24,512 research outputs found
Multi-Agent Orbit Design For Perception Enhancement Purpose
This paper develops a robust optimization based method to design orbits on
which the sensory perception of the desired physical quantities are maximized.
It also demonstrates how to incorporate various constraints imposed by many
spacecraft missions such as collision avoidance, co-orbital configuration,
altitude and frozen orbit constraints along with Sun-Synchronous orbit. The
paper specifically investigates designing orbits for constrained visual sensor
planning applications as the case study. For this purpose, the key elements to
form an image in such vision systems are considered and effective factors are
taken into account to define a metric for perception quality. The simulation
results confirm the effectiveness of the proposed method for several scenarios
on low and medium Earth orbits as well as a challenging Space-Based Space
Surveillance program application.Comment: 12 pages, 18 figure
Unmanned Aerial Systems for Wildland and Forest Fires
Wildfires represent an important natural risk causing economic losses, human
death and important environmental damage. In recent years, we witness an
increase in fire intensity and frequency. Research has been conducted towards
the development of dedicated solutions for wildland and forest fire assistance
and fighting. Systems were proposed for the remote detection and tracking of
fires. These systems have shown improvements in the area of efficient data
collection and fire characterization within small scale environments. However,
wildfires cover large areas making some of the proposed ground-based systems
unsuitable for optimal coverage. To tackle this limitation, Unmanned Aerial
Systems (UAS) were proposed. UAS have proven to be useful due to their
maneuverability, allowing for the implementation of remote sensing, allocation
strategies and task planning. They can provide a low-cost alternative for the
prevention, detection and real-time support of firefighting. In this paper we
review previous work related to the use of UAS in wildfires. Onboard sensor
instruments, fire perception algorithms and coordination strategies are
considered. In addition, we present some of the recent frameworks proposing the
use of both aerial vehicles and Unmanned Ground Vehicles (UV) for a more
efficient wildland firefighting strategy at a larger scale.Comment: A recent published version of this paper is available at:
https://doi.org/10.3390/drones501001
A Novel Optical/digital Processing System for Pattern Recognition
This paper describes two processing algorithms that can be implemented optically: the Radon transform and angular correlation. These two algorithms can be combined in one optical processor to extract all the basic geometric and amplitude features from objects embedded in video imagery. We show that the internal amplitude structure of objects is recovered by the Radon transform, which is a well-known result, but, in addition, we show simulation results that calculate angular correlation, a simple but unique algorithm that extracts object boundaries from suitably threshold images from which length, width, area, aspect ratio, and orientation can be derived. In addition to circumventing scale and rotation distortions, these simulations indicate that the features derived from the angular correlation algorithm are relatively insensitive to tracking shifts and image noise. Some optical architecture concepts, including one based on micro-optical lenslet arrays, have been developed to implement these algorithms. Simulation test and evaluation using simple synthetic object data will be described, including results of a study that uses object boundaries (derivable from angular correlation) to classify simple objects using a neural network
Innovative observing strategy and orbit determination for Low Earth Orbit Space Debris
We present the results of a large scale simulation, reproducing the behavior
of a data center for the build-up and maintenance of a complete catalog of
space debris in the upper part of the low Earth orbits region (LEO). The
purpose is to determine the performances of a network of advanced optical
sensors, through the use of the newest orbit determination algorithms developed
by the Department of Mathematics of Pisa (DM). Such a network has been proposed
to ESA in the Space Situational Awareness (SSA) framework by Carlo Gavazzi
Space SpA (CGS), Istituto Nazionale di Astrofisica (INAF), DM, and Istituto di
Scienza e Tecnologie dell'Informazione (ISTI-CNR). The conclusion is that it is
possible to use a network of optical sensors to build up a catalog containing
more than 98% of the objects with perigee height between 1100 and 2000 km,
which would be observable by a reference radar system selected as comparison.
It is also possible to maintain such a catalog within the accuracy requirements
motivated by collision avoidance, and to detect catastrophic fragmentation
events. However, such results depend upon specific assumptions on the sensor
and on the software technologies
Video analysis of events within chemical sensor networks
This paper describes how we deploy video surveillance techniques to monitor the activities within a sensor network in order to detect environmental events. This approach combines video and sensor networks in a completely different
way to what would be considered the norm. Sensor networks
consist of a collection of autonomous, self-powered
nodes which sample their environment to detect anything
from chemical pollutants to atypical sound patterns which
they report through an ad hoc network. In order to reduce
power consumption nodes have the capacity to communicate
with neighbouring nodes only. Typically these communications
are via radio waves but in this paper the sensor nodes communicate to a base station through patterns emitted
by LEDs and captured by a video camera. The LEDs are chemically coated to react to their environment and on doing so emit light which is then picked up by video analysis.
There are several advantages to this approach and to demonstrate we have constructed a controlled test environment.
In this paper we introduce and briefly describe this
environment and the sensor nodes but focus mainly on the
video capture, image processing and data visualisation techniques
used to indicate these events to a user monitoring the
network
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