scholarly journals ArielRad: the Ariel radiometric model

2020 ◽  
Vol 50 (2-3) ◽  
pp. 303-328 ◽  
Author(s):  
Lorenzo V. Mugnai ◽  
Enzo Pascale ◽  
Billy Edwards ◽  
Andreas Papageorgiou ◽  
Subhajit Sarkar
Keyword(s):  
Space Mission ◽  
Noise Model ◽  
Stationary Processes ◽  
Noise Sources ◽  
Photon Statistic ◽  
Cosmic Vision ◽  
Performance Requirements ◽  
Atmospheric Remote Sensing ◽  
Large Survey ◽  
Primary Mission

Abstract ArielRad, the Ariel radiometric model, is a simulator developed to address the challenges in optimising the space mission science payload and to demonstrate its compliance with the performance requirements. Ariel, the Atmospheric Remote-Sensing Infrared Exoplanet Large-survey, has been selected by ESA as the M4 mission in the Cosmic Vision programme and, during its 4 years primary operation, will provide the first unbiased spectroscopic survey of a large and diverse sample of transiting exoplanet atmospheres. To allow for an accurate study of the mission, ArielRad uses a physically motivated noise model to estimate contributions arising from stationary processes, and includes margins for correlated and time-dependent noise sources. We show that the measurement uncertainties are dominated by the photon statistic, and that an observing programme with about 1000 exoplanetary targets can be completed during the primary mission lifetime.

Ariel - The ESA M4 Space Mission to Focus on the Nature Of Exoplanets

2021 ◽  
Author(s):  
Theresa Lueftinger ◽  
Giovanna Tinetti ◽  
Paul Ecclestone ◽  
Jean-Christophe Salvignol ◽  
Salma Fahmy ◽  
...  
Keyword(s):  
Space Mission ◽  
Point Of View ◽  
Current Status ◽  
Additional Contribution ◽  
Vision Science ◽  
Cosmic Vision ◽  
Atmospheric Remote Sensing ◽  
Habitable Zones ◽  
Exoplanetary Atmospheres ◽  
Large Survey

<p>Ariel, the atmospheric remote-sensing infrared exoplanet large-survey, is the recently adopted M4 mission within the Cosmic Vision science programme of ESA. The goal of Ariel is to investigate the atmospheres of planets orbiting distant stars in order to address the fundamental questions on how planetary systems form and evolve and to investigate in unprecedented detail the composition of a large number of exoplanetary atmospheres. During its 4-year mission, Ariel will observe hundreds of exoplanets ranging from Jupiter- and Neptune-size down to super-Earth size, in a wide variety of environments, in the visible and the infrared. The main focus of the mission will be on warm and hot planets in orbits close to their star. Some of the planets may be in the habitable zones of their stars, however. The analysis of Ariel spectra and photometric data will allow to extract the chemical fingerprints of gases and condensates in the planets’ atmospheres, including the elemental composition for the most favourable targets. The Ariel mission has been developed by a consortium of more than 60 institutes from 15 ESA member state countries, including UK, France, Italy, Poland, Spain, the Netherlands, Belgium, Austria, Denmark, Ireland, Hungary, Sweden, Czech Republic, Germany, Portugal, with an additional contribution from NASA. In this talk, we will review the science goals of the mission and give insight into the current status, both from the ESA and the Ariel Mission Consortium point of view.  </p>

Observability of Exo-Atmospheres in emission using Ariel

2021 ◽  
Author(s):  
Andrea Bocchieri ◽  
Enzo Pascale ◽  
Lorenzo Mugnai ◽  
Quentin Changeat ◽  
Giovanna Tinetti
Keyword(s):  
Thermal Structure ◽  
Spectroscopic Observation ◽  
Space Mission ◽  
Tier 2 ◽  
Low Snr ◽  
Cosmic Vision ◽  
Atmospheric Remote Sensing ◽  
Statistical Sample ◽  
In Transit ◽  
Large Survey

<p>Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, is a medium-class space mission part of ESA's Cosmic Vision program, due for launch in 2029. Ariel is the first mission dedicated to the spectroscopic observation of a diverse, statistical sample of about 1000 transiting exoplanets, obtaining spectra in transit, eclipse, or both, to answer questions about their composition, formation and evolution. Ariel has adopted a four-tiered approach in which all targets are observed with different SNRs to optimise the science return from the mission. Ariel has two separate instruments (FGS and AIRS) that will perform simultaneous observations across the 0.5-7.8 micron spectral range, which encompasses both the peak emission of exoplanets and the spectral signatures of key molecules. This will enable Ariel to collect statistical information on the composition and the thermal structure of exo-atmospheres, allowing it to reveal underlying trends in exoplanetary populations. In particular, transit spectroscopy is expected to provide the bulk of information on the chemical composition of exo-atmospheres, while eclipses are necessary to constrain their thermodynamic state. In this framework, I report a preliminary study of Ariel targets observed in emission: at first, I investigate the information content from Tier 1 data, where spectra from the full population of Ariel targets are observed with low SNR, and binned as if Ariel were a multi-band photometer to increase the SNR. I then investigate the effectiveness of Ariel in detecting chemical-physical trends in exoplanetary populations observed in Tier 2, designed to reach SNR in excess of 7 on spectra binned to roughly half the spectral resolution of the focal planes, as specified by the mission requirements.</p>

PAOS, the Physical Optics Propagation model of the Ariel optical system

2021 ◽  
Author(s):  
Andrea Bocchieri ◽  
Enzo Pascale
Keyword(s):  
Extrasolar Planets ◽  
Optical Design ◽  
Maximum Amplitude ◽  
Space Mission ◽  
Propagation Model ◽  
Optical Systems ◽  
Physical Optics ◽  
Cosmic Vision ◽  
Atmospheric Remote Sensing ◽  
Cassegrain Telescope

<p>Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, is a medium-class space mission part of ESA's Cosmic Vision programme, due for launch in 2029. Ariel will survey a diverse sample of about 1000 extrasolar planets in the visible and infrared spectrum to answer questions about their composition, formation and evolution. Ariel mounts an off-axis Cassegrain telescope with a 1100 mm x 730 mm elliptical mirror and has two separate instruments (FGS and AIRS) that cover the 0.5-7.8 micron spectral range. To study the Ariel optical performance and related systematics, we developed PAOS, the Proper Ariel Optical Simulator, an End-to-End physical optics propagation model of the Ariel Telescope and subsystems based on PROPER, an optical propagation library for IDL, Python and Matlab. PAOS is a Python code that consists of a series of calls to PROPER library functions and procedures that reproduces the Ariel optical design, interleaved with additional code that can be specified according to the simulation. Using PAOS, we can investigate how diffraction affects the electromagnetic wavefront as it travels through the Ariel optical systems and the resulting PSFs in the photometric and spectroscopic channels of the mission. This enables to perform a large number of detailed analyses, both on the instrument side and on the optimisation of the Ariel mission. In particular, PAOS can be used to support the requirement on the maximum amplitude of the aberrations for the manufacturing of the Ariel primary mirror, as well as to develop strategies for in-flight calibration, e.g. focussing procedures for the FGS and AIRS focal planes, and to tackle systematics such as pointing jitter and vignetting. With the Ariel mission now in the process of finalizing the instrument design and the data analysis techniques, PAOS will greatly contribute in evaluating the Ariel payload performance with models to be included in the existing Ariel simulators such as ArielRad, the Ariel Radiometric model, and ExoSim, the Exoplanet Observation simulator, for the purpose of studying and optimising the science return from Ariel.</p>

scholarly journals Blind to Chemistry: Molecular Contaminant Films We Could Be Missing During Visual Inspections and the Potential Impact to System Performance

2020 ◽  
Vol 63 (1) ◽  
pp. 13-20
Author(s):  
Elaine Seasly ◽  
Walter Wrigglesworth
Keyword(s):  
System Performance ◽  
Space Mission ◽  
Performance Requirements ◽  
Mirror Reflectivity ◽  
Potential Impact ◽  
Contamination Levels ◽  
Inspection Techniques ◽  
The Impact ◽  
Reflectance Measurements ◽  
Test Process

Abstract Throughout the assembly, integration, and test process, molecular contamination levels of space mission hardware are monitored to meet system performance requirements. Qualitatively, reflective surfaces and witness mirrors are continuously inspected for the visible presence of molecular contaminant films. Quantitatively, periodic reflectance measurements of witness mirrors indicate changes of mirror reflectivity over time due to the accumulation of molecular contaminant films. However, both methods only consider the presence of a contaminant film and not the molecular composition. Additionally, there is a risk that hardware may appear to be “visibly clean” even with a molecular contaminant film present on critical surfaces. To address these issues, experiments were performed to quantify the maximum molecular contaminant film that could be missed in visual inspections on witness mirrors with five different contaminants present. The corresponding changes in mirror reflectivity were modeled using the program STACK to determine the impact to space mission hardware performance. The results of this study not only show the criticality in considering the chemical make-up of molecular contaminant films on system performance, but also the need to recognize and understand the limitations of traditional visual inspection techniques on detecting molecular contaminant films.

Radiation modes of propeller tonal noise

2021 ◽  
pp. 1-25
Author(s):  
Hanbo Jiang ◽  
Siyang Zhong ◽  
Han Wu ◽  
Xin Zhang ◽  
Xun Huang ◽  
...  
Keyword(s):  
Spherical Harmonics ◽  
Sound Field ◽  
Low Noise ◽  
Noise Model ◽  
Sound Waves ◽  
Tonal Noise ◽  
Noise Sources ◽  
Separate Source ◽  
Radial Forces ◽  
Flow Variables

Abstract This paper focuses on the radiation modes and efficiency of propeller tonal noise. The thickness noise and loading noise model of propellers has been formulated in spherical coordinates, thereby simplifying numerical evaluation of the integral noise source. More importantly, the radiation field can be decomposed and projected to spherical harmonics, which can separate source-observer positions and enable an analysis of sound field structures. Thanks to the parity of spherical harmonics, the proposed model can mathematically explain the fact that thrusts only produce antisymmetric sound waves with respect to the rotating plane. In addition, the symmetric components of the noise field can be attributed to the thickness, as well as drags and radial forces acting on the propeller surface. The radiation efficiency of each mode decays rapidly as noise sources approach the rotating centre, suggesting the radial distribution of aerodynamic loadings should be carefully designed for low-noise propellers. The noise prediction model has been successfully applied to a drone propeller and achieved a reliable agreement with experimental measurements. The flow variables employed as an input of the noise computation were obtained with computational fluid dynamics (CFD), and the experimental data were measured in an anechoic chamber.

Effect of Ge-Nanoislands on the Low-Frequency Noise in Si/SiOx/Ge Structures

2013 ◽  
Vol 854 ◽  
pp. 21-27 ◽  
Author(s):  
N.P. Garbar ◽  
Valeriya N. Kudina ◽  
V.S. Lysenko ◽  
S.V. Kondratenko ◽  
Yu.N. Kozyrev
Keyword(s):  
High Surface ◽  
Low Frequency ◽  
Noise Model ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Physical Processes ◽  
Noise Sources ◽  
Noise Component ◽  
First Time ◽  
Noise Models

Low-frequency noise of the structures with Ge-nanoclusters of rather high surface density grown on the oxidized silicon surface is investigated for the first time. It was revealed that the 1/f γ noise, where γ is close to unity, is the typical noise component. Nevertheless, the 1/f γ noise sources were found to be distributed nonuniformly upon the oxidized silicon structure with Ge-nanoclusters. The noise features revealed were analyzed in the framework of widely used noise models. However, the models used appeared to be unsuitable to explain the noise behavior of the structures studied. The physical processes that should be allowed for to develop the appropriate noise model are discussed.

AN EMPIRICAL STUDY OF THE PROBABILITY DENSITY FUNCTION OF HF NOISE (PART II)

2008 ◽  
Vol 08 (03n04) ◽  
pp. L305-L314 ◽  
Author(s):  
J. GIESBRECHT
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
South Australia ◽  
Noise Model ◽  
Modulation Recognition ◽  
Noise Sources ◽  
Noise Density ◽  
Automatic Modulation Recognition ◽  
Definition Of

The impetus for investigating the probability density function of high-frequency (HF) noise arises from the requirement for a better noise model for automatic modulation recognition techniques. Many current modulation recognition methods still assume Gaussian noise models for the transmission medium. For HF communications this can be an incorrect assumption. Whereas a previous investigation [1] focuses on the noise density function in an urban area of Adelaide Australia, this work studies the noise density function in a remote country location east of Adelaide near Swan Reach, South Australia. Here, the definition of HF noise is primarily of natural origins – it is therefore impulsive – and excludes man-made noise sources. A new method for measuring HF noise is introduced that is used over a 153 kHz bandwidth at various frequencies across the HF band. The method excises man-made signals and calculates the noise PDF from the residue. Indeed, the suitability of the Bi-Kappa distribution at modeling HF noise is found to be even more compelling than suggested by the results of the earlier investigation.

The Atmospheric Remote-sensing Infrared Exoplanets Large-survey (ARIEL) payload electronic subsystems

2016 ◽  
Author(s):  
M. Focardi ◽  
E. Pace ◽  
J. Colomé ◽  
I. Ribas ◽  
M. Rataj ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Atmospheric Remote Sensing ◽  
Large Survey

scholarly journals Research on Aerodynamic Noise Reduction for High-Speed Trains

2016 ◽  
Vol 2016 ◽  
pp. 1-21 ◽  
Author(s):  
Yadong Zhang ◽  
Jiye Zhang ◽  
Tian Li ◽  
Liang Zhang ◽  
Weihua Zhang
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Low Noise ◽  
Broadband Noise ◽  
Full Scale ◽  
Noise Model ◽  
Aerodynamic Noise ◽  
High Speed Train ◽  
Detached Eddy Simulation ◽  
Noise Sources

A broadband noise source model based on Lighthill’s acoustic theory was used to perform numerical simulations of the aerodynamic noise sources for a high-speed train. The near-field unsteady flow around a high-speed train was analysed based on a delayed detached-eddy simulation (DDES) using the finite volume method with high-order difference schemes. The far-field aerodynamic noise from a high-speed train was predicted using a computational fluid dynamics (CFD)/Ffowcs Williams-Hawkings (FW-H) acoustic analogy. An analysis of noise reduction methods based on the main noise sources was performed. An aerodynamic noise model for a full-scale high-speed train, including three coaches with six bogies, two inter-coach spacings, two windscreen wipers, and two pantographs, was established. Several low-noise design improvements for the high-speed train were identified, based primarily on the main noise sources; these improvements included the choice of the knuckle-downstream or knuckle-upstream pantograph orientation as well as different pantograph fairing structures, pantograph fairing installation positions, pantograph lifting configurations, inter-coach spacings, and bogie skirt boards. Based on the analysis, we designed a low-noise structure for a full-scale high-speed train with an average sound pressure level (SPL) 3.2 dB(A) lower than that of the original train. Thus, the noise reduction design goal was achieved. In addition, the accuracy of the aerodynamic noise calculation method was demonstrated via experimental wind tunnel tests.

scholarly journals Modelling, measurement and optimization of self-noise of hydrophone with preamplifier

2019 ◽  
Vol 283 ◽  
pp. 05004
Author(s):  
Yi Chen ◽  
Lisheng Zhou ◽  
Xiyang Guo ◽  
Tao He ◽  
Jun Zhang
Keyword(s):  
Input Resistance ◽  
The Self ◽  
Noise Model ◽  
Density Level ◽  
Noise Sources ◽  
Basic Principles ◽  
Low Frequencies ◽  
Leading Role ◽  
Noise Optimization ◽  
Measurement Results

Self-noise is an important specification of hydrophone with preamplifier. This paper presents the modelling, measurement and optimization of the self-noise of hydrophone with preamplifier. Through analyzing various noise sources of hydrophone and its preamplifier, an effective self-noise model of hydrophone with preamplifier was established, and the self-noise was mainly affected by the hydrophone quality factor, preamplifier noise and thermal noise of preamplifier input resistance. In order to measure the self-noise of hydrophone with preamplifier, a measurement system was constructed and used for measuring the self-noise of a RHSA30 hydrophone which manufactured by Hangzhou Applied Acoustics Research Institute (HAARI) and has a typical sensitivity of -173 dB. After optimization of the self-noise of RHSA30 hydrophone, the measured equivalent noise pressure spectral density level was close to 30 dB at the frequency of 1000 Hz. The measurement results proved that the preamplifier current noise which mainly coming from the Operational Amplifier played a leading role at low frequencies of hydrophone with preamplifier. And some basic principles for self-noise optimization of hydrophone with preamplifier were given at the end.

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