, 12 figures, will appear in Proc. SPIE 550

Prediction for new magnetoelectric fluorides

We use symmetry considerations in order to predict new magnetoelectric fluorides. In addition to these magnetoelectric properties, we discuss among these fluorides the ones susceptible to present multiferroic properties. We emphasize that several materials present ferromagnetic properties. This ferromagnetism should enhance the interplay between magnetic and dielectric properties in these materials.Comment: 12 pages, 4 figures, To appear in Journal of Physics: Condensed Matte

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