39 research outputs found
OSIRIS-REx Orbit Determination Performance During the Navigation Campaign
The OSIRIS-REx mission Navigation Campaign consists of three sub-phases: Approach,Preliminary Survey, and Orbital A. Approach was designed for initial characterization ofBennu while matching Bennu's heliocentric velocity. Preliminary Survey provided the firstspacecraft-based estimate of Bennu's mass. This phase consisted of five target flybys witha close approach distance of about 7 km. Orbital A was a two-month phase devoted to theNavigation Team learning the close proximity operations dynamics and environment aroundBennu and transitioning from center-finding optical navigation to landmark feature-basednavigation. This paper provides a detailed summary of the orbit determination performancethroughout the Navigation Campaign
Overcoming the Challenges Associated with Image-based Mapping of Small Bodies in Preparation for the OSIRIS-REx Mission to (101955) Bennu
The OSIRIS-REx Asteroid Sample Return Mission is the third mission in NASA's
New Frontiers Program and is the first U.S. mission to return samples from an
asteroid to Earth. The most important decision ahead of the OSIRIS-REx team is
the selection of a prime sample-site on the surface of asteroid (101955) Bennu.
Mission success hinges on identifying a site that is safe and has regolith that
can readily be ingested by the spacecraft's sampling mechanism. To inform this
mission-critical decision, the surface of Bennu is mapped using the OSIRIS-REx
Camera Suite and the images are used to develop several foundational data
products. Acquiring the necessary inputs to these data products requires
observational strategies that are defined specifically to overcome the
challenges associated with mapping a small irregular body. We present these
strategies in the context of assessing candidate sample-sites at Bennu
according to a framework of decisions regarding the relative safety,
sampleability, and scientific value across the asteroid's surface. To create
data products that aid these assessments, we describe the best practices
developed by the OSIRIS-REx team for image-based mapping of irregular small
bodies. We emphasize the importance of using 3D shape models and the ability to
work in body-fixed rectangular coordinates when dealing with planetary surfaces
that cannot be uniquely addressed by body-fixed latitude and longitude.Comment: 31 pages, 10 figures, 2 table
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Overcoming the Challenges Associated with Image-Based Mapping of Small Bodies in Preparation for the OSIRIS-REx Mission to (101955) Bennu
The OSIRISâREx Asteroid Sample Return Mission is the third mission in National Aeronautics and Space Administration (NASA)'s New Frontiers Program and is the first U.S. mission to return samples from an asteroid to Earth. The most important decision ahead of the OSIRISâREx team is the selection of a prime sampleâsite on the surface of asteroid (101955) Bennu. Mission success hinges on identifying a site that is safe and has regolith that can readily be ingested by the spacecraft's sampling mechanism. To inform this missionâcritical decision, the surface of Bennu is mapped using the OSIRISâREx Camera Suite and the images are used to develop several foundational data products. Acquiring the necessary inputs to these data products requires observational strategies that are defined specifically to overcome the challenges associated with mapping a small irregular body. We present these strategies in the context of assessing candidate sample sites at Bennu according to a framework of decisions regarding the relative safety, sampleability, and scientific value across the asteroid's surface. To create data products that aid these assessments, we describe the best practices developed by the OSIRISâREx team for imageâbased mapping of irregular small bodies. We emphasize the importance of using 3âD shape models and the ability to work in bodyâfixed rectangular coordinates when dealing with planetary surfaces that cannot be uniquely addressed by bodyâfixed latitude and longitude.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Dividend Stickiness in Japan
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The paper describes the introduction of an emphasis on âpersonal securityâ in human security thinking and practice, as part of the ultimately unsuccessful attempt to compartmentalize the pursuit of security. It reviews the past twenty years of attention to âpersonal securityâ: both in compartments that consider organized physical violence or threats to personal safety and property (âcitizen securityâ), and as parts of more wide-ranging examination of threats to fulfilment of basic needs and rights, for example in comprehensive mapping exercises undertaken in various UNDP Regional and National Human Development Reports or in studies of womenâs security. The paper reflects on the complex process of opening-up conventional security thinking and practice, seeking value-added and depth without shrinking into preconceived compartments
Evidence for widespread hydrated minerals on asteroid (101955) Bennu
Early spectral data from the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission reveal evidence for abundant hydrated minerals on the surface of near-Earth asteroid (101955) Bennu in the form of a near-infrared absorption near 2.7â”m and thermal infrared spectral features that are most similar to those of aqueously altered CM-type carbonaceous chondrites. We observe these spectral features across the surface of Bennu, and there is no evidence of substantial rotational variability at the spatial scales of tens to hundreds of metres observed to date. In the visible and near-infrared (0.4 to 2.4â”m) Bennuâs spectrum appears featureless and with a blue (negative) slope, confirming previous ground-based observations. Bennu may represent a class of objects that could have brought volatiles and organic chemistry to Earth
The dynamic geophysical environment of (101955) Bennu based on OSIRIS-REx measurements
The top-shaped morphology characteristic of asteroid (101955) Bennu, often found among fast-spinning asteroids and binary asteroid primaries, may have contributed substantially to binary asteroid formation. Yet a detailed geophysical analysis of this morphology for a fast-spinning asteroid has not been possible prior to the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. Combining the measured Bennu mass and shape obtained during the Preliminary Survey phase of the OSIRIS-REx mission, we find a notable transition in Bennuâs surface slopes within its rotational Roche lobe, defined as the region where material is energetically trapped to the surface. As the intersection of the rotational Roche lobe with Bennuâs surface has been most recently migrating towards its equator (given Bennuâs increasing spin rate), we infer that Bennuâs surface slopes have been changing across its surface within the last million years. We also find evidence for substantial density heterogeneity within this body, suggesting that its interior is a mixture of voids and boulders. The presence of such heterogeneity and Bennuâs top shape are consistent with spin-induced failure at some point in its past, although the manner of its failure cannot yet be determined. Future measurements by the OSIRIS-REx spacecraft will provide insight into and may resolve questions regarding the formation and evolution of Bennuâs top-shape morphology and its link to the formation of binary asteroids
When humans become data
In this chapter, I examine what and whom we imagine to be protecting when we use the language of ethics and transparency to describe research. How does the imagination of humans as data inform different approaches to transparency and ethics in research? I draw from my experiences in negotiating about data transparency with a funding agency to reflect on how different temporalities and spaces of research and violence alike inform interpretations of our responsibilities toward research interlocutors. The goal of the chapter is to synthesize recent research to advance an alternate orientation of transparency, away from a conceptualization informed by liability or âcheckboxâ compliance and toward a practice of reflexive openness
Children, violence, and social exclusion: negotiation of everyday insecurity in a Colombian barrio
Discourses on in/security are often concerned with structures and meta-narratives of the state and other institutions; however, such attention misses the complexities of the everyday consequences of insecurity. In Colombiaâs protracted conflict, children are disproportionately affected yet rarely consulted, rendering it difficult to account for their experiences in meaningful ways. This article draws on fieldwork conducted with conflict-affected children in an informal barrio community on the periphery of Colombiaâs capital, BogotĂĄ, to explore how children articulate experiences of insecurity. It examines how stereotypes of violence and delinquency reinforce insecurity; how multiple violences impact young peopleâs lives; and how children themselves conceive of responses to these negative experiences. These discussions are underpinned by a feminist commitment of attention to the margins and engage with those for whom insecurity is a daily phenomenon. The effects of deeply embedded insecurity, violence, and fear for young people in Colombia require a more nuanced theoretical engagement with notions of insecurity, as well as the complexities of connections and dissonances within everyday life