The ultraviolet (UV) band of the electromagnetic spectrum has potential as a host medium for the operation of guided weapons. Unlike in the infrared (IR), a target which is propelled by an air breathing jet engine generates no detectable radiation in the UV band, and is opaque to the background UV produced by the Sun. In theory the blocking of UV radiation from the sun causes a detectable ‘negative contrast’ between the target and the background. In order to determine the outcome of engagement scenarios between airborne platforms and guided weapon systems that utilise a guard channel operating in the UV, it is necessary to accurately model background UV levels. This paper presents a comparison between the atmospheric modelling code moderate resolution atmospheric transmission (MODTRAN®5) and measured data. The spectral irradiance levels generated by the MODTRAN®5 code are compared to those of the World Ozone and Ultraviolet Data Centre (WOUDC ) database, for various global positions and times of year. Radiance data collected at the Defence Academy of the United Kingdom (Shrivenham, England) for various observer geometries is also compared to that generated by the MODTRAN®5 code.
Ship self defense against heat-seeking anti-ship missiles is of great concern to modern naval forces. One way of protecting ships against these threats is to use infrared (IR) offboard countermeasures. These decoys need precise placement to maximize their effectiveness, and simulation is an invaluable tool used in determining optimum deployment strategies. To perform useful simulations, high-fidelity models of missiles are required. We describe the development of an imaging IR anti-ship missile model for use in countermeasure effectiveness simulations. The missile model’s tracking algorithm is based on a target recognition system that uses a neural network to discriminate between ships and decoys. The neural network is trained on shape- and intensity-based features extracted from simulated imagery. The missile model is then used within ship-decoy-missile engagement simulations, to determine how susceptible it is to the well-known walk-off seduction countermeasure technique. Finally, ship survivability is improved by adjusting the decoy model to increase its effectiveness against the tracker.
This paper describes the development of a target tracking algorithm for an anti-ship imaging infrared seeker. The
tracking algorithm uses feature extraction and machine learning to discriminate between a desired target ship and decoys within the seeker’s field of view. The algorithm is developed within a high fidelity simulation architecture, used to simulate engagements of infrared missiles against ships, aircraft and land vehicles. The proposed seeker tracking
algorithm will be evaluated in a naval engagement scenario, against a ship deploying countermeasures. The tracking
algorithm performs the tasks of object detection, feature extraction and target selection. Object detection is achieved via thresholding the image of the seeker’s field of view, and thereafter, shape and intensity based features are calculated for each resulting object. These features are then used as inputs to a neural network, which performs the task of target selection, to determine the seeker’s aim-point. Object features such as peak and average intensity, intensity moments, eccentricity, roundness, minimum, maximum and average radial perimeter distances are considered, to determine their discriminatory power. A training set of images of different ships and decoys, generated by the front end of a seeker model within the simulation architecture, is used to obtain a comprehensive collection of these features. An analysis is performed to determine which of the features are the most discriminatory and these are then used as inputs to the neural network. The neural network is trained on these features to recognise the difference between ships and decoys. Examples of the performance of the tracking algorithm will also be shown.
KEYWORDS: Imaging infrared seeker, Missiles, Reticles, 3D modeling, Sensors, Signal processing, Optical engineering, Systems modeling, Signal detection, Electro optical modeling
Man-portable air-defense (MANPAD) systems have developed sophisticated counter-countermeasures (CCM) to try and defeat any expendable countermeasure that is deployed by an aircraft. One of these is a seeker that is able to detect in two different parts of the electromagnetic spectrum. Termed two-color, the seeker can compare the emissions from the target and a countermeasure in different wavebands and reject the countermeasure. In this paper we describe the modeling process of a two-color infrared seeker using COUNTERSIM, a missile engagement and countermeasure software simulation tool. First, the simulations model a MANPAD with a two-color CCM which is fired against a fast jet model and a transport aircraft model releasing reactive countermeasures. This is then compared to when the aircraft releases countermeasures throughout an engagement up to the hit point to investigate the optimum flare firing time. The results show that the release time of expendable decoys as a countermeasure against a MANPAD with a two-color CCM is critical.
The use of flares of flares against 1st and 2nd generation man-portable air-defence (MANPAD) systems proved to be very
effective. This naturally led to the development of counter-countermeasures (CCM) that could be incorporated into the
MANPADs infrared (IR) seeker. One possible CCM is two-colour where the seeker detects in two separate IR bands. It
is designed to exploit the different spectral characteristics of the target and flare. In this paper we describe the modelling
process of a two-colour conical scan (conscan) IR seeker using CounterSim, a missile engagement and countermeasure
simulation software tool developed by Chemring Countermeasures Ltd. It starts by explaining the signal processing
needed to be able to reject the flare and track the target. The MANPAD model is then used in an engagement with a fast
jet model and a transport aircraft model. Flares are first deployed reactively then released throughout an engagement to
investigate the effect of flare release time and the viability of pre-emptive countermeasures.
This paper investigates feature based tracking algorithms that could be used within models of imaging infrared anti-ship
missile seekers in a simulation environment. The algorithms use global shape based object features such as Fourier
Descriptors or Hu Moments to track a target in rendered sensor images. A template of the desired target is saved during
acquisition, and matching is performed between the template and the features of unknown objects extracted from
subsequent sensor images. The centroid of the object that matches the best becomes the seeker aim-point. A seeker using
local features, generated by the Scale Invariant Feature Transform, to track objects will also be examined. It
discriminates between objects within the sensor images by clustering SIFT features that have neighbouring regions of
similar intensity. The cluster of features whose average neighbouring intensity is the closest to a desired target template
is chosen as the highest priority cluster. A variable radius distance metric is used to reject features in this cluster that are
too far from the seeker's previous aim-point. The new aim-point is calculated as the centroid of the cluster of remaining
features. Comparisons of the three algorithms' ability to track a naval vessel deploying countermeasures will be also
presented.
Imaging seekers used in modern Anti Ship Missiles (ASMs) use a variety of counter countermeasure (CCM) techniques
including guard gates and aspect ratio assessment in order to counter the use of IR decoys. In order to improve the
performance of EO/IR countermeasures it is necessary to accurately configure and place the decoys using a launcher that
is trainable in azimuth and elevation. Control of the launcher, decoy firing times and burst sequences requires the
development of algorithms based on multi-dimensional solvers. The modelling and simulation used to derive the
launcher algorithms is described including the countermeasure, threat, launcher and ship models. The launcher model
incorporates realistic azimuth and elevation rates with limits on azimuth and elevation arcs of fire. A Navier Stokes
based model of the IR decoy includes thermal buoyancy, cooling of the IR smoke and its extinction properties. All of
these factors affect the developing size, shape and radiance of the decoy. The hot smoke also influences the performance
of any co-located chaff or other obscurant material. Typical simulations are described against generic imaging ASM
seekers using shape discrimination or a guard gate.
Man-Portable Air-Defence (MANPAD) systems can employ a range of counter-countermeasures (CCM) to reject
expendable IR decoys. Three hypothetical MANPAD models are based on reticle types and CCM features that may be
found in 1st and 2nd generation MANPADs. These are used in simulations to estimate the probability of escaping hit
(PEH) when no IR decoys are used, when IR decoys are deployed reactively and when decoys are deployed preemptively.
These cases are simulated for seekers with no CCM and with a track angle bias CCM.
The results confirm that the rise rate CCM significantly reduces the PEH when IR decoys are used reactively. The use of
pre-emptive flares timed to deploy at or about the time when the seeker is uncaged increases the PEH significantly. A
more detailed investigation of the effects of aircraft aspect angle and flare timing on miss distance was carried out to
examine the effects of the CCM compared with no CCM. With the aircraft at an altitude of 1000m and a range of 2km
there is a critical period in which a flare needs to be released in order to achieve a significant miss distance when the
CCM is in use. The conical scan seeker used with the track angle bias CCM was the most effective combination
requiring the shortest time during which the flare had to be deployed. Further simulations at longer ranges and different
aircraft azimuth angles showed that there is a time window that is range dependant during which pre-emptive decoys are
fully effective independently of the aircraft azimuth or threat direction.
Military aircraft face a serious threat from early generation
Man-Portable Air-Defence (MANPAD) systems. Robust
countermeasures have to be used to counteract this threat. Most commonly these are used after the threat has been
launched and detected. The ideal solution is to defeat the system
pre-emptively before the missile is launched. One way
to achieve this is to fire pre-emptive flares giving the MANPAD another hot source to track and lock-on to. However,
use of pre-emptive flares can quickly deplete the flare magazines limiting the mission time and the area in which the
aircraft will be protected. In this paper we discuss the use of CounterSim, a missile engagement and countermeasure
simulation software tool, to investigate what effect the flare output and burn time may have on the effectiveness of preemptive
countermeasures. The first set of simulations looks at a flare of full intensity and burn time pre-emptively
released at the beginning of the simulations. Then, flares of reduced intensity and reduced burn time are used. In a
second set of simulations the pre-emptive flare release time is investigated by delaying the firing up to one second from
the beginning of the simulation.
With the ever present threat of MANPADS throughout the world the protection of civil aircraft is a desirable capability
that has special requirements in terms of certification, safety, logistics, affordability, environmental impact and
exportability. The Civil Aircraft Missile Protection System (CAMPS), which includes the CIV-IR (infrared) leaf-based
pyrophoric (not pyrotechnic) expendable countermeasure, is a system designed to meet these requirements. This paper
presents the operating aspects of the decoy, including discussion of design features necessary to ensure safety both on the
ground and in flight and assure successful deployment. The characteristics of the CIV-IR have been measured, both on
static single leaves in the laboratory and on deployed packs in field tests and aircraft trials. These measured properties
have been used in engagement modelling and simulation to assess the level of protection that can be afforded to
commercial airliners against generation 1 and 2 MANPADS threats. Aircraft flight trials with ground based seekers have
also been carried out to validate the modelling work. These combine to define the deployment patterns necessary for a
successful seduction of the MANPAD.
The proliferation of early generation Man-Portable Air-Defence (MANPAD) weapon worldwide results in a significant
threat to all aircraft. To develop successful countermeasures to the MANPAD a more detailed understanding of the
factors affecting the missile engagement is needed. This paper discusses the use of CounterSim, a missile engagement
and countermeasure simulation software tool, to model such scenarios. The work starts by analysing simple engagements
of a first generation MANPAD against a fast jet with no countermeasures being employed. The engagement simulations
cover typical MANPAD ranges and aircraft altitudes quoted in open source literature. From this set of base runs,
individual engagements are chosen for further analysis. These may have resulted in hits, misses or near misses. At each
time interval in the simulation the aircraft and missile velocities are used to calculate a projected point of closest
approach. This is then compared with the simulated impact point. The difference is defined as the ▵d error and plots are
produced for hits, misses and near misses. Features of the ▵d error plots are investigated to gain insights into the
potential countermeasure capability. Finally, the analysis of the ▵d error plots is used to investigate the possibility of
replicating the factors in a simulation that produce a miss through a pre-emptive flare deployment.
CounterSim is a countermeasures modelling and simulation application developed by Chemring engineers to study the use of expendable countermeasures in air, land and naval scenarios.
The CounterSim transmissometer model was originally developed in order to validate an obscurant model using measurement data from trials. In principle, it can also be used to assess line of sight transmission and detection times in military scenarios such as vehicle self protection, projected smoke to cover battlefields and littoral operations by ships supporting land operations. Ships could be facing land based threats in littoral operations.
Smokes can be regarded as a nuisance rather than an asset and users will want to minimise self obscuration of their EO/IR systems. The transmissometer model offers a means of monitoring obscuration in simulations for blue on red and red on blue effectors. The paper describes a simple littoral scenario and some of the issues that arise with the transmissometer model used to monitor lies of sight to and from platforms through ambient temperature obscurants and hot smoke. Requirements for the future development of a tracking transmissometer are outlined.
With the ever-growing demand for increased realism in defence modelling and simulation, smoke
modelling, which is computationally expensive, must be conducted on graphics hardware to enable
execution at fast rates with good fidelity. Visual smoke simulation has been successfully implemented
by many authors over recent years, but infrared smoke modelling adds new requirements with
additional challenges. This paper discusses the introduction of a Navier-Stokes staggered grid model
into CounterSim, our countermeasures simulation software, highlighting the problems and benefits of
using PC commodity graphics hardware for infrared applications and detailing the methodology used to
control mass loss and to model thermal cooling. Additionally, the need to use an adaptive grid is
explained, with the implications for both the simulation equations and the management of data storage,
particularly when mixtures of smoke products with widely differing properties may be present. The
focus is then shifted to rendering, highlighting the requirements for greater accuracy than the standard
eight bits per channel of visual applications. Problems with alpha blending on graphics hardware are
also discussed, and examples are presented that illustrate how changes in pixel format give rise to
sometimes startlingly different end results.
KEYWORDS: Missiles, Aerodynamics, Imaging infrared seeker, Kinematics, Modeling, Fourier transforms, Lead, Systems modeling, Signal processing, Control systems
Anti-aircraft infrared (IR) guided missile systems, such as man-portable air defence systems (MANPADS), may be equipped with a variety of counter-countermeasure techniques. One such technique could be to look at the trajectory differences of a fast moving jet aircraft and a deployed flare countermeasure (this is often known as relative kinematics). This paper investigates, via simulation, what improvement in aircraft protection against MANPADS might be achieved by modifying these trajectory differences through the use of advanced flare decoys and forward firing techniques.
This paper studies the Man-Portable Air Defence System (MANPADS) threat against large commercial aircraft using flight profile analysis, engagement modelling and simulation. Non-countermeasure equipped commercial aircraft are at risk during approach and departure due to the large areas around airports that would need to be secured to prevent the use of highly portable and concealable MANPADs. A software model (CounterSim) has been developed and was used to simulate an SA-7b and large commercial aircraft engagement. The results of this simulation have found that the threat was lessened when a escort fighter aircraft is flown in the 'Centreline Low' position, or 25 m rearward from the large aircraft and 15 m lower, similar to the Air-to-Air refuelling position. In the model a large aircraft on approach had a 50% chance of being hit or having a near miss (within 20m) whereas escorted by a countermeasure equipped F-16 in the 'Centerline Low' position, this was reduced to only 14%. Departure is a particularly vulnerable time for large aircraft due to slow climb rates and the inability to fly evasive manoeuvres. The 'Centreline Low' escorted departure greatly reduced the threat to 16% hit or near miss from 62% for an unescorted heavy aircraft. Overall the CounterSim modelling has showed that escorting a civilian aircraft on approach and departure can reduce the MANPAD threat by 3 to 4 times.
Countermeasures consisting of obscurants and decoys can be used separately or in combination in attempting to defeat an attack on an Armoured Fighting Vehicle (AFV) by an IR SACLOS missile system. The engagement can occur over a wide range of conditions of wind speed, wind direction and the AFV route relative to the SACLOS firing post. The countermeasures need to be evaluated over the full set of conditions. Simulation with a man in the loop can be expensive and very time consuming. Without using a man in the loop, a fully computer based simulation can be used to identify the scenarios in which defeat of the SACLOS system may be possible. These instances can be examined in more detail using the same simulation application or by using the conditions in a more detailed modelling and simulation facility. An IR imaging tracker is used instead of the man in the loop to simulate the SACLOS operator. The missile is guided onto the target by either the clear view of the AFV or by the AFV position predicted by the tracker while the AFV is obscured. The modelled scenarios feature a typical AFV modelled as a 3D object with a nominal 8 -12 μm signature. The modelled obscurant munitions are hypothetical but based on achievable designs based on current obscurant material performance and dissemination methods. Some general results and conclusions about the method are presented with a view of further work and the use of decoys with the obscurant to present a reappearing alternative target.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.