840 research outputs found
Photometric stability analysis of the Exoplanet Characterisation Observatory
Photometric stability is a key requirement for time-resolved spectroscopic
observations of transiting extrasolar planets. In the context of the Exoplanet
Characterisation Observatory (EChO) mission design, we here present and
investigate means of translating spacecraft pointing instabilities as well as
temperature fluctuation of its optical chain into an overall error budget of
the exoplanetary spectrum to be retrieved. Given the instrument specifications
as of date, we investigate the magnitudes of these photometric instabilities in
the context of simulated observations of the exoplanet HD189733b secondary
eclipse.Comment: submitted to MNRA
Detection of an atmosphere around the super-Earth 55 Cancri e
We report the analysis of two new spectroscopic observations of the
super-Earth 55 Cancri e, in the near infrared, obtained with the WFC3 camera
onboard the HST. 55 Cancri e orbits so close to its parent star, that
temperatures much higher than 2000 K are expected on its surface. Given the
brightness of 55 Cancri, the observations were obtained in scanning mode,
adopting a very long scanning length and a very high scanning speed. We use our
specialized pipeline to take into account systematics introduced by these
observational parameters when coupled with the geometrical distortions of the
instrument. We measure the transit depth per wavelength channel with an average
relative uncertainty of 22 ppm per visit and find modulations that depart from
a straight line model with a 6 confidence level. These results suggest
that 55 Cancri e is surrounded by an atmosphere, which is probably
hydrogen-rich. Our fully Bayesian spectral retrieval code, T-REx, has
identified HCN to be the most likely molecular candidate able to explain the
features at 1.42 and 1.54 m. While additional spectroscopic observations
in a broader wavelength range in the infrared will be needed to confirm the HCN
detection, we discuss here the implications of such result. Our chemical model,
developed with combustion specialists, indicates that relatively high mixing
ratios of HCN may be caused by a high C/O ratio. This result suggests this
super-Earth is a carbon-rich environment even more exotic than previously
thought.Comment: 10 pages, 10 figures, 4 tables, Accepted for publication in Ap
A scene model of exosolar systems for use in planetary detection and characterisation simulations
Instrumental projects that will improve the direct optical finding and
characterisation of exoplanets have advanced sufficiently to trigger organized
investigation and development of corresponding signal processing algorithms.
The first step is the availability of field-of-view (FOV) models. These can
then be submitted to various instrumental models, which in turn produce
simulated data, enabling the testing of processing algorithms. We aim to set
the specifications of a physical model for typical FOVs of these instruments.
The dynamic in resolution and flux between the various sources present in
such a FOV imposes a multiscale, independent layer approach. From review of
current literature and through extrapolations from currently available data and
models, we derive the features of each source-type in the field of view likely
to pass the instrumental filter at exo-Earth level.
Stellar limb darkening is shown to cause bias in leakage calibration if
unaccounted for. Occurrence of perturbing background stars or galaxies in the
typical FOV is unlikely. We extract galactic interstellar medium background
emissions for current target lists. Galactic background can be considered
uniform over the FOV, and it should show no significant drift with parallax.
Our model specifications have been embedded into a Java simulator, soon to be
made open-source. We have also designed an associated FITS input/output format
standard that we present here.Comment: 9 pages (+5 of appendices), 7 figures, accepted for publication in
Astronomy & Astrophysic
EChOSim: The Exoplanet Characterisation Observatory software simulator
EChOSim is the end-to-end time-domain simulator of the Exoplanet
Characterisation Observatory (EChO) space mission. EChOSim has been developed
to assess the capability EChO has to detect and characterize the atmospheres of
transiting exoplanets, and through this revolutionize the knowledge we have of
the Milky Way and of our place in the Galaxy. Here we discuss the details of
the EChOSim implementation and describe the models used to represent the
instrument and to simulate the detection. Software simulators have assumed a
central role in the design of new instrumentation and in assessing the level of
systematics affecting the measurements of existing experiments. Thanks to its
high modularity, EChOSim can simulate basic aspects of several existing and
proposed spectrometers for exoplanet transits, including instruments on the
Hubble Space Telescope and Spitzer, or ground-based and balloon borne
experiments. A discussion of different uses of EChOSim is given, including
examples of simulations performed to assess the EChO mission
A risk profile for identifying community-dwelling elderly with a highrisk of recurrent falling: results of a 3-year prospective study
Introduction: The aim of the prospective study reported here was to develop a risk profile that can be used to identify community-dwelling elderly at a high risk of recurrent falling. Materials and methods: The study was designed as a 3-year prospective cohort study. A total of 1365 community-dwelling persons, aged 65 years and older, of the population-based Longitudinal Aging Study Amsterdam participated in the study. During an interview in 1995/1996, physical, cognitive, emotional and social aspects of functioning were assessed. A follow-up on the number of falls and fractures was conducted during a 3-year period using fall calendars that participants filled out weekly. Recurrent fallers were identified as those who fell at least twice within a 6-month period during the 3-year follow-up. Results: The incidence of recurrent falls at the 3-year follow-up point was 24.9% in women and 24.4% in men. Of the respondents, 5.5% reported a total of 87 fractures that resulted from a fall, including 20 hip fractures, 21 wrist fractures and seven humerus fractures. Recurrent fallers were more prone to have a fall-related fracture than those who were not defined as recurrent fallers (11.9% vs. 3.4%; OR: 3.8; 95% CI: 2.3-6.1). Backward logistic regression analysis identified the following predictors in the risk profile for recurrent falling: two or more previous falls, dizziness, functional limitations, weak grip strength, low body weight, fear of falling, the presence of dogs/cats in the household, a high educational level, drinking 18 or more alcoholic consumptions per week and two interaction terms (high educationx18 or more alcohol consumptions per week and two or more previous falls x fear of falling) (AUC=0.71). Discussion: At a cut-off point of 5 on the total risk score (range 0-30), the model predicted recurrent falling with a sensitivity of 59% and a specificity of 71%. At a cut-off point of 10, the sensitivity and specificity were 31% and 92%, respectively. A risk profile including nine predictors that can easily be assessed seems to be a useful tool for the identification of community-dwelling elderly with a high risk of recurrent falling. © International Osteoporosis Foundation and National Osteoporosis Foundation 2006
The ARIEL Instrument Control Unit design for the M4 Mission Selection Review of the ESA's Cosmic Vision Program
The Atmospheric Remote-sensing Infrared Exoplanet Large-survey mission
(ARIEL) is one of the three present candidates for the ESA M4 (the fourth
medium mission) launch opportunity. The proposed Payload will perform a large
unbiased spectroscopic survey from space concerning the nature of exoplanets
atmospheres and their interiors to determine the key factors affecting the
formation and evolution of planetary systems. ARIEL will observe a large number
(>500) of warm and hot transiting gas giants, Neptunes and super-Earths around
a wide range of host star types, targeting planets hotter than 600 K to take
advantage of their well-mixed atmospheres. It will exploit primary and
secondary transits spectroscopy in the 1.2-8 um spectral range and broad-band
photometry in the optical and Near IR (NIR). The main instrument of the ARIEL
Payload is the IR Spectrometer (AIRS) providing low-resolution spectroscopy in
two IR channels: Channel 0 (CH0) for the 1.95-3.90 um band and Channel 1 (CH1)
for the 3.90-7.80 um range. It is located at the intermediate focal plane of
the telescope and common optical system and it hosts two IR sensors and two
cold front-end electronics (CFEE) for detectors readout, a well defined process
calibrated for the selected target brightness and driven by the Payload's
Instrument Control Unit (ICU).Comment: Experimental Astronomy, Special Issue on ARIEL, (2017
Super Earth Explorer: A Coronagraphic Off-Axis Space Telescope
The Super-Earth Explorer is an Off-Axis Space Telescope (SEE-COAST) designed
for high contrast imaging. Its scientific objective is to make the
physico-chemical characterization of exoplanets possibly down to 2 Earth radii
>. For that purpose it will analyze the spectral and polarimetric properties of
the parent starlight reflected by the planets, in the wavelength range 400-1250
nmComment: Accepted in Experimental Astronom
Spatio-temporal gait analysis based on human-smart rollator interaction
The ability to walk is typically related to several biomechanical components that are involved in the gait cycle (or stride), including free mobility of joints, particularly in the legs; coordination of muscle activity in terms of timing and intensity; and normal sensory input, such as vision and vestibular system. As people age, they tend to slow their gait speed, and their balance is also affected. Also, the retirement from the working life and the consequent reduction of physical and social activity contribute to the increased incidence of falls in older adults. Moreover, older adults suffer different kinds of cognitive decline, such as dementia or attention problems, which also accentuate gait disorders and its consequences. In this paper we present a methodology for gait identification using the on-board sensors of a smart rollator: the i-Walker. This technique provides the number of steps performed in walking exercises, as well as the time and distance travelled for each stride. It also allows to extract spatio-temporal metrics used in medical gait analysis from the interpretation of the interaction between the individual and the i-Walker. In addition, two metrics to assess users’ driving skills, laterality and directivity, are proposed.Peer ReviewedPostprint (author's final draft
Long term durability of protected silver coating for the mirrors of Ariel mission telescope
Ariel (Atmospheric Remote-sensing Infrared Exoplanet Large survey) is the fourth medium-size mission in ESA “Cosmic Vision” program. It is scheduled to launch in 2029. Ariel will conduct spectroscopic and photometric observations of a large sample of known exoplanets to survey their atmospheres with the transit method. Ariel is based on a 1 m class telescope designed for the visible and near infrared spectrum, but optimized specifically for spectroscopy in the waveband between 1.95 and 7.8 μm. Telescope and instruments will be operating in cryogenic conditions in the range 40-50 K. The telescope mirrors will be manufactured in aluminum 6061, with a protected silver coating deposited onto the optical surface to enhance reflectivity and prevent oxidation and corrosion. During the preliminary definition phase of the development work, leading to mission adoption, a silver coating with space heritage was selected and underwent a qualification process on disc-shaped samples of the mirrors substrate material. The samples were deposited through magnetron sputtering and then subjected to a battery of tests, including environmental durability tests, accelerated aging, cryogenic tests and mechanical resistance tests. Further to the qualification, the samples have been stored in cleanroom conditions and periodically re-examined and measured to detect any sign of coating degradation. The test program, still ongoing at the time of writing this article, consists of visual inspection with a high intensity lamp, spectral reflectance measurements and Atomic Force Microscopy (AFM) evaluation of nanometric surface features. The goal is to ensure stability of the optical performance, in terms of coating reflectance, during a time span comparable to the period that the actual mirrors of the telescope will spend in average cleanroom conditions. This study presents the interim results after three years of storage
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