Sunday, August 1, 2021

How work laser communication in space?

Laser communication in space is the use of free-space optical communication in outer space. Communication may be fully in space (an inter-satellite laser link) or in a ground-to-satellite or satellite-to-ground application. The main advantage of using laser communication over radio waves is increased bandwidth, enabling the transfer of more data in less time.

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.

In 1992, the Galileo probe proved successful one-way detection of laser light from Earth as two ground-based lasers were seen from 6 million km by the out-bound probe.

In November 2001, the world’s first laser intersatellite link 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.

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.
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 communications experiments were performed over three months during late 2013 and early 2014.

In June 2021, the U.S. Space Development Agency plans to launch two 12U cubesats aboard a SpaceX Falcon 9 rideshare mission to sun-synchronous orbit. The mission is expected to demonstrate laser communication links between the satellites and a remotely controlled MQ-9 Reaper.

In April 2021 NASA’s Laser Communications Relay Demonstration should launch as part of USAF STP-3, to communications between GEO and the Earth’s surface.

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.

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.

Japan’s NICT will demonstrate in 2022 the fastest bidirectional lasercom link between the GEO orbit and the ground at 10 Gbit/s by using the HICALI (High-speed Communication with Advanced Laser Instrument) lasercom terminal on board the ETS-9 (Engineering Test Satellite IX) satellite, as well as the first intersatellite link at the same high speed between a CubeSat in LEO and HICALI in GEO one year later.

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