FIBER OPTIC LOOP ANTENNA FOR THE MEASUREMENT OF ELECTRIC CURRENTS IN SPACE.

A DEMONSTRATION OF A TECHNIQUE TO MEASURE ELECTRIC CURRENTS IN SPACE, BASED UPON A SENSING OF MAGNETIC FIELD INDUCED CIRCULAR BIREFRINGENCE IN A SINGLE MODE OPTICAL FIBER IS PROPOSED. THE USE OF LOW LOSS SINGLE MODE OPTICAL FIBER IN A CLOSED LOOP GIVES THE ANTENNA A HIGH DEGREE OF IMMUNITY TOSTRAY MAGNETIC FIELDS. SENSITIVITY IS FURTHER ENHANCED THROUGH USE OF AN OPTRA DEVELOPED 2-FREQUENCY HENE LASER AS A SOURCE FOR A COHERENT HETERODYNE OPTICAL RECEIVER. SENSITIVITY WILL BE TESTED USING THE OPTRA 2-FREQUENCY HENE LASER AS A SOURCE AND A COHERENT HETERODYNE OPTICAL DETECTOR. IN ADDITION THE USE OF A COMPLEX HOMODYNE RECEIVER WITH A LOW POWER DIODE LASER AS A SOURCE WILL BE EXPLORED. BOTH THESE TECHNIQUES ALLOW FOR A LARGE SIGNAL BANDWIDTH WITH THE FINAL, POST-DETECTION BANDWIDTH LIMITED ONLY BY THE AVERAGING TIME CONSTANT CHOSEN. THE MINIMAL WEIGHT AND STOWAGE REQUIREMENT OF THE ANTENNA SHOULD MAKE ITWELL SUITED FOR DEPLOYMENT FROM BOTH MANNED AND UNMANNED SPACE CRAFT. WHILE THE TECHNIQUE WILL ONLY BE DEMONSTRATED FOR A SINGLE AXIS, A READY CAPABILITY EXISTS TO EXPAND IT TOTHE MEASUREMENT OF VECTOR QUANTITIES.