MISSILE WARNING DEVICE AND A METHOD FOR WARNING OF A MISSILE

Description

[0001] The present invention relates to a missile warning device and a method for warning of a missile, and more particularly to a passive missile warning device with tracking. BACKGROUND OF THE INVENTION

[0002] Missile warning systems are a necessary component of self-protection systems (e.g., those of aircraft) whose primary task is to detect and declare missiles. Since such missiles can pose a potential threat to the object being warned (hereinafter referred to as the target object; this can be the carrier of the missile warning system or a third object), a detection triggers a notification to a suitable higher-level system so that appropriate countermeasures can be initiated.

[0003] Passive missile warning systems can be based on optical signals, for example, by detecting the missile's hot exhaust stream. For this purpose, one or more spatially resolving cameras, each operating in a specific spectral range, can be used. However, such cameras generally detect all objects within a detection area that have a signature in the camera's spectral range. These often include a variety of non-threatening sources, such as fire, lamps, or even missiles that would not hit the target object. The actual threat lies in missiles that are moving toward the target object and could therefore, in principle, pose a threat.

[0004] A distinction between threatening and non-threatening sources (verification) is made within a classifier. For this purpose, characteristic features (e.g., an intensity profile or other characteristic signature) associated with the source in question are used. Ideally, as a result of the classification, only actual threats are detected and reported to an appropriate self-protection system of the target and / or the pilot for further countermeasures (declaration).

[0005] When adjusting the classifier, a compromise must typically be found between a low false alarm rate (FAR) and a maximum probability of threat declaration (POD).

[0006] Fig. 3 illustrates the schematic relationship between the false alarm rate (FAR) and the threat declaration probability (POD). A first graph 310 shows non-threatening objects that were incorrectly declared as an alarm. Graph 310 represents the false alarm probability (FAR). A second graph 320 shows the probability (1-POD) that a threatening object is incorrectly not declared as an alarm. A threshold is used for the declaration, with a first lower threshold (e.g., 30%) triggering a pre-alarm and a second, higher threshold (e.g., 70%) triggering an alarm. If the threshold were zero (left side of the diagram), all objects would trigger an alarm. As a result, all non-threatening objects trigger an alarm / pre-alarm.As the threshold value increases, the FAR decreases (see first graph 310) and the probability value (1-POD) (second graph 320) increases. A threshold value of 100 (as a percentage of the sensor signal range) means that all objects are declared non-threatening. As the threshold value decreases, there are fewer and fewer dangerous objects for which no warning is issued (see second graph 320).

[0007] The higher the declaration threshold, the lower the false alarm rate. At the same time, however, the probability that an actual threat will be mistakenly interpreted as a false alarm and thus suppressed increases. The same applies if the declaration threshold is set too low, which leads to a large number of false alarms – but with a high probability that an actual threat will be detected.

[0008] If the available countermeasures are limited, it is always advantageous to avoid high false alarm rates, as otherwise there is a risk that no countermeasures will be available in the event of an actual threat. Exceptions to this would be countermeasures that do not wear out, such as direct infrared countermeasures (DIRCM). If a target object is protected by such systems, a higher false alarm rate can be accepted for a missile warning system in favor of warning time or POD. This can be taken into account, for example, by appropriate advance warnings. With a low declaration threshold, such advance warnings achieve a shorter declaration time and / or a higher POD at a higher FAR.

[0009] In addition to detecting fire, such as rockets, missile warning systems can also be used to detect enemy fire with non-powered projectiles (HFI: Hostal Fire Indication). Depending on the spectral range, the muzzle flash, the hot bullet, or, in the case of tracer ammunition, the tracer is detected.

[0010] A known system, for example, is disclosed in US Pat. No. 3,653,016, which combines a broadband solar cell detector with a UV-sensitive detector in series, enabling confirmation of an event previously detected by the solar cell detector. However, the results for this system are still unsatisfactory.

[0011] Another known system is disclosed in EP 2 911 092 A1. This system comprises one or more photodetectors for detection and a high-resolution camera for verification and spatial localization of lightning events. An integral attribute of this localization system is the generation of two detection signal data sets – one by the photodetectors and another by the camera. The spatial localization of a lightning event is thus performed using two data sets, whereby only an approximate determination of the position is made based on the first data set, and the position of the lightning event must then be searched for within the second data set.

[0012] Document WO 2006 / 083278 A2 discloses a DIRCM system (DIRCM: direct infrared counter measures) that first identifies a target object using a missile warning system in a wide field of view and then aligns a fine tracker system to the target object based on an angle approximately determined within the wide field of view. The fine tracker system covers a narrow field of view, within which the target object is first located and can then be precisely tracked. Localization is performed using stored data from the missile warning system.

[0013] Document US 2017 / 0183104 A1 discloses a system for countermeasures by an aircraft against the direction finding, and in particular Doppler determination, of a threatening object by a radar device. The threatening object is disclosed in particular as a radar device that is configured to be switched from an acquisition mode to a tracking mode.

[0014] Document US 2002 / 0133294 A1 discloses a method and device for collision avoidance, particularly for aircraft. In particular, the positions of the aircraft are determined by the Global Positioning System, and evasive maneuvers are calculated based on this.

[0015] Furthermore, European patent application EP 3 591 427 A1 constitutes a prior art document within the meaning of Article 54(3) EPC.

[0016] The problem of warning of a missile, which requires the location and tracking of the instantaneous spatial position of the missile while it is still in flight and / or requires faster verification, is therefore only inadequately addressed.

[0017] Overall, there is a need for improved systems that do not have the above-mentioned problems and offer a high level of security. BRIEF DESCRIPTION OF THE INVENTION

[0018] At least some of the above-mentioned problems are solved by a missile warning device according to claim 1 and a method according to claim 10. The dependent claims relate to advantageous developments.

[0019] The present invention relates to a missile warning device and in particular to a passive missile warning device. The missile warning device comprises a sensor (e.g. a camera or an infrared sensor), a recording device (e.g. an electronic data storage device) and an evaluation unit (e.g. a processor for electronic data processing). The sensor is designed to detect a potential missile (in a suitably selected spectral range). The recording device is designed for continuous (e.g. rolling) storage of detector data from the sensor for a predefined period of time (e.g. an expected flight time of a missile to be detected). The evaluation unit is designed to receive detector data generated by the sensor in a pre-classification in order to detect a detection signal (e.g.To detect the potential missile (localized intensity maxima) and compare them with a declaration threshold. Once the declaration threshold is exceeded, to generate a warning signal (e.g., a pre-alarm) for the potential missile. Furthermore, the evaluation unit is designed to perform a classification verification of the potential missile when a warning signal is present by chronologically tracing the associated detection signal using the detector data stored in the recording device.

[0020] It is understood that the recording device and evaluation unit may comprise multiple components and may also be at least partially integrated into the sensor. For example, a comparison with threshold values can be performed within the sensor itself. Optionally, detector data can also be stored within the sensor.

[0021] The adjective "potentially" used above refers in particular to potentially dangerous missiles such as projectiles or rockets. Such objects generate signals that can be distinguished from other signals (e.g., a stationary background).

[0022] The terms "pre-classification" and "classification" used above should be understood in a broad sense. For example, pre-classification or classification may simply involve the detection of an intensity peak in the detector data and does not necessarily have to determine the precise characteristics of the missile.

[0023] The term "declaration threshold" used above does not necessarily refer directly to the intensity of pixels received by the sensor. Rather, an analysis of the detected events (e.g., over time) is carried out, at least in the evaluation unit, so that the declaration threshold refers, for example, to derived quantities (e.g., how quickly the intensity of pixels changes over time).

[0024] The evaluation unit is designed to perform the pre-classification and the classification based on the detector data and / or the stored detector data of a single sensor.

[0025] In particular, the missile warning system uses the detector data set of a single detector to perform its function, which can achieve increased verification speed or overall faster alarm issuance.

[0026] Optionally, the evaluation unit is further configured to issue an alarm upon verification of a potential missile and / or upon reaching a further declaration threshold by the detection signal, wherein this further declaration threshold is greater than the declaration threshold for the warning signal.

[0027] The warning or alarm can be triggered immediately after the respective declaration threshold is detected as being exceeded. The specific choice of the (further) declaration threshold represents an optimization problem to combine a low false alarm rate with high reliability (high POD). For example, the declaration threshold can be set to 30 and trigger a pre-warning (higher FAR at higher POD). For example, a further declaration threshold of 70 can trigger an alarm (lower FAR at lower POD).

[0028] Optionally, the evaluation unit is further designed to detect and track a detection signal above a certain threshold value that lies below the declaration threshold value within the detector data during the pre-classification.

[0029] Optionally, the sensor or the evaluation unit are further configured to detect a position or direction of the potential missile during detection. The evaluation unit can also be configured to analyze the detector data and / or the stored detector data for a range around the position or direction.

[0030] In this context and in the following, a position should always be understood as the position within the detector data, and not necessarily the three global spatial coordinates. Since the sensor "looks" in a specific direction, this position generally always defines a specific direction. A range around the position or direction should be understood in particular as spatial filtering, so that only areas in the immediate vicinity of the detected position are analyzed.

[0031] Optionally, the evaluation unit is further designed to use information from the detection signal obtained in the pre-classification after the warning signal has been generated for the classification.

[0032] The information can, for example, include the position of the detection signal that triggered the warning signal, or the change in the position or intensity of the detection signal over time. This information can be used within the classification to restrict parameters for tracking the detection signal in the stored detector data. This restriction of parameters can, for example, consist of a restriction to a range around the position or direction of the detection signal. Restricting parameters significantly facilitates tracing the detection signal of the observed potential missile within the detector data, allowing a much lower threshold to be used when tracing within the stored detector data. A low threshold typically leads to an undesirably high false alarm rate.However, this false alarm rate is significantly reduced by restricting parameters.

[0033] Optionally, the evaluation unit is designed to carry out the tracing in time up to a possible firing event, wherein the firing event is a temporally localized maximum in the stored detector data or an earliest possible sensor signal within the tracing.

[0034] Optionally, the evaluation unit is further configured to store the detector data stored in the recording device for a predetermined period of time and / or to delete them after a predetermined period of time, wherein the predetermined period of time depends on an expected flight time of the potential missile to a target object that is to be warned by the missile warning device.

[0035] Storage by the evaluation unit is necessary for tracking purposes. The predetermined duration of the recording can depend on the expected flight time of the potential missile to a target object that is to be warned by the missile warning system. For example, the predetermined duration can be in a range between 10 seconds and 60 seconds, or between 15 seconds and 50 seconds, or approximately 20 seconds or approximately 30 seconds. As is generally the case, the term "deletion" does not necessarily refer to physical deletion, but rather merely to the authorization to overwrite the corresponding data area. The specified time ranges are merely examples. It is understood that the time range is, in particular, adjustable and can be adapted to the specific circumstances and to the expected missiles and their speed.

[0036] Optionally, the evaluation unit is designed to compare at least sections of the detection signal in the stored detector data with a specific missile signature (previously known to the evaluation unit) during classification in order to classify the missile as potentially dangerous.

[0037] A potentially dangerous missile exhibits a specific missile signature. The evaluation unit can compare this missile signature with known missile signatures as part of the classification process, thus improving the verification of the potential missile and reducing the probability of false alarms.

[0038] Optionally, the recording device is further configured to store only those detector data acquired by the sensor that are above a threshold value. The signals can also be continuously compressed and stored as compressed image data. The sensor is optionally configured to perform local or global segmentation in real time and to transmit only object data to the evaluation unit. In contrast to image data, object data can, for example, be data suitable for identifying objects or their properties (e.g., what they are and where they are located).

[0039] Storing detector data only above a threshold, as well as compressing it, can reduce the amount of stored detector data and / or anticipate the implementation of a threshold during traceback. Transmitting object data can facilitate verification.

[0040] The present invention also relates to a method for warning of a missile. The method comprises the steps: Continuously storing detector data from a sensor in a recording device for a predefined period of time, detecting a potential missile by identifying a detection signal, generating a warning signal for the potential missile after the detection signal exceeds a declaration threshold, verifying the potential missile by tracing the detection signal back in time using the detector data stored in the recording device.

[0041] This is a missile warning system that does not require any signals to be emitted (a passive warning system). Any filters present filter the expected wavelength range.

[0042] Optionally, the procedure further comprises the steps Issuing and forwarding an alarm after verifying the potential missile and / or after the detection signal reaches a threshold above the declaration threshold.

[0043] Optionally, the method includes using information from the previous identification of the detection signal to verify the potential missile.

[0044] Optionally, the method further includes performing time backtracking to a possible firing event, wherein the firing event is a temporally localized maximum in the recorded detector data or an earliest possible sensor signal within the backtracking. BRIEF DESCRIPTION OF THE CHARACTERS

[0045] The embodiments of the present invention will be more fully understood from the following detailed description and the accompanying drawings, which, however, should not be construed to limit the disclosure to the specific embodiments, but are for explanation and understanding only. Fig. 1 shows a schematic diagram of a missile warning system according to one embodiment of the present invention. Fig. 2A shows a missile signature with the responses of a missile warning system according to one embodiment of the present invention. Fig. 2B shows a missile signature with the responses of a missile warning system according to another possible embodiment of the present invention. Fig. 3 shows a schematic relationship between FAR and POD. DETAILED DESCRIPTION OF THE FIGURES

[0046] Fig. 1 shows the schematic diagram of a missile warning device according to an embodiment of the present invention. The missile warning device structurally comprises a sensor 110, a recording device 120, and an evaluation unit 130 (here delimited by the dashed parallelogram). The sensor 110 is designed to detect a potential missile 10. The sensor 110 forwards the signals received as detector data 111 to both the recording device 120 and the evaluation device 130. The recording device 120 is designed to store the detector data 111 continuously (rolling) for a predetermined period of time.

[0047] The evaluation unit 130 is designed to fulfill two functions, represented here by rectangles inside the evaluation unit 131: First, it is designed to receive the detector data 111 in a pre-classification 131 and to identify detection signals 230 triggered by potential missiles 10 therein, as well as to trigger a warning signal 133 after a specified declaration threshold S2 is exceeded by a detection signal 230. Optionally, this function is designed to identify a detection signal 230 above a certain threshold S1 in the detector data 111, to track it, and to trigger a warning signal 133 only when the declaration threshold S2 is reached. Secondly, the evaluation unit 130 is designed to carry out a verification of the potential missile 10 based on a trace 220 within the stored detector data 121 when the warning signal 133 is present in a classification 132.The tracing 220 can be performed with a significantly lower threshold value S 0 . Optionally, the tracing 220 is supported by restricting the search parameters based on the information in the previously identified detection signal 230, wherein the restriction can include, for example, a position or a direction and / or the previously detected temporal profile of the detection signal 230. If the potential missile 10 is verified as such by the classification 132, or if the detection signal 230 exceeds a higher threshold value S 3 , the evaluation unit 130 issues an alarm 140.

[0048] Fig. 2A illustrates the operation of an embodiment of the present invention.

[0049] In the left part of the figure, a schematic example of a missile signature 210 over time (signal versus time) is shown twice, arranged one above the other. The missile signature 210 can, for example, be an optical signal generated by a missile 10 that can be detected in the visible, IR, or UV spectral range. The missile signature 210 initially comprises a launch section 211, which is generated, for example, during a rocket launch or a firing of the missile 10. This is followed by an acceleration section 212 (so-called booster section), which corresponds to an acceleration phase of the missile 10 and is associated with an increased intensity of the generated radiation. Finally, the missile signature 210 comprises a flight section 213 (a so-called sustainer signal), which is generated over the normal flight time.

[0050] In the right-hand part of the figure, the detector data 111 are shown in a top left field, and the stored detector data 121 are shown in a bottom left field; furthermore, the detector data 111 filtered by the threshold value S1 of the pre-classification 131 are shown in a top right field 231, and the stored detector data 121 filtered by the threshold value So of the classification 132 are shown in a bottom right field 232.

[0051] The upper part of the figure illustrates the pre-classification 131 of the evaluation unit 130 as an example: The missile signature 210 is detected by the evaluation unit as a detection signal 230. In this example, exceeding the threshold value S1 at time t1 by the detection signal 230 triggers tracking of the missile signature 210 by the evaluation unit 130 within the detector data 111. If the missile signature 210 exceeds the declaration threshold value S2, here at time t2, the evaluation unit 130 generates a warning signal 133.

[0052] The lower part of the figure illustrates, by way of example, the classification 132 by the evaluation unit 130. After the warning signal 133 is triggered at time t2, the evaluation unit 130 performs a backtracking 220 of the flight signature 210 within the stored detector data 121. The backtracking 220 comprises an analysis of the detection signal 230 in the stored detector data 121 above a low threshold value So. A high false alarm rate resulting from the low threshold value So is compensated, for example, by limiting the analysis of the detector data 121 to a local area around the position of the detection signal 230.Optionally, the tracking 220 may include a comparison with a flight signature 210 known to the evaluation unit 130 and / or may be improved and accelerated via further information already available through the pre-classification 131 of the detection signal 230, such as the temporal change of the detection signal 230 detected in the pre-classification 131.

[0053] Shown is the situation in which the detection signal 230 contained in the detector data 121 by the potential missile 10 can be verified with sufficient accuracy by tracing 220 as the missile signature 210 of a dangerous missile 10. Tracing 220 takes the time from t2 to t. At time t, the verification is complete, and the evaluation unit 230 triggers an alarm 140, which is forwarded to a higher-level system.

[0054] For a better understanding, Fig. 2A In addition, a time t3 is noted at which the evaluation unit 130 would have verified the missile signature 210 using a method without tracing. Optionally, the evaluation unit 130 is configured to trigger an alarm 140 upon reaching the threshold value S3 (here at time t3) if the tracing 220 has not led to a successful verification up to time t3.

[0055] Fig. 2B illustrates the operation of another embodiment of the present invention. The figure is structured as follows: Fig. 2A , however, in Fig. 2B the detection thresholds S1, S2, and S3 of the evaluation unit are reduced to S1', S2', and S3'. This increases the number of detection signals 230 and the probability of false alarms. However, detection and reaching of the declaration threshold S2' for issuing the warning signal 133 occur earlier for the same missile signal 210 (namely at times t1' and t2', respectively, instead of t1 and t2, respectively). Due to the lower threshold value S0, the tracing 220 again allows verification of the missile signal, and the time t' at which an alarm 140 is issued is again before the time t3' at which the detection signal 230 reaches the higher threshold value S3' and the evaluation unit 130 issues an alarm 140. Compared to the situation in which the missile warning device operates without tracking 220 and only issues an alarm 140 when the detection signal 230 has reached the original threshold S3 (this corresponds to the situation in 。 Fig. 2A situation shown without tracing 220) the embodiment leads to Fig. 2B to an earlier alarm with the same false alarm rate.

[0056] The features of the invention disclosed in the description, the claims and the figures may be essential for the realization of the invention both individually and in any combination. LIST OF REFERENCE SYMBOLS

[0057] 10potential missile 110sensor 111detector data 120recording device 121stored detector data 130evaluation unit 131pre-classification for identifying a detection signal 132classification for tracing a detection signal 133warning signal 140alarm 210missile signature 211launch signal 212acceleration signal 213flight signal 230detection signal 231detector data above threshold S1 232detector data above threshold S0 310false alarm probability (FAR) 320probability of non-detection (1-POD) S0, S1, S2, S3threshold values t1, t2, t3times at which the missile signature 210 exceeds the threshold values S1, S2, S3 reaches tTime at which the traceback 220 is completed

Claims

1. A missile detector, in particular a passive missile detector, comprising: a sensor (110) for detecting a potential missile (10); a recording device (120) for continuously storing detector data (121) of the sensor (110) for a predefined period of time; an evaluation unit (130) which is designed: - to receive detector data (111) generated by the sensor (110) in a pre-classification (131) from the sensor (110), to detect a detection signal (230) of the potential missile (10) in the detector data (111) and to compare it with a declaration threshold value (S2) and, after the declaration threshold value (S2) has been exceeded, to generate a warning signal (133) ahead of the potential missile (10), and - to carry out a verification of the potential missile (10) in a classification (132) if there is a warning signal (133) by temporally tracing (220) the associated detection signal (230) using the detector data (121) stored in the recording device (120), wherein the evaluation unit (130) is designed to carry out the pre-classification (131) and the classification (132) on the basis of the detector data (111) and / or the stored detector data (121) of a single sensor (110).

2. The missile detector according to one of the preceding claims, wherein the evaluation unit (130) is further designed to output at least one of the following alarms: - an alarm (140) when the potential missile (10) is verified, - an alarm (140) when a further declaration threshold value (S3) is reached by the detection signal (230), wherein the further declaration threshold value (S3) is greater than the declaration threshold value (S2) of the warning signal (133).

3. The missile detector according to either of the preceding claims, in which the evaluation unit (130) is further designed to detect and trace, in the pre-classification (131), within the detector data (111), a detection signal (230) above a certain threshold value (S1) below the declaration threshold value (S2).

4. The missile detector according to any of the preceding claims, wherein - the sensor (110) or the evaluation unit (130) are further designed to detect a position or a direction of the potential missile (10) and - the evaluation unit (130) is designed to analyze the detector data (111) and / or the stored detector data (121) for a range around the position or the direction.

5. The missile detector according to any of the preceding claims, wherein the evaluation unit (130) is designed to use the information of the detection signal (230) obtained in the pre-classification (131) for the classification (132) after generation of the warning signal (133).

6. The missile detector according to any of the preceding claims, wherein the evaluation unit (130) is designed to carry out the tracing (220) temporally up to a possible launch event (211), wherein the launch event (211) is a temporally localized maximum in the stored detector data (121) or an earliest possible sensor signal within the tracing (220).

7. The missile detector according to any of the preceding claims, wherein the evaluation unit (130) is further designed to store the detector data (121) stored in the recording device (120) for a predetermined period of time and / or to delete them after a predetermined period of time, wherein the predetermined period of time depends on an expected flight time of the potential missile (10) to a target object that is to be warned by the missile detector.

8. The missile detector according to any of the preceding claims, wherein a potentially dangerous missile (10) has a certain missile signature (210), and the evaluation unit (130) is further designed to compare, during the classification (132), at least portions of the detection signal (230) in the stored detector data (121) with the certain missile signature (210), in order to classify the missile (10) as potentially dangerous.

9. The missile detector according to any of the preceding claims, - wherein the recording device (130) is designed to store only the detector data (111) generated in the sensor (110) which are above a threshold value (S0), and in particular to compress them continuously and to store them as compressed image data, and - wherein the sensor (110) is designed to perform a local or global segmentation in real time and transmit only object data to the evaluation unit (130).

10. A method for warning ahead of a missile (10), comprising the following steps: - continuously storing detector data (111) of a sensor (110) in a recording device (120) for a predefined period of time, - detecting a potential missile (10) by identifying a detection signal (230), - generating a warning signal (133) ahead of the potential missile (10) after a declaration threshold value (S2) has been exceeded by the detection signal (230), - verifying the potential missile (10) by temporally tracing (220) the detection signal (230) using the detector data (121) stored in the recording device (120), wherein the pre-classification (131) and the classification (132) are carried out on the basis of the detector data (111) and / or the stored detector data (121) of a single sensor (110).

11. The method according to claim 10, extended by the step of: - issuing and forwarding an alarm (140) after the potential missile (10) has been verified and / or after a threshold value (S3) above the declaration threshold value (S2) has been reached by the detection signal (230).

12. The method according to claim 10 or claim 11, in which verifying the potential missile (10) uses information from the previous identification of the detection signal (230).

13. The method according to any of claims 10 to 12, in which the temporal tracing (220) is carried out up to a possible launch event (211), wherein the launch event (211) is a temporally localized maximum in the recorded detector data (121) or an earliest possible sensor signal within the tracing (220).