Closure Phase Research Articles

How narrow is the M87* ring? I. The choice of closure likelihood function

ABSTRACT Event Horizon Telescope (EHT) observations of the core of the galaxy M87 suggest an observational appearance dominated by a ring of approximately 40 $\mu$as in diameter. The thickness of the ring is less certain: imaging efforts constrained it to be less than half the diameter (consistent with an imaging resolution of 20 $\mu$as), while visibility-domain modelling suggested a variety of fractional widths, including as low as $10{{\ \rm per\ cent}}$ on some days. The fractional width is very interesting as it has the potential to discriminate between different astrophysical scenarios for the source; in fact, the 10–$20{{\ \rm per\ cent}}$ range is so narrow as to be in tension with theoretical expectations. In the first of a series of papers on the width of the observed ring, we reproduce a subset of EHT visibility-domain modelling results and we explore whether alternative data analysis methods might favour thicker rings. We point out that the closure phase (and closure amplitude) likelihood function is not independent of residual station gain amplitudes, even at high signal-to-noise, and explore two approximations of practical interest: one standard in the field (and employed by the EHT collaboration), and a new one that we propose. Analysing the public data, we find that the new likelihood approximation prefers somewhat thicker rings, more in line with theoretical expectations. Further analysis is needed, however, to determine which approximation is better for the EHT data.

Wave interference in railway track due to multiple wheels

A resonance pattern at frequencies from around 400 Hz to 1000 Hz has often been observed from measured rail accelerations. Such resonances are important for rail noise and corrugation. Although this pattern has been reported and discussed in several papers in terms of wave reflections between multiple wheels, the aim of this study is to investigate the generation mechanism of this resonance phenomenon in detail, and to give both mathematical and physical insight. An infinite Timoshenko beam with continuous supports is adopted for modeling the track system, and the point and transfer receptances of the rail for a stationary harmonic excitation are explicitly obtained by the residue theorem. A frequency-domain method is then presented to calculate the power spectral densities of the wheel-track coupled system responses to stochastic irregularities with the moving irregularity model. It is found that the multiple peaks can be explained by using the phase closure principle. Moreover, total reflection between the two wheels may occur at around 700 Hz, which results in the highest peak in the response.

Stop voicing contrast in Lio

Typologically, two-way or three-way voicing contrasts in stops can be reliably defined along the VOT continuum, that is, by measuring the gap between the start of voicing and the stop burst, which can be negative or positive. In the literature, three main categories are therefore derived: prevoiced, unaspirated, and aspirated stops (Keating, 1984; Lisker and Abramson, 1964; and Cho et al., 2019). For Lio, an understudied Austronesian language of Central Flores (Eastern Indonesia), it has been claimed that the stop voicing contrast is realized with prevoicing for voiced stops and aspiration for voiceless stops (Elias, 2018). However, it is unclear how long the aspiration is, and whether Lio voiceless stops can be characterized as unaspirated or aspirated; furthermore, this claim was not based on an acoustic analysis, and relied heavily on one speaker. This study offers a descriptive analysis on voicing contrasts in Lio stops. The acoustic analysis reveals that the contrast is one of ‘true voicing’, with the closure phase of voiced stops presenting voicing (prevoiced) and short-lag VOT voiceless stops (unaspirated). This study will offer a valuable contribution to voicing contrasts typology, especially compared to Cho et al. (2019), and serves as a building block for future Lio research.

The GRAVITY young stellar object survey

Context. Protoplanetary disks drive some of the formation process (e.g., accretion, gas dissipation, formation of structures) of stars and planets. Understanding such physical processes is one of the most significant astrophysical questions. HD 163296 is an interesting young stellar object for which infrared and sub-millimeter observations have shown a prominent circumstellar disk with gaps plausibly created by forming planets. Aims. This study aims to characterize the morphology of the inner disk in HD 163296 with multi-epoch, near-infrared interferometric observations performed with GRAVITY at the Very Large Telescope Interferometer. Our goal is to depict the K-band (λ0 ~ 2.2 μm) structure of the inner rim with milliarcsecond (sub-au) angular resolution. Our data is complemented with archival Precision Integrated-Optics Near-infrared Imaging ExpeRiment (H-band; λ0 ~ 1.65 μm) data of the source. Methods. We performed a gradient descent parametric model fitting to recover the sub-au morphology of our source. Results. Our analysis shows the existence of an asymmetry in the disk surrounding the central star of HD 163296. We confirm variability of the disk structure in the inner ~2 mas (0.2 au). While variability of the inner disk structure in this source has been suggested by previous interferometric studies, this is the first time that it is confirmed in the H- and K-bands by using a complete analysis of the closure phases and squared visibilities over several epochs. Because of the separation from the star, position changes, and the persistence of this asymmetric structure on timescales of several years, we argue that it is probably a dusty feature (e.g., a vortex or dust clouds) made by a mixing of silicate and carbon dust and/or refractory grains, inhomogeneously distributed above the mid-plane of the disk.

Real-time analysis of intraoperative delays and variations in intraoperative workflow with level of experience of the primary surgeon in small animal surgery.

To describe the causes of intraoperative delays and the changes in delays and surgical workflow with the level of training of the primary surgeon. Prospective observational study. Seventy-three small animal surgical procedures performed at an academic teaching institution between January 17, 2018 and April 10, 2018. Procedures (trainee=37, faculty=36) totaling 103.2h were observed and video recorded. Operative time was allocated to the surgical approach, exploration, exposure, intervention, and closure phases. Suballocations were made to specific tasks within these categories (such as cutting or hemostasis). Intraoperative delays and reasons were recorded. Differences in use of time between trainee and faculty surgeons were analyzed. Delays constituted 9.2% (±4.4) of the operative time, of which 6.5%(±3.6) were surgeon controlled and 2.6% (±2.7) were non-surgeon controlled. Surgeons preparing instrumentation outside of the operative field and retrieval of equipment from supply areas were the greatest contributors to delays. Intraoperative delays did not increase when the trainee was placed in the primary surgeon role (P= .78). During the approach faculty surgeons spent proportionally less time on hemostasis (P= .02), and during closure they spent less time suturing (P= .03) than trainees. Trainee surgeons did not have greater intraoperative delays. Delays were created when surgeons prepared their own instrumentation. Workflow differed between experts and trainees. Advancing a trainee surgeon into the primary role is unlikely to increase intraoperative delays, which can be reduced by the inclusion of trained scrub technicians. A focus on efficient hemostasis and fluidity when suturing may improve operative efficiency for surgical trainees.

Breathing-swallow dysfunction in COPD: How silent aspiration may be contributing to exacerbations.

Breathing-swallow dysfunction in COPD: How silent aspiration may be contributing to exacerbations.

First stellar photons for an integrated optics discrete beam combiner at the William Herschel Telescope.

We present the first on-sky results of a four-telescope integrated optics discrete beam combiner (DBC) tested at the 4.2 m William Herschel Telescope. The device consists of a four-input pupil remapper followed by a DBC and a 23-output reformatter. The whole device was written monolithically in a single alumino-borosilicate substrate using ultrafast laser inscription. The device was operated at astronomical H-band (1.6 µm), and a deformable mirror along with a microlens array was used to inject stellar photons into the device. We report the measured visibility amplitudes and closure phases obtained on Vega and Altair that are retrieved using the calibrated transfer matrix of the device. While the coherence function can be reconstructed, the on-sky results show significant dispersion from the expected values. Based on the analysis of comparable simulations, we find that such dispersion is largely caused by the limited signal-to-noise ratio of our observations. This constitutes a first step toward an improved validation of the DBC as a possible beam combination scheme for long-baseline interferometry.

Appinitic and high Ba[sbnd]Sr magmatism in central Brazil: Insights into the late accretion stage of West Gondwana

Large amounts of high BaSr magmatism can be produced as the result of late accretion or decompression in the final stages of continental arc evolution in orogenic systems and leads to continental crustal growth. This type of magmatism often occurs associated with mega-shear zones and displays geochemical signatures that indicate magmas deriving from the melting of enriched lithospheric mantle. Such enrichment may be an indication of slab-derived fluid and/or melt interaction, released from subducted material. The high BaSr granitoids of the Brasiliano Paraguay Belt, Tocantins Province, central Brazil, comprise two suites that crystallized approximately 40 My apart from each other. Both suites are composed of metaluminous to slightly peraluminous rocks (ASI = 0.64–1.09) with magnesian character, and present high Ba (~1430 ppm), Sr (~800 ppm), K2O (~4 wt%), LREE and LILE contents. The negative εNd(T) values (−6.32 and − 6.65) associated with high contents of incompatible elements indicate an evolution from partial melting of mantle-derived magma previously metasomatized by subducted slab fluids. Crystallization ages of 557 ± 5.7 Ma and 554 ± 2.9 Ma have been obtained for the older, high MgK calc-alkaline suite. It evolved from high Cr and Ni mantle-derived appinitic magma to coeval granodiorites by crystal fractionation accompanied by minor crustal contamination. The younger, 515 ± 3.6 Ma-old suite displays an elevated concentration in some HFSEs, show alkali-calcic affinity and is represented by high-K monzogranites. A model proposed for the two hybrid suites is based on a slab break-off and a subsequent lithospheric delamination after 40 My, where the heat flux generated by mantle upwelling led to a partial melting of the enriched subcontinental lithospheric mantle beneath the continental crust. The older calc-alkaline suite represents the end process of magmatic arc accretion in the central Tocantins Province. The younger one is compatible with a transitional shoshonitic to A-type affinity, associated to post-collisional collapse stage of the orogen at Cambrian times. The petrogenesis of the investigated rocks requires an ocean closure phase at ca. 590 Ma, which could be linked to the consumption of the Clymene Ocean toward Amazonian Craton, recording a new collisional event in the central West Gondwana.

First light of a holographic aperture mask: Observation at the Keck OSIRIS Imager

Context. As an interferometric technique, sparse aperture masking (SAM) is capable of imaging beyond the diffraction limit of single telescopes. This makes SAM an important technique for studying processes such as planet formation at Solar System scales. However, it comes at the cost of a reduction in throughput, typically by 80–90%. Aims. We report on the design, construction, and commissioning of a prototype aperture masking technology implemented at the Keck OH-Suppressing Infrared Integral Field Spectrograph (OSIRIS) Imager: the holographic aperture mask. Holographic aperture masking (HAM) aims at (i) increasing the throughput of SAM by selectively combining all subapertures across a telescope pupil in multiple interferograms using a phase mask, and (ii) adding low-resolution spectroscopic capabilities. Methods. Using liquid-crystal geometric phase patterns, we manufacture a HAM mask that uses an 11-hole SAM design as the central component and a holographic component comprising 19 different subapertures. Thanks to a multilayer liquid-crystal implementation, the mask has a diffraction efficiency higher than 96% from 1.1 to 2.5 micron. We create a pipeline that extracts monochromatic closure phases from the central component as well as multiwavelength closure phases from the holographic component. We test the performance of the HAM mask in the laboratory and on-sky. Results. The holographic component yields 26 closure phases with spectral resolutions between R ∼ 6.5 and R ∼ 15, depending on the interferogram positions. On April 19, 2019, we observed the binary star HDS 1507 in the Hbb filter (λ0 = 1638 nm and Δλ = 330 nm) and retrieved a constant separation of 120.9 ± 0.5 mas for the independent wavelength bins, which is in excellent agreement with literature values. For both the laboratory measurements and the observations of unresolved reference stars, we recorded nonzero closure phases – a potential source of systematic error that we traced to polarization leakage of the HAM optic. We propose a future upgrade that improves the performance, reducing this effect to an acceptable level. Conclusions. Holographic aperture masking is a simple upgrade of SAM with increased throughput and a new capability of simultaneous low-resolution spectroscopy that provides new differential observables (e.g., differential phases with wavelength).

Resolving the Hot Dust Disk of ESO323-G77

Abstract Infrared interferometry has led to a paradigm shift in our understanding of the dusty structure in the central parsecs of active galactic nuclei (AGNs). The dust is now thought to comprise a hot (∼1000 K) equatorial disk, some of which is blown into a cooler (∼300 K) polar dusty wind by radiation pressure. In this paper, we utilize the new near-IR interferometer GRAVITY on the Very Large Telescope Interferometer (VLTI) to study a Type 1.2 AGNs hosted in the nearby Seyfert galaxy ESO 323-G77. By modeling the squared visibility and closure phase, we find that the hot dust is equatorially extended, consistent with the idea of a disk, and shows signs of asymmetry in the same direction. Furthermore, the data is fully consistent with the hot dust size determined by K-band reverberation mapping as well as the predicted size from a CAT3D-WIND model created in previous work using the spectral energy distribution of ESO 323-G77 and observations in the mid-IR from VLTI/MID-infrared Interferometric instrument).

Modeling vaccination rollouts, SARS-CoV-2 variants and the requirement for non-pharmaceutical interventions in Italy

Despite progress in clinical care for patients with coronavirus disease 2019 (COVID-19)1, population-wide interventions are still crucial to manage the pandemic, which has been aggravated by the emergence of new, highly transmissible variants. In this study, we combined the SIDARTHE model2, which predicts the spread of SARS-CoV-2 infections, with a new data-based model that projects new cases onto casualties and healthcare system costs. Based on the Italian case study, we outline several scenarios: mass vaccination campaigns with different paces, different transmission rates due to new variants and different enforced countermeasures, including the alternation of opening and closure phases. Our results demonstrate that non-pharmaceutical interventions (NPIs) have a higher effect on the epidemic evolution than vaccination alone, advocating for the need to keep NPIs in place during the first phase of the vaccination campaign. Our model predicts that, from April 2021 to January 2022, in a scenario with no vaccine rollout and weak NPIs ({cal{R}}_0 = 1.27), as many as 298,000 deaths associated with COVID-19 could occur. However, fast vaccination rollouts could reduce mortality to as few as 51,000 deaths. Implementation of restrictive NPIs ({cal{R}}_0 = 0.9) could reduce COVID-19 deaths to 30,000 without vaccinating the population and to 18,000 with a fast rollout of vaccines. We also show that, if intermittent open–close strategies are adopted, implementing a closing phase first could reduce deaths (from 47,000 to 27,000 with slow vaccine rollout) and healthcare system costs, without substantive aggravation of socioeconomic losses.

Time Series Phase Unwrapping Based on Graph Theory and Compressed Sensing

Time Series SAR interferometry (InSAR) (TS-InSAR) has been widely applied to monitor the crustal deformation with centimeter- to millimeter-level accuracy. Phase unwrapping (PU) errors have proven to be one of the main sources of bias that hinder achieving such high accuracy. In this article, a new time series PU approach is developed to improve the unwrapping accuracy. The rationale behind the proposed method is to first improve the sparse unwrapping by mitigating the phase gradients in a 2-D network and then correcting the unwrapping errors in time, based on the triplet phase closure. Rather than the commonly used Delaunay network, we employ the all-pairs-shortest-path (APSP) algorithm from graph theory to maximize the temporal coherence of all edges and to approach the phase continuity assumption in the 2-D spatial domain. Next, we formulate the PU error correction in the 1-D temporal domain as compressed sensing (CS) problem, according to the sparsity of the remaining phase ambiguity cycles. We finally estimate phase ambiguity cycles by means of integer linear programming (ILP). The comprehensive comparisons using synthetic and real Sentinel-1 data covering Lost Hills, California, confirm the validity of the proposed 2-D + 1-D unwrapping approach and its superior performance compared to previous methods.

Improved field performance of Fourier telescopy in real atmosphere turbulence using new phase closure iteration for object spatial spectrum reconstruction

Fourier telescopy is a remote imaging method that generates several interfering fringes from a coherent laser transmitter array. In this technique, the spatial spectrum of an object is acquired by sweeping fringes of different spatial frequencies and directions on the object. Most traditional triplet phase closure iterations are accomplished by three beams and are used to alleviate the phase aberration induced by atmospheric effects. For reducing the effect of scintillation, which is an atmospheric turbulence effect, we propose a phase closure method wherein the complex amplitude of four beams are combined in iteration. We evaluated the performance of the proposed method both theoretically and experimentally. We conducted the field experiments at 200 m and 1.2 km. The results demonstrated that the proposed phase closure method performs well in enhancing the image quality in a multibeam array when there is scintillation in the atmosphere.

The asymmetric inner disk of the Herbig Ae star HD 163296 in the eyes of VLTI/MATISSE: evidence for a vortex?

Context. A complex environment exists in the inner few astronomical units of planet-forming disks. High-angular-resolution observations play a key role in our understanding of the disk structure and the dynamical processes at work. Aims. In this study we aim to characterize the mid-infrared brightness distribution of the inner disk of the young intermediate-mass star HD 163296 from early VLTI/MATISSE observations taken in the L- and N-bands. We put special emphasis on the detection of potential disk asymmetries. Methods. We use simple geometric models to fit the interferometric visibilities and closure phases. Our models include a smoothed ring, a flat disk with an inner cavity, and a 2D Gaussian. The models can account for disk inclination and for azimuthal asymmetries as well. We also perform numerical hydrodynamical simulations of the inner edge of the disk. Results. Our modeling reveals a significant brightness asymmetry in the L-band disk emission. The brightness maximum of the asymmetry is located at the NW part of the disk image, nearly at the position angle of the semimajor axis. The surface brightness ratio in the azimuthal variation is 3.5 ± 0.2. Comparing our result on the location of the asymmetry with other interferometric measurements, we confirm that the morphology of the r < 0.3 au disk region is time-variable. We propose that this asymmetric structure, located in or near the inner rim of the dusty disk, orbits the star. To find the physical origin of the asymmetry, we tested a hypothesis where a vortex is created by Rossby wave instability, and we find that a unique large-scale vortex may be compatible with our data. The half-light radius of the L-band-emitting region is 0.33 ±0.01 au, the inclination is 52°−7°+5°, and the position angle is 143° ± 3°. Our models predict that a non-negligible fraction of the L-band disk emission originates inside the dust sublimation radius for μm-sized grains. Refractory grains or large (≳10 μm-sized) grains could be the origin of this emission. N-band observations may also support a lack of small silicate grains in the innermost disk (r ≲ 0.6 au), in agreement with our findings from L-band data.

Development of the RACI Model for Processes of the Closure Phase in Construction Programs

Recently, the construction industry has seen an increase in construction program level projects in which a number of projects are carried out simultaneously. These projects thus require more systematic management than traditional management methods due to both their complexity and the diverse stakeholders involved. When multiple projects overlap at the same time, it can create a gap between the contractor’s results and the user’s expectations at the closure phase of the construction program. These can include situations such as when handover is delayed, conflicts and frictions occur, and complaints from users mount. Therefore, an approach is needed to increase user satisfaction at the program level. This study presents a systematic closing management plan to increase user satisfaction for a smoother handover at the closure phase. The closure process was identified through case studies of activities in the closure phase. In addition, after identifying the stakeholder groups participating in the closure phase, responsibilities and roles were proposed as RACI (Responsible, Accountable, Consulted, and Informed) models by mapping the closure phase of processes and stakeholders. This model shows who is responsible and accountable for, consulted on, and informed about work processes in the closure phase of the program. From a user’s point of view, program closure signifies the beginning of operation and maintenance. We intend to contribute to the increase of user satisfaction by suggesting when and in what work activities the user will be involved in construction products from the user’s perspective.

Kernel Phase and Coronagraphy with Automatic Differentiation

Abstract The accumulation of aberrations along the optical path in a telescope produces distortions and speckles in the resulting images, limiting the performance of cameras at high angular resolution. It is important to achieve the highest possible sensitivity to faint sources, using both hardware and data analysis software. While analytic methods are efficient, real systems are better modeled numerically, but numerical models of complicated optical systems with many parameters can be hard to understand, optimize, and apply. Automatic differentiation or “backpropagation” software developed for machine-learning applications now makes calculating derivatives with respect to aberrations in arbitrary planes straightforward for any optical system. We apply this powerful new tool to the problem of high-angular-resolution astronomical imaging. Self-calibrating observables such as the “closure phase” or “bispectrum” have been widely used in optical and radio astronomy to mitigate optical aberrations and achieve high-fidelity imagery. Kernel phases are a generalization of closure phases valid in the limit of small phase errors. Using automatic differentiation, we reproduce existing kernel phase theory within this framework and demonstrate an extension to the case of a Lyot coronagraph, which is found to have self-calibrating combinations of speckles. which are resistant to phase noise, but only in the very high-wave-front-quality regime. As an illustrative example, we reanalyze Palomar adaptive optics observations of the binary α Ophiuchi, finding consistency between the new pipeline and the existing standard. We present a new Python package morphine that incorporates these ideas, with an interface similar to the popular package poppy, for optical simulation with automatic differentiation. These methods may be useful for designing improved astronomical optical systems by gradient descent.

Optically thin circumstellar medium in theβLyr A system

The complex binary systemβLyr A has an extensive observational dataset: light curves (from far UV to far IR), interferometric squared visibility, closure phase, triple product measurements, spectral-energy distribution, high-resolution spectroscopy, differential visibility amplitude, and also a differential phase. In particular, we used spectra from the Ondřejov 2m telescope from 2013 to 2015 to measure the emission in Hα, He I, Si II, Ne I, or C IIlines, and differential interferometry by CHARA/VEGA from the 2013 campaign to measure wavelength-dependent sizes across Hαand He I6678. This allowed us to constrain not only optically thick objects (primary, secondary, accretion disc), but also optically thin objects (disc atmosphere, jets, shell). We extended our modelling tool, Pyshellspec (based on Shellspec; a 1D local thermodynamical equilibrium radiative transfer code), to include all new observables, to compute differential visibilities/phases, to perform a Doppler tomography, and to determine a jointχ2metric. After an optimisation of 38 free parameters, we derived a robust model of theβLyr A system. According to the model, the emission is formed in an extended atmosphere of the disc, two perpendicular jets expanding at ∼700 km s−1, and a symmetric shell with the radius ∼70 R⊙. The spectroscopy indicates a low abundance of carbon, 10−2of the solar value. We also quantified systematic differences between datasets, and we discuss here alternative models with higher resolutions, additional asymmetries, or He-rich abundances.

The GRAVITY young stellar object survey

Context. 51 Oph is a Herbig Ae/Be star that exhibits strong near-infrared CO ro-vibrational emission at 2.3 μm, most likely originating in the innermost regions of a circumstellar disc. Aims. We aim to obtain the physical and geometrical properties of the system by spatially resolving the circumstellar environment of the inner gaseous disc. Methods. We used the second-generation Very Large Telescope Interferometer instrument GRAVITY to spatially resolve the continuum and the CO overtone emission. We obtained data over 12 baselines with the auxiliary telescopes and derive visibilities, and the differential and closure phases as a function of wavelength. We used a simple local thermal equilibrium ring model of the CO emission to reproduce the spectrum and CO line displacements. Results. Our interferometric data show that the star is marginally resolved at our spatial resolution, with a radius of ~10.58 ± 2.65R⊙. The K-band continuum emission from the disc is inclined by 63° ± 1°, with a position angle of 116° ± 1°, and 4 ± 0.8 mas (0.5 ± 0.1 au) across. The visibilities increase within the CO line emission, indicating that the CO is emitted within the dust-sublimation radius. By modelling the CO bandhead spectrum, we derive that the CO is emitted from a hot (T = 1900–2800 K) and dense (NCO = (0.9–9) × 1021 cm−2) gas. The analysis of the CO line displacement with respect to the continuum allows us to infer that the CO is emitted from a region 0.10 ± 0.02 au across, well within the dust-sublimation radius. The inclination and position angle of the CO line emitting region is consistent with that of the dusty disc. Conclusions. Our spatially resolved interferometric observations confirm the CO ro-vibrational emission within the dust-free region of the inner disc. Conventional disc models exclude the presence of CO in the dust-depleted regions of Herbig AeBe stars. Ad hoc models of the innermost disc regions, that can compute the properties of the dust-free inner disc, are therefore required.

Methods to avoid being affected by non-zero closure phase in InSAR time series analysis in a multi-reference stack

Abstract This work discusses InSAR time series analysis using multi-reference stacks with exclusively short time intervals. A 5 months long stack of Sentinel-1 acquisitions over a high alpine territory that includes fast moving landslides is used. Use of the multi-look phases becomes problematic due to non-zero closure phase. The errors induced by non-zero phase closure can be avoided by the use of single-look phases for all scatterers, including distributed scatterers. A weighted least-squares solution of the deformation time-series is obtained using the multi-reference stack interferometric single-look phases. Quality control is done during the regression analysis, the conversion to the time series, and considering the temporal coherence. Spatial filtering of the single-look phase time series can be used to further reduce the phase noise present in areas with intermediate coherence levels.

A case study of management and disposal of TENORMs: radiological risk estimation by TSD Dose and RESRAD-ONSITE

<abstract> <p>Naturally Occurring Radioactive Materials (NORMs) and Technologically Enhanced NORMs (TENORMs) are among the principal sources of radiation exposure for humans and for the environment. Therefore, the assessment of the impact of NORMs and TENORMs waste on human health is a key issue for their management and for acceptance of disposal sites. The radiological doses to workers and public due to TENORMs disposal depend on the waste inventory, on the usage of the site during operational activities and post closure phase and on the presence of dwelling areas in the vicinity of the disposal site. In the present study it is presented a methodology to preliminary assess the feasibility of a disposal of TENORMs, mainly constituted by phosphate sludges, originated from phosphoric acid industry activities. The hypothetical case study here presented is inspired by a real case study. Different possible scenarios have been considered. The potential doses to workers and to the public on-site have been estimated by the use of the TSD Dose and the RESRAD on-site codes both during the production life cycle of the site and once it ended. Sensitivity analyses were conducted to evaluate the impact of some key parameters, such the coverage thickness and wind velocity, on potential risk for workers and public.</p> </abstract>