Optical ranging and data communication in space-based applications

Ranging measurements in the radio band have been extensively used in space-based applications, for example in GNSS for navigation and GRACE for mapping the Earth-s gravity field. However, the increasing demand for high-bandwidth communication and precision ranging will make optical systems ideal for these applications. Our investigations are focused on inter-spacecraft laser ranging and data communication for the LISA mission using Direct Sequence Spread Spectrum (DS/SS) modulation onto the laser links. We present the setup of an optical experiment to test the levels of performance achievable with a single laser link as well as a new hardware prototype based on FPGA (Field Programmable Gate Array) processing. This prototype performs the phase readout of the interferometric signal at microcycle sensitivity, ranging measurements at sub-meter accuracy, data communication at rates of several kilobits per seconds and is compatible with inter-spacecraft clock noise transmission and digital laser offset-phase locking.