Long range imaging systems have applications in vessel traffic monitoring, border and coastal observation, and generic surveillance. Often, sign reading and identification capabilities are required, and medium or long-wave infrared systems are simply not the best solution for these tasks, because of the low scene contrast. Among reflected light imagers, the short-wave infrared has a competitive advantage over the visible and near-infrared spectrum, being less affected by path attenuation, scattering and turbulence. However, predicting a SWIR system long range performance still represents a challenge because of the need of an accurate atmospheric modelling. In this paper, we present the key limiting performance factors for long range applications, and how we used popular atmospheric models to extract the synthetic simulation parameters needed for range performance prediction. We then present a case study for a long range application, where the main requirement is to read a vessel name at distances greater than 10km. The results show a significant advantage of SWIR over visible and near-infrared solutions for long range identification tasks.
The paper introduces the analysis carried out by Selex ES (SE) for the development of a third generation IRST system
based on large format MWIR sensors, separable in blue and red bands. In the feasibility study, physical constraints have
been evaluated relying on different optics and scanning options.
The goal is a system based on distributed heads to cover 360° with a resolution better than 0.3 mrad and high frame rate
that allow to take advantage of the typical atmospheric phenomena of the maritime environment as scintillation and super
and sub refraction.
Two critical aspects were investigated:
(i) the setting of an adequate scanning mechanism to assure a high frame rate and (ii) the stitching of the collected
images while maintaining the bit-depth so as to avoid abrupt changes of SNR at the seams between two subsequent
Modern thermal cameras acquire IR images with a high dynamic range because they have to sense with high thermal resolution the great temperature changes of monitored scenarios in specific surveillance applications. Initially developed for visible light images and recently extended for display of IR images, high dynamic range compression (HDRC) techniques aim at furnishing plain images to human operators for a first intuitive comprehension of the sensed scenario without altering the features of IR images. In this context, the maritime scenario represents a challenging case to test and develop HDRC strategies since images collected for surveillance at sea are typically characterized by high thermal gradients among the background scene and classes of objects at different temperatures. In the development of a new IRST system, Selex ES assembled a demonstrator equipped with modern thermal cameras and planned a measurement campaign on a maritime scenario so as to collect IR sequences in different operating conditions. This has led to build up a case record of situations suitable to test HDRC techniques. In this work, a survey of HDRC approaches is introduced pointing out advantages and drawbacks with focus on strategies specifically designed to display IR images. A detailed analysis of the performance is discussed in order to address the task of visualization with reference to typical issues of IR maritime images, such as robustness to the horizon effect and displaying of very warm objects and flat areas.
This paper presents a soft-real time simulator for IRST (InfraRed Search and Track) systems with ATR (Automatic
Target Recognition) embedded functions to test airborne applications performance. The IR camera model includes
detector, optics, available Field-of-Regard, etc., and it is integrated with the motion platform local stabilization system
to consider all factors impacting IR images. The atmosphere contributions are taken into account by means of a link to
ModTran computer program. Sensor simulation allows derivation and assessment of IR Figures of Merit (NEI, NETD,
SNR...). IR signatures of targets derive both from data collected in specific trial campaigns and from laboratory built
models. The simulation of the scan procedure takes into account different policies (ground points paths or defined
angular volume) and different platform motion strategies (continuous or step steering scan). The scan process includes
Kalman technique to face unexpected variations of aircraft motion. Track and ATR processors are simulated and run
consistently on the output of the sensor model. The simulator functions are developed in MatLab and SIMULINK and
then exported in C code to be integrated in soft real-time environment.
The use of this simulator supports the definition and design of the IRST systems especially for the evaluation of the
most demanding operative requirements. An application of this simulator is for the NEURON UCAV (Unmanned
Combat Air Vehicle) technological demonstrator, which accommodates on board both IRST and ATR tasks.
Modern naval warfare asks for alerting system able to detect classical & asymmetric threats in support to radar in
environment in which radar has reduced performance (on or near the sea surface). More, capability to offer high
resolution images helps in ship identification, coastal & harbor surveillance as well as night navigation and rescue.
All these tasks can be performed by an infrared search and track (IRST) system.
This paper describes the IRST named Silent Acquisition and Surveillance System (SASS), developed for the Italian
Navy and the tests jointly carried out by SELEX GALILEO and Italian Navy to characterize the system.
Within the RTP 8.2 one of the main goals of the START programme is to develop a software simulator which incorporates the results of the research activities devoted to evaluate new IRST technologies and technical solutions which can be the basis of new concepts for future generations IRSTs. The software simulator development is based on the use of a commercial framework to speed up its implementation. The main simulator features are: modularity, expandability, capability to simulate the IRST behavior in different situation and under various scenarios. It is based on an analytical and statistical approach and provides an easy user interface with friendly tools for data supplying and results presentation.
The reliability of some algorithms commonly used in inferring surface temperature from infrared radiation has been investigated. Single-band, two-color and multiwavelength pyrometry methods have been considered. The signal received by the pyrometer was computer simulated by taking into account the spectral emissivity of the target, the effects of atmospheric absorption and self-emission, the selective transmittance of the optics, the contributions due to surrounding bodies and the spectral response of detector. The reliability of the algorithms was obtained by computing the difference between the true target temperature and the calculated one. Results indicate that a good knowledge of target emissivity and atmospheric transmittance is required to achieve a reasonable accuracy. The simulation allows also to predict the increase of temperature error when the atmospheric radiance is not negligible or when a low-emissivity target reflects the radiation from surrounding bodies into the field of view.