Nonlinear Attitude Filtering: A Comparison Study

This paper contains a concise comparison of a number of nonlinear attitude filtering methods that have attracted attention in the robotics and aviation literature. With the help of previously published surveys and comparison studies, the vast literature on the subject is narrowed down to a small pool of competitive attitude filters. Amongst these filters is a second-order optimal minimum-energy filter recently proposed by the authors. Easily comparable discretized unit quaternion implementations of the selected filters are provided. We conduct a simulation study and compare the transient behaviour and asymptotic convergence of these filters in two scenarios with different initialization and measurement errors inspired by applications in unmanned aerial robotics and space flight. The second-order optimal minimum-energy filter is shown to have the best performance of all filters, including the industry standard multiplicative extended Kalman filter (MEKF)

Epistemic geographies of climate change: the IPCC and the spaces, boundaries and politics of knowing

Science, like other realms of human activity, has its geographies. It proceeds in and through space, and participates in the construction of the political and cultural geographies by which human interactions with the nonhuman come to be known, understood and governed. The phenomenon of climate change stands at this juncture of science, politics, and the elemental materiality of the nonhuman. High-profile controversies about the physical reality, effects and management of the changing climate point to more deep-seated contestations about the place of science in modern democratic societies. This thesis engages with literatures on the historical and cultural geographies of science in order to open-up questions about the situatedness of climate change knowledges, the contested boundaries between the scientific and the political, and the spatial politics of relating epistemic claims to normative interventions in the world. The thesis proceeds through a series of linked case studies which traverse a range of emergent transnational spaces of knowledge production. It begins inside the Intergovernmental Panel on Climate Change (IPCC) and moves through the contested spaces of international climate diplomacy at the 2009 Copenhagen climate talks and through diverse cultures of knowledge authorisation in Indian climate politics. The thesis develops the notions of ‘boundary spaces’ and ‘epistemic geographies’ to capture the emergence, conjuncture and contestation of different modes of knowing and governing climate change. By following the objects of climate change knowledges – like visualisations, numerical targets, simulation models and predictions – conceptual distinctions between the spaces of knowledge production and consumption break down. Instead, a picture emerges of travelling knowledges which emphasises mutability, interpretive flexibility, and the spatial and discursive co-production of the epistemic and the normative. It is argued that by moving from ‘geographies of science’ to ‘epistemic geographies’, the hybridity of science and politics can be more effectively written-in to our accounts of contemporary knowledge politics

What triggers a radio AGN? The intriguing case of PKSB 1718-649

We present new Australia Telescope Compact Array (ATCA) observations of the young (< 10^2 years) radio galaxy PKS B1718-649. We study the morphology and the kinematics of the neutral hydrogen (HI) disk (M(HI) = 1.1x 10^10 M(sun), radius ~ 30 kpc). In particular, we focus on the analysis of the cold gas in relation to the triggering of the nuclear activity. The asymmetries at the edges of the disk date the last interaction with a companion to more than 1 Gyr ago. The tilted-ring model of the HI disk shows that this event may have formed the disk as we see it now, but that it may have not been responsible for triggering the AGN. The long timescales of the interaction are incompatible with the short ones of the radio activity. In absorption, we identify two clouds with radial motions which may represent a population that could be involved in the triggering of the radio activity. We argue that PKS B1718-649 may belong to a family of young low-excitation radio AGN where, rather than through a gas rich merger, the active nuclei (AGN) are triggered by local mechanisms such as accretion of small gas clouds.Comment: 8 pages, 9 figures, Accepted to A&

Science advice for global challenges: learning from trade-offs in the IPCC

In the context of ongoing debates about the place of knowledge and expertise in the governance of global challenges, this article seeks to promote cross-sectoral learning about the politics and pitfalls of global science advice. It begins with the intertwined histories of the Intergovernmental Panel on Climate Change (IPCC) and the global climate policy regime, before examining the politics of different ‘framings’ of the climate problem and the challenges of building and communicating scientific consensus. We then identify three important trade-offs which the IPCC has had to negotiate: global versus local; scientific disinterestedness versus policy-relevance; and consensus versus plurality. These lessons are especially timely as global institutions begin to convene knowledge to address urgent sustainable development challenges posed by anti-microbial resistance (AMR). While the IPCC experience does not provide a wholly transportable model for science advice, we show why similar trade-offs need to be addressed at an early stage by architects of advisory systems for AMR as well as other global challenges

Public crises, public futures

This article begins to map out a novel approach to analyzing contemporary contexts of public crisis, relationships between them and possibilities that these scenes hold out for politics. The article illustrates and analyses a small selection of examples of these kinds of contemporary scenes and calls for greater attention to be given to the conditions and consequences of different forms and practices of public and political mediation. In offering a three-fold typology to delineate differences between ‘abject’, ‘audience’ and ‘agentic’ publics the article begins to draw out how political and public futures may be seen as being bound up with how the potentialities, capacities and qualities that publics are imagined to have and resourced to perform. Public action and future publics are therefore analysed here in relation to different versions of contemporary crisis and the political concerns and publics these crises work to articulate, foreground and imaginatively and practically support