In the months since the publication of the first results, the noise performance of LISA Pathfinder has improved because of reduced Brownian noise due to the continued decrease in pressure around the ...test masses, from a better correction of noninertial effects, and from a better calibration of the electrostatic force actuation. In addition, the availability of numerous long noise measurement runs, during which no perturbation is purposely applied to the test masses, has allowed the measurement of noise with good statistics down to 20 μHz. The Letter presents the measured differential acceleration noise figure, which is at (1.74±0.05) fm s^{-2}/sqrtHz above 2 mHz and (6±1)×10 fm s^{-2}/sqrtHz at 20 μHz, and discusses the physical sources for the measured noise. This performance provides an experimental benchmark demonstrating the ability to realize the low-frequency science potential of the LISA mission, recently selected by the European Space Agency.
Weak lensing, which is the deflection of light by matter along the line of sight, has proven to be an efficient method for constraining models of structure formation and reveal the nature of dark ...energy. So far, most weak-lensing studies have focused on the shear field that can be measured directly from the ellipticity of background galaxies. However, within the context of forthcoming full-sky weak-lensing surveys such as Euclid , convergence maps (mass maps) offer an important advantage over shear fields in terms of cosmological exploitation. While it carry the same information, the lensing signal is more compressed in the convergence maps than in the shear field. This simplifies otherwise computationally expensive analyses, for instance, non-Gaussianity studies. However, the inversion of the non-local shear field requires accurate control of systematic effects caused by holes in the data field, field borders, shape noise, and the fact that the shear is not a direct observable (reduced shear). We present the two mass-inversion methods that are included in the official Euclid data-processing pipeline: the standard Kaiser & Squires method (KS), and a new mass-inversion method (KS+) that aims to reduce the information loss during the mass inversion. This new method is based on the KS method and includes corrections for mass-mapping systematic effects. The results of the KS+ method are compared to the original implementation of the KS method in its simplest form, using the Euclid Flagship mock galaxy catalogue. In particular, we estimate the quality of the reconstruction by comparing the two-point correlation functions and third- and fourth-order moments obtained from shear and convergence maps, and we analyse each systematic effect independently and simultaneously. We show that the KS+ method substantially reduces the errors on the two-point correlation function and moments compared to the KS method. In particular, we show that the errors introduced by the mass inversion on the two-point correlation of the convergence maps are reduced by a factor of about 5, while the errors on the third- and fourth-order moments are reduced by factors of about 2 and 10, respectively.
Context.
Stage IV weak lensing experiments will offer more than an order of magnitude leap in precision. We must therefore ensure that our analyses remain accurate in this new era. Accordingly, ...previously ignored systematic effects must be addressed.
Aims.
In this work, we evaluate the impact of the reduced shear approximation and magnification bias on information obtained from the angular power spectrum. To first-order, the statistics of reduced shear, a combination of shear and convergence, are taken to be equal to those of shear. However, this approximation can induce a bias in the cosmological parameters that can no longer be neglected. A separate bias arises from the statistics of shear being altered by the preferential selection of galaxies and the dilution of their surface densities in high-magnification regions.
Methods.
The corrections for these systematic effects take similar forms, allowing them to be treated together. We calculated the impact of neglecting these effects on the cosmological parameters that would be determined from
Euclid
, using cosmic shear tomography. To do so, we employed the Fisher matrix formalism, and included the impact of the super-sample covariance. We also demonstrate how the reduced shear correction can be calculated using a lognormal field forward modelling approach.
Results.
These effects cause significant biases in Ω
m
,
σ
8
,
n
s
, Ω
DE
,
w
0
, and
w
a
of −0.53
σ
, 0.43
σ
, −0.34
σ
, 1.36
σ
, −0.68
σ
, and 1.21
σ
, respectively. We then show that these lensing biases interact with another systematic effect: the intrinsic alignment of galaxies. Accordingly, we have developed the formalism for an intrinsic alignment-enhanced lensing bias correction. Applying this to
Euclid
, we find that the additional terms introduced by this correction are sub-dominant.
The science operations of the LISA Pathfinder mission have demonstrated the feasibility of sub-femto-g free fall of macroscopic test masses necessary to build a gravitational wave observatory in ...space such as LISA. While the main focus of interest, i.e., the optical axis or the x-axis, has been extensively studied, it is also of great importance to evaluate the stability of the spacecraft with respect to all the other degrees of freedom (d.o.f.). The current paper is dedicated to such a study: the exhaustive and quantitative evaluation of the imperfections and dynamical effects that impact the stability with respect to its local geodesic. A model of the complete closed-loop system provides a comprehensive understanding of each component of the in-loop coordinates spectral density. As will be presented, this model gives very good agreement with LISA Pathfinder flight data. It allows one to identify the noise source at the origin and the physical phenomena underlying the couplings. From this, the stability performance of the spacecraft with respect to its geodesic is extracted as a function of frequency. Close to 1 mHz, the stability of the spacecraft on the XSC, YSC and ZSC d.o.f. is shown to be of the order of 5.0×10−15 m s−2 Hz−1/2 for X, 6.0×10−14 m s−2 Hz−1/2 for Y, and 4.0×10−14 m s−2 Hz−1/2 for Z. For the angular d.o.f., the values are of the order of 3×10−12 rad s−2 Hz−1/2 for ΘSC, 5×10−13 rad s−2 Hz−1/2 for HSC, and 3×10−13 rad s−2 Hz−1/2 for ΦSC. Below 1 mHz, however, the stability performances are worsened significantly by the effect of the star tracker noise on the closed-loop system. It is worth noting that LISA is expected to be spared from such concerns, as differential wave-front sensing, an attitude sensor system of much higher precision, will be utilized for attitude control.
Abstract
Introduction
Dental emergencies in isolated groups have always been difficult to treat. Especially in people or groups who cannot be evacuated and who need urgent dental assistance: ...long-term submarine missions, long-term spaceship trips, military or non-governmental organizations deployments in conflict areas, military maneuvers, etc. The dental and evacuation problems could put the success of the mission at risk, with relevant associated economic and strategic costs. Our study summarizes current evidence about dental problems in isolated personnel (submarines and Antarctic missions) compared to other non-isolation conditions (military deployment in conflict area, military maneuvers) with the objective to assess the need for specific dental equipment in special long-term isolation conditions.
Materials and Methods
We searched Medline, Cochrane Library, and Dentalgate between 1960 and 2017 for studies reporting dental disease in long-term isolation conditions (minimum 1 month) versus non-isolation conditions. We conducted the systematic review with all studies fitting the inclusion criteria. The comparison of the incidence rate was performed fitting a Poisson regression model to see the effect of the individual’s condition on the incidence of dental event.
Results
Thirty-eight studies were included in the systematic review. Antarctic missions showed a higher dental incidence rate compared to non-isolation conditions, but submarine missions showed the lowest dental incidence rate. In the sub-analysis of acute dental events, those with great impact on unit effectiveness, the incidence rates were higher. Caries and secondary decay events were the most prevalent dental problem in all conditions, followed by periodontal pathology and fractures of teeth or tooth problems not due to tooth decay in isolation conditions, and then by molar problems and endodontic problems in non-isolation conditions. The most common acute dental events were third molar problems and endodontic problems in all conditions.
Conclusion
This systematic review shows that the incidence of dental pathology in long-term isolation conditions may seem relatively infrequent but it exists and is relevant. Dental events are unpredictable, unrelated to trauma, and caused mainly by poor dental status. Preventive measures considerably reduce dental prevalence.
ABSTRACT
The Euclid mission will observe well over a billion galaxies out to z ∼ 6 and beyond. This will offer an unrivalled opportunity to investigate several key questions for understanding galaxy ...formation and evolution. The first step for many of these studies will be the selection of a sample of quiescent and star-forming galaxies, as is often done in the literature by using well-known colour techniques such as the ‘UVJ’ diagram. However, given the limited number of filters available for the Euclid telescope, the recovery of such rest-frame colours will be challenging. We therefore investigate the use of observed Euclid colours, on their own and together with ground-based u-band observations, for selecting quiescent and star-forming galaxies. The most efficient colour combination, among the ones tested in this work, consists of the (u − VIS) and (VIS − J) colours. We find that this combination allows users to select a sample of quiescent galaxies complete to above $\sim 70{{\ \rm per\ cent}}$ and with less than 15${{\ \rm per\ cent}}$ contamination at redshifts in the range 0.75 < z < 1. For galaxies at high-z or without the u-band complementary observations, the (VIS − Y) and (J − H) colours represent a valid alternative, with $\gt 65{{\ \rm per\ cent}}$ completeness level and contamination below 20${{\ \rm per\ cent}}$ at 1 < z < 2 for finding quiescent galaxies. In comparison, the sample of quiescent galaxies selected with the traditional UVJ technique is only $\sim 20{{\ \rm per\ cent}}$ complete at z < 3, when recovering the rest-frame colours using mock Euclid observations. This shows that our new methodology is the most suitable one when only Euclid bands, along with u-band imaging, are available.
Context. Future weak lensing surveys, such as the Euclid mission, will attempt to measure the shapes of billions of galaxies in order to derive cosmological information. These surveys will attain ...very low levels of statistical error, and systematic errors must be extremely well controlled. In particular, the point spread function (PSF) must be estimated using stars in the field, and recovered with high accuracy. Aims. The aims of this paper are twofold. Firstly, we took steps toward a nonparametric method to address the issue of recovering the PSF field, namely that of finding the correct PSF at the position of any galaxy in the field, applicable to Euclid . Our approach relies solely on the data, as opposed to parametric methods that make use of our knowledge of the instrument. Secondly, we studied the impact of imperfect PSF models on the shape measurement of galaxies themselves, and whether common assumptions about this impact hold true in an Euclid scenario. Methods. We extended the recently proposed resolved components analysis approach, which performs super-resolution on a field of under-sampled observations of a spatially varying, image-valued function. We added a spatial interpolation component to the method, making it a true 2-dimensional PSF model. We compared our approach to PSFEx , then quantified the impact of PSF recovery errors on galaxy shape measurements through image simulations. Results. Our approach yields an improvement over PSFEx in terms of the PSF model and on observed galaxy shape errors, though it is at present far from reaching the required Euclid accuracy. We also find that the usual formalism used for the propagation of PSF model errors to weak lensing quantities no longer holds in the case of an Euclid -like PSF. In particular, different shape measurement approaches can react differently to the same PSF modeling errors.
Since the starting of Space Age astronaut's health has been a subject of the utmost importance. To date, numerous studies describe the effect of microgravity on the body health of the astronauts. ...Some of these studies analyzed dental diseases and were conducted in conditions of microgravity and simulated microgravity, during short or long periods. Taking into account the increase of long space missions, it is necessary to systematically review the oral health events related with short and long periods spent in space missions with all the available evidence.
To identify all relevant oral diseases attributed to the effects of microgravity, we performed a rigorous systematic review regarding the published articles regarding microgravity and dental diseases from 1969 to 2018. Databases such as Pubmed, Cochrane, Scielo, Google Scholar and the NASA were consulted. Additional studies from the reference lists of the selected articles were included in order to get a greater complete overview. Ten scientific documents (containing 12 studies) with a direct relation with oral/dental health and microgravity were assessed.
Five studies about short period missions (≤30 days) were included. The studies showed increases of cortisol as well as salivary immunoglobulin A (IgA) and salivary IgG. Seven studies about long period missions (>30–220 days) were included, and the more important fact retrieved was the increase of anaerobic bacteriae.
Future long-term missions to Mars or to space stations will require 18–24 months of exposure to microgravity, that, added to other conditions, could have potentially deleterious effects on human physiology, including oral health. Preventive measures, adequate material and training of the crew have to be applied to avoid an oral health event to jeopardize the mission.
•Astronaut's health is of the utmost importance for future space missions.•Long-term microgravity exposition could have deleterious effects on oral physiology.•Radiation, isolation, stress also affect oral and systemic health in space.•The added effect on health of all long term space conditions should be studied.•Prevention, adequate material and training are essential for mission's success.
Abstract
LISA Pathfinder (LPF) was a technology pioneering mission designed to test key technologies required for gravitational wave detection in space. In the low frequency regime (milliHertz and ...below), where space-based gravitational wave observatories will operate, temperature fluctuations play a crucial role since they can couple into the interferometric measurement and the test masses’ free-fall accuracy in many ways. A dedicated temperature measurement subsystem, with noise levels in 10 $\mu$K Hz−1/2 down to 1 mHz was part of the diagnostics unit onboard LPF. In this paper we report on the temperature measurements throughout mission operations, characterize the thermal environment, estimate transfer functions between different locations, and report temperature stability (and its time evolution) at frequencies as low as 10 $\mu$Hz, where typically values around 1 K Hz−1/2 were measured.
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