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We examined the feasibility of administering neuropsychological tests via videoconference. Twenty-nine participants from central Alberta volunteered for the study. All were 60 years of age or older and were without neurological or psychiatric disturbance. All the participants were tested under two experimental conditions: face to face and via videoconference (at a bandwidth of 336 or 384 kbit/s). Memory and learning, letter fluency, expressive word knowledge, reasoning, verbal attention and visual–spatial processing were examined. Scores for expressive word knowledge were similar in the two test conditions, although larger differences were found in the visual–spatial processing scores. Following the final testing session, participants were given a questionnaire which explored their reactions to the technology. There was no significant difference in the proportions of participants who expressed a preference for each mode of testing. All participants were comfortable with the technology.

A simplified gravitational reference sensor (S-GRS) is an ultra-precise inertial sensor for future Earth geodesy missions. These sensors measure or compensate for all non-gravitational accelerations of the host spacecraft to remove them in the data analysis and recover spacecraft motion due to Earth’s gravity field. Low–low satellite-to-satellite tracking missions like GRACE-FO that use laser ranging interferometers (LRI) are limited by the acceleration noise performance of their electrostatic accelerometers and temporal aliasing associated with Earth’s gravity field. The current accelerometers, used in the GRACE missions, have a limited sensitivity of ∼ 10 - 10 m/s 2 /Hz 1 / 2 around 1 mHz. The S-GRS is estimated to be at least 40 times more sensitive than the GRACE accelerometers and over 500 times more sensitive if operated on a drag-compensated platform. This improvement 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 grounding wire used in GRACE, and replacing it with a UV LED-based charge management system. This allows future missions to take advantage of the sensitivity of the GRACE-FO LRI in the gravity recovery analysis. The S-GRS concept is a simplified version of the flight-proven LISA Pathfinder (LPF) GRS. Performance estimates are based on models vetted during the LPF flight and the expected spacecraft environment based on GRACE-FO data. The relatively low volume ( ∼ 10 4  cm 3 ), mass ( ∼  13 kg), and power ( ∼  20 W) enable the use of S-GRS on microsatellites, reducing launch costs and allowing more satellite pairs to improve the temporal resolution of gravity field maps. The S-GRS design and analysis, as well as its gravity recovery performance in two candidate mission architectures, are discussed in this article.

The Drag-Free and Attitude Control System is a central element of LISA technology, ensuring the very high dynamic stability of spacecraft and test masses required in order to reach the sensitivity that gravitational wave astronomy in space requires. Applying electrostatic forces on test-masses is unavoidable but should be restricted to the minimum necessary to keep the spacecraft-test masses system in place, while granting the optimal quality of test-mass free-fall. To realise this, we propose a new test-mass suspension scheme that applies forces and torques only in proportion to any differential test mass motion observed, and we demonstrate that the new scheme significantly mitigates the amount of suspension forces and torques needed to control the whole system. The mathematical method involved allows us to derive a new observable measuring the differential acceleration of test masses projected on the relevant sensitive axes, which will have important consequences for LISA data calibration, processing and analysis.

In this article I would like to share with readers of Notes and Records some of the early initiatives taken by government in the 1960s, which helped to promote a variety of nongovernmental developments! in Botswana and so contributed to the evolution of a more participative and better informed civil society.

The orbiting LISA instrument is designed to detect gravitational waves in the millihertz band, produced by sources including galactic binaries and extreme mass ratio inspirals, among others. The detector consists of three spacecraft, each carrying a pair of free-falling test masses. A technology-demonstration mission, LISA Pathfinder, was launched in 2015, and observed several sudden changes in test mass acceleration, referred to as \"glitches.\" Similar glitches in the full LISA mission have the potential to contaminate the Time-Delay Interferometry outputs that are the detector's primary data product. In this paper, we describe an optimization technique using maximum likelihood estimation for detecting and removing glitches with a known waveform.

The presence of free charge on isolated proof-masses, such as those within space-borne gravitational reference sensors, causes a number of spurious forces which will give rise to associated acceleration noise. A complete discusssion of each charge induced force and its linear acceleration noise is presented. The resulting charge acceleration noise contributions to the LISA mission are evaluated using the LISA Pathfinder performance and design. It is shown that one term is largely dominant but that a full budget should be maintained for LISA and future missions due to the large number of possible contributions and their dependence on different sensor parameters.

The Laser Interferometer Space Antenna (LISA), space-based gravitational wave observatory involves a complex multidimensional closed-loop dynamical system. Its instrument performance is expected to be less efficiently isolated from platform motion than was its simpler technological demonstrator, LISA Pathfinder. It is of crucial importance to understand and model LISA dynamical behavior accurately to understand the propagation of dynamical excitations through the response of the instrument down to the interferometer data streams. More generally, simulation of the system allows for the preparation of the processing and interpretation of in-flight metrology data. In this work, we present a comprehensive mathematical modeling of the closed-loop system dynamics and its numerical implementation within the LISA Consortium simulation suite. We provide, for the first time, a full time-domain numerical demonstration of post-processing Time Delay Interferometer techniques combining multiple position measurements with realistic control loops to create a synthetic Michelson interferometer. We show that in the absence of physical coupling to spacecraft and telescope motion (through tilt-to-length, stiffness and actuation cross-talk) the effect of noisy spacecraft motion is efficiently suppressed to a level below the noise originating in the rest of the instrument.

Many applications require charge neutralisation of isolated test bodies and this has been successfully done using photoelectric emission from surfaces which are electrically benign(gold) or superconducting (niobium). Gold surfaces nominally have a high work function (\\( 5.1\\)\\,eV)which should require deep UV photons for photoemission. In practice it has been found that it can be achieved with somewhat lower energy photons with indicative work functions of (\\( 4.1-4.3\\)\\,eV). A detailed working understanding of the process is lacking and this work reports on a study of the photoelectric emission properties of 4.6x4.6 cm^2 gold plated surfaces, representative of those used in typical satellite applications with a film thickness of 800 nm, and measured surface roughnesses between 7 and 340 nm. Various UV sources with photon energies from 4.8 to 6.2 eV and power outputs from 1 nW to 1000 nW, illuminated a ~0.3 cm^2 of the central surface region at angles of incidence from 0 to 60 degrees. Final extrinsic quantum yields in the range 10 ppm to 44 ppm were reliably obtained during 8 campaigns, covering a ~3 year period, but with intermediate long-term variations lasting several weeks and, in some cases, bake-out procedures at up to 200 C. Experimental results were obtained in a vacuum system with a baseline pressure of ~10^-7 mbar at room temperature. A working model, designed to allow accurate simulation of any experimental configuration, is proposed.

The Laser Interferometer Space Antenna (LISA) mission is being developed by ESA with NASA participation. As it has recently passed the Mission Adoption milestone, models of the instruments and noise performance are becoming more detailed, and likewise prototype data analyses must as well. Assumptions such as Gaussianity, stationarity, and data continuity are unrealistic, and must be replaced with physically motivated data simulations, and data analysis methods adapted to accommodate such likely imperfections. To this end, the LISA Data Challenges have produced datasets featuring time-varying and unequal constellation armlength, and measurement artifacts including data interruptions and instrumental transients. In this work, we assess the impact of these data artifacts on the inference of Galactic Binary and Massive Black Hole properties. Our analysis shows that the treatment of noise transients and gaps is necessary for effective parameter estimation, as they substantially corrupt the analysis if unmitigated. We find that straightforward mitigation techniques can significantly if imperfectly suppress artifacts. For the Galactic Binaries, mitigation of glitches was essentially total, while mitigations of the data gaps increased parameter uncertainty by approximately 10%. For the Massive Black Hole binaries the particularly pernicious glitches resulted in a 30% uncertainty increase after mitigations, while the data gaps can increase parameter uncertainty by up to several times. Critically, this underlines the importance of early detection of transient gravitational waves to ensure they are protected from planned data interruptions.

The Laser Interferometer Space Antenna (LISA) mission is being developed by ESA with NASA participation. As it has recently passed the Mission Adoption milestone, models of the instruments and noise performance are becoming more detailed, and likewise prototype data analyses must as well. Assumptions such as Gaussianity, Stationarity, and continuous data continuity are unrealistic, and must be replaced with physically motivated data simulations, and data analysis methods adapted to accommodate such likely imperfections. To this end, the LISA Data Challenges have produced datasets featuring time-varying and unequal constellation armlength, and measurement artifacts including data interruptions and instrumental transients. In this work, we assess the impact of these data artifacts on the inference of Galactic Binary and Massive Black Hole properties. Our analysis shows that the treatment of noise transients and gaps is necessary for effective parameter estimation. We find that straightforward mitigation techniques can significantly suppress artifacts, albeit leaving a non-negligible impact on aspects of the science.