Showing papers in "Proceedings of SPIE in 2018"

The Athena X-ray Integral Field Unit

Abstract: The X-ray Integral Field Unit (X-IFU) is the high resolution X-ray spectrometer of the ESA Athena X-ray observatory. Over a field of view of 5' equivalent diameter, it will deliver X-ray spectra from 0.2 to 12 keV with a spectral resolution of 2.5 eV up to 7 keV on ~5 arcsecond pixels. The X-IFU is based on a large format array of super-conducting molybdenum-gold Transition Edge Sensors cooled at about 90 mK, each coupled with an absorber made of gold and bismuth with a pitch of 249 microns. A cryogenic anti-coincidence detector located underneath the prime TES array enables the non X-ray background to be reduced. A bath temperature of about 50 mK is obtained by a series of mechanical coolers combining 15K Pulse Tubes, 4K and 2K Joule-Thomson coolers which pre-cool a sub Kelvin cooler made of a 3He sorption cooler coupled with an Adiabatic Demagnetization Refrigerator. Frequency domain multiplexing enables to read out 40 pixels in one single channel. A photon interacting with an absorber leads to a current pulse, amplified by the readout electronics and whose shape is reconstructed on board to recover its energy with high accuracy. The defocusing capability offered by the Athena movable mirror assembly enables the X-IFU to observe the brightest X-ray sources of the sky (up to Crab-like intensities) by spreading the telescope point spread function over hundreds of pixels. Thus the X-IFU delivers low pile-up, high throughput (>50%), and typically 10 eV spectral resolution at 1 Crab intensities, i.e. a factor of 10 or more better than Silicon based X-ray detectors. In this paper, the current X-IFU baseline is presented, together with an assessment of its anticipated performance in terms of spectral resolution, background, and count rate capability. The X-IFU baseline configuration will be subject to a preliminary requirement review that is scheduled at the end of 2018.

BICEP Array: A multi-frequency degree-scale CMB polarimeter

Abstract: Bicep Array is the newest multi-frequency instrument in the Bicep/Keck Array program. It is comprised of four 550mm aperture refractive telescopes observing the polarization of the cosmic microwave background (CMB) at 30/40, 95, 150 and 220/270 GHz with over 30,000 detectors. We present an overview of the receiver, detailing the optics, thermal, mechanical, and magnetic shielding design. Bicep Array follows Bicep3's modular focal plane concept, and upgrades to 6" wafer to reduce fabrication with higher detector count per module. The first receiver at 30/40GHz is expected to start observing at the South Pole during the 2019-20 season. By the end of the planned Bicep Array program, we project 0.002 l σ(r) l 0.006, assuming current modeling of polarized Galactic foreground and depending on the level of delensing that can be achieved with higher resolution maps from the South Pole Telescope.

A novel methodology for quality assessment of voxelized point clouds

Abstract: Recent trends in multimedia technologies indicate a significant growth of interest for new imaging modalities that aim to provide immersive experiences by increasing the engagement of the user with the content. Among other solutions, point clouds denote an alternative 3D content representation that allows visualization of static or dynamic scenes in a more immersive way. As in many imaging applications, the visual quality of a point cloud content is of crucial importance, as it directly affects the user experience. Despite the recent efforts from the scientific community, subjective and objective quality assessment for this type of visual data representation remains an open problem. In this paper, we propose a new, alternative framework for quality assessment of point clouds. In particular, we develop a rendering software, which performs real-time voxelization and projection of the 3D point clouds onto 2D planes, while allowing interaction between the user and the projected views. These projected images are then employed by two-dimensional objective quality metrics, in order to predict the perceptual quality of the displayed stimuli. Benchmarking results, using subjective ratings that were obtained through experiments in two test laboratories, show that our framework provides high predictive power and outperforms the state of the art in objective quality assessment of point cloud imaging.

The Lynx X-Ray Observatory: Concept Study Overview and Status

Abstract: Lynx, one of four strategic mission concepts under study for the 2020 Astrophysics Decadal Survey, will provide leaps in capability over previous and planned X-ray missions, and will provide synergistic observations in the 2030s to a multitude of space- and ground-based observatories across all wavelengths. Lynx will have orders of magnitude improvement in sensitivity, on-axis sub-arcsecond imaging with arcsecond angular resolution over a large field of view, and high-resolution spectroscopy for point-like and extended sources. The Lynx architecture enables a broad range of unique and compelling science, to be carried out mainly through a General Observer Program. This Program is envisioned to include detecting the very first supermassive black holes, revealing the high-energy drivers of galaxy and structure formation, characterizing the mechanisms that govern stellar activity - including effects on planet habitability, and exploring the highest redshift galaxy clusters. An overview and status of the Lynx concept are summarized.

CARMENES: high-resolution spectra and precise radial velocities in the red and infrared

Abstract: The CARMENES instrument has been operational at the 3.5 m telescope of Calar Alto Observatory since January 2016. It consists of two cross-dispersed ´echelle spectrographs covering the wavelength range from 0.52 to 1.71 µm. CARMENES is currently conducting a radial-velocity survey of more than 300 M dwarfs, with a sensitivity sufficient to detect terrestrial planets in their habitable zones. This survey has already yielded a comprehensive spectral atlas of 324 M dwarfs, and it is providing a wealth of diagnostic information on activity in cool stars. The CARMENES Survey data have confirmed a number of known M star planets, and revealed previously unknown planets of GJ 15 A, GJ 1148, and GJ 617 A. CARMENES data have also been used to determine the mass of the transiting planet K2-18 b, and to measure atomic and molecular absorption in planetary atmospheres through transit spectroscopy.

Paradigms for biologically inspired design

Abstract: Biologically inspired design is attracting increasing interest since it offers access to a huge biological repository of well proven design principles that can be used for developing new and innovative products. Biological phenomena can inspire product innovation in as diverse areas as mechanical engineering, medical engineering, nanotechnology, photonics, environmental protection and agriculture. However, a major obstacle for the wider use of biologically inspired design is the knowledge barrier that exist between the application engineers that have insight into how to design suitable products and the biologists with detailed knowledge and experience in understanding how biological organisms function in their environment. The biologically inspired design process can therefore be approached using different design paradigms depending on the dominant opportunities, challenges and knowledge characteristics. Design paradigms are typically characterized as either problem-driven, solution-driven, sustainability driven, bioreplication or a combination of two or more of them. The design paradigms represent different ways of overcoming the knowledge barrier and the present paper presents a review of their characterization and application.

Status of the mid-IR ELT imager and spectrograph (METIS)

Abstract: The Mid-Infrared ELT Imager and Spectrograph (METIS) is one of three first light instruments on the ELT. It will provide high-contrast imaging and medium resolution, slit-spectroscopy from 3 – 19um, as well as high resolution (R ~ 100,000) integral field spectroscopy from 2.9-5.3µm. All modes observe at the diffraction limit of the ELT, by means of adaptive optics, yielding angular resolutions of a few tens of milliarcseconds. The range of METIS science is broad, from Solar System objects to active galactic nuclei (AGN). We will present an update on the main science drivers for METIS: circum-stellar disks and exoplanets. The METIS project is now in full steam, approaching its preliminary design review (PDR) in 2018. In this paper we will present the current status of its optical, mechanical and thermal design as well as operational aspects. We will also discuss the challenges of building an instrument for the ELT, and the required technologies.

PICO: Probe of Inflation and Cosmic Origins

Abstract: The Probe of Inflation and Cosmic Origins (PICO) is a NASA-funded study of a Probe-class mission concept. The toplevel science objectives are to probe the physics of the Big Bang by measuring or constraining the energy scale of inflation, probe fundamental physics by measuring the number of light particles in the Universe and the sum of neutrino masses, to measure the reionization history of the Universe, and to understand the mechanisms driving the cosmic star formation history, and the physics of the galactic magnetic field. PICO would have multiple frequency bands between 21 and 799 GHz, and would survey the entire sky, producing maps of the polarization of the cosmic microwave background radiation, of galactic dust, of synchrotron radiation, and of various populations of point sources. Several instrument configurations, optical systems, cooling architectures, and detector and readout technologies have been and continue to be considered in the development of the mission concept. We will present a snapshot of the baseline mission concept currently under development.

Exoplanet science with a space-based mid-infrared nulling interferometer

Abstract: One of the long-term goals of exoplanet science is the (atmospheric) characterization of a large sample (>100) of terrestrial planets to assess their potential habitability and overall diversity. Hence, it is crucial to quantitatively evaluate and compare the scientific return of various mission concepts. Here we discuss the exoplanet yield of a space-based mid-infrared (MIR) nulling interferometer. We use Monte-Carlo simulations, based on the observed planet population statistics from the Kepler mission, to quantify the number and properties of detectable exoplanets (incl. potentially habitable planets) and we compare the results to those for a large aperture optical/NIR space telescope. We investigate how changes in the underlying technical assumptions (sensitivity and spatial resolution) impact the results and discuss scientific aspects that influence the choice for the wavelength coverage and spectral resolution. Finally, we discuss the advantages of detecting exoplanets at MIR wavelengths, summarize the current status of some key technologies, and describe what is needed in terms of further technology development to pave the road for a space-based MIR nulling interferometer for exoplanet science.

Concept design of the LiteBIRD satellite for CMB B-mode polarization

Abstract: LiteBIRD is a candidate for JAXA’s strategic large mission to observe the cosmic microwave background (CMB) polarization over the full sky at large angular scales. It is planned to be launched in the 2020s with an H3 launch vehicle for three years of observations at a Sun-Earth Lagrangian point (L2). The concept design has been studied by researchers from Japan, U.S., Canada and Europe during the ISAS Phase-A1. Large scale measurements of the CMB B-mode polarization are known as the best probe to detect primordial gravitational waves. The goal of LiteBIRD is to measure the tensor-to-scalar ratio (r) with precision of r < 0:001. A 3-year full sky survey will be carried out with a low frequency (34 - 161 GHz) telescope (LFT) and a high frequency (89 - 448 GHz) telescope (HFT), which achieve a sensitivity of 2.5 μK-arcmin with an angular resolution 30 arcminutes around 100 GHz. The concept design of LiteBIRD system, payload module (PLM), cryo-structure, LFT and verification plan is described in this paper.

A graph learning approach for light field image compression

Abstract: In recent years, light field imaging has attracted the attention of the academic and industrial communities thanks to its enhanced rendering capabilities that allow to visualise contents in a more immersive and interactive way. However, those enhanced capabilities come at the cost of a considerable increase in content size when compared to traditional image and video applications. Thus, advanced compression schemes are needed to efficiently reduce the volume of data for storage and delivery of light field content. In this paper, we introduce a novel method for compression of light field images. The proposed solution is based on a graph learning approach to estimate the disparity among the views composing the light field. The graph is then used to reconstruct the entire light field from an arbitrary subset of encoded views. Experimental results show that our method is a promising alternative to current compression algorithms for light field images, with notable gains across all bitrates with respect to the state of the art.

Review of high-contrast imaging systems for current and future ground- and space-based telescopes I: coronagraph design methods and optical performance metrics

Abstract: The Optimal Optical Coronagraph (OOC) Workshop at the Lorentz Center in September 2017 in Leiden, the Netherlands gathered a diverse group of 25 researchers working on exoplanet instrumentation to stimulate the emergence and sharing of new ideas In this first installment of a series of three papers summarizing the outcomes of the OOC workshop, we present an overview of design methods and optical performance metrics developed for coronagraph instruments The design and optimization of coronagraphs for future telescopes has progressed rapidly over the past several years in the context of space mission studies for Exo-C, WFIRST, HabEx, and LUVOIR as well as ground-based telescopes Design tools have been developed at several institutions to optimize a variety of coronagraph mask types We aim to give a broad overview of the approaches used, examples of their utility, and provide the optimization tools to the community Though it is clear that the basic function of coronagraphs is to suppress starlight while maintaining light from off-axis sources, our community lacks a general set of standard performance metrics that apply to both detecting and characterizing exoplanets The attendees of the OOC workshop agreed that it would benefit our community to clearly define quantities for comparing the performance of coronagraph designs and systems Therefore, we also present a set of metrics that may be applied to theoretical designs, testbeds, and deployed instruments We show how these quantities may be used to easily relate the basic properties of the optical instrument to the detection significance of the given point source in the presence of realistic noise

Review of high-contrast imaging systems for current and future ground-based and space-based telescopes: Part II. Common path wavefront sensing/control and coherent differential imaging

Abstract: The Optimal Optical Coronagraph (OOC) Workshop held at the Lorentz Center in September 2017 in Leiden, the Netherlands, gathered a diverse group of 25 researchers working on exoplanet instrumentation to stimulate the emergence and sharing of new ideas. In this second installment of a series of three papers summarizing the outcomes of the OOC workshop, we present an overview of common path wavefront sensing/control and Coherent Differential Imaging techniques, highlight the latest results, and expose their relative strengths and weaknesses. We layout critical milestones for the field with the aim of enhancing future ground/space based high contrast imaging platforms. Techniques like these will help to bridge the daunting contrast gap required to image a terrestrial planet in the zone where it can retain liquid water, in reflected light around a G type star from space.

The Origins Space Telescope: mission concept overview

Abstract: The Origins Space Telescope (OST) will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did the universe evolve in response to its changing ingredients? How common are life-bearing planets? To accomplish its scientific objectives, OST will operate at mid- and far-infrared wavelengths and offer superlative sensitivity and new spectroscopic capabilities. The OST study team will present a scientifically compelling, executable mission concept to the 2020 Decadal Survey in Astrophysics. To understand the concept solution space, our team studied two alternative mission concepts. We report on the study approach and describe both of these concepts, give the rationale for major design decisions, and briefly describe the mission-enabling technology.

Astronomical x-ray optics using mono-crystalline silicon: high resolution, light weight, and low cost

Abstract: X-ray astronomy critically depends on X-ray optics. The capability of an X-ray telescope is largelydetermined by the point-spread function (PSF) and the photon-collection area of its mirrors, the same astelescopes in other wavelength bands. Since an X-ray telescope must be operated above the atmosphere inspace and that X-rays reflect only at grazing incidence, X-ray mirrors must be both lightweight and thin, bothof which add significant technical and engineering challenge to making an X-ray telescope. In this paper wereport our effort at NASA Goddard Space Flight Center (GSFC) of developing an approach to making an Xraymirror assembly that can be significantly better than the mirror assembly currently flying on the ChandraX-ray Observatory in each of the three aspects: PSF, effective area per unit mass, and production cost per uniteffective area. Our approach is based on the precision polishing of mono-crystalline silicon to fabricate thinand lightweight X-ray mirrors of the highest figure quality and micro-roughness, therefore, having thepotential of achieving diffraction-limited X-ray optics. When successfully developed, this approach will makeimplementable in the 2020s and 2030s many X-ray astronomical missions that are currently on the drawingboard, including sounding rocket flights such as OGRE, Explorer class missions such as STAR-X andFORCE, Probe class missions such as AXIS, TAP, and HEX-P, as well as large missions such as Lynx.

Time-domain spectral-element ultrasound waveform tomography using a stochastic quasi-Newton method

Abstract: Waveform inversion for ultrasound computed tomography (USCT) is a promising imaging technique for breast cancer screening. However, the improved spatial resolution and the ability to constrain multiple parameters simultaneously demand substantial computational resources for the recurring simulations of the wave equation. Hence, it is crucial to use fast and accurate methods for numerical wave propagation, on the one hand, and to keep the number of required simulations as small as possible, on the other hand. We present an efficient strategy for acoustic waveform inversion that combines (i) a spectral-element continuous Galerkin method for solving the wave equation, (ii) conforming hexahedral mesh generation to discretize the scanning device, (iii) a randomized descent method based on mini-batches to reduce the computational cost for misfit and gradient computations, and (iv) a trust-region method using a quasi-Newton approximation of the Hessian to iteratively solve the inverse problem. This approach combines ideas and state-of-the-art methods from global-scale seismology, large-scale nonlinear optimization, and machine learning. Numerical examples for a synthetic phantom demonstrate the efficiency of the discretization, the effectiveness of the mini-batch approximation and the robustness of the trust-region method to reconstruct the acoustic properties of breast tissue with partial information.

Point cloud subjective evaluation methodology based on reconstructed surfaces

Abstract: Point clouds have been gaining importance as a solution to the problem of efficient representation of 3D geometric and visual information. They are commonly represented by large amounts of data, and compression schemes are important for their manipulation transmission and storing. However, the selection of appropriate compression schemes requires effective quality evaluation. In this work a subjective quality evaluation of point clouds using a surface representation is analyzed. Using a set of point cloud data objects encoded with the popular octree pruning method with different qualities, a subjective evaluation was designed. The point cloud geometry was presented to observers in the form of a movie showing the 3D Poisson reconstructed surface without textural information with the point of view changing in time. Subjective evaluations were performed in three different laboratories. Scores obtained from each test were correlated and no statistical differences were observed. Scores were also correlated with previous subjective tests and a good correlation was obtained when compared with mesh rendering in 2D monitors. Moreover, the results were correlated with state of the art point cloud objective metrics revealing poor correlation. Likewise, the correlation with a subjective test using a different representation of the point cloud data also showed poor correlation. These results suggest the need for more reliable objective quality metrics and further studies on adequate point cloud data representations.

The large UV/optical/infrared surveyor (LUVOIR): decadal mission study update

Abstract: NASA commissioned the study of four large mission concepts, including the Large Ultraviolet / Optical / Infrared (LUVOIR) Surveyor, to be evaluated by the 2020 Decadal Survey in Astrophysics. In response, the Science and Technology Definition Team (STDT) identified a broad range of science objectives for LUVOIR that include the direct imaging and spectral characterization of habitable exoplanets around sun-like stars, the study of galaxy formation and evolution, the exchange of matter between galaxies, star and planet formation, and the remote sensing of Solar System objects. To meet these objectives, the LUVOIR Study Office, located at NASA's Goddard Space Flight Center (GSFC), completed the first design iteration of a 15-m segmented-aperture observatory that would be launched by the Space Launch System (SLS) Block 2 configuration. The observatory includes four serviceable instruments: the Extreme Coronagraph for Living Planetary Systems (ECLIPS), an optical / near-infrared coronagraph capable of delivering 10(exp -10) contrast at inner working angles as small as 2 lambda/D; the LUVOIR UV Multi-object Spectrograph (LUMOS), which will provide low- and medium-resolution UV (100 - 400 nm) multi-object imaging spectroscopy in addition to far-UV imaging; the High Definition Imager (HDI), a high-resolution wide-field-of-view NUV-Optical-NIR imager; and Pollux, a high-resolution UV spectro-polarimeter being contributed by Centre National d'Etudes Spatiales (CNES). The study team has executed a second design iteration to further improve upon the 15-m concept, while simultaneously studying an 8-m concept. In these proceedings, we provide an update on these two architectures.

The Imaging X-Ray Polarimetry Explorer (IXPE): technical overview II

Abstract: The Imaging X-ray Polarimetry Explorer (IXPE) will add polarization to the properties (time, energy, and position) observed in x-ray astronomy. A NASA Astrophysics Small Explorer (SMEX) in partnership with the Italian Space Agency (ASI), IXPE will measure the 2–8-keV polarization of a few dozen sources during the first 2 years following its 2021 launch. The IXPE Observatory includes three identical x-ray telescopes, each comprising a 4-m-focal-length (grazingincidence) mirror module assembly (MMA) and a polarization-sensitive (imaging) detector unit (DU), separated by a deployable optical bench. The Observatory’s Spacecraft provides typical subsystems (mechanical, structural, thermal, power, electrical, telecommunications, etc.), an attitude determination and control subsystem for 3-axis stabilized pointing, and a command and data handling subsystem communicating with the science instrument and the Spacecraft subsystems.

Optical investigation of porous TiO2 in mesostructured solar cells

Abstract: Porous TiO2 films are a crucial part of mesostructured solar cells (MSCs), both dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs). However, the literature does not provide a clear description of the optical properties especially of the refractive index and scattering for those films relevant to MSCs. In DSSCs, two different porous TiO2 layers are included, the mesoporous active layer and the blocking layer. While the first is essential for the charge separation, electron collection and ion conduction, the second is intended for suppressing the loss of generated electrons to the electrolyte. Both layers consist of the same chemical compound, TiO2, but they have different porosities. For PSCs, the perovskite is deposited on a mesoporous TiO2 structure for enhancing the I–V characteristics This paper investigates TiO2 films really used in fabricated MSCs. We utilize a technique allowing the determination of the effective refractive index and the film porosity for two different film kinds fabricated using sol-gel methods, discussed in our previous work, to determine the thickness of TiO2 films typically used in fabricating MSCs.

Reflective Coatings for the Future X-Ray Mirror Substrates

Abstract: We present the development of the reflective coating by magnetron sputtering deposition onto precisely-fabricated thin X-ray mirrors. Our goal is to remove distortion induced by the coating and then keep their surface pro les. We first addressed the uniform coating to minimize the distortion by introducing a mask to control the spatial distribution of the coating thickness. The uniformity was finally achieved within 1%. We next tried a platinum single-layer coating on a glass substrate with a dimension of 200 mm 125 mm. The distortion caused by the frontside coating with a thickness of 320 A was found to be at most 1 m, smaller than the previous results obtained from the non-uniform coating. We then carried out the platinum coating with the same amount of the thickness on the backside surface of the glass substrate. The surface pro le of the glass substrate was fully recovered, indicating that the residual stress was successfully balanced by the backside coating. Furthermore, we tried to an iridium single-layer coating with a thickness of 150 Aon the silicon mirrors. The frontside coating caused the degradation of the imaging quality by 7:5 arcsec in half-power width. However, the backside coating with the same amount of the thickness reduced this degradation to be 3:4 arcsec. Finally, an additional backside coating with a thickness of 100 A and the annealing to relax the residual stress were found to eliminate the distortion completely; the final degradation of the imaging quality was only 0:4 arcsec.

Remote spectral measurements of the blood volume pulse with applications for imaging photoplethysmography

Abstract: Imaging photoplethysmography uses camera image sensors to measure variations in light absorption related to the delivery of the blood volume pulse to peripheral tissues. The characteristics of the measured BVP waveform depends on the spectral absorption of various tissue components including melanin, hemoglobin, water, and yellow pigments. Signal quality and artifact rejection can be enhanced by taking into account the spectral properties of the BVP waveform and surrounding tissue. The current literature regarding the spectral relationships of remote PPG is limited. To supplement this fundamental data, we present an analysis of remotely-measured, visible and near-infrared spectroscopy to better understand the spectral signature of remotely measured BVP signals. To do so, spectra were measured from the right cheek of 25, stationary participants whose heads were stabilized by a chinrest. A collimating lens was used to collect reflected light from a region of 3 cm in diameter. The spectrometer provided 3 nm resolution measurements from 500-1000 nm. Measurements were acquired at a rate of 50 complete spectra per second for a period of five minutes. Reference physiology, including electrocardiography was simultaneously and synchronously acquired. The spectral data were analyzed to determine the relationship between light wavelength and the resulting remote-BVP signal-to-noise ratio and to identify those bands best suited for pulse rate measurement. To our knowledge this is the most comprehensive dataset of remotely-measured spectral iPPG data. In due course, we plan to release this dataset for research purposes.

James Webb Space Telescope (JWST) optical telescope element and integrated science instrument module (OTIS) cryogenic test program and results

Abstract: In 2017, the James Webb Space Telescope Optical Telescope Element and Integrated Science Instrument Module (OTIS) underwent cryogenic optical testing at the Johnson Space Center. In this paper, we summarize the successful execution and results of this 100-day test, which was a major program milestone. We summarize the as-run test configuration and provide a top-level as-run timeline. We also provide the top-level functional, optical, thermal, and operational results from the test. We summarize the key technical issues encountered and the resolution of those issues. The results of the OTIS test indicate that the payload should be fully capable of delivering on JWST's exciting scientific potential.

The science case for POLLUX: a high-resolution UV spectropolarimeter onboard LUVOIR

Abstract: POLLUX is a high-resolution, UV spectropolarimeter proposed for the 15-meter primary mirror option of LUVOIR1 . The instrument Phase 0 study is supported by the French Space Agency (CNES) and performed by a consortium of European scientists. POLLUX has been designed to deliver high-resolution spectroscopy (R ≥ 120,000) over a broad spectral range (90-390 nm). Its unique spectropolarimetric capabilities will open-up a vast new parameter space, in particular in the unexplored UV domain and in a regime where high-resolution observations with current facilities in the visible domain are severely photon starved. POLLUX will address a range of questions at the core of the LUVOIR Science portfolio. The combination of high resolution and broad coverage of the UV bandpass will resolve narrow UV emission and absorption lines originating in diffuse media, thus permitting the study of the baryon cycle over cosmic time: from galaxies forming stars out of interstellar gas and grains, and stars forming planets, to the various forms of feedback into the interstellar and intergalactic medium (ISM and IGM), and active galactic nuclei (AGN). UV circular and linear polarimetry will reveal the magnetic fields for a wide variety of objects for the first time, from AGN outflows to a diverse range of stars, stellar explosions (both supernovae and their remnants), the ISM and IGM. It will enable detection of polarized light reflected from exoplanets (or their circumplanetary material and moons), characterization of the magnetospheres of stars and planets (and their interactions), and measurements of the influence of magnetic fields at the (inter)galactic scale. In this paper, we outline the key science cases of POLLUX, together with its high-level technical requirements. The instrument design, its estimated performances, and the required technology development are presented in a separated proceeding 2 .

STROBE-X: a probe-class mission for x-ray spectroscopy and timing on timescales from microseconds to years

Abstract: We describe the Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X), a probeclass mission concept that will provide an unprecedented view of the X-ray sky, performing timing and spectroscopy over both a broad energy band (0.2–30 keV) and a wide range of timescales from microseconds to years. STROBE-X comprises two narrow-field instruments and a wide field monitor. The soft or low-energy band (0.2–12 keV) is covered by an array of lightweight optics (3-m focal length) that concentrate incident photons onto small solid-state detectors with CCD-level (85–175 eV) energy resolution, 100 ns time resolution, and low background rates. This technology has been fully developed for NICER and will be scaled up to take advantage of the longer focal length of STROBE-X. The higher-energy band (2–30 keV) is covered by large-area, collimated silicon drift detectors that were developed for the European LOFT mission concept. Each instrument will provide an order of magnitude improvement in effective area over its predecessor (NICER in the soft band and RXTE in the hard band). Finally, STROBE-X offers a sensitive wide-field monitor (WFM), both to act as a trigger for pointed observations of X-ray transients and also to provide high duty-cycle, high time-resolution, and high spectral-resolution monitoring of the variable X-ray sky. The WFM will boast approximately 20 times the sensitivity of the RXTE All-Sky Monitor, enabling multi-wavelength and multi-messenger investigations with a large instantaneous field of view. This mission concept will be presented to the 2020 Decadal Survey for consideration.

The primordial inflation polarization explorer (PIPER): current status and performance of the first flight

Abstract: The Primordial Inflation Polarization ExploreR (PIPER) is a balloon-borne instrument optimized to measure the polarization of the CMB at large angular scales It will map 85% of the sky over a series of conventional balloon flights from the Northern and Southern hemispheres, measuring the B-mode polarization power spectrum over a range of multipoles from 2-300 covering both the reionization bump and the recombination peak, with sensitivity to measure the tensor-to-scalar ratio down to r = 0007 PIPER will observe in four frequency bands centered at 200, 270, 350, and 600 GHz to characterize dust foregrounds The instrument has background-limited sensitivity provided by fully cryogenic (17 K) optics focusing the sky signal onto kilo-pixel arrays of time-domain multiplexed Transition-Edge Sensor (TES) bolometers held at 100 mK Polarization sensitivity and systematic control are provided by front-end Variable-delay Polarization Modulators (VPMs) PIPER had its engineering ight in October 2017 from Fort Sumner, New Mexico This papers outlines the major components in the PIPER system discussing the conceptual design as well as specific choices made for PIPER We also report on the results of the engineering flight, looking at the functionality of the payload systems, particularly VPM, as well as pointing out areas of improvement

Preliminary jitter stability results for the large UV/optical/infrared (LUVOIR) surveyor concept using a non-contact vibration isolation and precision pointing system

Abstract: The need for high payload dynamic stability and ultra-stable mechanical systems is an overarching technology need for large space telescopes such as the Large Ultraviolet / Optical / Infrared (LUVOIR) Surveyor concept The LUVOIR concept includes a 15-meter-diameter segmented-aperture telescope with a suite of serviceable instruments operating over a range of wavelengths between 100 nm to 25 μm Wavefront error (WFE) stability of less than 10 picometers RMS of uncorrected system WFE per wavefront control step represents a drastic performance improvement over current space-based telescopes being fielded Through the utilization of an isolation architecture that involves no mechanical contact between the telescope and the host spacecraft structure, a system design is realized that maximizes the telescope dynamic stability performance without driving stringent technology requirements on spacecraft structure, sensors or actuators Through analysis of the LUVOIR finite element model and linear optical model, the wavefront error and Line- Of-Sight (LOS) jitter performance is discussed in this paper when using the Vibration Isolation and Precision Pointing System (VIPPS) being developed cooperatively with Lockheed Martin in addition to a multi-loop control architecture The multi-loop control architecture consists of the spacecraft Attitude Control System (ACS), VIPPS, and a Fast Steering Mirror on the instrument While the baseline attitude control device for LUVOIR is a set of Control Moment Gyroscopes (CMGs), Reaction Wheel Assembly (RWA) disturbance contribution to wavefront error stability and LOS stability are presented to give preliminary results in this paper CMG disturbance will be explored in further work to be completed

Diagnosis of crack damage on structures based on image processing techniques and R-CNN using unmanned aerial vehicle (UAV)

Abstract: In this paper, we developed techniques to identify and quantify the damage (crack) to bridges based on images obtained by the unmanned aerial vehicle (UAV). The scope of the research includes image acquisition using UAV, the classification system of crack based on Deep-learning and algorithms of detection and quantification using improved Image Processing Techniques (IPTs). A conventional crack detection method using only IPTs can be applied marginally according to the image acquisition environment (lights, shadows, etc.), so we proposed the techniques based on Deep-learning to find the crack part in the region of interest (ROI) from the other types of damage or non-crack. After classifying the crack part in the ROI, improved IPTs are applied to the detected regions to quantify cracks at 300 micrometers. Performances of the technique were evaluated through preliminary test and field test. The non-contact bridge damage detection technology using UAV can be applied to the actual bridge inspection field It is expected to have more performance than existing bridge inspection methods.

Analysis of dielectric fluid transducers

Abstract: Dielectric fluid transducers (DFTs) are electrostatic devices which alternate solid compliant dielectric layers/electrodes with dielectric fluid layers, and they enable the conversion of electrical energy into mechanical work (and vice versa) through capacitance variations associated with a modification of their shape. Compared to other capacitive transducers, e.g., dielectric elastomer transducers, DFTs feature better tolerance to electrical break-down and larger ratio between converted energy and stored elastic energy. To date, practical DFT topologies have been proposed and demonstrated for both actuation and generation purposes, showing promising performance in terms of converted energy density and efficiency. This paper presents an overview on operating principles/layouts, introduces a simplified analytical modelling approach and proposes some figure of merit to evaluate the performances of this new class of transducers.

Single Conjugate Adaptive Optics for METIS

Abstract: METIS is the Mid-infrared Extremely large Telescope Imager and Spectrograph, one of the first generation instruments of ESO’s 39m ELT. All scientific observing modes of METIS require adaptive optics (AO) correction close to the diffraction limit. Demanding constraints are introduced by the foreseen coronagraphy modes, which require highest angular resolution and PSF stability. Further design drivers for METIS and its AO system are imposed by the wavelength regime: observations in the thermal infrared require an elaborate thermal, baffling and masking concept. METIS will be equipped with a Single-Conjugate Adaptive Optics (SCAO) system. An integral part of the instrument is the SCAO module. It will host a pyramid type wavefront sensor, operating in the near-IR and located inside the cryogenic environment of the METIS instrument. The wavefront control loop as well as secondary control tasks will be realized within the AO Control System, as part of the instrument. Its main actuators will be the adaptive quaternary mirror and the field stabilization mirror of the ELT. In this paper we report on the phase B design work for the METIS SCAO system; the opto-mechanical design of the SCAO module as well as the control loop concepts and analyses. Simulations were carried out to address a number of important aspects, such as the impact of the fragmented pupil of the ELT on wavefront reconstruction. The trade-off that led to the decision for a pyramid wavefront sensor will be explained, as well as the additional control tasks such as pupil stabilization and compensation of non-common path aberrations.