Radio frequency-based relative navigation

Abstract

For distributed systems in space, knowledge of the relative position and velocity is required to maintain the relative geometry of the satellites within certain boundaries. This knowledge can be obtained using an autonomous relative navigation system based on radio frequency (RF) signals. The design aspects of such a system are detailed in this chapter. As all RF-based relative navigation systems are based on GNSS technology, the discussion is limited to this technology only. Navigation is performed by measuring the range (rate) between the satellites, which allows, in combination with a relative dynamics model and the exchange of data between the satellites, an onboard estimation of the relative state of the satellites. Obtaining accurate and unambiguous measurements requires a balanced signal design that minimizes measurement errors, but which also takes into account multiple access and formation safety considerations. Hardware-induced measurement biases should be minimized and hardware (self-) calibration is mandatory to achieve satisfactory performance in space. Details on the design, testing, and performance of one particular system, the FFRF, are provided.