Space-based radar: narrowing the main-beam clutter spectrum through the use of a high-aspect-ratio antenna

With a space-based surveillance radar, the ability to detect slow-moving targets is compromised by returns from the Earth´s surface illuminated by the main beam of the antenna. An antenna design is presented that minimises the spectral width of main-beam Earth clutter returned to space-based radars. The design maximises the aspect ratio of the antenna and aligns its long dimension with the satellite velocity vector. This ensures that the main-beam return is concentrated between two cones of constant velocity (isodops) whose separation is inversely proportional to the length of the antenna.