Space-based tethered phased-array antenna

Abstract

An unsupported, flexible, quasi-linear phased-array antenna within a space-based radar system which is tethered to a host satellite in free space. The antenna is formed by a plurality of antenna elements which are connected serially along a common axis. The antenna points in an Earth-pointing direction via gravity-gradient forces acting thereon. The phased-array antenna is capable of radiating a narrow electromagnetic beam in the end-fire direction along the array either in a spot or conical beam for detecting, identifying and tracking moving targets on or near the Earth's surface. According to one aspect of the invention, the phased-array antenna forms an elongated conductor which moves through a magnetic field in space for generating electrical power.

What is claimed is: 
     
       1. A phased-array antenna for use in a space-based radar system that radiates a narrow, steerable, electromagnetic beam in a specified direction to detect, identify and track targets on or near the surface of the earth, said antenna comprising: a plurality of antenna elements having a predetermined spacing from one another;   interconnecting means for operatively interconnecting said antenna elements to form an array having a proximal end operatively connected to a satellite and a distal end, said distal end being unsupported and unfixed; and   communications means disposed within said interconnecting means for conveying radar signals between said satellite and said antenna elements.   
     
     
       2. The phased-array antenna as in claim 1, further comprising a means for producing phase shift control signals for controlling the phase of said radar signals, thereby steering a resultant beam produced by said antenna. 
     
     
       3. The phased-array antenna system as in claim 1, wherein said antenna elements are non-rigidly connected by said interconnecting means such that said antenna is bendable both along its length and about said satellite. 
     
     
       4. The phased-array antenna as in claim 1, wherein said antenna elements are interconnected to form a substantially linear array. 
     
     
       5. The phased-array antenna system as in claim 1, wherein said predetermined spacing is between approximately 1/5 and 1/6 Γ. 
     
     
       6. The phased-array antenna system as in claim 1, wherein said array of antenna elements radiates said electromagnetic beam in a substantially end-fire direction. 
     
     
       7. The phased-array antenna system as in claim 1, wherein said first and second antenna elements are cross-dipole radiating antennas. 
     
     
       8. A phased-array antenna for use within a space-based radar system which provides a steerable, end-fire, electromagnetic beam to detect, identify and track targets on or near the surface of the earth, comprising: a plurality of antenna elements having a predetermined spacing from one another and receiving phase shifted radar signals so as to produce said beam; and   interconnecting means for operatively connecting said first and second antenna elements to form an array having a proximal end operatively connected to a satellite and a distal end, said distal end being unsupported and unfixed.   
     
     
       9. The phased-array antenna system as in claim 8, further comprising means for producing phase shift control signals for controlling the phase of said radar signals, thereby steering a resultant beam produced by said antenna. 
     
     
       10. The phased-array antenna system as in claim 9, wherein said predetermined spacing is between approximately 1/5 and 1/6 Γ. 
     
     
       11. The phased-array antenna system as in claim 9, wherein said antenna elements are cross-dipole radiating antennas.