Scattering matrices and expansion coefficients of Martian analogue palagonite particles

We present measurements of ratios of elements of the scattering matrix of Martian analogue palagonite particles for scattering angles ranging from 3 to 174 degrees and a wavelength of 632.8 nm. To facilitate the use of these measurements in radiative transfer calculations we have devised a method that enables us to obtain, from these measurements, a normalized synthetic scattering matrix covering the complete scattering angle range from 0 to 180 degrees. Our method is based on employing the coefficients of the expansions of scattering matrix elements into generalized spherical functions. The synthetic scattering matrix elements and/or the expansion coefficients obtained in this way, can be used to include multiple scattering by these irregularly shaped particles in (polarized) radiative transfer calculations, such as calculations of sunlight that is scattered in the dusty Martian atmosphere.Comment: 34 pages 7 figures 1 tabl

Smart Emission - Building a Spatial Data Infrastructure for an Environmental Citizen Sensor Network

Item does not contain fulltextSmart Emission is a citizen sensor network using low-cost sensors that enables citizens to gather data about environmental quality, like air quality, noise load, vibrations, light intensities and heat stress. This paper introduces the design and development of the data infrastructure for the Smart Emission initiative and discusses challenges for the future. The Spatial Data Infrastructure (SDI) is open and accessible on the Internet using open geospatial standards and (Web-) client applications. Smart Emission as a citizen sensor network offers several possibilities for heterogonous applications, from health determination to spatial planning purposes, environmental monitoring for sustainable traffic management, climate adaptation in cities and city planning.Geospatial Sensor Webs Conference 2016 (GSW 2016), 29 augustus 201

The effects of disk and dust structure on observed polarimetric images of protoplanetary disks

Imaging polarimetry is a powerful tool for imaging faint circumstellar material. For a correct analysis of observations we need to fully understand the effects of dust particle parameters, as well as the effects of the telescope, atmospheric seeing, and assumptions about the data reduction and processing of the observed signal. Here we study the major effects of dust particle structure, size-dependent grain settling, and instrumental properties. We performed radiative transfer modeling using different dust particle models and disk structures. To study the influence of seeing and telescope diffraction we ran the models through an instrument simulator for the ExPo dual-beam imaging polarimeter mounted at the 4.2m William Herschel Telescope (WHT). Particle shape and size have a strong influence on the brightness and detectability of the disks. In the simulated observations, the central resolution element also contains contributions from the inner regions of the protoplanetary disk besides the unpolarized central star. This causes the central resolution element to be polarized, making simple corrections for instrumental polarization difficult. This effect strongly depends on the spatial resolution, so adaptive optics systems are needed for proper polarization calibration. We find that the commonly employed homogeneous sphere model gives results that differ significantly from more realistic models. For a proper analysis of the wealth of data available now or in the near future, one must properly take the effects of particle types and disk structure into account. The observed signal depends strongly on the properties of these more realistic models, thus providing a potentially powerful diagnostic. We conclude that it is important to correctly understand telescope depolarization and calibration effects for a correct interpretation of the degree of polarization.Comment: Accepted for publication in A&

Replacing the AMOR with the miniDOAS in the ammonia monitoring network in the Netherlands

In this paper we present the continued development of the miniDOAS, an active differential optical absorption spectroscopy (DOAS) instrument used to measure ammonia concentrations in ambient air. The miniDOAS has been adapted for use in the Dutch National Air Quality Monitoring Network. The miniDOAS replaces the life-expired continuous-flow denuder ammonia monitor (AMOR). From September 2014 to December 2015, both instruments measured in parallel before the change from AMOR to miniDOAS was made. The instruments were deployed at six monitoring stations throughout the Netherlands. We report on the results of this intercomparison. Both instruments show a good uptime of ca. 90 %, adequate for an automatic monitoring network. Although both instruments produce 1 min values of ammonia concentrations, a direct comparison on short timescales such as minutes or hours does not give meaningful results because the AMOR response to changing ammonia concentrations is slow. Comparisons between daily and monthly values show good agreement. For monthly averages, we find a small average offset of 0.65 ± 0.28 µg m−3 and a slope of 1.034 ± 0.028, with the miniDOAS measuring slightly higher than the AMOR. The fast time resolution of the miniDOAS makes the instrument suitable not only for monitoring but also for process studies

Atmospheric aerosol characterization with a ground-based SPEX spectropolarimetric instrument

Stars and planetary system

Two instruments based on differential optical absorption spectroscopy (DOAS) to measure accurate ammonia concentrations in the atmosphere

We present two Differential Optical Absorption Spectroscopy (DOAS) instruments built at RIVM: the RIVM DOAS and the miniDOAS. Both instruments provide virtually interference-free measurements of NH3 concentrations in the atmosphere, since they measure over an open path, without suffering from inlet problems or interference problems by ammonium aerosols dissociating on tubes or filters. They measure concentrations up to at least 200 mu g m(-3), have a fast response, low maintenance demands, and a high up-time. The RIVM DOAS has a high accuracy of typically 0.15 mu g m(-3) for ammonia for 5-min averages and over a total light path of 100 m. The miniDOAS has been developed for application in measurement networks such as the Dutch National Air Quality Monitoring Network (LML). Compared to the RIVM DOAS it has a similar accuracy, but is significantly reduced in size, costs, and handling complexity. The RIVM DOAS and miniDOAS results showed excellent agreement (R-2 = 0.996) during a field measurement campaign in Vredepeel, the Netherlands. This measurement site is located in an agricultural area and is characterized by highly variable, but on average high ammonia concentrations in the air. The RIVM-DOAS and miniDOAS results were compared to the results of the AMOR instrument, a continuous-flow wet denuder system, which is currently used in the LML. Averaged over longer time spans of typically a day, the (mini) DOAS and AMOR results agree reasonably well, although an off-set of the AMOR values compared to the (mini) DOAS results exists. On short time scales, the (mini) DOAS shows a faster response and does not show the memory effects due to inlet tubing and transport of absorption fluids encountered by the AMOR. Due to its high accuracy, high uptime, low maintenance and its open path, the (mini) DOAS shows a good potential for flux measurements by using two (or more) systems in a gradient set-up and applying the aerodynamic gradient technique

Enhancing national environmental monitoring through local citizen science

Citizen science, the active participation of the public in scientific research projects, is a rapidly expanding field in open science and open innovation. It provides an integrated model of public knowledge production and engagement with science. As a growing worldwide phenomenon, it is invigorated by evolving new technologies that connect people easily and effectively with the scientific community. Catalysed by citizens’ wishes to be actively involved in scientific processes, as a result of recent societal trends, it also offers contributions to the rise in tertiary education. In addition, citizen science provides a valuable tool for citizens to play a more active role in sustainable development. This book identifies and explains the role of citizen science within innovation in science and society, and as a vibrant and productive science-policy interface. The scope of this volume is global, geared towards identifying solutions and lessons to be applied across science, practice and policy. The chapters consider the role of citizen science in the context of the wider agenda of open science and open innovation, and discuss progress towards responsible research and innovation, two of the most critical aspects of science today

Satellietdata voor emissies: gebruikersbehoeften

Satellieten worden onder andere gebruikt om te meten hoeveel broeikasgassen en vervuilende stoffen er worden uitgestoten in de lucht. Verschillende organisaties, zoals het RIVM, overheden en onderzoekers, gebruiken deze data. Satellieten worden steeds beter en kunnen steeds preciezer meten. Vanwege deze ontwikkelingen is het voor Nederland belangrijk om goed voorbereid te zijn op het gebruik van data van satellieten in de toekomst. Daarom heeft het Netherlands Space Office (NSO) het RIVM gevraagd in kaart te brengen welke behoeften gebruikers of toekomstige gebruikers van de data over de uitstoot van broeikasgassen of luchtvervuilende stoffen hebben. De NSO kan deze uitkomsten gebruiken om strategische beslissingen te nemen over satellieten van de toekomst. Voor het onderzoek zijn 24 (mogelijke) gebruikers van satellietdata geïnterviewd. De opvallendste uitkomst hieruit is dat zij vooral tegen praktische problemen aanlopen. Ze kunnen bijvoorbeeld de data niet goed vinden of ze weten niet hoe ze data kunnen gebruiken. Of ze hebben geen geld om met de data aan de slag te gaan. Er is geld en kennis nodig om de data gebruiksvriendelijk en makkelijker toegankelijk te maken en ze betekenis te geven. Een belangrijke stap naar een oplossing hiervoor is dat organisaties meer gaan samenwerken om bijvoorbeeld kennis uit te wisselen. De geïnterviewden stellen dit zelf als oplossing voor. Een mogelijkheid hiervoor is een meer open community te organiseren in Nederland, maar het liefst ook internationaal. Naast de praktische behoeften zijn er technische wensen en eisen, en wetenschappelijke behoeften en interesses. Zo hebben (mogelijke) gebruikers de behoefte aan preciezere metingen van kleine oppervlakten zodat van steeds kleinere bronnen kan worden achterhaald welke stoffen die uitstoten. Naar verwachting kan de combinatie van satellietmetingen met andere databronnen, zoals uitgebreidere metingen op de grond, veel nieuwe inzichten geven. De satellietinstrumenten kunnen bestaande databronnen niet vervangen, maar er wel een belangrijke aanvulling op zijn.Satellites are used, among other things, for measuring emissions of greenhouse gases and pollutants into the air. These data are used by various organisations, such as RIVM, and by public authorities and researchers. Satellites are getting better and better and are able to make ever more precise measurements. In view of these developments, it is important for the Netherlands to be well prepared for the use of satellite data in the future. This is why the Netherlands Space Office (NSO) has asked RIVM to identify the needs among existing or future users of greenhouse gas or air pollutant emissions data. The NSO can use the results in its strategic decisions on the satellites of the future. For the purpose of this study, we have interviewed 24 existing and potential users of satellite data. The most notable finding is that the problems they encounter are mostly of a practical nature. For example, they have difficulty finding the data they need or do not know how to use them. Or they lack the funds to work with the data. There is a need for funding and knowledge to make the data more accessible and user-friendly. An important step in that direction will be made if organisations intensify their cooperation, for example to share knowledge. The interviewees themselves proposed this as a solution. This could be achieved by organising a more open community - in the Netherlands, but preferably also internationally. In addition to practical needs, interviewees expressed technical wishes and demands, as well as needs and interests of a scientific nature. For example, existing and potential users need more precise measurements of small surfaces, enabling them to identify substances emitted by ever smaller sources. A combination of satellite measurements and other data sources, such as more extensive ground measurements, is expected to yield many new insights. While satellite instruments will not be able to replace existing data sources, they can provide important supplementary data