On 12 February 2015 Martin Agnew, R&T and Innovations Coordinator at Airbus Defence and Space, gave a lecture to the Space Group at No. 4 Hamilton Place. Stephen Glynn FRAeS, Satellite Programme Manager at Eutelsat and member of the RAeS Space Group, has kindly written the following report about the event.
Martin Agnew is responsible for coordinating research, technology and innovation at Airbus Defence and Space (Communications, Intelligence and Security). He showed how laser communications are suitable for communications with Low Earth Orbit (LEO) satellites and other mobile platforms such as Unmanned Aerial Vehicles (UAV) with substantially higher data rates than classical RF systems.
He started by recalling some of the significant developments in free space laser communications. The Semiconductor-laser Inter-satellite Link Experiment (SILEX) was successfully performed in 2001 between the SPOT 4 LEO satellite and the Artemis Geostationary (GEO) satellite. In 2008 a different technology was employed to establish links between two LEO satellites, TerraSAR-X of Germany and NFIRE of the US. In October 2013 NASA demonstrated laser communications between a lunar orbiter and the Earth using the Lunar Atmosphere and Dust Environment Explorer (LADEE). A major development took place in November 2014 when optical inter satellites links were established between the Copernicus Sentinel-1A satellite in LEO and the Alphasat GEO satellite employing an upgraded form of the Laser Communication Terminal used for the TerraSAR-X and NFIRE links. The Laser Communication Terminal was developed by Tesat-Spacecom of Germany with support from the German Space Operations Centre (DLR). The successful demonstration paved the way for the European Data Relay System (EDRS) which will have its first fully operational payload (EDRS-A) hosted on the Eutelsat 9B satellite to be launched in mid 2015.
EDRS is a Private Public Partnership between ESA and Airbus Defence and Space which will provide bi-directional optical links up to 1.8 Gbit/s. A second EDRS geostationary satellite or node (EDRS-C) is planned to be established using the SmallGEO platform of OHB System, Germany. EDRS-A and EDRS-C will provide RF feeder links to European ground stations in Ka-band at data rates matching the optical links. Still further nodes around the Earth are being envisaged as part of the GlobeNet expansion of EDRS.
EDRS will provide a so called SpaceDataHighway enabling the provision of LEO and UAV data on demand in near real time. LEO satellites currently have data downlinks constrained by their limited transit times over fixed ground stations. The Copernicus Sentinel satellites equipped with Laser Communication Terminals are anchor customers for EDRS. They will be used for a variety of applications depending upon their instrumentation including mapping of flooding and oil spills as well as land observation, earthquake prediction and climate change monitoring.
The speaker went on to explain how mass and costs of the LEO laser terminals could be substantially decreased by integrating the laser communications functions with the telescopes or other optical systems of the LEO satellites, enabling compatibility with much smaller platforms. These satellites would repoint to the GEO relay satellites to download their data in short bursts. His vision of the future is an expanded SpaceDataHighway with a strong uptake in LEO satellites equipped with laser terminals, more GEO relay satellites which would also offer GEO to GEO links, laser connections between manned and unmanned aircraft as well as between aircraft and the ground when below clouds and aircraft and the GEO relay satellites when above clouds.