TACSI (TACtical SImulation) is an existing simulator used as a tactical environment for manned simulators at Saab Aerosystems. TACSI can also be used as a stand-alone desktop development and simulation tool. TACSI simulates a large number of entities and functions such as platforms, sensors, weapons, signatures, communication, multisensor fusion, decision support etc. TACSI has a rule based pilot model and uses High Level Architecture (HLA) for interfacing with other simulation models. This model, a development of TACSI, simulates the flight dynamics, IR-signature and IR-seeker operation. The dynamic behaviour of the aircraft, the IRCM, the missile and the IR-seeker are modelled. The IR-contrast seen by the seeker through the atmosphere in front of the aircraft and the IRCM are spectrally and dynamically modelled. The seeker operation behaviour and function are also modelled. To implement this in a real-time simulation system simplifications are necessary. This paper describes the simplifications to model the IR-contrast and the seeker function. This model is used to analyse the effect of IR countermeasures (IRCM) on a missile IR-seeker.
A simulator (GSIM) for missile seekers that can be used as a general tool in missile seeker performance analysis has been developed. The simulator contains all the subsystems of a typical missile system and can simulate a missile flight scenario from launch, via target acquisition and tracking, to arrival at the target. GSIM has a fully graphical user interface and runs under Matlab on a regular modern PC. Due to a modular approach, the simulator can easily be upgraded and adapted to different prerequisites. It contains a choice of targets against sky, sea or ground backgrounds. Weather conditions, visibility, and time-of-day are taken into account when seeker images are generated. The effects of detector noise and dome heating are also modeled. The results can be presented as movies from the flight, showing both the seeker image as well as trajectories for the missile and target.
We report on the development of methods and equipment which facilitates the measurement of the Modulation Transfer Function (MTF) of IR optics exposed to both high and low temperatures. The MTF is a very powerful measure of the quality of any optical system, and is a common way to test the performance. However, because of the large apparatus needed to perform the testing it is generally not possible to measure the MTF at temperatures other than room temperature. A thermally insulating enclosure was designed in which the optics under test is placed on a temperature-controlled fixture. The enclosure permits the radiation to reach the optics under test and allows the MTF measurement probe to reach the image plane. Meanwhile the MTF measurement bench is kept at room temperature. In this way it is possible to vary the temperature of the optics under test between -30 °C and +85 °C and simultaneously measure the MTF. Using the same equipment it is also possible to measure bore sight error, ensquared energy, and focus position as a function of temperature. A commercially available MTF measurement bench was specially adapted for this purpose. Measurements can be made both on- and off axis and both MWIR and LWIR measurements are possible.
There is a trend today towards a reduction in target signatures, the signatures becoming increasingly adapted to the background in which the targets operate. In addition, new types of countermeasures are making the task for optical seekers increasingly difficult. One way to increase the capability of detecting low-signature targets in a countermeasure environment is to utilize not only the magnitude of the signature but also its distribution over the spectrum. For collection of information regarding the spectral signatures of targets, countermeasures and backgrounds, a multispectral imaging MWIR sensor has been developed by us. This device utilizes the high frame rate made possible by modern FPA arrays. Such an array has been combined with a rapidly rotating filter wheel, thereby producing images of 128 by 128 pixels in six wavelength bands in the 2 - 5 micrometer region at a frame rate exceeding 30 Hz in each band. The sensor has a field-of-view of 3.7 degrees and a pixel resolution of 0.5 mrad. The sensor has the capability to perform two point correction in real time, thereby compensating for the different dynamic ranges in each spectral band. An extensive measurement program is in progress for gathering data for targets, countermeasures and backgrounds. Selected results from this program are presented.