Study of mesocale exchange processes utilizing LANDSAT air mass cloud imagery

There are no author-identified significant results in this report

Study of Mesoscale Exchange Processes Utilizing LANDSAT Air Mass Cloud Imagery

There are no author-identified significant results in this report

Study of Mesoscale Exchange Processes Utilizing Landsat Air Mass Cloud Imagery

There are no author-identified significant results in this report

Searching for tidal tails - investigating galaxy harassment

Galaxy harassment has been proposed as a physical process that morphologically transforms low surface density disc galaxies into dwarf elliptical galaxies in clusters. It has been used to link the observed very different morphology of distant cluster galaxies (relatively more blue galaxies with 'disturbed' morphologies) with the relatively large numbers of dwarf elliptical galaxies found in nearby clusters. One prediction of the harassment model is that the remnant galaxies should lie on low surface brightness tidal streams or arcs. We demonstrate in this paper that we have an analysis method that is sensitive to the detection of arcs down to a surface brightness of 29 B mag/arcsec^2 and then use this method to search for arcs around 46 Virgo cluster dwarf elliptical galaxies. We find no evidence for tidal streams or arcs and consequently no evidence for galaxy harassment as a viable explanation for the relatively large numbers of dwarf galaxies found in the Virgo cluster.Comment: Accepted for publication in MNRA

The dwarf low surface brightness population in different environments of the Local Universe

The nature of the dwarf galaxy population as a function of location in the cluster and within different environments is investigated. We have previously described the results of a search for low surface brightness objects in data drawn from an East-West strip of the Virgo cluster (Sabatini et al., 2003) and have compared this to a large area strip outside of the cluster (Roberts et al., 2004). In this talk I compare the East-West data (sampling sub-cluster A and outward) to new data along a North-South cluster strip that samples a different region (part of sub-cluster A, and the N,M clouds) and with data obtained for the Ursa Major cluster and fields around the spiral galaxy M101. The sample of dwarf galaxies in different environments is obtained from uniform datasets that reach central surface brightness values of ~26 B mag/arcsec^2 and an apparent B magnitude of 21 (M_B=-10 for a Virgo Cluster distance of 16 Mpc). We discuss and interpret our results on the properties and distribution of dwarf low surface brightness galaxies in the context of variuos physical processes that are thought to act on galaxies as they form and evolve.Comment: 10 pages, 3 figures, to appear in "Dark Galaxies and Lost Baryons", IAU244 conference proceeding

A unified approach to cooperative and non-cooperative sense-and-avoid

Cooperative and non-cooperative Sense-and-Avoid (SAA) capabilities are key enablers for Unmanned Aircraft Vehicle (UAV) to safely and routinely access all classes of airspace. In this paper state-of-the-art cooperative and non-cooperative SAA sensor/system technologies for small-to-medium size UAV are identified and the associated multi-sensor data fusion techniques are introduced. A reference SAA system architecture is presented based on Boolean Decision Logics (BDL) for selecting and sorting non-cooperative and cooperative sensors/systems including both passive and active Forward Looking Sensors (FLS), Traffic Collision Avoidance System (TCAS) and Automatic Dependent Surveillance - Broadcast (ADS-B). After elaborating the SAA system processes, the key mathematical models associated with both non-cooperative and cooperative SAA functions are presented. The analytical models adopted to compute the overall uncertainty volume in the airspace surrounding an intruder are described. Based on these mathematical models, the SAA Unified Method (SUM) for cooperative and non-cooperative SAA is presented. In this unified approach, navigation and tracking errors affecting the measurements are considered and translated to unified range and bearing uncertainty descriptors, which apply both to cooperative and non-cooperative scenarios. Simulation case studies are carried out to evaluate the performance of the proposed SAA approach on a representative host platform (AEROSONDE UAV) and various intruder platforms. Results corroborate the validity of the proposed approach and demonstrate the impact of SUM towards providing a cohesive logical framework for the development of an airworthy SAA capability, which provides a pathway for manned/unmanned aircraft coexistence in all classes of airspace

A GNSS Integrity Augmentation System for Ground Vehicle Operations

The employment of GNSS for the navigation of autonomous ground vehicles has so far been applied to mining operations in Australia. Autonomous systems enable the development of navigation strategies such as global path-planning and path optimization for vehicle fleets, thereby lowering overall carbon emissions. Furthermore, autonomous ground vehicle operations can significantly improve safety ratings by eliminating human error arising from stress, fatigue and boredom. Widespread use of GNSS-based autonomous vehicles for ground operations is presently hindered by stringent safety regulations. This places strict integrity requirements on GNSS receivers, which must be able to detect GNSS signal errors and faults, and alert the navigation system in a timely manner. An integrity augmentation system is presented in this paper that can detect GNSS error sources and faults, and alert the navigation system of an autonomous ground vehicle in a timely manner. The system is developed by modelling GNSS error sources like antenna masking, signal attenuation and multipath and assigning threshold values for generating integrity alerts. The performance of the system in terms of GNSS fault detection is validated through a realistic simulation in a 3-D virtual ground environment. Trajectories representing the paths followed by vehicles are generated using a dynamic model of a generic fourwheeled ground vehicle. The integrity augmentation system was demonstrated to successfully detect GNSS errors and respond by issuing predictive (caution flags) and reactive (warning flags) in a timely manner for a range of trajectories and maneuvers