When NASA’s Artemis II astronauts traveled around the Moon in April 2026, radio was not their only connection to Earth.
A laser communications terminal aboard Orion exchanged 484 GB of data during the 10-day mission, reaching downlink speeds of 260 Mbps. It was the first laser communications system flown on a crewed deep-space mission.
Artemis II followed a series of increasingly ambitious tests. NASA’s TBIRD experiment sent 4.8 TB to Earth in five minutes. European satellites already relay data using lasers. NASA has received optical signals from more than 300 million miles away.
The advantage is clear. Laser links can move much more data than comparable radio systems using smaller, lighter hardware.
The challenge is keeping the connection alive.
How Laser Communications Work in Space
Laser communication encodes data onto a tightly focused beam of light.
It does not transmit information faster than radio. Both travel at the speed of light. The difference is how much information the link can carry.
NASA says optical systems can provide 10 to 100 times the data transmission rate of comparable radio links while using smaller, lighter hardware and less power.
That matters because spacecraft generate increasingly large datasets from cameras, scientific instruments, and Earth observation sensors.
More Data in the Same Ground Contact
A satellite in low Earth orbit may only be visible from a particular ground station for a few minutes.
NASA’s TeraByte InfraRed Delivery experiment showed what higher optical bandwidth can achieve. The CubeSat transmitted 4.8 TB of error-free data in a five-minute pass at 200 Gbps.
The contact did not last any longer. More data simply fitted into it.
For Earth-observation and science missions, that can mean returning more imagery or measurements before the spacecraft disappears over the horizon.
Smaller communications hardware can also leave more mass, power, and physical space for sensors, propulsion, and other mission systems.
The Biggest Challenge Is Pointing
A narrow beam concentrates more energy towards the receiver than a wider radio signal. That improves efficiency, but leaves much less room for error.
ESA says its European Data Relay System laser terminals can locate and lock onto a target only 135 mm wide from around 45,000 km away.
Even a tiny angular error can become a large miss over that distance.
Spacecraft also vibrate, change attitude, and experience temperature shifts that can move optical components.
Terminals therefore use coarse pointing to find the target, tracking sensors to measure its position, and fine steering systems to keep the beam locked while data is transmitted.
Deep Space Makes Every Photon Count
NASA’s Deep Space Optical Communications experiment tested those principles at much greater distances aboard the Psyche spacecraft.
In December 2023, DSOC streamed ultra-high-definition video to Earth at 267 Mbps from a distance of more than 19 million miles. Later, ground systems received spacecraft data from 307 million miles away.
By September 2025, the experiment had received 13.6 terabits of data.
Across interplanetary distances, only a tiny proportion of the transmitted photons reach the receiving telescope.
That makes the link budget a fight against loss. Laser power matters, but so do telescope size, beam divergence, pointing accuracy, detector sensitivity, and losses elsewhere in the optical system.
The Atmosphere Can Break a Ground Link
A space-to-space laser avoids Earth’s atmosphere. A beam traveling to a ground station does not.
Dense cloud can block an optical link entirely. Haze and aerosols weaken it, while atmospheric turbulence can distort the beam.
One solution is geographic diversity. If one optical ground station is covered by cloud, another site may have clear skies.
Adaptive optics can also compensate for some atmospheric distortion by measuring changes in the incoming wavefront and correcting them.
Weather, therefore, becomes part of the communications architecture rather than simply a ground-operations issue.
Every Optical Surface Uses Link Margin
The beam may pass through or reflect from several components before leaving the spacecraft, including mirrors, beamsplitters, filters, and windows.
Each surface can reduce the amount of useful light that eventually reaches the receiver.
A mirror reflecting slightly less light than expected may appear insignificant on its own. Across several components, those losses accumulate.
Surface errors can also distort the wavefront and increase beam divergence, making the distant receiver harder to hit or the incoming signal harder to focus.
Absorbed light creates heat, which can alter alignment or optical performance.
This is why coating performance matters alongside the laser itself. Optics designed for demanding high-power laser systems need to maintain low absorption, high damage thresholds, and stable spectral performance.
Space Optics Have to Keep Working
A laboratory optic can be cleaned, adjusted, or replaced.
An optic aboard a spacecraft may never be touched again.
It has to survive launch and then operate through vacuum, radiation, and temperature changes while continuing to meet its optical specification.
Performance on day one is therefore only part of the requirement. The same components may need to maintain that performance after thousands of hours in service.
For a communications system already working with a limited photon budget, gradual changes in transmission, reflection, or beam quality can matter.
Laser Links Are Becoming Networks
Optical communications are also moving beyond individual demonstrations.
Europe’s European Data Relay System allows low-Earth-orbit satellites to transmit data by laser to relay satellites in geostationary orbit rather than waiting for the next ground-station pass.
By June 2023, ESA said EDRS had completed more than 75,000 links and transferred more than 4.5 petabytes of data.
ESA’s HydRON project goes further, with plans for an optical network linking satellites across different orbits with ground infrastructure.
That makes interoperability increasingly important. Common standards can allow terminals, relay systems, and ground stations built by different organizations to operate as parts of the same network.
Radio Is Not Going Away
Laser communications solve problems that radio struggles with, but they introduce limitations of their own.
Cloud can close an optical ground link. Pointing requirements are demanding. Some missions do not need the additional capacity.
Radio remains mature and reliable.
Future spacecraft are therefore likely to use both technologies: optical links for moving large datasets when conditions allow, with radio providing other communications and resilience.
The bigger change is not replacing radio with lasers.
It is giving spacecraft more ways to move more data over greater distances.