A Space Multi-Beam Multi-Link Capable Laser Communications Terminal for Satellites

Abstract

Free-space optical communication has proven to have many advantages over traditional radio communications. For instance, the hardware power efficiency and limited beam spread increase data rates for lower power consumption. Furthermore, the technology does not suffer from decreased bandwidth due to crowding. Free-space optical communication is usually done using laser communication terminals. In the past the focus has been on increasing the data rates for a single link and this has led to an exponential rise in the data rate performance. However, these modules have been limited to single beams and are hence capable of only one link. This decreases the number of users, networking, and relay capabilities of optical communication satellites. The advent of MEMS Micro-Mirror Arrays (MMA) and Spatial Light Modulators (SLM) have allowed for compact and lightweight control of wavefronts. These applications would also allow for scalable independent steering of multiple laser beams. The Delft University of Technology is conducting a study of a compact and scalable multi-beam terminal using these beam steering methods[1]. The terminal consists of a MEMS MMA for high frequency response in the aperture with a high resolution SLM for the beam steering and shaping. This terminal is designed for spacecraft-to-ground and spacecraft-to-spacecraft duplex communications. It is expected to support up to 10 or more duplex links in one terminal and, therefore, suitable for usage in small satellites and mega-constellations. The high resolution can also be used for sub-aperture wavefront correction in future. This paper discusses the design of the multi-beam terminal.