: Low-low satellite-to-satellite tracking missions like GRACE-FO that utilize laser ranging intereferometers are technologically limited by the acceleration noise performance of the electrostatic accelerometers, in addition to temporal aliasing issues associated with the dynamic gravity field measurements. The current accelerometers, used in the GRACE and GRACE-FO mission have a limited sensitivity of ~10 –10 m/s 2 Hz 1/2 around 1 mHz. Meanwhile, the LISA Pathfinder mission, which was a technology demonstrator for the future ESA/NASA LISA gravitational wave mission, demonstrated an acceleration noise performance of 2×10 –15 m/s 2 Hz 1/2 around 1 mHz. The results of LISA Pathfinder and extensive ground testing using precision torsion pendula indicate that a simplified version of the LISA Pathfinder gravitational reference sensor (GRS) could be used in future Earth geodesy missions beyond GRACE-FO. Such a sensor would have an acceleration noise below 10 –12 m/s 2 Hz 1/2 , which is understood to be the desired performance for future Earth geodesy missions utilizing laser interferometry for intersatellite ranging. This sensor could be directly integrated with the laser interferometer, potentially relaxing requirements on spacecraft attitude measurement and control, or it could be operated as a stand-alone instrument with a stable structural reference to the laser interferometer reference point. The improved performance is enabled by increasing the mass of the sensor’s test mass, increasing the gap between the test mass and its electrode housing, removing the small grounding wire used in the GRACE accelerometers and replacing them with a UV

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As the first inter-spacecraft laser interferometer, the Laser Ranging Interferometer (LRI) on the GRACE Follow-On Mission will demonstrate interferometry technology relevant to the LISA mission. This paper focuses on the completed LRI Laser Ranging Processor (LRP), which includes heterodyne signal phase tracking at mu cycle/root Hz precision, differential wavefront sensing, offset frequency phase locking and Pound-Drever-Hall laser stabilization. The LRI design has characteristics that are similar to those for LISA: 1064nm NPRO laser source, science bandwidth in the mHz range, MHz-range intermediate frequency and Doppler shift, detected optical power of tens of picoWatts. Laser frequency stabilization has been demonstrated at a level below 30 Hz/root Hz, better than the LISA requirement of 300 Hz/root Hz. The LRP has completed all performance testing and environmental qualification and has been delivered to the GRACE Follow-On spacecraft. The LRI is poised to test the LISA techniques of tone-assisted time delay interferometry and arm-locking. GRACE Follow-On launches in 2017.

The last century has seen enormous progress in our understanding of the Universe. We know the life cycles of stars, the structure of galaxies, the remnants of the big bang, and have a general understanding of how the Universe evolved. We have come remarkably far using electromagnetic radiation as our tool for observing the Universe. However, gravity is the engine behind many of the processes in the Universe, and much of its action is dark. Opening a gravitational window on the Universe will let us go further than any alternative. Gravity has its own messenger: Gravitational waves, ripples in the fabric of spacetime. They travel essentially undisturbed and let us peer deep into the formation of the first seed black holes, exploring redshifts as large as z ~ 20, prior to the epoch of cosmic re-ionisation. Exquisite and unprecedented measurements of black hole masses and spins will make it possible to trace the history of black holes across all stages of galaxy evolution, and at the same time constrain any deviation from the Kerr metric of General Relativity. eLISA will be the first ever mission to study the entire Universe with gravitational waves. eLISA 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 early processes at TeV energies, has guaranteed sources in the form of verification binaries in the Milky Way, and can probe the entire Universe, from its smallest scales around singularities and black holes, all the way to cosmological dimensions.

S. Ballmer, 13 B. C. Barish, 12 C. Barker, 14 D. Barker,14 M. Barnes, 12, b B. Barr,35 M. A. Barton,12 K. Bayer,13 R. Beausoleil, 26, c K. Belczynski,23 R. Bennett, 35, d S. J. Berukoff, 1, e J. Betzwieser, 13 B. Bhawal,12 I. A. Bilenko,20 G. Billingsley,12 E. Black,12 K. Blackburn, 12 L. Blackburn, 13 B. Bland,14 B. Bochner, 13, f L. Bogue, 12 R. Bork,12 S. Bose, 40 P. R. Brady, 39 V. B. Braginsky, 20

Anthropologists have long been interested in the survival of Indian cultural traits in the New World. In this article, we present results of an ongoing project with a Costa Rican community that descends from East Indian indentured servants. We focus on the group's marriage patterns and how these patterns might have helped keep the community as a cohesive ethnic group. We investigate the group's level of inbreeding by computing the inbreeding coefficient using two different methods. We show that the community has been successful at keeping its inbreeding low, despite its small size, by allowing marriage with nonmembers of the community. We propose that unless consanguineous marriages are allowed virtually all of the community's marriages will be with noncommunity members. Absorption into tourism, as well as the community's staunch avoidance of consanguineous marriages and virtually universal marriage with noncommunity members, will likely contribute to their disappearance as a viable ethnic group.

Anthropologists have long been interested in the survival of Indian cultural traits in the New World. In this article, we present results of an ongoing project with a Costa Rican community that descends from East Indian indentured servants. We focus on the group's marriage patterns and how these patterns might have helped keep the community as a cohesive ethnic group. We investigate the group's level of inbreeding by computing the inbreeding coefficient using two different methods. We show that the community has been successful at keeping its inbreeding low, despite its small size, by allowing marriage with nonmembers of the community. We propose that unless consanguineous marriages are allowed virtually all of the community's marriages will be with noncommunity members. Absorption into tourism, as well as the community's staunch avoidance of consanguineous marriages and virtually universal marriage with noncommunity members, will likely contribute to their disappearance as a viable ethnic group.

We describe a new architecture for laser displacement metrology with a drastic reduction in the size and complexity of the optical head. Connected by a single optical fiber, the compact heads are easy to integrate and readily multiplexed to support applications requiring large numbers of sensors. The approach is made possible by modulating the outgoing laser light with a binary random noise code, allowing the detected signals to be discriminated based on their propagation delay. We demonstrate a displacement resolution of 1.1 nm rms.

Signal extraction is a vital link between science and systems-engineering requirements. In this paper we present a Terrestrial Planet Finder (TPF) interferometer planet-signal-extraction algorithm and demonstrate the performance of several nulling-interferometer designs on canonical TPF astronomical scenes. We create the output response of a linear phase-chopping dual Bracewell nulling interferometer and a matrix version of the correlation method employed to generate dirty images. We derive general and specific map parameters, such as signal-to-noise ratio, signal-to-artifact ratio, and detection confidence, used for individual maps or comparing array architectures. We implement a matrix form of CLEAN that removes map artifacts, produces reconstructed images, and retrieves planetary signals. Monte Carlo simulations show that some fixed-length structurally connected interferometer configurations can detect Earth-like planets for systems at 10 pc in the presence of stellar Poisson noise. Since angular resolution depends on baseline length, a design that can vary array configuration for each specific scene is superior to an interferometer with a fixed array length. Thus, a flexible free-flying architecture should satisfy the science requirements for more TPF candidates, compared to a fixed-length structurally connected architecture.

We report on a search for gravitational waves from binary black hole inspirals in the data from the second science run of the LIGO interferometers. The search focused on binary systems with component masses between 3 and 20 solar masses. Optimally oriented binaries with distances up to 1 Mpc could be detected with efficiency of at least 90%. We found no events that could be identified as gravitational waves in the 385.6 hours of data that we searched.

Abstract—Radio,ranging,signals have,been,used extensively for mapping,the Earth’s gravity,field. The latest example,is the GRACE (Gravity Recovery,and,Climate Experiment) mis- sion which,uses centimeter-wavelength radio signals to measure changes,in distance,between,two,spacecraft,with,sub-micron accuracy. Range,change,is determined,by measuring,changes in the phase,of the transmitted,radio signal. Improved,range accuracy,can,be,achieved,by,using,lasers with,one,micron wavelengths,for the ranging signal. The laser phase measurement electronics must cope with higher signal dynamics,due to Doppler shifts and more noise in the measured phase (which, multiplied by the smaller wavelength, still results in a more accurate ranging,measurement). A new,phase,measurement,system,has been developed,and tested to meet these requirements. It is based on the digital signal processing,system,used for GPS receivers and,the GRACE mission. High-speed digitizers sample,the laser phase signal, which is digitally filtered in a field-programmable gate array. The resulting phase measurement,system,is capable of measuring,the phase,of signal frequencies,up,to 20 MHz and,frequency,rate up to 100 Hz/s with microcycle,accuracy,at mHz,frequencies,in the presence,of laser noise. The system,also includes output,of the phase measurement,at a rate of 1 MHz which,can be used in locking one,laser transmitter,to another. The phase measurement,system,may,also have other applications with demanding measurement requirements, including on the LISA gravitational-wave mission. Index Terms—Phasemeter, laser ranging, gravity wave, LISA,

We search for coincident gravitational wave signals from inspiralling neutron star binaries using LIGO and TAMA300 data taken during early 2003. Using a simple trigger exchange method, we perform an intercollaboration coincidence search during times when TAMA300 and only one of the LIGO sites were operational. We find no evidence of any gravitational wave signals. We place an observational upper limit on the rate of binary neutron star coalescence with component masses between 1 and 3M of 49 per year per Milky Way equivalent galaxy at a 90% confidence level. The methods developed during this search will find application in future network inspiral analyses.

The LISA phasemeter is required to measure the phase of an electrical signal with an error less than 3 mu cycles/root Hz over times scales from 1 to 1000 seconds. This phase sensitivity must be achieved in the presence of laser phase fluctuations 10(8) times larger than the target sensitivity. Other challenging aspects of the measurement are that the heterodyne frequency varies from 2 to 20 MHz and the signal contains multiple frequency tones that must be measured. The phasemeter architecture uses high-speed analog to digital conversion followed by a digital phase locked loop. An overview of the phasemeter architecture is presented along with results for the breadboard LISA Phasemeter demonstrating that critical requirements are met.

This paper reviews recent progress with technology being developed for the Terrestrial Planet Finder Interferometer (TPF-I). TPF-I is a mid-infrared space interferometer being designed with the capability of detecting Earth-like planets in the habitable zones around nearby stars. TPF-I is in the early phase of its development. The science requirements of the mission are described along with the current design of the interferometer. The goals of the nulling and formation-flying testbeds are reviewed. Progress with TPF-I technology milestones are highlighted.

The LIGO interferometers are operating as gravitational wave observatories, with a noise level near an order of magnitude of the goal and the first scientific data recently taken. This data has been analyzed for four different categories of gravitational wave sources; millisecond bursts, inspiralling binary neutron stars, periodic waves from a known pulsar, and stochastic background. Research and development is also underway for the next generation LIGO detector, Advanced LIGO.

We place direct upper limits on the amplitude of gravitational waves from 28 isolated radio pulsars by a coherent multidetector analysis of the data collected during the second science run of the LIGO interferometric detectors. These are the first direct upper limits for 26 of the 28 pulsars. We use coordinated radio observations for the first time to build radio-guided phase templates for the expected gravitational-wave signals. The unprecedented sensitivity of the detectors allows us to set strain upper limits as low as a few times 10(-24). These strain limits translate into limits on the equatorial ellipticities of the pulsars, which are smaller than 10(-5) for the four closest pulsars.

We report on the first joint search for gravitational waves by the TAMA and LIGO collaborations. We looked for millisecond-duration unmodelled gravitational-wave bursts in 473 hr of coincident data collected during early 2003. No candidate signals were found. We set an upper limit of 0.12 events per day on the rate of detectable gravitational-wave bursts, at 90% confidence level. From simulations, we estimate that our detector network was sensitive to bursts with root-sum-square strain amplitude above approximately 1-3x10^{-19} Hz^{-1/2} in the frequency band 700-2000 Hz. We describe the details of this collaborative search, with particular emphasis on its advantages and disadvantages compared to searches by LIGO and TAMA separately using the same data. Benefits include a lower background and longer observation time, at some cost in sensitivity and bandwidth. We also demonstrate techniques for performing coincidence searches with a heterogeneous network of detectors with different noise spectra and orientations. These techniques include using coordinated signal injections to estimate the network sensitivity, and tuning the analysis to maximize the sensitivity and the livetime, subject to constraints on the background.

We perform a search for gravitational wave bursts using data from the second science run of the LIGO detectors, using a method based on a wavelet time-frequency decomposition. This search is sensitive to bursts of duration much less than a second and with frequency content in the 100-1100 Hz range. It features significant improvements in the instrument sensitivity and in the analysis pipeline with respect to the burst search previously reported by LIGO. Improvements in the search method allow exploring weaker signals, relative to the detector noise floor, while maintaining a low false alarm rate, O(0.1) mu Hz. The sensitivity in terms of the root-sum-square (rss) strain amplitude lies in the range of h(rss)similar to 10(-20)-10(-19) Hz(-1/2). No gravitational wave signals were detected in 9.98 days of analyzed data. We interpret the search result in terms of a frequentist upper limit on the rate of detectable gravitational wave bursts at the level of 0.26 events per day at 90% confidence level. We combine this limit with measurements of the detection efficiency for selected waveform morphologies in order to yield rate versus strength exclusion curves as well as to establish order-of-magnitude distance sensitivity to certain modeled astrophysical sources. Both the rate upper limit and its applicability to signal strengths improve our previously reported limits and reflect the most sensitive broad-band search for untriggered and unmodeled gravitational wave bursts to date.

We use 373 hours (approximate to 15 days) of data from the second science run of the LIGO gravitational-wave detectors to search for signals from binary neutron star coalescences within a maximum distance of about 1.5 Mpc, a volume of space which includes the Andromeda Galaxy and other galaxies of the Local Group of galaxies. This analysis requires a signal to be found in data from detectors at the two LIGO sites, according to a set of coincidence criteria. The background (accidental coincidence rate) is determined from the data and is used to judge the significance of event candidates. No inspiral gravitational-wave events were identified in our search. Using a population model which includes the Local Group, we establish an upper limit of less than 47 inspiral events per year per Milky Way equivalent galaxy with 90% confidence for nonspinning binary neutron star systems with component masses between 1 and 3M.