Apparatus and method for up finding

A system for up finding in a projectile flight, the system comprising:

• a communication transmitter which transmits polarized reference signals to a remote projectile;
• a guidance sub-system being mounted on the projectile, the guidance sub-system having a magnetometer and at least two communication receivers, one of the communication receivers being a polarized communication receiver and the other being a non-polarized communication receiver;
• the magnetometer measuring a magnetic field of earth and transmitting magnetic field measurement signals to a processing unit of the guidance sub-system;
• the non-polarized communication receiver being arranged to receive the polarized reference signals and configured to detect an amplitude of the polarized reference signals, the detected amplitude of the polarized reference signals being substantially unaffected by rotation of the projectile;
• the polarized communication receiver being arranged to receive the polarized reference signals and configured to detect the amplitude of the polarized reference signals received thereby, the detected amplitude of the polarized reference signals received by the polarized communication receiver is a modulated signal based on rotation of the projectile;
• the polarized and the non-polarized communication receivers transmitting the detected amplitudes of the polarized reference signals to the processing unit;
• the processing unit comprising at least one processor for determining a rough up direction of the projectile flight relative to earth based on the magnetic field measurement signals transmitted from the magnetometer, and the processing unit determining alignment of a vertical axis of the projectile relative to the earth based on ratios of the detected amplitudes of the polarized reference signals received by the polarized and the non-polarized communication receivers, and
• the processing unit transmitting control signals to control actuators to adjust flight control surfaces of the projectile based at least on the rough up direction and the alignment of the vertical axis of the projectile.