Acquisition, Tracking, And Pointing (ATP) Concepts And Devices For Space-Based Neutral Particle Beam (SBNPB)

Abstract

The most stressing requirements for acquisition, pointing, and tracking (ATP) operation in a Strategic Defense Initiative (SDI) environment are precision tracking and pointing, rapid retargeting, and target low-level signature detection. The ATP device-to-target ranges are extremely large and not only must active vibration isolation and jitter suppression be employed but so must active wavefront control of HEL (High Energy Laser) illuminator/tracking/ranging lasers that are combined with extremely accurate alignment systems. The system incorporates high-technology subsystems-level hardware in the areas of optics, electro-optics, and electro-mechanics that stress the state of the art. The ATP consists of a coarse and a precision-passive IR acquisition and tracking sensor coupled to a precision-active UV tracker that references boresight, range, and target motion to an NPB-pointing control system. This paper introduces the subject with an overall ATP system diagram outlining optical and electro-optic signal paths for trackers,pointers, alignment, beam steering and control, and target handover. The requirements for tracking and pointing accuracy/precision exceed the capability of current inertial attitude sensors; therefore, boresight calibration for closed-loop precision tracking with respect to (WRT) a local body frame is considered. The inertial reference frame is utilized for large-angle slews, target acquisition on a tracker sensor, and slew settling. Once the target is acquired, the inertial frame is transitioned to the local body frame for tracking control where a stable boresight alignment reference is maintained between the inertial and local body frame. The subject of vibration isolation and jitter suppression WRT sensors, actuators, lasers, and structures is addressed by identifying the fundamental error sources that impact pointing precision and methods for compensation or attenuation. Logical system requirement flowdown and breakout of details are provided to support the rationale for the concept and feasibility of design approach. Finally, alignment system and tracker system relationships are addressed with a brief description of control for boresight alignment (local body WRT inertial frame), alignment relay transfer and beam steering (local body frame), track error (local body frame), pointing error (local body frame), and target handback (inertial frame).