Free-space laser ranging and data communication

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 in high-bandwidth communication and precision ranging will make optical systems ideal for these applications. Our investigations are focused on interspacecraft laser ranging and data communication for the LISA mission using Direct Sequence Spread Spectrum (DSSS) modulation onto the laser links. We present the optical experimental setup under construction 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 to perform high-accuracy phase readout of the optical signal, ranging measurements, data communication, clock noise demodulation and laser-phase locking.