Fastest satellite datalink

The fastest data connection between a satellite in orbit and a receiving station on the ground was achieved by the experimental TeraByte InfraRed Delivery (TBIRD) system, designed and developed by NASA and the Massachusetts Institute of Technology Lincoln Laboratory (both USA). TBIRD, which uses an infrared laser light to transmit data, was launched into orbit onboard NASA's Pathfinder Technology Demonstrator 3 satellite on 25 May 2022. On April 28, 2023, TBIRD downlinked 4.8 terabytes of error-free data in under 5 minutes (4 minutes, 57 seconds) on a 200-gigabit-per-second data downlink. That is equivalent to downloading almost a million songs in 5 minutes.

Traditionally, satellite communications are handled by radio transmitters. Even with some complex optimization tricks, the fastest speeds achievable with these connections don't rise above a few hundred megabits per second. The largest geostationary communications satellites have data throughput capacities of up to 500 gigabits, but this is achieved though the use of hundreds of individual transmission channels and requires a satellite about the size of shipping container.

Slow data transfer rates are currently an annoying bottleneck for many space-based research platforms, particularly space observatories. As the size of the images produced by these platforms increase with each generation of new camera technology, so too does the amount of time required to transmit this data back to Earth using radio-based data links.

This is a particularly big problem for sky survey telescopes, such as NASA's TESS or the ESA's Gaia satellite, which take hundreds of massive digital images every night as they map the sky for "transients" (moving or changing objects). Gaia, for example, requires 14 hours of transmission time to downlink each night's observations.

The goal of the TBIRD payload is to showcase the high-data-rate burst delivery capabilities of laser communications from a CubeSat in low-Earth orbit to Earth. In addition to its extremely compact size, weight, and powerful, the TBIRD system includes several novel features to overcome problems with laser-based communications. TBIRD used a specialized version of an automatic-repeat-request (ARQ) protocol designed to achieve error-free laser communication through the atmosphere.

TBIRD is just one of a number of laser-based communications systems that NASA tested in 2023 and 2024. Others include the Deep Space Optical Communications (DSOC) test, which uses a laser transmitter fitted to the Psyche spacecraft (currently on a years-long mission to the asteroid belt); the Laser Communications Relay Demonstration (LCRD), which tested geosychronous laser relay satellites; and the Integrated LCRD LEO User Modem and Amplifier Terminal (ILLUMA-T), which demonstrated two-way communications with the International Space Station.