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

Orbital and meteorological factors pertinent to satellite transmissions of facsimile weather charts Final report

Automatic picture transmission system on Nimbus and earth synchronous satellites for transmission of weather chart

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

Management, processing and dissemination of sensory data for the Earth Resource Technology Satellite

Data center for management, processing, and dissemination of photographic products generated by ERT

Características del zooplancton del área costera de la plataforma patagónica austral (Argentina)

El estudio del zooplancton en áreas de desove y cría de peces es de particular trascendencia en la región costera patagónica sur (50º-55º S), dado que allí se distribuye la población continental de sardina fueguina Sprattus fuegensis (Jenyns, 1842); esta especie es exclusivamente zooplanctófaga a lo largo de todo su ciclo vital y se le atribuye el papel de especie forrajera en el sector austral del mar Argentino. En el otoño y la primavera de 1996 se colectaron muestras de zooplancton en el área mediante arrastres oblicuos fondo-superficie con un muestreador Nackthai provisto de una red de 400 μm de luz de malla y flujómetro digital. El material se separó en dos grupos según el tamaño (mayor y menor de 5 mm) y se pesaron las fracciones resultantes (peso húmedo). En ambas estaciones del año, la biomasa de la fracción menor fue normalmente igual, e incluso superó en ocasiones, a la concentración de la fracción mayor. Dada su importancia para los objetivos de este trabajo, se analizó en detalle la composición y abundancia numérica de la fracción menor de 5 mm, que se mostró compuesta casi exclusivamente por copépodos calanoideos, dominados por las especies Drepanopus forcipatus Giesbrecht, 1888 y Calanus australis Brodsky, 1959. La biomasa, la abundancia de individuos y el número de especies fueron mayores en primavera. En esta estación Drepanopus forcipatus fue la especie dominante en casi toda el área, constituyendo hasta el 90 % del total de individuos. Calanus australis fue relativamente más importante en otoño, periodo en que dominó, en particular, en la zona de Bahía Grande. Estos dos copépodos pueden considerarse especies clave en la estructuración de las tramas tróficas del área.Fil: Sabatini, Marina Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; ArgentinaFil: Giménez, J.. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Biología; ArgentinaFil: Rocco, V.. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; Argentin

Opportunities offered by naturally occurring materials in lightweight aerostructures design

The raising concerns towards the environmental impact of the air transport sector have led the international regulation authorities to put pressure on the aeronautical industry in order to achieve ambitious goals both in the short and medium-term. The expected growth in the aviation sector for the upcoming years poses a greater challenge to both airplane manufacturers and operators who need to adopt revolutionary solutions to provide an effective response towards a more sustainable energy supply, including steep reductions in pollutant emissions and a significant improvement in recyclability. Natural materials are a viable path to address this challenge as they rely upon sustainable production processes and offer considerable advantages in terms of renewability, recyclability and biodegradability. Furthermore, evidences from recent research suggest that some natural materials offer mechanical properties equivalent or even better than conventional materials used for engineering applications in the aerospace sector. This paper presents a review of the progresses achieved in the use of natural based materials in aeronautical structures. Most of these materials are in the form of polymer based composites with either the inclusion of natural reinforcing fibres and resins or other types of natural materials used as core constituents in sandwich components, such as cork based composites. The presented data were collected from different research works and cover a broad range of loading conditions as experienced by aircraft under normal operational scenarios and taking into consideration relevant airworthiness requirements, such as fire resistance and damage tolerance. Results are very encouraging and support the use of natural based materials in aircraft structural components, opening a window of tangible opportunities for the design of more fuel efficient and environmentally sustainable aircraft in the near future

LIDAR obstacle warning and avoidance system for unmanned aerial vehicle sense-and-avoid

The demand for reliable obstacle warning and avoidance capabilities to ensure safe low-level flight operations has led to the development of various practical systems suitable for fixed and rotary wing aircraft. State-of-the-art Light Detection and Ranging (LIDAR) technology employing eye-safe laser sources, advanced electro-optics and mechanical beam-steering components delivers the highest angular resolution and accuracy performances in a wide range of operational conditions. LIDAR Obstacle Warning and Avoidance System (LOWAS) is thus becoming a mature technology with several potential applications to manned and unmanned aircraft. This paper addresses specifically its employment in Unmanned Aircraft Systems (UAS) Sense-and-Avoid (SAA). Small-to-medium size Unmanned Aerial Vehicles (UAVs) are particularly targeted since they are very frequently operated in proximity of the ground and the possibility of a collision is further aggravated by the very limited see-and-avoid capabilities of the remote pilot. After a brief description of the system architecture, mathematical models and algorithms for avoidance trajectory generation are provided. Key aspects of the Human Machine Interface and Interaction (HMI2) design for the UAS obstacle avoidance system are also addressed. Additionally, a comprehensive simulation case study of the avoidance trajectory generation algorithms is presented. It is concluded that LOWAS obstacle detection and trajectory optimisation algorithms can ensure a safe avoidance of all classes of obstacles (i.e., wire, extended and point objects) in a wide range of weather and geometric conditions, providing a pathway for possible integration of this technology into future UAS SAA architectures

A laser obstacle detection and avoidance system for manned and unmanned aircraft applications

This paper presents the key design features, the numerical simulations and the experimental ground/flight test activities performed to verify the functionalities of an obstacle detection and avoidance system suitable for various classes of manned and unmanned aircraft. The Laser Obstacle Avoidance and Monitoring (LOAM) system is proposed as one of the key non-cooperative sensors adopted for avoiding obstacles/intruders in the context of a future Sense-and-Avoid (SAA) capability. After a brief description of the system architecture and of the main data processing algorithms, avoidance trajectory generation and performance estimation models are described. A simulation of the avoidance trajectory generation algorithm is performed in a realistic scenario. Additionally, a brief overview of ground and flight test activities performed on various platforms and their main results is also presented. Some of the key aspects of the LOAM Human Machine Interface and Interaction (HMI2) design are also outlined. The demonstrated detection and avoidance performances and the robust trajectory generation algorithm ensure a safe avoidance of all classes of obstacles (i.e. ground and aerial) in all weather conditions and flight phases

Low-cost sensors based multi-sensor data fusion techniques for RPAS navigation and guidance

In order for Remotely Piloted Aircraft Systems (RPAS) to coexist seamlessly with manned aircraft in non-segregated airspace, enhanced navigational capabilities are essential to meet the Required Navigational Performance (RNP) levels in all flight phases. A Multi-Sensor Data Fusion (MSDF) framework is adopted to improve the navigation capabilities of an integrated Navigation and Guidance System (NGS) designed for small-sized RPAS. The MSDF architecture includes low-cost and low weight/volume navigation sensors suitable for various classes of RPAS. The selected sensors include Global Navigation Satellite Systems (GNSS), Micro-Electro-Mechanical System (MEMS) based Inertial Measurement Unit (IMU) and Vision Based Sensors (VBS). A loosely integrated navigation architecture is presented where an Unscented Kalman Filter (UKF) is used to combine the navigation sensor measurements. The presented UKF based VBS-INS-GNSS-ADM (U-VIGA) architecture is an evolution of previous research performed on Extended Kalman Filter (EKF) based VBS-INS-GNSS (E-VIGA) systems. An Aircraft Dynamics Model (ADM) is adopted as a virtual sensor and acts as a knowledge-based module providing additional position and attitude information, which is pre-processed by an additional/local UKF. The E-VIGA and U-VIGA performances are evaluated in a small RPAS integration scheme (i.e., AEROSONDE RPAS platform) by exploring a representative cross-section of this RPAS operational flight envelope. The position and attitude accuracy comparison shows that the E-VIGA and U-VIGA systems fulfill the relevant RNP criteria, including precision approach in CAT-II. A novel Human Machine Interface (HMI) architecture is also presented, whose design takes into consideration the coordination tasks of multiple human operators. In addition, the interface scheme incorporates the human operator as an integral part of the control loop providing a higher level of situational awareness