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Although credibility has been a key concept in Communication research for decades, there still is no consensus on its conceptualization and measurement. Indeed, scholars have criticized the lack of theory-driven approaches, conceptual inconsistencies between subconstructs of credibility, and the problems of applying them to the contemporary media environment. This literature review of quantitative studies of credibility published between 1951 and 2018 explores state-of-the-art definitions and measures of credibility (N = 259). While most studies make a conceptual distinction between source, media, and message credibility, measurement scales do not follow this traditional trinity. Instead, we propose moving toward a dual-credibility model.

The aim of the paper is to study the role of Facebook as a source of political information for Polish media users. The study combines a survey, a content analysis of Polish-language news items disseminated through Facebook, and computational methods. Findings revealed that Facebook has already gained a position as a crucial agent of political communication across generations in Poland. Most Poles use social media for acquisition of information about politics at least once a day and Facebook is the most popular source among them, what is especially apparent among young people (18–25 years old). Friends and family play also an important role in this process as either gatekeepers or opinion leaders. Additionally, our study revealed that topic (politics) and context (elections) matter when it comes to news consumption and news sharing on social media.

Prejudices against minorities are amplified by distorted media coverage that highlights these groups disproportionally in crime coverage. But while the specifications of alleged criminals’ affiliations to minority groups—so-called minority signification—has been studied after key events and between outlets, no research has yet investigated changes over a longer time, including different key events and outlets. Using a partly automated content analysis, our research fills this gap with a case study of minority signification in Germany from 2014 to 2019. We show that first, culturally more distant nationalities are slightly overrepresented while European nationalities are underrepresented in crime news compared with German crime statistics. Second, some spikes in the data could be linked to key events but others remain unexplained. Third, the political-right newspaper mentions minority affiliations most, the tabloid second, and the political-left outlet mentions them least. Surprisingly, this pattern changes over the years.

The rise of news content on social media has been accompanied by a hope that people with lower socioeconomic status and less interest in political affairs would be “accidentally” exposed to news. By combining tracking and survey data from a Dutch online panel (N = 413), we analyze how political interest, income, and education influence social media news exposure and consumption. Higher levels of political interest are associated with higher amounts of news exposure on Facebook and more news items consumed via social media. Users engage less often in news-related follow-up behavior after consuming news items via social media than after consuming news items referred via news websites. If social media news use seems to occur particularly for those who are already interested in current affairs and makes follow-up consumption less likely, the specificities of the social media ecosystems might accelerate rather than level inequalities in news use.

This article aims to explain the perceived quality of online news articles. Discovering which elements of a news story influence readers' perceptions could drive online popularity, which is the paramount factor of digital news readership. This work explores an approach to use tree-based machine learning algorithms to address this problem based on selected characteristics, which measure engagement, drawn from prior research mostly developed by communication scientists. A proposed extended model is used to examine the association between the engagement features and perceived quality concerning all the articles depending mainly on their genre. To demonstrate the capacity of using predictive analytics to facilitate journalistic news writing the proposed methodology is applied on a novel data set with 200K articles in total constructed from a blog site. The results of phase A, indicate interesting correlations between the features and the perceived quality of the articles. In stage B, the paper seeks to extract a set of rules that can be used as guidelines for authors in the writing of their next articles, indicating the probability of popularity that their articles may gain if these rules are taken into consideration. © 2021 - IOS Press. All rights reserved.

Using data from the Infrared Array Camera on the Spitzer Space Telescope, we present photometric observations of a sample of 100 trans-Neptunian objects (TNOs) beyond 2.2 {\mu}m. These observations, collected with two broad-band filters centered at 3.6 and 4.5 {\mu}m, were done in order to study the surface composition of TNOs, which are too faint to obtain spectroscopic measurements. With this aim, we have developed a method for the identification of different materials that are found on the surfaces of TNOs. In our sample, we detected objects with colors that are consistent with the presence of small amounts of water and were able to distinguish between surfaces that are predominately composed of complex organics and amorphous silicates. We found that 86% of our sample have characteristics that are consistent with a certain amount of water ice, and the most common composition (73% of the objects) is a mixture of water ice, amorphous silicates, and complex organics. 23% of our sample may include other ices such as carbon monoxide, carbon dioxide, methane or methanol. Additionally, only small objects seem to have surfaces dominated by silicates. This method is a unique tool for the identification of complex organics and to obtain the surface composition of extremely faint objects. Also, this method will be beneficial when using the James Webb Space Telescope for differentiating groups within the trans-Neptunian population., Comment: Accepted for publication in PSJ on October 13, 2020

Through the lens of the LSST Science Collaborations’ experience, we advocate for new, improved ways to fund large, complex collaborations as they work in preparation for and on peta-scale surveys. We advocate for the establishment of programs to support research and infrastructure that enables innovative collaborative research on such scales.

Democratic nations around the globe are facing increasing levels of false and misleading information circulating on social media and news websites, propagating alternative sociopolitical realities. One of the most innovative actors in this process has been the Russian state, whose disinformation campaigns have influenced elections and shaped political discourse globally. A key element of these campaigns is the content produced by state-funded outlets like RT and Sputnik, whose articles are republished by underfunded or sympathetic local media, as well as coordinated groups that attempt to shape mainstream political narratives. Using a tailored text-as-data approach, we examine the thematic and linguistic differences in articles produced by U.S. and Russian state-funded and mainstream outlets in Serbia. We use 11 features (frames and in-text characteristics) to construct an article country-source classifier with a high degree of accuracy. The article contributes toward an understanding of the structural characteristics of Russian statefunded news in the Western Balkans, enhances the application of computational text analysis in Serbian, and provides suggestions for the application of text-as-data methods to the study of online disinformation.

Using data from the Infrared Array Camera on the Spitzer Space Telescope, we present photometric observations of a sample of 100 trans-Neptunian objects (TNOs) beyond 2.2 ��m. These observations, collected with two broad-band filters centered at 3.6 and 4.5 ��m, were done in order to study the surface composition of TNOs, which are too faint to obtain spectroscopic measurements. With this aim, we have developed a method for the identification of different materials that are found on the surfaces of TNOs. In our sample, we detected objects with colors that are consistent with the presence of small amounts of water and were able to distinguish between surfaces that are predominately composed of complex organics and amorphous silicates. We found that 86% of our sample have characteristics that are consistent with a certain amount of water ice, and the most common composition (73% of the objects) is a mixture of water ice, amorphous silicates, and complex organics. 23% of our sample may include other ices such as carbon monoxide, carbon dioxide, methane or methanol. Additionally, only small objects seem to have surfaces dominated by silicates. This method is a unique tool for the identification of complex organics and to obtain the surface composition of extremely faint objects. Also, this method will be beneficial when using the James Webb Space Telescope for differentiating groups within the trans-Neptunian population., Accepted for publication in PSJ on October 13, 2020

This chapter introduces the notion of “news unbundling”, the phenomenon that in today’s online media landscape, news items are distributed separately. In contrast to newspaper articles that were bundled in one newspaper edition, items from very different sources are distributed via various channels. Thus, the same item can arrive at the user via different pathways, including news sites, news aggregators, and social media. Therefore, the chapter proposes to conceptualize and measure (online) news exposure as a network of users and news items. The proposed model allows to for integrative research perspectives by seeing channel and brand as properties of edges and nodes, while putting the news item itself in a central role, allowing to test communication theory in an unbundled news ecosystem. It allows to answer flow-of-information questions such as via which route a given piece of information reaches a recipient and how this can be predicted; or to test online agenda-setting effects.

Uncovering their readers’ perceptions is of key importance for every news media organization to find methods to improve the quality of their product. It has the potential to facilitate journalists’ work in attracting attention and gaining a loyal audience. Discovering which elements of a news story influence readers’ perceptions has been a cross-disciplinary research goal for the past years, because it can play a crucial role in news dissemination and consumption in the digital age. Drawing upon literature in the various areas such as journalism, psychology, computer science, and AI, this paper proposes a machine learning approach that explores three dimensions of article features that can help predicting the online behavior of the reader. Results show that how the story is written, the topic, and certain aspects of the author’s online reputation can affect reader endorsements and the perceived quality of an article. CCS CONCEPTS • Computing methodologies → Natural language processing; • Applied computing → Document management and text processing.

Computational communication science (CCS) offers an opportunity to accelerate the scope and pace of discovery in communication research. This article argues that CCS will profit from adopting open science practices by fostering the reusability of data and code. We discuss the goals and challenges related to creating reusable data and code and offer practical guidance to individual researchers to achieve this. More specifically, we argue for integration of the research process into reusable workflows and recognition of tools and data as academic work. The challenges and road map are also critically discussed in terms of the additional burden they place on individual scholars, which culminates in a call to action for the field to support and incentivize the reusability of tools and data.

The social-scientific research process is usually considered to consist of reviewing literature and theory, followed by the generation of research questions or hypotheses, the collection of data, their analysis, and writing up the findings. In this chapter, we argue that in the age of Big Data, social scientists have to increasingly consider a step that can be located between the collection and analysis of data: the storage of the data. Based on the notion of data architecture, we discuss how the choices made at his stage impact the ways the data can be used and the research questions that can be answered. In particular, we compare file dumps, relational databases, document stores, and graph databases. We develop a scheme to make a choice for one of these approaches based on four criteria: the need for preprocessing, the properties of the data, the research design, the available infrastructure, and the available expertise. We conclude by summarizing their strengths and weaknesses along two dimensions: ease-of-storage versus reliability-of-retrieval and ease-of-use versus power-to-explore.

Available from the Minor Planet Center.

This entry describes what so‐called Big Data are and how they can be analyzed in communication science and the computational social sciences more broadly. It briefly addresses the epistemological questions around this type of analysis and its historical development in communication science and related disciplines. The entry then moves on to a more practical description of the technical requirements, the structure of such datasets, and their storage in different types of databases. It gives an overview of different analytical approaches, including, but not limited to, visualizations, supervised and unsupervised machine learning, natural language processing, and network analysis. Ethical implications and future directions are discussed.

We present a community-led assessment of the solar system investigations achievable with NASA's next-generation space telescope, the Wide Field InfraRed Survey Telescope (WFIRST). WFIRST will provide imaging, spectroscopic, and coronagraphic capabilities from 0.43-2.0 $\mu$m and will be a potential contemporary and eventual successor to JWST. Surveys of irregular satellites and minor bodies are where WFIRST will excel with its 0.28 deg$^2$ field of view Wide Field Instrument (WFI). Potential ground-breaking discoveries from WFIRST could include detection of the first minor bodies orbiting in the Inner Oort Cloud, identification of additional Earth Trojan asteroids, and the discovery and characterization of asteroid binary systems similar to Ida/Dactyl. Additional investigations into asteroids, giant planet satellites, Trojan asteroids, Centaurs, Kuiper Belt Objects, and comets are presented. Previous use of astrophysics assets for solar system science and synergies between WFIRST, LSST, JWST, and the proposed NEOCam mission are discussed. We also present the case for implementation of moving target tracking, a feature that will benefit from the heritage of JWST and enable a broader range of solar system observations., Comment: 58 pages, 14 figures, 7 tables

We analyze the trajectory of near-Earth asteroid 2009~BD, which is a candidate target of the NASA Asteroid Redirect Mission. The small size of 2009 BD and its Earth-like orbit pose challenges to understanding the dynamical properties of 2009 BD. In particular, nongravitational perturbations, such as solar radiation pressure and the Yarkovsky effect, are essential to match observational data and provide reliable predictions. By using Spitzer Space Telescope IRAC observations and our model for the thermophysical properties and the nongravitational forces acting on 2009 BD we obtain probabilistic derivations of the physical properties of this object. We find two physically possible solutions. The first solution shows 2009 BD as a 2.9 ± 0.3 m diameter rocky body with an extremely high albedo that is covered with regolith-like material, causing it to exhibit a low thermal inertia. The second solution suggests 2009 BD to be a 4 ± 1 m diameter asteroid with albedo 0.45 ± 0.35 that consists of a collection of individual bare rock slabs. We are unable to rule out either solution based on physical reasoning. 2009 BD is the smallest asteroid for which physical properties have been constrained, providing unique information on the physical properties of objects in the size range smaller than 10 m.

Near-Earth objects (NEOs) are small solar system bodies whose orbits bring them close to the Earth’s orbit. We are carrying out a Warm Spitzer Cycle 11 Exploration Science program entitled NEOSurvey—a fast and efficient flux-limited survey of 597 known NEOs in which we derive a diameter and albedo for each target. The vast majority of our targets are too faint to be observed by NEOWISE, though a small sample has been or will be observed by both observatories, which allows for a cross-check of our mutual results. Our primary goal is to create a large and uniform catalog of NEO properties. We present here the first results from this new program: fluxes and derived diameters and albedos for 80 NEOs, together with a description of the overall program and approach, including several updates to our thermal model. The largest source of error in our diameter and albedo solutions, which derive from our single-band thermal emission measurements, is uncertainty in η, the beaming parameter used in our thermal modeling; for albedos, improvements in solar system absolute magnitudes would also help significantly. All data and derived diameters and albedos from this entire program are being posted on a publicly accessible Web page at nearearthobjects.nau.edu .

Beleidsmakers, wetenschappers en anderen vrezen dat gepersonaliseerd nieuws kan leiden tot filter bub- bles, unieke informatieruimtes voor iedereen. Filter bubbles zouden een gevaar vormen voor onze democratie. Op basis van de politieke voorkeuren van een gebruiker kan een gepersonaliseerde nieuwssite bepaalde onderwerpen of meningen bijvoorbeeld een meer of minder prominente plek geven. Er wordt gedacht dat personalisatie tot een nieuwe vorm van verzuiling kan leiden, waarbij gebruikers van online gepersonaliseerd nieuws weinig verschillende politieke ideeën tegenkomen. In deze bijdrage bespreken we empirisch onderzoek naar de omvang en effecten van personalisatie. Hierbij onderscheiden we zelfge- selecteerde personalisatie, waarbij mensen expliciet aangeven over welke onderwerpen zij informatie willen ontvangen, en vooraf geselecteerde personalisatie, waarbij algoritmes bepalen over welke onder- werpen gebruikers informatie ontvangen. We concluderen dat er tot nu toe weinig empirisch bewijs is dat de zorgen over filter bubbles rechtvaardigt.

While Twitter has become an increasingly important platform for public opinion formation, little is known about its use in recent Latin American election campaigns. We therefore investigate the case of the presidential elections in Brazil in October 2014, in order to analyze communication structures in actual and para-social inter- actions with presidential candidates. In particular, while Twitter makes it easy for ordinary citizens to express their opinion online, it is maybe even more important that they can also address and communicate with persons who would otherwise not be reach- able at all. Politicians are probably the most important group in this regard. Based on N = 1,891,657 tweets containing an @mention of a candidate in the Brazilian elections of 2014, we investigate which actual or para-social interactions with the candidates take place. Furthermore, because framing literature suggests that all ac- tors involved in a discussion on social media will try to highlight specific aspects and interpretations of issues and events, we used techniques of co-word analysis to investigate the ways in which the main candidates were framed by the Twitter users. The results give insight into the deliberative potential of Twitter: they show how the candidates are presented to the social media community and thus how this presentation may be reflected in public opinion.

Large-area surveys operating at mid-infrared wavelengths have proven to be a valuable means of discovering and characterizing minor planets. Through the use of radiometric models, it is possible to derive physical properties such as diameters, albedos, and thermal inertia for large numbers of objects. Modern detector array technology has resulted in a significant improvement in spatial resolution and sensitivity compared with previous generations of space-based infrared telescopes, giving rise to a commensurate increase in the number of objects that have been observed at these wavelengths. Space-based infrared surveys of asteroids therefore offer an effective means of rapidly gathering information about small body populations' orbital and physical properties. The AKARI, WISE/NEOWISE, Spitzer, and Herschel missions have significantly increased the number of minor planets with well-determined diameters and albedos., Comment: Chapter for Asteroids IV book (accepted for publication)

We have completed a spectroscopic observing campaign to complement the ExploreNEOs Warm Spitzer program. ExploreNEOs or “The Warm Spitzer NEO Survey: Exploring the history of the inner Solar System and near-Earth space” was allocated 500 hours over two years (2009-2011) to determine diameters and albedos for approximately 600 near-Earth objects using the 3.6 and 4.5 micron IRAC bands. We present the results of the SpeX component of our campaign. In order to increase our sample size we also include all near-infrared observations of ExploreNEOs targets in the MIT-UH-IRTF Joint Campaign for Spectral Reconnaissance. Our complete dataset includes 125 observations of 92 objects from our survey and 213 observations of 154 objects from the MIT survey. The combination of the two surveys includes near-infrared spectroscopy of 187 ExploreNEOs targets. We find no correlation between spectral band parameters and ExploreNEOs albedos and diameters. We identified all potential ordinary chondrites within our sample and determined likely ordinary chondrite types using the equations derived by Dunn et al. 2010. Our resulting proportions of H, L, and LL ordinary chondrites are different than those previously calculated for ordinary chondrite-like near-Earth objects and meteorite falls.

The JAXA mission Hayabusa 2, scheduled for launch in 2014 or 2015, will rendez-vous with 1999 JU3 and will return samples of surface regolith to Earth. Mission planning benefits greatly from accurate pre-encounter determinations of physical properties such as size, albedo, and thermal inertia (indicating the presence or absence of fine surface regolith). We observed the thermal emission (3.6 and 4.5 micron) of 1999 JU3 using "Warm Spitzer" in Jan-May 2013, at high SNR and spanning a range in solar phase angle of 55-88 degrees. We obtained two thermal lightcurves at different observing geometries, plus 12 shorter "point-and-shoot" observations for phase-angle coverage. If the spin-axis solution proposed by Müller et al. (2011) is correct, we obtained the first thermal observations of the afternoon side, important for thermal-inertia determinations, and our lightcurves were taken with sub-Spitzer latitudes on both the Northern and Southern hemisphere. A first analysis of our Spitzer data confirms previous estimates of diameter 0.9 km) and geometric albedo 0.07). The two lightcurves, taken three months apart, differ significantly in shape, further constraining existing models of shape and spin axis. Our observations will lead to a much improved determination of the thermal inertia of 1999 JU3, to be presented at the meeting. We will also address the question of a possible thermal-inertia variegation over the surface of this primitive NEO, which would have profound implications on the sample-taking mechanism.

The near-Earth object (NEO) population is thought to comprise a number of "dormant" short-period comets [1]. One of the most promising NEO candidates for a cometary origin is (3552) Don Quixote, due to its comet-like orbit and albedo. We present the discovery of cometary activity in (3552) Don Quixote based on thermal-infrared obser- vations made with the Spitzer Space Telescope. Our observations clearly show the presence of a coma and a tail which we identify as molecular line emission from CO2 and thermal emission from dust. Our discovery indicates that more NEOs may harbor volatiles than previously expected.

In modern democratic societies, mediated spaces for public discourse are essential. We argue that when mainstream media only partly fulfill their task in providing a platform for public discourse, social media might serve as an important space for deliberation. We explore the challenges the discourse on the dictatorial past in Brazil is facing in traditional media and the expectations that are voiced concerning the role of Twitter. In a second step, we examine quantitatively to which extent these expectations are actually put into practice. While the discourse on Twitter is more balanced and diverse than in traditional media and includes sources that are neglected by the latter, real deliberation does not take place. Espaços mediados são essenciais em sociedades democráticas. Caso os meios de comunicação não cumprem suficientemente a tarefa de disponibilizar uma plataforma para o discurso público, as mídias sociais podem servir como um espaço importante para deliberação. Este artigo pretende pesquisar os desafios que o discurso sobre o passado ditatorial do Brasil está enfrentando nas mídias tradicionais, e também as expectativas a respeito do papel do Twitter. Em seguida, através de uma análise quantitativa é pesquisado até que ponto essas expectativas são realizadas. O discurso no Twitter é mais equilibrado e diversificado do que nas mídias tradicionais e inclui fontes que não são usadas por as mídias tradicionais. Apesar disso, deliberação genuína não acontece.

Social media offer a space for deliberation and can serve as an important tool in democracy. However, little is known about the extent to which this is happening - especially outside the US and Europe and unrelated to uprisings in non-democratic societies. We argue that in defect democracies, mainstream media only partly fulfill their task to provide a platform for public discourse. Instead, social media might serve as deliberation space. Following the division’s call for work from Latin America, we explore the challenges the discourse on the dictatorial past in Brazil faces in traditional media and the expectations concerning the role of Twitter. In a second step, we examine quantitatively to which extent these expectations are put into practice. Results suggest that, while the discourse on Twitter is more balanced and diverse than in traditional media and includes sources that are neglected by the latter, real deliberation does not take place.

In today’s media landscape with an abundance of news outlets, it is often assumed that news media use becomes increasingly fragmented and polarized. Based on a large-scale survey of the Austrian population, fine-grained patterns of news exposure are explored. Criteria for the interpretation of these patterns as fragmented and polarized are discussed. We find that most people use several outlets. Most of their outlets overlap, and only some additional preferences really differ. Although Austria offers many news sources on the national level, the region of residence largely determines the choice for a specific news diet—which indicates that selectivity based on personal attitudes and psychological traits may play a less important role than situational or structural context factors.

The short dynamical lifetime of near-Earth objects (NEOs) compared to the age of the Solar System implies the existence of sources of replenishment in order to maintain the observed population of NEOs. Main belt asteroids and Jupiter family comets (JFCs), which can end up in typical NEO orbits via planetary perturbations and non-gravitational forces, are the most important sources of replenishment of NEOs. JFCs that become NEOs suffer accelerated loss of their near-surface volatiles, evolving into inactive "dormant" or "extinct" comets that are observationally indistinguishable from low albedo asteroids. Dynamically, however, they retain "comet-like" orbital characteristics. Knowledge of the fraction of extinct comets in the NEO population is important for assessing the amount of cometary material that has been transported to Earth. Furthermore, identifying inactive comet candidates facilitates detailed investigations of the final phase of comet evolution. We present an independent analysis of the fraction of former cometary objects in the NEO population. Due to the large number of NEOs we use a statistical approach to identify dormant or extinct comets based on dynamical and physical properties. We utilize (1) the Tisserand parameter with respect to Jupiter, (2) the minimum orbit intersection distance with respect to Jupiter and (3) albedo measurements. Our albedos are determined from thermal-IR observations made by the Warm Spitzer Space Telescope Exploration Science project "ExploreNEOs", using thermal modeling. The main goal of this work is to estimate the fraction of dormant or extinct comets in the NEO population. We will further provide a list of former comet candidate objects and assess their accessibility with spacecraft via the delta-V parameter. We enhance our investigation by adding data from the literature to our sample and compare our results to earlier published works based on independent analyses. MM acknowledges support by the DFG SPP 1385.

International audience; We present a summary of current efforts to find a Kuiper Belt Object that is within reach of the New Horizons spacecraft after its encounter with Pluto.

We have undertaken a spectroscopic observing campaign to complement the ExploreNEOs Warm Spitzer program. The combination of Spitzer derived albedos and diameters with spectroscopic data will enhance our understanding of the NEO population.

The construct of credibility has received more scholarly attention than most other communication variables. In a systematic meta-analysis of leading international communication journals (1951-2011), we examined how source, message, and media credibility are conceptualized and measured. Results suggest that various scales to measure credibility reveal inconsistency in theoretical reflection, lack operational precision, and led to insufficient replication and validation of the credibility construct. The findings provide a critical examination of 60 years of credibility research in media and communication studies.

Today’s online news environment has made it easy to select news outlets that cover the topics one is personally interested in and contain the political viewpoints one shares. This might lead to a fragmentation of the audience long these two lines. Previous research often has been limited to either examining the diversity of the media offer or of the audience’s media choices. This study of online news use in Austria does both to systematically assess whether such an effect exists. It first investigates actual content differences between online news outlets based on an automated content analysis (N=3,607) of content overlap and a manual content analysis (N=2,069) of topics and political bias of the coverage. In a second step, we use survey data (N=2,829) to investigate in how far online news users select outlets with topics and viewpoints that match their interests and political preferences. Results indicate that the content of different news outlets differs in terms of the topics covered, but not in terms of a general political leaning. While this precondition for audience fragmentation thus is met to some extent, we found only little evidence that people use these differences to match them with their personal interests.

The largest Mars trojan, 5261 Eureka, is one of two prototype "Sa" asteroids in the Bus-Demeo taxonomy [1]. Analysis of its visible/near-IR spectrum [2] led to the conclusion that it might represent either an angritic analog or an olivine-rich composition such as an R chondrite. Spitzer IRS data (5-30 μm) have enabled us to resolve this ambiguity. The thermal-IR spectrum exhibits strong olivine reststrahlen features consistent with a composition of ? Fo60-70. Laboratory spectra of R chondrites, brachinites, and chassignites are dominated by similar features.

Space missions to NEOs are being planned at all major space agencies, and recently a manned mission to an NEO was announced as a NASA goal. Efforts to find and select suitable targets (plus backup targets) are severely hampered by our lack of knowledge of the physical properties of dynamically favorable NEOs. In particular, current mission scenarios tend to favor primitive low-albedo objects. For the vast majority of NEOs the albedo is unknown. Here we report new constraints on the size and albedo of 65 NEOs with rendezvous deltaV < 7 km/s. Our results are based on thermal-IR flux data obtained in the framework of our ongoing (2009--2011) ExploreNEOs survey (Trilling et al. 2010) using NASA's "Warm Spitzer" space telescope. As of 2010 July 14, we have results for 293 objects in hand (including the 65 low-deltaV NEOs presented here); before the end of 2011 we expect to have measured the size and albedo of ~ 700 NEOs (including probably ~ 160 low-deltaV NEOs). While there are reasons to believe that primitive volatile-rich materials are universally low in albedo, the converse need not be true: the orbital evolution of some dark objects likely has caused them to lose their volatiles by coming too close to the Sun. For all our targets, we give the closest perihelion distance they are likely to have reached (using orbital integrations from Marchi et al. 2009) and corresponding upper limits on the past surface temperature. Low-deltaV objects for which both albedo and thermal history may suggest a primitive composition include (162998) 2001 SK162, (68372) 2001 PM9, and (100085) 1992 UY4., Accepted to AJ

Near the ecliptic, LSST is expected to detect approximately 4000 moving objects per 9.6 square degree field of view. Each pointing (with mag limits r 24.5) will be revisited within 30-45 minutes, several times per month. Automated software will provide the means to link these individual detections into orbits. The result will be publicly available catalogs of hundreds of thousands of NEOs and Jupiter Trojans, millions of asteroids, tens of thousands of TNOs, as well as thousands of other objects such as comets and irregular satellites of the major planets. These catalogs will contain final orbits as well as the individual (multi-color) observations, calibrated to high precisision in astrometry ( 50 mas) and photometry ( 0.01 mag). With these large datasets, LSST will provide new insights into links between populations of moving objects, such as the relationship between Main Belt asteroids and NEOs. Models of solar system evolution, such as the Nice model, can be tested against an order of magnitude larger statistical sample, providing much stronger constraints than are currently possible. With high accuracy multi-color photometry, lightcurves and colors will be determined for a significant fraction of the objects detected. Using sparse lightcurve inversion, spin state and shape models will be derived for tens of thousands of main belt asteroids. Derivation of proper elements for Main Belt asteroids will greatly enlarge existing asteroid families, particularly at smaller sizes, and precise color information will facilitate further division. More unpredictable discoveries, such as the potential for observing a real-time collision, could lead to new insights into physical properties, the size distribution at very small diameters, the orbital evolution of asteroids, or the discovery of possible space mission targets.

We are carrying out the ExploreNEOs project in which we observe more than 600 near Earth Objects (NEOs) at 3.6 and 4.5 microns with Warm Spitzer. For each NEO we derive diameter and albedo. We present our results to date, which include studies of individual objects, results for our entire observed sample, and, by extrapolation, results for the entire NEO population. We also present several avenues of future work.

In the ongoing debate on the role of the Internet in public discourse, it is often assumed that online news fundamentally changes mass communication. But is there a relationship between online news use and a differentiation in overall news consumption patterns? The results of a large-scale survey conducted in the Netherlands suggest that online news use does not substantially alter patterns of offline media use: People turn to both online and offline news in order to obtain a broad news overview, background information and news updates. Exposure to online news for these three purposes is actually associated with an increased use of offline sources. As these effects persist after controlling for sociodemographics, personality traits and political attitudes, we argue that online news rather offer new opportunities to keep in touch with the news than that they encourage people to abandon traditional forms of mass communication.

In order to complement the ExploreNEOs program, we are characterizing surface compositions of near-Earth objects (NEOs) with near-infrared (NIR) spectroscopy (0.7 to 2.5 microns). The core ExploreNEOs program is an ambitious exploration of the history of near-Earth space using NASA's Spitzer space telescope. Currently in the middle of its two-year timeline, that ongoing project will ultimately observe 700 NEOs using the Infrared Array Camera (IRAC) in two photometric bands (3.6 and 4.5 microns). The proposed goals of the ExploreNEOs survey are to measure the size distribution of NEO population; to measure the fraction of NEOs likely to be dead comet nuclei, with implications for the flux of organic material onto the Earth; to measure the albedo distribution of NEOs; and to study properties of individual NEOs, including their thermal properties and densities, and detailed properties of a subset of "ground-truth" objects. Whereas the Spitzer photometry will provide accurate estimates of size and albedo for most targets, albedo is only a general indicator of potential composition. NIR spectroscopy complements the Spitzer results by enabling direct determination of surface compositions. The NIR measurements thereby contribute to the overall goals of the ExploreNEOs program by allowing the team to assess the mix of mineralogies among NEOs and to infer the contributions from dead comets to the NEO population. NASA's Infrared Telescope Facility (IRTF) is the main observatory used for the NIR spectral measurements. Of the ˜700 Spitzer targets, 127 are viewable and bright enough for spectroscopy with the IRTF. Thus far, we have obtained NIR spectra of 42 of the ExploreNEO targets. We will present these data along with compositional analysis.

Near Earth Asteroids (NEAs- 0.983AU

For faint asteroids, it is not practical to obtain near-infrared spectra. However, it may be possible to use broadband photometry to infer spectral classifications and study composition. As a test of this, we processed SpeX near-infrared asteroid spectral data to simulate colors that would be obtained through photometry. We have found that certain color combinations (for example, z-J and H-K) can prove diagnostic in asteroid spectral classification. To this end, we have defined certain color-color regions that make it possible to define an asteroid as being a likely candidate for a certain spectral type. The regions identified define V and D type asteroids, the S-Q group, and the C-X group. Knowledge and use of these regions will significantly increase the usefulness of NIR broadband photometry in the study of near earth objects and allow characterization of asteroids that are too faint to be observed spectroscopically. Work on this project is made possible through the NSF REU program at Northern Arizona University and by funding from the Spitzer Space Telescope/JPL/Caltech.

The Warm Spitzer NEO survey, ExploreNEOs, will observe approximately 700 Near Earth Asteroids. Several of these objects are known to be binary asteroid systems. Binary systems are interesting due to the unique opportunity they present for determining the masses and densities of their constituent bodies. The calculations rely on a variety of data sources. The geometric albedo and effective diameter of the system are known via ExploreNEOs. Ground based light curve observations can give the orbital period and the secondary to primary diameter ratio of the system. In some cases, Arecibo radar observations provide the semi-major axis of the system. We report here the bulk density of one of these binaries in particular, asteroid 1999DJ4. The density derived is 1.6 g/cm3. For those cases where radar data is unavailable, we address the effectiveness and difficulties of using transit timing of a binary asteroid to determine the semi-major axis of the system . We discuss the viability of finding a bulk density based solely on Warm Spitzer observations and ground based light curve data.

We report on observations of near-Earth objects (NEOs) performed with IRAC as part of our on-going (2009-2011) Warm Spitzer NEO survey ("ExploreNEOs"), the primary aim of which is to provide sizes and albedos of some 700 NEOs. The emphasis of the work described here is an assessment of the overall accuracy of our survey results, which are based on a semi-empirical generalized model of asteroid thermal emission. The set of some 170 NEOs in our current Warm Spitzer results catalog contains 28 for which published taxonomic classifications are available, and 14 for which relatively reliable published diameters and albedos are available. From a comparison of the Warm Spitzer results with results expected on the basis of previous observations, we conclude that Warm Spitzer diameters and albedos are accurate to about 25% and 50%, respectively. Cases in which agreement with results from the literature is worse than expected are highlighted and discussed; these include the potential spacecraft target 138911 2001 AE2. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.

A Warm Spitzer survey of approximately 700 near-Earth objects (NEOs) has been started to derive albedos and diameters of the numerous small bodies. We present a ground-based NEO observation program designed to complement the Spitzer data. By using a variety of observational techniques, we aim to obtain optical magnitudes, lightcurves and compositional information for many of these objects. We have begun a program to obtain high-quality optical magnitudes of all 700 Spitzer targets, using a variety of telescope facilities with a range of apertures (from 0.36 m to 8 m). For a subset of our targets, we will also obtain lightcurves, which will be used as a proxy for the larger sample. We plan to obtain spectra of 250 objects from the Spitzer NEO sample and broadband spectrophotometric measurements of another 100. These spectroscopic results will allow us to derive compositions for nearly half our sample and act as a ground-truth for the larger, complete sample. Observations are already scheduled on the NASA Infrared Telescope Facility (SpeX as well as MIRSI, which will be used to confirm our Spitzer thermal observations and modeling), NOAO SMARTS telescopes, the Las Campanas 1-meter and several smaller telescopes. We will continue to expand the range of facilities used, matching aperture with target brightness. This catalog of objects will serve as a reference sample for a wide variety of future NEO studies.