Navigational system using infra-red horizon sensors

Claim 1

A TRACKER UNIT COMPRISING: A FRAME, A SCANNING MIRROR MOUNTED ON SAID FRAME, STEPPING MEANS FOR INCREMENTALLY ROTATING SAID FRAME THROUGH A RELATIVELY LARGE ARC TO SWEEP THE NOMINAL LINE OF SIGHT OF SAID MIRROR THROUGH PREDETERMINED ANGULAR INCREMENTS IN A SCANNING PLANE FIXED IN RELATION TO SAID FRAME, MEANS FOR CONTINUOUSLY OSCILLATING SAID MIRROR THROUGH A RELATIVELY SMALL ARC SOLELY ABOUT AN AXIS PERPENDICULAR TO SAID SCANNING PLANE WHEREBY THE LIME OF SIGHT OF SAID MIRROR MAY SWEEP BACK AND FORTH ACROSS A RADIATION DISCONTINUITY DISPOSED IN SAID SCANNING PLANE WHEN THE LINE OF SIGHT OF SAID MIRROR IS STEPPED INTO CLOSE COINCIDENCE WITH A LINE FROM SAID MIRROR TO SAID DISCONTINUITY, TRANSDUCING MEANS ON SAID FRAME FOR DETECTING VARIATIONS IN RADIANT ENERGY REFLECTED BY SAID MIRROR AND FOR CONVERTING SAID VARIATION OF RADIANT ENENERGY INTO ELECTRICAL VOLTAGE VARIATIONS, MEANS FOR CONVERTING SAID ELECTRICAL VOLTAGE VARIATIONS INTO A D.-C. VOLTAGE OF A MAGNITUDE CORRESPONDING TO THE DEGREE OF THE ANGLE THAT SAID NOMINAL LINE OF SIGHT IS DISPLACED FROM A LINE FROM SAID MIRROR TO SAID RADIATION DISCONTINUITY, AND MEANS FOR PRODUCING A D.-C. VOLTAGE CORRESPONDING TO THE NUMBER OF STEPS THAT SAID FRAME IS ROTATED FROM ONE OF THE LIMITS OF SAID RELATIVELY LARGE ARC.