<title>Status of BMDO/IST lasercom advanced technology demonstration</title>

Abstract

Laser communications between satellites, high flying aircraft (such as JSTARS), and the ground offer the potential to transfer extremely high amounts of information faster and with a much smaller package than is possible using current radio frequency and microwave technologies. This can be especially important in downlinking time sensitive satellite reconnaissance information because the satellite stays within range of a ground station or aircraft for only a few minutes. A capability to downlink from a satellite to an aircraft can provide all weather performance, and multiple data transfers for every satellite orbit. Over the last few years, SDIO (now BMDO) has funded a number of technology efforts through the US Army Space and Strategic Defense Command reducing the risks associated with laser communications. This paper describes one of these efforts which is now being carried forward to an Advanced Technology Demonstration at ThermoTrex Corporation. The program will lead to the demonstration of high data rate communications of 270 MBPS (Mega Bits Per Second) to 1.08 GBPS (Giga Bits Per Second) between high altitude aircraft and possibly between a satellite and the ground. The Laser Communications Terminals incorporate Atomic Line Filter technology for background light rejection during acquisition, reactionless Roto-Lok offset cable drive gimbals for fast slewing and high accuracy pointing, and direct digital modulation of semiconductor diode lasers detected with low noise avalanche photodiodes. We present designs and preliminary performance results for both a simplified terminal appropriate for a near term satellite-to-ground data transfer experiment, and a full capability terminal appropriate for ground, aircraft, or satellite operations.