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S-band
Technology

S-band

Conventional spacecraft radio band; the baseline Orion comms link O2O laser is outpacing by 200x.

Last refreshed: 5 April 2026

Key Question

If S-band worked for Apollo, why is NASA trying to replace it on Artemis II?

Timeline for S-band

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Common Questions
Why is S-band too slow for Artemis?
S-band supports roughly 1–2 Mbps at lunar distance. Modern missions need higher-definition video and larger data transfers; the O2O laser demonstrated 20–260 Mbps over the same link in 2026.Source:
What radio system does the Orion spacecraft use?
Orion uses S-band as its primary voice and telemetry link, with the O2O laser optical terminal running in parallel on Artemis II as a technology demonstration.Source: NASA
How fast is NASA’s new laser compared to S-band radio?
The O2O laser demonstrated 20–260 Mbps on Artemis II, up to 200 times faster than S-band at lunar distance, and downlinked 100 gigabytes by Day 4.Source:

Background

S-band radio has been the backbone of deep-space human spaceflight communications since the Apollo programme. Orion relies on S-band as its primary voice and telemetry link, operating in the 2–4 GHz frequency range. At lunar distance, S-band typically supports data rates of 1–2 Mbps under good conditions, which was adequate for Apollo but constraining for modern high-definition video and large data transfers.

The Artemis II mission is running O2O, a laser optical terminal, in parallel with S-band to demonstrate an alternative. By Day 4, O2O had downlinked over 100 gigabytes at speeds of 20–260 Mbps, up to 200 times the throughput achievable over S-band at the same distance.

S-band remains the operational fallback and handles critical voice and command traffic. The O2O results support the long-term case for replacing S-band with optical links on future Artemis missions and deep-space probes, where bandwidth demands will continue to grow.