GB899540A - Method and apparatus for indicating the distance between a target and a projectile fired at a target from a firing point - Google Patents

Abstract

899,540. Pulse radar. DEL MAR ENGINEERING LABORATORIES. Jan. 5, 1959, No. 348/59. Class 40(7). [Also in Group XX] A method for determining the miss-distance between a target and a projectile fired at it comprises providing at the firing point a visual record of the target and projectile as seen from the firing point (e.g. on successive frames of a film strip), directing radar signals at the target and projectile and receiving echo signals back therefrom, converting such echo signals to visual form and transferring said visual indications to the visual record of the target and projectile. The target 100 may be a towed aerial target, and the projectile fired from an aircraft, in which the tracking apparatus is also housed. The recording camera 22 has a reel of film 50 moving intermittently in known manner through a gate 52; a pair of lenses 57, 58 form the normal objective, through which an image of the target and projectile is thrown on the film. The radar unit 14 transmits a series of pulses which are received back as reflections from both target and projectile, and arranged to be shown as luminous marks on the screen 31 of a cathode ray tube 30. Three such indicator marks are visible, therefore, on the screen, spaced out along the x-axis: mark "a" (representing the outgoing pulse) and marks "b" and "c" (representing the reflected pulses from projectile and target respectively). By means of a pair of mirrors 82, 86 and a further pair of lenses 74, 76 the luminous indicator marks on the cathode ray tube screen 31 are also projected on to the film 50. The arrangement is such that the marks a, b, c appear in between the optical picture frames A 1 , A 2 , A 3 . . . As shown in Fig. 9, the successive images "b" traverse across the film frames in a direction opposite to that of the successive images "c", because the target is approaching the firing-point, while the projectile is receding from it. When the images "b" and "c" coincide (as in B 6 , corresponding to picture frame A 6 ), the target and projectile are at equal distances from the firing point, and picture A 6 represents the cross-point where the projectile crosses the path of the target. From measurements made on the frame A 6 it is possible to calculate the miss-distance. It is also possible, by feeding regularly timed pulses to the system, to produce range fiduciary marks on the cathode ray tube screen, which hence will also appear on the film strip and thus provide comparison measurements for the miss-distance as recorded on the film strip.