A research team from MIT, NASA, and other prestigious universities has made significant advancements in space-to-ground laser communication. By creating the current quickest communication link, they were able to quadruple their previous record. A satellite with this technology could send over 2 terabytes of data in only one 5-minute pass over a ground station, with remarkable transmission speeds of 200 gigabits per second. This amazing development creates a wide range of opportunities for scientific investigation and discovery.
The vast consequences of this accomplishment are emphasised by Jason Mitchell, an aeronautical engineer with NASA's Space Communications and Navigation programme, who says, "The implications are far-reaching because, put simply, more data means more discoveries."
TeraByte InfraRed Delivery (TBIRD), the ground-breaking communication link, runs from an orbit 530 kilometres above the surface of the Earth. TBIRD was launched into orbit in May of the previous year, and by June, a ground-based receiver in California had originally attained downlink rates of up to 100 Gb/s. This speed is more than 1,000 times faster than conventional radio links used for satellite communications, and it is 100 times faster than the fastest internet rates available in most cities.
High-speed laser-based internet for satellites has not yet been realised, but terrestrial data networks rely on laser communications using fibre optics. Radio waves are currently used largely by commercial satellite operators and space organisations to communicate with space objects. While radio waves have a considerably lower frequency than infrared light used in laser communications, the latter can transmit data at far higher rates.
The scientific team is also eager to expand the settings in which this ground-breaking technology can be used. Mitchell underlines their ambitions to improve TBIRD's functionality to support additional lunar missions in the future. Achieving data rates in the range of 1 to 5 gigabits per second (Gb/s) may not seem like a substantial gain given the enormous distance of about 400,000 kilometres between the Earth and the moon. Mitchell contends that even these seemingly low data rates would significantly improve communication capabilities for lunar missions because traversing such a huge distance is no easy task.
Kat Riesing, an aerospace engineer and a member of the TBIRD team at MIT Lincoln Laboratory, explains the limitations faced by current satellites, stating, "There are satellites currently in orbit limited by the amount of data they are able to downlink, and this trend will only increase as more capable satellites are launched." She further highlights the significance of TBIRD in enabling missions that collect vital data on Earth's climate, resources, and astrophysics applications, such as black hole imaging.
TBIRD's idea was first created by MIT Lincoln Laboratory as a low-cost, high-speed data access option for spacecraft in 2014. The team used components that were made widely available and initially intended for terrestrial purposes to cut expenses. These parts include fast, large-volume data storage systems and high-rate optical modems made for fibre optic communication.
The NASA Pathfinder Technology Demonstrator 3 (PTD-3) satellite, a small CubeSat that weighs about 12 kilograms and is about the size of two stacked cereal boxes, carried TBIRD when it was launched. The TBIRD payload, which was no bigger than a typical tissue box, was put into orbit on May 25, 2022, by SpaceX's Transporter-5 rideshare mission from Florida's Cape Canaveral Space Force Station.
Additionally, atmospheric influences and weather conditions can cause laser beams from orbit to Earth to distort, resulting in loss of power and data. The group created their own variation of automated repeat request (ARQ), a protocol that manages transmission faults, to overcome these difficulties. To request that any lost or damaged data frames be retransmitted by the satellite, the ground terminal sends a low-rate uplink signal.
