Geophysical gradiometer including means for determining spacing between airborne bodies

Claim 1

IN A SYSTEM FOR MEASURING A MAGNETIC GRADIENT IN THE EARTH''S MAGNETIC FIELD COMPRISING AN AIRPLANE, TWO AERODYNAMIC BODIES TOWED BY SAID AIRPLANE AT DIFFERENT HEIGHTS WITH RESPECT TO THE EARTH''S SURFACE, AND AT KNOWN DISTANCES BEHIND SAID AIRPLANE, EACH OF SAID AERODYNAMIC BODIES CONTAINING A DEVICE FOR MEASURING THE EARTH''S MAGNETIC FIELD, RECORDING MEANS IN SAID AIRPLANE AND MEANS ELECTRICALLY INTERCONNECTING SAID DEVICES AND THE RECORDING EQUIPMENT IN SAID AIRPLANE, THE IMPROVEMENT OF MEANS FOR MEASURING THE SPACING BETWEEN SAID AERODYNAMIC BODIES COMPRISING A LIGHT SOURCE IN EACH OF SAID AERODYNAMIC BODIES, MEANS FOR PULSING SAID LIGHT SOURCES TO DIRECT A LIGHT BEAM FROM EACH OF SAID BODIES TOWARD SAID AIRPLANE INCLUDING A POWER AMPLIFIER, AND MEANS FOR DETECTING SAID LIGHT BEAMS AND MEASURING THE ANGLE THEREBETWEEN COMPRISING A ROTATABLE MIRROR, MEANS FOR ROTATING SAID MIRROR AT A KNOWN SPEED, SAID MIRROR BEING ARRANGED TO SEQUENTIALLY REFLECT SAID LIGHT BEAMS FROM THE INDIVIDUAL SOURCES, PULSE MEANS FOR CREATING SEPARATE ELECTRICAL PULSES CORRESPONDING TO SAID REFLECTED LIGHT BEAMS AND MEANS FOR MEASURING THE TIME BETWEEN SAID SEPARATE PULSES AS A MEASURE OF THE ANGLE BETWEEN SAID LIGHT BEAMS WHEREBY THE SPACING BETWEEN SAID TWO AERODYNAMIC BODIES IS DETERMINED FROM SAID ANGLE AND THE KNOWN DISTANCES TO SAID BODIES SO THAT SPACING VARIATIONS MAY BE DETERMINED TO PROVIDE MAGNETIC GRADIENT MEASUREMENTS ACCURATELY REPRESENTING THE EARTH''S MAGNETIC FIELD.