The detection and tracking of ballistic missiles during launch or after cloud-break using satellite-based EO-sensors is a promising means for pre-instructing fire control radars precisely. This way, the countermeasure can be initiated in time. At Fraunhofer IOSB, a design concept for satellite-based early warning has been developed in cooperation with German defense industries.
In recent years NATO published a list of 30 countries being able to produce their own ballistic missiles within the next few decades. The majority of these states are located in the Middle East - and most European states would be within the range of attacks. The deployment of a satellite based early warning system will contribute eminently to enhance the vantage point on ballistic missile attacks by detecting ballistic missiles minutes ahead of the fire control radar. This way, valuable time for initiating the countermeasure is gained. To ensure a timely recognition from a space-based point of view, electro-optical (EO) systems that would detect the infrared (IR) signal emitted by the missile plume are best suitable.
Reliable early warning and target tracking can only be conducted, if the ratio between the ballistic missile signal and the observed background (terrestrial and atmospheric) is exceeding a certain threshold. To ensure a sufficiently high value, the selection of the spectral band of the sensor is of high importance: Only this way, the subsequent computing time for applying image exploitation algorithms is minimized. In order to evaluate the performance of those algorithms, test sequences need to be created as realistic as possible. Since both, background and target signature, depend on the environmental conditions, a detailed knowledge of the meteorology and climatology is necessary. Trials for measuring these environmental characteristics serve as a basis, but might only constitute the conditions during a rather short period of time. To represent the entire variation of meteorology and climatology, the application of comprehensive modelling tools is essential.
|Overview of the atmospheric effects on the background signal as observed from a satellite-based sensor.|
Radiative transfer models are commonly used to evaluate sensor performance and tracking algorithms. For modelling the background as observed from a satellite-based sensor, the software MATISSE is applied. MATISSE was developed by ONERA (France) and is currently refined and upgraded in cooperation with Fraunhofer IOSB. Before applying tools like MATISSE in different fields of research, an extensive validation process has to be performed. With many decades of expertise in measuring, characterizing and modelling atmospheric and meteorological effects, Fraunhofer IOSB has tested and validated MATISSE. Within this process, different spectral ranges as well as seasonal, diurnal and climatological influences on the IR signature of the background have been taken into account.
For modelling the signature of a ballistic missile, several optical signature prediction models are in use. Again, these models need to be validated in different fields of application. For this purpose, Fraunhofer IOSB has carried out several measurement trials and used the outputs to establish a database used to test and evaluate such simulation tools.
Comparison of a MODIS satellite image
In order to estimate the performance of a certain EO sensor design for its designated application in space, realistic test sequences are created and subsequently evaluated by a detection and tracking algorithm. For these sequences, not only the entire observation geometry including detector and sensor is simulated, but also atmospheric effects influencing the performance of such an EO system. Having taken these into account, the according IR signatures of the background and propagation path (clouds, surface, meteorology) are added. To complete the sequences, the background image is overlaid with the time and height dependent signature of a ballistic missile along the coordinates of its trajectory.
Simulation of the field-of-view of satellite-based early warning sensor. The red rectangular
Having considered all possible limitations on the satellite-based early warning system caused by environmental conditions, a conclusion on an appropriate sensor design can be given. Under the guidance of WTD 81, Fraunhofer IOSB has teamed up with several German Defense industries to develop and build a technology demonstration system for future satellite-based early warning.
Video: MAXUS 9 Raketen Start (SSC) Esrange Space Center near Kiruna.