Device for measuring the distance to an approaching target, comprising - a platform which can be tracked to the target; - a first passive infrared detection device, which is mounted fixedly on the platform and which is configured to sense and lock onto the approaching target and to supply data concerning the current position of the target; - a further passive infrared detection device, which is arranged at an azimuthal distance (a) from the first passive detection device so as to be pivotable on the platform and/or trackable to the target, and which is also configured to sense and lock onto the approaching target; - a storage, measurement and control system, which is connected to the first passive infrared sensing device; - an azimuthal drive, which is configured in such a way that the platform can be tracked to the target in a horizontal direction, the azimuthal drive being connected to the storage, measurement and control system, and the device being configured in such a way that the first passive infrared detection device is locked onto the target and follows it continuously, in that the azimuthal drive is constantly supplied with data from the storage, measurement and control system; - a computer, which is connected to both passive infrared detection devices (3, 4) and to the storage, measurement and control system, - a device, which is also connected to the computer and which is configured in such a way that the distance from the first passive infrared detection device to the target is determined from the angle (α) between the sensing directions of the two detection devices (3, 4) together with the distance (a) between the two sensing devices (3, 4) when they are both locked onto the target, wherein the two passive infrared detection devices (3, 4) each have a resolution in the range of 0.01 to 0.1 mrad; wherein the storage, measurement and control system is configured in such a way that the angular speed of the platform is determined on the basis of the current position of the target and passed to the computer; and wherein the computer is configured in such a way that an output signal relevant to the launch of a weapon is outputted. - a platform which can be tracked to the target; - a first passive infrared detection device, which is mounted fixedly on the platform and which is configured to sense and lock onto the approaching target and to supply data concerning the current position of the target; - a further passive infrared detection device, which is arranged at an azimuthal distance (a) from the first passive detection device so as to be pivotable on the platform and/or trackable to the target, and which is also configured to sense and lock onto the approaching target; - a storage, measurement and control system, which is connected to the first passive infrared sensing device; - an azimuthal drive, which is configured in such a way that the platform can be tracked to the target in a horizontal direction, the azimuthal drive being connected to the storage, measurement and control system, and the device being configured in such a way that the first passive infrared detection device is locked onto the target and follows it continuously, in that the azimuthal drive is constantly supplied with data from the storage, measurement and control system; - a computer, which is connected to both passive infrared detection devices (3, 4) and to the storage, measurement and control system, - a device, which is also connected to the computer and which is configured in such a way that the distance from the first passive infrared detection device to the target is determined from the angle (α) between the sensing directions of the two detection devices (3, 4) together with the distance (a) between the two sensing devices (3, 4) when they are both locked onto the target, wherein the two passive infrared detection devices (3, 4) each have a resolution in the range of 0.01 to 0.1 mrad; wherein the storage, measurement and control system is configured in such a way that the angular speed of the platform is determined on the basis of the current position of the target and passed to the computer; and wherein the computer is configured in such a way that an output signal relevant to the launch of a weapon is outputted.