Actual Flux Research Articles

Assessing the performance of a large-scale irrigation system by estimations of actual evapotranspiration obtained by Landsat satellite images resampled with cubic convolution

Remote sensing techniques allow monitoring the Earth surface and acquiring worthwhile information that can be used efficiently in agro-hydrological systems. Satellite images associated to computational models represent reliable resources to estimate actual evapotranspiration fluxes, ETa, based on surface energy balance. The knowledge of ETa and its spatial distribution is crucial for a broad range of applications at different scales, from fields to large irrigation districts. In single plots and/or in irrigation districts, linking water volumes delivered to the plots with the estimations of remote sensed ETa can have a great potential to develop new cost-effective indicators of irrigation performance, as well as to increase water use efficiency. With the aim to assess the irrigation system performance and the opportunities to save irrigation water resources at the “SAT Llano Verde” district in Albacete, Castilla-La Mancha (Spain), the Surface Energy Balance Algorithm for Land (SEBAL) was applied on cloud-free Landsat 5 Thematic Mapper (TM) images, processed by cubic convolution resampling method, for three irrigation seasons (May to September 2006, 2007 and 2008). The model allowed quantifying instantaneous, daily, monthly and seasonal ETa over the irrigation district. The comparison between monthly irrigation volumes distributed by each hydrant and the corresponding spatially averaged ETa, obtained by assuming an overall efficiency of irrigation network equal to 85%, allowed the assessment of the irrigation system performance for the area served by each hydrant, as well as for the whole irrigation district. It was observed that in all the investigated years, irrigation volumes applied monthly by farmers resulted generally higher than the corresponding evapotranspiration fluxes retrieved by SEBAL, with the exception of May, in which abundant rainfall occurred. When considering the entire irrigation seasons, it was demonstrated that a considerable amount of water could have been saved in the district, respectively equal to 26.2, 28.0 and 16.4% of the total water consumption evaluated in the three years.

Distribution and isotopic signature of deep gases in submerged soils in an island of the Lower Delta of the Paraná River, Argentina.

Subsoil CH4 and CO2 concentrations, δ13C-CH4 and δ13C-CO2 signatures, total organic carbon (TOC) and δ13C-TOC, together with C/N ratio of organic matter, were evaluated throughout a soil profile up to the atmosphere to understand the dynamics of CH4 and CO2 in the waterlogged environment of an island of the Lower Delta of the Paraná River, Argentina. The analysis of the vertical profile showed that a significant fraction of CH4 exists as gas trapped within the sediment column, compared to CH4 dissolved in soil solution. CH4 concentration measurements in sub-saturated soils showed that free CH4 is 1 order of magnitude smaller than CH4 recovered from soil cores by ultrasonic degassing. The highest concentrations of CH4 occurred at the 90-120-cm layer. At this depth, δ13C-CH4 values resulting from methanogenesis were around - 71‰, which is well within the range of CH4 produced from CO2 reduction, and δ13C values of the associated CO2 were enriched (~ - 7‰). Isotope mass balance models used to calculate the fraction of oxidized CH4 indicated that around 30% of the CH4 produced was oxidized prior to atmospheric release. In contrast to methanogenesis, during oxidation processes δ13C-CH4 shifts to more positive values. The mineralogical, textural, isotopic, and geochemical characterization of subsoil sediments with abundant organic matter, like Paraná Delta, demonstrated that CH4 storage capacity of the soil, production, consumption, and transport are the main factors in regulating the actual flux rates of CH4 to the atmosphere.

Demonstration of Multigroup Multiband Cross Section Generation in Monte Carlo Simulations

This is the investigation into the generation of high-fidelity multigroup multiband cross sections from Monte Carlo neutron transport simulations. Previous methods for generating multigroup multiband (MGMB) cross sections, and multigroup cross sections, assume an approximate shape for the scalar flux. This approximate flux shape is the product of an energy-dependent spectrum and a cross-section-dependent self-shielding factor for the material of interest. Since, these methods assume a scalar flux a priori, the cross sections generated may not be sufficiently consistent with the actual scalar flux of any particular problem. Instead, in our approach we tally both the reaction rate and the flux for each energy group and cross section magnitude band using the Mercury Monte Carlo particle transport code and compute the group-band cross sections from these tallies. This approach eliminates the need for assuming a flux by using a Monte Carlo simulation to calculate these cross sections. The increased physical fidelity of MGMB also requires more data storage, since more than one cross section value needs to be stored per energy group. However, this storage tradeoff could be mitigated by using less energy groups.

Characterization of oil-producing yeast Lipomyces starkeyi on glycerol carbon source based on metabolomics and 13C-labeling.

Lipomyces starkeyi is an oil-producing yeast that can produce triacylglycerol (TAG) from glycerol as a carbon source. The TAG was mainly produced after nitrogen depletion alongside reduced cell proliferation. To obtain clues for enhancing the TAG production, cell metabolism during the TAG-producing phase was characterized by metabolomics with 13C labeling. The turnover analysis showed that the time constants of intermediates from glycerol to pyruvate (Pyr) were large, whereas those of tricarboxylic acid (TCA) cycle intermediates were much smaller than that of Pyr. Surprisingly, the time constants of intermediates in gluconeogenesis and the pentose phosphate (PP) pathway were large, suggesting that a large amount of the uptaken glycerol was metabolized via the PP pathway. To synthesize fatty acids that make up TAG from acetyl-CoA (AcCoA), 14 molecules of nicotinamide adenine dinucleotide phosphate (NADPH) per C16 fatty acid molecule are required. Because the oxidative PP pathway generates NADPH, this pathway would contribute to supply NADPH for fatty acid synthesis. To confirm that the oxidative PP pathway can supply the NADPH required for TAG production, flux analysis was conducted based on the measured specific rates and mass balances. Flux analysis revealed that the NADPH necessary for TAG production was supplied by metabolizing 48.2% of the uptaken glycerol through gluconeogenesis and the PP pathway. This result was consistent with the result of the 13C-labeling experiment. Furthermore, comparison of the actual flux distribution with the ideal flux distribution for TAG production suggested that it is necessary to flow more dihydroxyacetonephosphate (DHAP) through gluconeogenesis to improve TAG yield.

Characterization of the radiative heating stage in the end-forming process of PVC pipes

The end-forming of polyvinyl chloride (PVC) pipes is a manufacturing process aimed at deforming one end of a tube to allow connections between pipes. The deformation is preceded by a heating stage which leads to softening of the material and which, if not properly carried out, may cause unacceptable defects in the final product. The heating stage in the end-forming process often occurs within ovens equipped with infrared short-wave (SW) lamps, favoring the penetration of thermal radiation into the material. The lamps are placed at certain angular positions, making it necessary to impose a rotary motion to the pipe, to allow a circumferentially uniform heating. In this work a transient analysis of the end-forming heating stage has been conducted by means of two finite-element models, creating a design tool for the complete characterization of the process. The first model makes use of a time-dependent heat generation term which takes into account the actual heat flux distribution incident at the outer surface of the pipe, leading to the identification of suitable angular velocities to achieve uniform heating. In the second model, a local temperature control has been introduced in order to characterize the process in terms of heating time. To the best authors’ knowledge, this is the first numerical instrument able to completely characterize the heating stage of the end-forming process of PVC pipes.

Plans for Liquid Metal Divertor in Tokamak Compass

The COMPASS tokamak (R = 0.56 m, a = 0.2 m, BT = 1.3 T, Ip ~ 300 kA, pulse duration 0.4 s) operates in ITER-like plasma shape in H-mode with Type-I ELMs. In 2019, we plan to install into the divertor a test target based on capillary porous system filled with liquid lithium/tin. This single target will be inclined toroidally in order to be exposed to ITER-relevant surface heat flux (20 MW/m2). Based on precisely measured actual heat fluxes, our simulations predict (for 45° inclination, without accounting for the lithium vapor shielding) the surface temperature rises up to 700°C within 120 ms of the standard ELMy H-mode heat flux with ELM filaments reaching hundreds MW/m2. Significant lithium vaporization is expected. The target surface will be observed by spectroscopy, fast visible and infrared cameras. The scientific program will be focused on operational issues (redeposition of the evaporated metal, ejection of droplets, if any) as well as on the effect on the plasma physics (improvement of plasma confinement, L–H power threshold, Zeff, etc.). After 2024, a closed liquid divertor may be installed into the planned COMPASS Upgrade tokamak (R = 0.84 m, a = 0.3 m, BT = 5 T, Ip = 2 MA, Pin = 8 MW, pulse duration ~2 s) with ITER-relevant heat fluxes loading the entire toroidal divertor.

Orbital altitude dust at Mars, its implication and a prototype for its detection

Dust at orbital altitude on Mars could be mainly due to interplanetary source, cometary source or natural satellites of Mars. Recent work and MAVEN observations predict that dust at orbital altitudes could be interplanetary in nature. Since, the source of such particles is not understood unambiguously, it remains a puzzling question to space scientist about what is a source of it. An instrument on future Mars orbiter, which can measure the dust particle parameters like mass, velocity and flux, may be helpful to address such issues.In this article, dust flux at orbital altitudes on Mars is presented in the initial part. To study origin, abundance, distribution, flux and seasonal variation of dust at orbital altitude on Mars, a Mars Orbit Dust Experiment (MODEX) has been proposed and development of its prototype has been initiated at Physical Research Laboratory. Though, earlier dust detectors by other researchers might have been designed using the impact plasma theory, they are not found with thorough explanation explicitly, in the literature. We have presented the impact plasma theory for the first time to explain detector target design. Also, a prototype dust detector, its front end electronics and initial testing results using a pulse laser are reported here. The ions and electrons of impact plasma have been separated using biased electrodes. The results demonstrate the possible use of pulse laser for testing the impact ionization dust detector, prior to calibrating the dust detector using a dust accelerator facility. The detector under development could provide actual dust flux coming to Mars and using the measurements, one can understand the origin, abundance, distribution, flux and seasonal variation of dust.

Application of membrane distillation for the treatment of anaerobic membrane bioreactor effluent: An especial attention to the operating conditions

This study was carried out by applying the direct contact membrane distillation (DCMD) into the treatment of effluent from anaerobic membrane bioreactor. The treatment efficiency of DCMD was highly emphasized, which was expected to be improved through the optimization of operating conditions. Three operating conditions, including temperature difference, cross-flow velocity and membrane pore size, were considered. The relative flux (the ratio of actual flux to initial flux) increased from 0.50 to 0.98 as the operating conditions changed and that was enhanced by the increment of temperature difference and cross-flow velocity. Regarding the wastewater treatment efficiency, except for ammonia nitrogen, the interception ratio was greater than 90.0%, which even reached 99.0% for CODCr, protein and polysaccharide by optimizing operating conditions. In addition, the interception ratio of PO43--P almost reached 100.0% under any operating condition. Further study about membrane fouling was carried out, and the crystallization fouling was found to be the main fouling type.

Estimating actual and potential bare soil evaporation from silty pyroclastic soils: Towards improved landslide prediction

The estimation of evaporative fluxes and their effects on soil suction is assuming a prominent role in the field of interpretation and early-warning prediction of rainfall-induced landslides. Evaporation models refer essentially to sands or plastic (silty and clayey) soils. Models validated specifically for non-plastic silty pyroclastic soils, usually characterized by very high porosity, are instead unavailable. This deficit arises although silty pyroclastic covers are widely spread across the world, increasingly involved in rainfall-induced landslides and recognized showing particular hydrological behaviour. A number of questions may be raised about the issue: (i) may any evaporative models be reliably extended to silty pyroclastic soils?; (ii) what atmospheric variables need to be monitored at least to reliably predict evaporation fluxes in these soils?; and (iii) how accurate evaporation estimations are if they are referred to silty pyroclastic covers for early warning purposes? This study addresses these questions by assessing the capabilities of several simplified models in estimating evaporative (potential and actual) fluxes for silty pyroclastic soils. To this aim, a large-scale lysimeter, consisting in a silty pyroclastic layer exposed to the atmosphere and comprehensively monitored for both weather forcing and hydrological soil variables, is adopted. It provides a dataset of observations suitable to calibrate and validate the selected evaporation models. Moreover, the availability of weather observations makes it possible to define the minimum set of equipment required to attain reliable evaporation estimation. This study shows that: (i) the adoption of a literature-based calibration can produce misleading estimates of actual evaporation, whereas the model performances after a lysimeter-based recalibration are satisfactory; (ii) reducing the weather measurements can induce an overestimation of predicted fluxes up to 50%; and (iii) the investigated models quite accurately predict water out-coming fluxes while running in early warning predictions.

A combined ANN-GA and experimental based technique for the estimation of the unknown heat flux for a conjugate heat transfer problem

The major objectives in the design of thermal systems are obtaining the information about thermophysical, transport and boundary properties. The main purpose of this paper is to estimate the unknown heat flux at the surface of a solid body. A constant area mild steel fin is considered and the base is subjected to constant heat flux. During heating, natural convection heat transfer occurs from the fin to ambient. The direct solution, which is the forward problem, is developed as a conjugate heat transfer problem from the fin and the steady state temperature distribution is recorded for any assumed heat flux. In order to model the natural convection heat transfer from the fin, an extended domain is created near the fin geometry and air is specified as a fluid medium and Navier Stokes equation is solved by incorporating the Boussinesq approximation. The computational time involved in executing the forward model is then reduced by developing a neural network (NN) between heat flux values and temperatures based on back propagation algorithm. The conjugate heat transfer NN model is now coupled with Genetic algorithm (GA) for the solution of the inverse problem. Initially, GA is applied to the pure surrogate data, the results are then used as input to the Levenberg- Marquardt method and such hybridization is proven to result in accurate estimation of the unknown heat flux. The hybrid method is then applied for the experimental temperature to estimate the unknown heat flux. A satisfactory agreement between the estimated and actual heat flux is achieved by incorporating the hybrid method.

Effect of Dual Surface Cooling on the Temperature Distribution of a Nuclear Fuel Pellet

Heat removal from nuclear reactor core has been one of the major Engineering considerations in the construction of nuclear power plant. At the center of this consideration is the nuclear fuel pellet whose burning efficiency determines the rate of heat transfer to the coolant. This research, focuses on the study of temperature distribution of solid fuel, temperature distribution of annular fuel with external cooling and the temperature distribution of annular fuel with internal and external cooling. We analyzed the different distribution and made a conclusion on the possibility of improving temperature management of Nuclear fuel rod, by designing fuel pellets based on this geometrical and thermal Analysis. To date, a lot of studies has been done on the thermal and geometrical properties of Nuclear fuel pellet, it is observed that annular fuel pellet with simulteneous internal and external cooling can achieve better temperature distribution which leads to high linear heat generation rate, thus generating more power in the design [1]. It has also been observed that annular fuel pellets has low fission gas release [10]. In large LOCA, the peak cladding temperature of annular fuel is about 600 which is significantly less than that of solid fuel (920 ), this is due to the fact that annular fuel cladding has lower initial temperature and the thinner annular fuel can be cooled more efficiently than the solid fuel. One of drawbacks of annular fuel technology is “the fuel gap conductance assymmetry” which is caused by outward thermal expansion, it has a potential effect on the MDNBR (Minimum Departure from Nucleate Boiling Ratio), which is the minimum ratio of the critical to actual heat flux found in the core [10]. In this model, we used the ceramic fuel pellet of UO2 as our case study. All the parameters in this model are assumed parameters of UO2. The Heat Transfer tool (ANSYS APDL) was used to validate the Analytical Model of this research.

Potential of European <sup>14</sup>CO<sub>2</sub> observation network to estimate the fossil fuel CO<sub>2</sub> emissions via atmospheric inversions

Abstract. Combining measurements of atmospheric CO2 and its radiocarbon (14CO2) fraction and transport modeling in atmospheric inversions offers a way to derive improved estimates of CO2 emitted from fossil fuel (FFCO2). In this study, we solve for the monthly FFCO2 emission budgets at regional scale (i.e., the size of a medium-sized country in Europe) and investigate the performance of different observation networks and sampling strategies across Europe. The inversion system is built on the LMDZv4 global transport model at 3.75∘ × 2.5∘ resolution. We conduct Observing System Simulation Experiments (OSSEs) and use two types of diagnostics to assess the potential of the observation and inverse modeling frameworks. The first one relies on the theoretical computation of the uncertainty in the estimate of emissions from the inversion, known as “posterior uncertainty”, and on the uncertainty reduction compared to the uncertainty in the inventories of these emissions, which are used as a prior knowledge by the inversion (called “prior uncertainty”). The second one is based on comparisons of prior and posterior estimates of the emission to synthetic “true” emissions when these true emissions are used beforehand to generate the synthetic fossil fuel CO2 mixing ratio measurements that are assimilated in the inversion. With 17 stations currently measuring 14CO2 across Europe using 2-week integrated sampling, the uncertainty reduction for monthly FFCO2 emissions in a country where the network is rather dense like Germany, is larger than 30 %. With the 43 14CO2 measurement stations planned in Europe, the uncertainty reduction for monthly FFCO2 emissions is increased for the UK, France, Italy, eastern Europe and the Balkans, depending on the configuration of prior uncertainty. Further increasing the number of stations or the sampling frequency improves the uncertainty reduction (up to 40 to 70 %) in high emitting regions, but the performance of the inversion remains limited over low-emitting regions, even assuming a dense observation network covering the whole of Europe. This study also shows that both the theoretical uncertainty reduction (and resulting posterior uncertainty) from the inversion and the posterior estimate of emissions itself, for a given prior and “true” estimate of the emissions, are highly sensitive to the choice between two configurations of the prior uncertainty derived from the general estimate by inventory compilers or computations on existing inventories. In particular, when the configuration of the prior uncertainty statistics in the inversion system does not match the difference between these prior and true estimates, the posterior estimate of emissions deviates significantly from the truth. This highlights the difficulty of filtering the targeted signal in the model–data misfit for this specific inversion framework, the need to strongly rely on the prior uncertainty characterization for this and, consequently, the need for improved estimates of the uncertainties in current emission inventories for real applications with actual data. We apply the posterior uncertainty in annual emissions to the problem of detecting a trend of FFCO2, showing that increasing the monitoring period (e.g., more than 20 years) is more efficient than reducing uncertainty in annual emissions by adding stations. The coarse spatial resolution of the atmospheric transport model used in this OSSE (typical of models used for global inversions of natural CO2 fluxes) leads to large representation errors (related to the inability of the transport model to capture the spatial variability of the actual fluxes and mixing ratios at subgrid scales), which is a key limitation of our OSSE setup to improve the accuracy of the monitoring of FFCO2 emissions in European regions. Using a high-resolution transport model should improve the potential to retrieve FFCO2 emissions, and this needs to be investigated.

ANALYSIS OF THERMAL DESIGN OF HEATING UNITS WITH METEOROLOGICAL CLIMATE PECULIARITIES

This article is devoted to the analysis of thermal design of heating units, one of the compulsory calculations of heating systems, which ensures their stable and efficient operation. The article analyses the option of a single-pipe heating system with shifted end-capping areas and the overhead supply main; the difference is shown in the calculation results between heat balance equation of the heating unit and calculation of the actual heat flux (heat transfer coefficient) taking into account deviation from the standardized (technical passport) operating conditions. The calculation of the thermal conditions of residential premises is given, the deviation of the internal air temperature is shown taking into account the discrepancy between the calculation results for thermal energy.

Design of magnetic Circuit Simulation for Curing Device of Anisotropic MRE

The strength of magnetic field during fabrication of magnetorheological elastomer (MRE) plays a crucial role in order to form a pre-structured MRE. So far, gaussmeter were used to determine the magnetic intensity subjected to the MRE during curing. However, the magnetic flux reading through that measurement considered less accurate. Therefore, a simulation should be done to figure out the magnetic flux concentration around the sample. This paper investigates the simulation of magnetic field distribution in a curing device used during curing stage of anisotropic magnetorheological elastomer (MRE). The target in designing the magnetic circuit is to ensure a sufficient and uniform magnetic field to all the MRE surfaces during the curing process. The magnetic circuit design for the curing device was performed using Finite Element Method Magnetic (FEMM) to examine the magnetic flux density distribution in the device. The material selection was first done instantaneously during a magnetic simulation process. Then, the experimental validation of simulation was performed by measuring and comparing the actual flux generated within the specimen type and the one from the FEMM simulation. İt apparent that the data from FEMM simulation shows an agreement with the actual measurement. Furthermore, the FEMM results showed that the magnetic design is able to provide sufficient and uniform magnetic field all over the surfaces of the MRE.

On the Use of the Eddy Covariance Latent Heat Flux and Sap Flow Transpiration for the Validation of a Surface Energy Balance Model

Actual evapotranspiration is assessed via surface energy balance at an hourly rate. However, a robust estimation of daily evapotranspiration from hourly values is required. Outcomes of surface energy balance are frequently determined via measures of eddy covariance latent heat flux. Surface energy balance can be applied on images acquired at different times and spatial resolutions. In addition, hourly actual evapotranspiration needs to be integrated at a daily rate for operational uses. Questions arise whether the validation of surface energy balance models can benefit from complementary in situ measures of latent heat flux and sap flow transpiration. Here, validation was driven by image acquisition time, spatial resolution, and temporal integration. Thermal and optical images were collected with a proximity-sensing platform on an olive orchard at different acquisition times. Actual latent heat fluxes from canopy and sap flux at tree trunks were measured with a flux tower and heat dissipation probes. The latent heat fluxes were then further analyzed. A surface energy balance was applied over proximity sensing images re-sampled at different spatial resolutions with resulting latent heat fluxes compared to in situ ones. A time lag was observed and quantified between actual latent heat fluxes from canopy and sap flux at the tree trunk. Results also indicate that a pixel resolution comparable to the average canopy size was suitable for estimating the actual evapotranspiration via a single source surface energy balance model. Images should not be acquired at the beginning or the end of the diurnal period. Findings imply that sap flow transpiration can be used to measure surface energy balance at a daily rate or when images are found at an hourly rate near noon, and the existing time lag between the latent heat flux at the canopy and the sap flow at the trunk does not need to be taken into account.

Full Coupling Between the Atmosphere, Surface, and Subsurface for Integrated Hydrologic Simulation

AbstractAn ever increasing community of earth system modelers is incorporating new physical processes into numerical models. This trend is facilitated by advancements in computational resources, improvements in simulation skill, and the desire to build numerical simulators that represent the water cycle with greater fidelity. In this quest to develop a state‐of‐the‐art water cycle model, we coupled HydroGeoSphere (HGS), a 3‐D control‐volume finite element surface and variably saturated subsurface flow model that includes evapotranspiration processes, to the Weather Research and Forecasting (WRF) Model, a 3‐D finite difference nonhydrostatic mesoscale atmospheric model. The two‐way coupled model, referred to as HGS‐WRF, exchanges the actual evapotranspiration fluxes and soil saturations calculated by HGS to WRF; conversely, the potential evapotranspiration and precipitation fluxes from WRF are passed to HGS. The flexible HGS‐WRF coupling method allows for unique meshes used by each model, while maintaining mass and energy conservation between the domains. Furthermore, the HGS‐WRF coupling implements a subtime stepping algorithm to minimize computational expense. As a demonstration of HGS‐WRF's capabilities, we applied it to the California Basin and found a strong connection between the depth to the groundwater table and the latent heat fluxes across the land surface.

Thermal neutron flux measurement using self-powered neutron detector (SPND) at out-core locations of TRIGA PUSPATI Reactor (RTP)

The thermal neutron flux measurement has been conducted at the out-core location using self-powered neutron detectors (SPNDs). This work represents the first attempt to study SPNDs as neutron flux sensor for developing the fault detection system (FDS) focusing on neutron flux parameters. The study was conducted to test the reliability of the SPND’s signal by measuring the neutron flux through the interaction between neutrons and emitter materials of the SPNDs. Three SPNDs were used to measure the flux at four different radial locations which located at the fission chamber cylinder, 10cm above graphite reflector, between graphite reflector and tank liner and fuel rack. The measurements were conducted at 750 kW reactor power. The outputs from SPNDs were collected through data acquisition system and were corrected to obtain the actual neutron flux due to delayed responses from SPNDs. The measurements showed that thermal neutron flux between fission chamber location near to the tank liner and fuel rack were between 5.18 × 1011 nv to 8.45 × 109 nv. The average thermal neutron flux showed a good agreement with those from previous studies that has been made using simulation at the same core configuration at the nearest irradiation facilities with detector locations.

Test of a SiPM-scintillator-based muon detector at the Gran Sasso National Laboratory

The aim of the present work was to determine the characteristics of a tracking scintillation detector by measuring cosmic muons above- and underground at the Gran Sasso National Laboratory (LNGS). The detector has been designed for demonstrational purposes and had never been involved in scientific research before. It is a compact, layered detector using plastic scintillator bars and silicon photomultipliers (SiPM). In the present setup no energy information is used. In the underground laboratory we had to deal with a very low rate of muons (6 orders of magnitude less than on the surface). For this reason we optimized the trigger configuration. During the evaluation process we designed and optimized a maximum likelihood line fitting method which is able to deal with the high dark count rate and the non optimized detection efficiency of the detector. We also carried out simulations to calculate the actual flux and intensity from the measured ones. Finally, we compared our results with the literature and they were found to be in agreement.

Amplitude variations of modulated RV Tauri stars support the dust obscuration model of the RVb phenomenon

Context. RV Tauri-type variables are pulsating post-AGB stars that evolve rapidly through the instability strip after leaving the Asymptotic Giant Branch. Their light variability is dominated by radial pulsations. Members of the RVb subclass show an additional variability in form of a long-term modulation of the mean brightness, for which the most popular theories all assume binarity and some kind of circumstellar dust. Here we address if the amplitude modulations are consistent with the dust obscuration model. Aims. We measure and interpret the overall changes of the mean amplitude of the pulsations along the RVb variability. Methods. We compiled long-term photometric data for RVb-type stars, including visual observations of the American Association of Variable Star Observers, ground-based CCD photometry from the OGLE and ASAS projects and ultra-precise space photometry of one star, DF Cygni, from the Kepler space telescope. After converting all the observations to flux units, we measure the cycle-to-cycle variations of the pulsation amplitude and correlate them to the actual mean fluxes. Results. We find a surprisingly uniform correlation between the pulsation amplitude and the mean flux: they scale linearly with each other for a wide range of fluxes and amplitudes. It means that the pulsation amplitude actually remains constant when measured relative to the system flux level. The apparent amplitude decrease in the faint states has long been noted in the literature but it was always claimed to be difficult to explain with the actual models of the RVb phenomenon. Here we show that when fluxes are used instead of magnitudes, the amplitude attenuation is naturally explained by periodic obscuration from a large opaque screen, one most likely corresponding to a circumbinary dusty disk that surrounds the whole system.

Combined Instrumentation Package COMARS+ for the ExoMars Schiaparelli Lander

In order to measure aerothermal parameters on the back cover of the ExoMars Schiaparelli lander the instrumentation package COMARS+ was developed by DLR. Consisting of three combined aerothermal sensors, one broadband radiometer sensor and an electronic box the payload provides important data for future missions. The aerothermal sensors called COMARS combine four discrete sensors measuring static pressure, total heat flux, temperature and radiative heat flux at two specific spectral bands. The infrared radiation in a broadband spectral range is measured by the separate broadband radiometer sensor. The electronic box of the payload is used for amplification, conditioning and multiplexing of the sensor signals. The design of the payload was mainly carried out using numerical tools including structural analyses, to simulate the main mechanical loads which occur during launch and stage separation, and thermal analyses to simulate the temperature environment during cruise phase and Mars entry. To validate the design an extensive qualification test campaign was conducted on a set of qualification models. The tests included vibration and shock tests to simulate launch loads and stage separation shocks. Thermal tests under vacuum condition were performed to simulate the thermal environment of the capsule during the different flight phases. Furthermore electromagnetic compatibility tests were conducted to check that the payload is compatible with the electromagnetic environment of the capsule and does not emit electromagnetic energy that could cause electromagnetic interference in other devices. For the sensor heads located on the ExoMars back cover radiation tests were carried out to verify their radiation hardness. Finally the bioburden reduction process was demonstrated on the qualification hardware to show the compliance with the planetary protection requirements. To test the actual heat flux, pressure and infrared radiation measurement under representative conditions, aerothermal tests were performed in an arc-heated wind tunnel facility. After all qualification tests were passed successfully, the acceptance test campaign for the flight hardware at acceptance level included the same tests than the qualification campaign except shock, radiation hardness and aerothermal tests. After passing all acceptance tests, the COMARS+ flight hardware was integrated into the Schiaparelli capsule in January 2015 at the ExoMars integration site at Thales Alenia Space in Turin. Although the landing of Schiaparelli failed, resulting in the loss of most COMARS+ flight data because they were stored on the lander, some data points were directly transmitted to the orbiter at low sampling rate during the entry phase. These data indicate that all COMARS+ sensors delivered useful data until parachute deployment with the exception of the plasma black-out phase. Since measured structure and sensor housing temperatures are far below predicted pre-flight values, a new calibration using COMARS+ spare sensors at temperatures below 0 °C is necessary.