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A technique for accumulating airborne visible and infrared spectroradiometric data from missile plumes and re-entry objects establishes the requirements for a precision tracking front surface mirror. The processing of target radiation, reflected by the tracking mirror into an infrared tracker telescope, to derive target coordinate information, is described. The derivation of transformed target error signals to command the motion of the hydraulically driven tracking mirror is outlined. A description of the servo-electronics system, with selected circuitry, is given. The dynamic characteristics of the system, as determined from preliminary field tests, indicate that the system has a tracking rate capability of 10Â°/sec with an accuracy better than 60 seconds of arc. The detection sensitivity of the infrared tracker telescope is 1.6Ã10-10w/cm2 in the 2-to 6-Â¿ region, and is sufficient to provide 10-miile tracking ranges against a jet target in a sunlit cumulus cloud background. In a typical installation, aiming of the tracking mirror is provided by a 7Ã35, 10Â° field of view sighting telescope which is automatically slaved by the tracking mirror when acquisition and target tracking occurs, thereby providing continuous observation of the target. As an alternative to visual aiming, an automatic search program is generated by an accurate electro-mechanical programmer, which is described. Target acquisition, in an automatic mode of operation, is accomplished through the use of a simple logic circuit which provides electronic background discrimination by virtue of signal pulse width.