Laser communication in space
In outer space, the communication range of free-space optical communication is currently of the order of several thousand kilometers, suitable for inter-satellite service. It has the potential to bridge interplanetary distances of millions of kilometers, using optical telescopes as beam expanders.
Demonstrations and tests
In November 2001, the world's first laser data connection was achieved in space by the European Space Agency satellite Artemis, providing an optical data transmission link with the CNES Earth observation satellite SPOT 4.
In May 2005, a two-way distance record for communication was set by the Mercury laser altimeter instrument aboard the MESSENGER spacecraft. This diode-pumped infrared neodymium laser, designed as a laser altimeter for a Mercury orbit mission, was able to communicate across a distance of 24 million km (15 million miles), as the craft neared Earth on a fly-by.
In 2008, the ESA used laser communication technology designed to transmit 1.8 Gbit/s across 45,000 km, the distance of a LEO-GEO link. Such a terminal was successfully tested during an in-orbit verification using the German radar satellite TerraSAR-X and the American NFIRE satellite. The two Laser Communication Terminals (LCT) used during these tests were built by the German company Tesat-Spacecom in cooperation with the German Aerospace Center (DLR).
In January 2013, NASA used lasers to beam an image of the Mona Lisa to the Lunar Reconnaissance Orbiter roughly 390,000 km (240,000 mi) away. To compensate for atmospheric interference, an error correction code algorithm similar to that used in CDs was implemented.
In September 2013, a laser communication system was one of four science instruments launched with the NASA Lunar Atmosphere and Dust Environment Explorer (LADEE) mission. After a month-long transit to the Moon and a 40-day spacecraft checkout, the laser comm experiments were performed over three months during late 2013 and early 2014. Initial data returned from the Lunar Laser Communication Demonstration (LLCD) equipment on LADEE set a space communication bandwidth record in October 2013 when early tests using a pulsed laser beam to transmit data over the 385,000 kilometres (239,000 mi) between the Moon and Earth passed data at a "record-breaking download rate of 622 megabits per second (Mbps)", and also demonstrated an error-free data upload rate of 20 Mbps from an Earth ground station to LADEE in Lunar orbit. The LLCD is NASA's first attempt at two-way space communication using an optical laser instead of radio waves, and is expected to lead to operational laser systems on NASA satellites in future years.
In November 2013, laser communication from a jet platform Tornado was successfully demonstrated for the first time. A laser terminal of the German company Mynaric (formerly ViaLight Communications) was used to transmit data at a rate of 1 Gbit/s over a distance of 60 km and at a flight speed of 800 km/h. Additional challenges in this scenario were the fast flight maneuvers, strong vibrations, and the effects of atmospheric turbulence. The demonstration was financed by EADS Cassidian Germany and performed in cooperation with the German Aerospace Center DLR.
In November 2014, the first ever use of gigabit laser-based communication as part of the European Data Relay System (EDRS) was carried out. Further system and operational service demonstrations were carried out in 2014. Data from the EU Sentinel-1A satellite in LEO was transmitted via an optical link to the ESA-Inmarsat Alphasat in GEO and then relayed to a ground station using a conventional Ka band downlink. The new system can offer speeds up to 7.2 Gbit/s.
In December 2014, NASA's OPALS announced a breakthrough in space-to-ground laser communication, uploading at a speed of 400 megabits per second. The system is also able to re-acquire tracking after the signal is lost due to cloud cover. The OPALS experiment was launched on 18 April 2014 to the ISS to further test the potential for using a laser to transmit data to Earth from space.
In February 2016, Google X announced to have achieved a stable laser communication connection between two stratospheric balloons over a distance of 62 miles (100 km) as part of Project Loon. The connection was stable over many hours and during day and nighttime and reached a data rate of 155 Mbit/s.
In June 2018, Facebook's Connectivity Lab (related to Facebook Aquila) was reported to have achieved a bidirectional 10 Gbit/s air-to-ground connection in collaboration with Mynaric. The tests were carried out from a conventional Cessna aircraft in 9 km distance to the optical ground station. While the test scenario had worse platform vibrations, atmospheric turbulence and angular velocity profiles than a stratospheric target platform the uplink worked flawlessly and achieved 100% throughput at all times. The downlink throughput occasionally dropped to about 96% due to a non-ideal software parameter which was said to be easily fixed.
Laser communications in deep space will be tested on the Psyche mission to the main-belt asteroid 16 Psyche, planned to launch in 2022. The system is called Deep Space Optical Communications, and is expected to increase spacecraft communications performance and efficiency by 10 to 100 times over conventional means.
Multinational corporations like SpaceX, Facebook and Google and a series of startups are currently pursuing various concepts based on laser communication technology. The most promising commercial applications can be found in the interconnection of satellites or high-altitude platforms to build up high-performance optical backbone networks. Other applications include transmitting large amounts of data directly from a satellite, aircraft or Unmanned Aerial Vehicle (UAV) to the ground.
Multiple companies want to use laser communication in space for satellite constellations in low Earth orbit to provide global high-speed Internet access. Similar concepts are pursued for networks of aircraft and stratospheric platforms.
|Project||Project Concept||Environment||Scenario||Data rate||Supplier||Status|
|European Data Relay System (EDRS) [a]||Data relay to GEO satellites from LEO Earth observation satellites and for intelligence, surveillance and reconnaissance missions||GEO, LEO||Space-to-space||1.8 Gbit/s||Tesat-Spacecom ||Operational|
|Laser Light Communications||Satellite constellation for global telecommunications building an optical backbone network in space||MEO||Space-to-space, Space-to-ground||100 Gbit/s||Ball Aerospace & Technologies||Development|
|BridgeSat ||Direct data downstream from LEO Earth observation satellites to the ground||LEO||Space-to-ground||1 Gbit/s||Surrey Satellite Technology ||Development|
|Cloud Constellation||Secure data storage on satellites and secure intercontinental connections||LEO||Space-to-space||Development|
|LeoSat||Satellite mega-constellation for global telecommunications||LEO||Space-to-space||Thales Alenia Space ||Development|
|SpaceX Starlink||Satellite mega-constellation for global telecommunications||LEO||Space-to-space||Development|
|Telesat LEO constellation||Satellite mega-constellation for global telecommunications||LEO||Space-to-space||Development|
|Analytical Space ||In-space hybrid RF/optical data relay network for Earth observation satellites||LEO||Space-to-ground||Development|
|Google Loon ||Telecommunications for rural and remote areas provided by a network of stratospheric balloons||Stratosphere||Air-to-air||0.155 Gbit/s||Development|
|Facebook Aquila ||Telecommunications for rural and remote areas provided by a network of high-altitude platforms||Stratosphere||Air-to-air, Air-to-ground||10 Gbit/s||Mynaric ||Development|
|Airborne Wireless Network ||Telecommunications and in-flight entertainment provided by a network of commercial aircraft||Troposphere||Air-to-air||10 Gbit/s||Mynaric ||Development|
A substantial market for laser communication equipment may establish when these projects will be fully realized. New advancements by equipment suppliers is enabling laser communications while reducing the cost. Beam modulation is being refined, as its software, and gimbals. Cooling problems have been addressed and photon detection technology is improving. Currently active notable companies in the market include:
|Ball Aerospace & Honeywell ||in development|
|LGS Innovations ||in development|
|Sony ||in development|
|Surrey Satellite Technology||in development|
|Tesat-Spacecom ||in production|
|Thales Alenia Space|
|Transcelestial  ||in development|
Secure communications have been proposed using a laser N-slit interferometer where the laser signal takes the form of an interferometric pattern, and any attempt to intercept the signal causes the collapse of the interferometric pattern.  This technique uses populations of indistinguishable photons and has been demonstrated to work over propagation distances of practical interest and, in principle, it could be applied over large distances in space.
Assuming available laser technology, and considering the divergence of the interferometric signals, the range for satellite-to-satellite communications has been estimated to be approximately 2,000 km. These estimates are applicable to an array of satellites orbiting the Earth. For space vehicles or space stations, the range of communications is estimated to increase up to 10,000 km. This approach to secure space-to-space communications was selected by Laser Focus World as one of the top photonics developments of 2015.
- European Data Relay System
- Lunar Laser Communication Demonstration
- Laser Communications Relay Demonstration
- Satellite constellation
- Boroson, Don M. (2005), Optical Communications: A Compendium of Signal Formats, Receiver Architectures, Analysis Mathematics, and Performance Characteristics, retrieved 8 Jan 2013
- "Another world first for Artemis: a laser link with an aircraft". European Space Agency. December 18, 2006. Retrieved June 28, 2011.
- Steen Eiler Jørgensen (October 27, 2003). "Optisk kommunikation i deep space– Et feasibilitystudie i forbindelse med Bering-missionen" (PDF). Dansk Rumforskningsinstitut. Retrieved June 28, 2011. (Danish) Optical Communications in Deep Space, University of Copenhagen
- "NASA To Test Laser Communications With Mars Spacecraft". Space.com. Retrieved 2018-02-24.
- "A worlds first". Retrieved 5 September 2015.
- "Space probe breaks laser record: A spacecraft has sent a laser signal to Earth from 24 million km (15 million miles) away in interplanetary space". BBC News. January 6, 2006. Retrieved June 28, 2011.
- Laser Communication Terminals: An Overview Archived 2016-09-11 at the Wayback Machine
- Tesat-Spacecom Website
- TerraSAR-X NFIRE test
- Peckham, Matt (January 21, 2013). "NASA Beams Mona Lisa Image Into Space". TIME. Retrieved 22 January 2013.
- "NASA launches robotic explorer to moon from Va.; trouble develops early in much-viewed flight". Toledo Blade. Associated Press. 2013-09-07. Archived from the original on 2016-05-15. Retrieved 2016-05-15.
- Messier, Doug (2013-10-23). "NASA Laser System Sets Record with Data Transmissions From Moon". Parabolic Arc. Retrieved 2013-10-23.
- Belz, Lothar (2013-12-19). "Optical data link successfully demonstrated between fighter plane and ground station". Archived from the original on 2013-12-30.
- Extreme Test for the ViaLight Laser Communication Terminal MLT-20 – Optical Downlink from a Jet Aircraft at 800 km/h, Dec. 2013
- Laserkommunikation zwischen Jet und Bodenstation
- "First image download over new gigabit laser connection in space". Retrieved 3 Dec 2014.
- "Laser link offers high-speed delivery". ESA. 28 November 2014. Retrieved 5 December 2014.
- Landau, Elizabeth (9 December 2014). "OPALS: Light Beams Let Data Rates Soar". Jet Propulsion Laboratory. NASA. Retrieved 18 December 2014.
- L. Smith, Stephanie; Buck, Joshua; Anderson, Susan (21 April 2014). "JPL Cargo Launched to Space Station". Jet PropulsionLaboratory. NASA. Retrieved 2014-04-22.
- "Google Laser-Beams the Film Real Genius 60 Miles Between Balloons". WIRED. Retrieved 2018-02-24.
- Price, Rob (29 June 2018). "Facebook tested plane-mounted lasers that fire super high-speed internet over California — here are the photos". Business Insider. Retrieved 21 July 2018.
- Greicius, Tony (14 September 2017). "Psyche Overview". Nasa. Retrieved 18 September 2017.
- Deep Space Communications via Faraway Photons. Leonard. NASA, 18 October 2017.
- J. Horwath; M. Knapek; B. Epple; M. Brechtelsbauer (July 21, 2006). "Broadband Backhaul Communication for Stratospheric Platforms: The Stratospheric Optical Payload Experiment (STROPEX)" (PDF). SPIE.
- "Inside The World's First Space-Based Commercial Laser-Relay Service". aviationweek.com. Retrieved 2018-02-24.
- "HALO Global Network by Laser Light Communications". Retrieved 2018-11-13.
- "Ball Corp Prime Contractor for Laser Light's Satellite Fleet - Analyst Blog". NASDAQ.com. 2014-09-11. Retrieved 2018-02-24.
- Harris, David L. (March 12, 2015). "This Boston startup is building a faster way to send data from satellites — using lasers". Retrieved February 24, 2018.
- Ltd, SPIE Europe. "Miniature satellites to transmit optical data from space". optics.org. Retrieved 2018-02-24.
- Ltd, SPIE Europe. "Thales signs deal on optically connected satellites". optics.org. Retrieved 2018-02-24.
- "With $200 Million, MIT's The Engine Makes Its First Investments In 'Tough Tech'". www.wbur.org. Retrieved 2018-02-24.
- Newton, Casey (2016-07-21). "Inside the test flight of Facebook's first internet drone". TheVerge.com. Retrieved 2018-02-24.
- "AWN to Test First Aircraft Broadband Clusters This Year - Via Satellite -". Via Satellite. 2017-08-18. Retrieved 2018-02-24.
- "ViaLight to Develop Laser Terminals for AWN IFC Network - Via Satellite -". Via Satellite. 2017-08-23. Retrieved 2018-02-24.
- "Big Gains On Horizon For Laser Communications Suppliers". aviationweek.com. Retrieved 2018-02-24.
- Russell, Kendall (17 April 2018). "Honeywell, Ball to Develop Optical Communication Links - Via Satellite -". Via Satellite. Retrieved 21 April 2018.
- "DARPA Awards Optical Satellite Terminal Contract to LGS Innovations - Via Satellite -". Via Satellite. 2016-05-18. Retrieved 2018-02-24.
- "Sony to launch space business". Nikkei Asian Review. Retrieved 21 April 2018.
- hermes (2017-03-22). "Space buffs make light work of data transfer". The Straits Times. Retrieved 2018-02-24.
- F. J. Duarte (May 2002). "Secure interferometric communications in free space". Optics Communications. 205 (4): 313–319. Bibcode:2002OptCo.205..313D. doi:10.1016/S0030-4018(02)01384-6.
- F. J. Duarte (January 2005). "Secure interferometric communications in free space: enhanced sensitivity for propagation in the metre range". Journal of Optics A: Pure and Applied Optics. 7 (1): 73–75. Bibcode:2005JOptA...7...73D. doi:10.1088/1464-4258/7/1/011.
- F. J. Duarte, T. S. Taylor, A. M. Black, W. E. Davenport, and P. G. Varmette, N-slit interferometer for secure free-space optical communications: 527 m intra interferometric path length , J. Opt. 13, 035710 (2011).
- F. J. Duarte and T. S. Taylor, Quantum entanglement physics secures space-to-space interferometric communications, Laser Focus World 51(4), 54-58 (2015).
- J. Wallace, Technology Review: Top 20 technology picks for 2015 showcase wide scope of photonics advances, Laser Focus World 51(12), 20-30 (2015).