SE516372C2 - Sensor system for detecting missiles - has four sensors in circle around protected area each scanning 90 Deg. sectors in two sky pointing detection fields to measure missile parameters - Google Patents

Abstract

The sensor system for detecting low flying missiles includes a number of sensors around the protected target. Four sensors (2) are arranged at 90 deg. angles around the target (6). The sensors are connected to a central control that can implement counter- measures against missiles. Each sensor scans a 90 deg. arc of the sky and has two detection fields (9,10). The time of passage of a missile (8) through the detection fields and its angles with respect to the sensor are measured. This allows the speed and direction to be established. The sensors point skywards to avoid ground reflections.

Description

1 6 3 7 2 2 relatively simple means a target can be detected and that the position of the target can be determined with good accuracy.

The position of a sensor station can be determined by the grouping of the sensor station and stored in a memory unit included by the sensor station. According to another embodiment, the position can be determined by means of a radio navigation system included in the sensor station, such as GPS. With knowledge of the position of the sensor station and the position of a target relative to the sensor station, a close-range weapon intended to protect the protected object can be given a clear indication of the position of the target.

Preferably, the position of a target is indicated after it has passed the two detection fields by means of three orthogonal coordinate values related to a coordinate system common to the sensor system. Rapid rough indication to a close-range weapon can take place through sector indication already when the first detection field is passed.

Preferably, the position of the target is indicated as belonging to a circular sector of 360 / n °, where n is equal to the number of input sensor stations. In a preferred embodiment with four sensor stations, this means rough indication in sectors of 90 °.

Advantageously, the speed of the target is determined by means of speed measuring means arranged in the sensor stations in the form of speed measuring radar. By using speed measuring radar, a value with great accuracy of the target speed is obtained. In applications with moderate requirements for the accuracy of the velocity value, an expected velocity of the target based on knowledge of velocity intervals within which the target in question fl is applied can alternatively be used for measurement.

For further relaxation of the air, according to a further advantageous embodiment, the detector units of the sensor stations may comprise a line camera.

The invention will be described in more detail below with reference to the accompanying drawings, in which Figure 1 shows a schematic overview view of a sensor system according to the invention, Figure 2 shows an overview of the two detection fields belonging to a sensor station, Figure 3 shows a robot's passage between a sensor station. associated measurement times, figure 4 shows how fl height and transverse distance can be calculated and 5 figure 5 shows a schematic block diagram for a sensor station included in the sensor system according to the invention.

According to the schematic overview view of the sensor system shown in Figure 1, four sensor stations 1-4 are included. The stations are suitably of IR type. The sensor stations are distributed in the terrain substantially along the periphery of a circle 5. In the center of the circle 5 is found the object 6 which is the subject of protection. In the vicinity of the protected object are also the close protection weapons 7 that are to protect the protected object 6.

A target approaching the sensor system has been designated 8 and may consist of, for example, a low-flying cruise missile.

The four IR sensor stations 1-4 span the sky in a band above the sensor.

When a target 8 with an IR signature passes over the area where the sensor system is placed, this is detected by means of two consecutive measurements slightly different in elevation angle. Based on the two measurements, the position and height of the target can be calculated in accordance with the description below. Here it can be observed that the position of a target can be roughly indicated already at its first detection. The sensor system can be said to create a "stumbling block" over which object, even terrain tracking, should not be able to dodge without detection. After the target position has been calculated, the short-range weapons 7 are assigned in three coordinates to combat the target 8.

With today's threat picture, terrain-following robots with speeds around 200 ni / s, a "trip wire" or circle 5 with a radius R of about 2 km should be adequate. In the event that higher speeds become relevant, the radius R as well as the number of input sensor stations can be increased.

With reference to Figures 1-4, it is shown below how the position of a target is determined and communicated to the local protection weapons 7.

As shown in Figures 2 and 3, an IR sensor station 1-4 spans the space in a first and a second detection field 9,10. The angle between the two detection fields has been given the designation ot and is known. At time TO the target 8 passes the first detection field 9 and at time T; the second detection field 10.

The passage time T between the detection fields is given by the expression: TITI-Tg 516 372 fi OIIIIO When the passage time is known by measurement and the angle a between the detection fields 9,10 is known, the inclined target passage distance Elevation temp, see figure 3, can be estimated or measured. A speed measuring radar can be used to measure the speed. The following relationship can be established: Elevation temp = (T * Vmissil) / tan (a) Based on the inclined target passage distance and the angle ß to the detection direction 18 according to fi figure 4 in which detection took place, the target fl eye height "Height" and transverse distance "Transverse" relative to the sensor station can be calculated as follows: Elevation = Elevation attenuation * sin (ß) Transverse = Elevation wmp * cos (ß) The calculated transverse distance is along the curved detection field of the sensor station, so the distance must be converted to Cartesian distance relative to the sensor station. The position of the target relative to the sensor station can now be calculated as follows: Targetx = R * sin (T vars / R) Target = - R * cos (T trans / R) Target, = Height Instruction to the short-range weapons is obtained based on the sensor station position and calculated target position as follows connection: Instructionx = Sensor position + targetx Instruction view = Sensor position + target Instructionz = Sensor position, + target, The sensor positions are obtained from a storage medium in which the position of the sensor station is stored after position measurement at the sensor station grouping. 5 to 51.6 572 I I 'IDO Olli vrvuoø v b Figure 5 shows an example in schematic block diagram form of how a sensor station can be constructed.

A detector unit 11 is arranged to operate in a 90 degree side angle sector along the arc of the circle 5. In a circle with a radius of 2 kilometers, this means that the largest distance at which a detector unit can see a target is 1571 m.

Each detector unit spans the air 180 ° above along the arc in its quadrant. The detector unit operates in two different detection fields 9,10, which each supply their own detector array 12,13. Advantageously, a line camera operating near the infrared area of the detector unit is used. Compared to a scanning camera, the line camera has the advantage of maintaining continuous monitoring. At the short detection distances in question, a good probability of detection is obtained even against only aerodynamically heated targets. If a line camera with 1024 pixels is used, a resolution of 180 ° is obtained! 1024 pixels, i.e. 0.18 ° / pixel. This means that a pixel at the largest distance corresponds to 4.9 m at a radius of 2 km.

The detector unit 11 waits for a signal from the detection field 9, which lies outside the circle 5 or the "trip wire" corresponding to the detection field 10. When the detection field 9 detects a target, a timer 14 is started. The timer is stopped when the target passes the detection field 10.

At the same time as a target is detected by the detection field 9, a speed measuring radar 15 is started which measures the target speed Vml-ss fl. A memory unit 16 stores the position of the sensor station, which is measured at an earlier stage in the grouping of the sensor station. The memory unit can also store the value of the angle ot between the detection fields 9,10. Based on the information provided by the detector unit 11, timer 14, radam 15 and memory unit 16, a calculation circuit 17 can calculate the position of the target in accordance with previously reported relationships. After performing calculations, the protective weapons are assigned to a target position x, y, z with very high accuracy.

Claims (9)

a ... 516 372 6 Patent claims Sensor system comprising a plurality of sensor stations for monitoring an area intended to accommodate a protection object, characterized in that the sensor stations are distributed substantially along the periphery of a circle in the central part of which a protection object is intended to be accommodated, each sensor station comprising a detector unit detector unit is arranged to span the arc upwards against a celestial background in an assigned side angle sector in two detection fields designed as fields curved along the arc with different elevation angles, and that in each sensor station the time of a target path between the detection fields is measured and the target position relative to the sensor station is calculated. , measured or estimated velocity of the target, angle between the detection fields and measured angle to the target. Sensor system according to the preceding claim, characterized in that the sensor stations are at least four in number. Sensor system according to one of the preceding claims, characterized in that the sensor stations comprise speed measuring means. Sensor system according to claim 3, characterized in that the speed measuring means are constituted by speed measuring radar. Sensor system according to one of the preceding claims, characterized in that the detector units of the sensor stations comprise a line camera. Sensor system according to one of the preceding claims, characterized in that the position of a sensor station is determined during the grouping of the sensor station and stored in a memory unit comprised by the sensor station. Sensor system according to one of Claims 1 to 5, characterized in that the position of a sensor station is determined by means of a radio navigation system included in the sensor station, such as GPS. 516 372 7 Sensor system according to one of the preceding claims, characterized in that the position of the target is roughly indicated as lying within a circular sector of 360 / n °, where n is equal to the number of input sensor stations when the first detection field is passed. Sensor system according to one of the preceding claims, characterized in that the position of the target after the target has passed the two detection fields is indicated by means of three orthogonal coordinate values related to a coordinate system common to the sensor system.