Antenna array based line-of-sight estimation using a GNSS-like inter-satellite ranging system

This paper proposes a line-of-sight estimation method using the inter-satellite ranging system based on antenna arrays. GNSS-like technology is inherited such that an existing GNSS receiver is modified to operate as a transceiver and locally generate the inter-satellite ranging signals. Carrier phase measurements are the fundamentals for precise estimation. A robust integer-cycle ambiguity resolution method by modifying the well-known LAMBDA method is implemented. The LOS vector of unit length is used as a priori additional constraint to improve the integer fixing performance. Arranging multiple antenna elements in an array on different positions on the spacecraft can help to resolve ambiguities with more redundancy and observability. Different antenna array geometries are analysed with the attempt of achieving single frequency, single epoch integer ambiguity resolution with high success rate. To this end, it is proven that the number of antenna elements should be more than three, and it is better to have a larger spacing between antennas. The angular separation between two antenna baselines is the factor that can be less considered for ambiguity resolution; however, it influences the LOS accuracy significantly.