Relative orientation estimation in formation flying satellites

Satellite precision formation flying (PFF) is a concept in which multiple spacecraft communicate via an inter-satellite link (ISL) and cooperate to achieve the goal of a single, more complex satellite. This enables the creation of virtual scientific structures such as interferometers or imagers that would not be deployable in space because of their physical dimensions. PFF requires precise knowledge of the relative orientation and distance between the involved satellites. Determining the relative orientation is similar to estimating the angle of arrival (AoA) of the ISL. This paper presents an AoA estimation technique specific to Orthogonal Frequency-Division Multiplexing (OFDM) communications systems. The AoA is calculated using the preamble that is necessary to synchronize the ISL. It is estimated from the phase of the correlation at maximum. The AoA estimator is evaluated under various SNR conditions using MATLAB simulations. The results show that the estimator accuracy improves as the distance between the receiver antennas approaches the half-wavelength condition.