LunaNet relay

Architecture and services

LunaNet is structured as a service-oriented architecture in which distributed nodes — located at Earth ground stations, in lunar orbit, and on the lunar surface — cooperate to deliver four main categories of service: networking, navigation, detection and information, and radio and optical science. Earlier formulations grouped these as networking, position/navigation/timing (PNT), and science utilization, but the current NASA framing expands the taxonomy to four categories.

The communications framework is built on Delay/Disruption Tolerant Networking (DTN), which allows data to be stored and forwarded when links are intermittent. This removes the need for pre-scheduled Earth contact windows and enables more autonomous surface and orbital operations. The architecture is explicitly designed to be extensible and scalable, allowing additional nodes from new providers to join the network as the lunar economy grows.

For navigation, LunaNet provides the measurements needed for onboard orbit determination, guidance, and surface positioning, aiming to give lunar assets Earth-independent PNT capability. The architecture supports both broadcast and point-to-point navigation services, analogous to terrestrial GNSS but adapted for the cislunar environment. All providers must reference a common Lunar Reference System (LRS) and Lunar Time System, defined in the LNIS Applicable Document AD-5, so that position and time data from different providers can be combined seamlessly.

LunaNet Interoperability Specification (LNIS)

The LunaNet Interoperability Specification (LNIS) is the primary standards document that defines how LunaNet-compliant systems must interface. It specifies agreed protocols, frequency bands, signal structures, and reference systems so that different LunaNet Service Providers (LNSPs) can serve common users. LNIS is developed through tri-lateral working groups among NASA, ESA, and JAXA, with input from the Consultative Committee for Space Data Systems (CCSDS) and the Interagency Operations Advisory Group (IOAG).

Version 4 of LNIS was published on 12 September 2022 and served as the basis for early procurements by all three founding partners. Version 5, published online on 7 February 2025 following approval at a joint Directorate Program Management Council on 29 January 2025, is considerably expanded and altered relative to v4. LNIS v5 specifies that interoperable link-layer services initially require CCSDS AOS frames or fixed-length USLP frames. The LunaNet Signal-In-Space (LSIS) v1, which defines the Augmented Forward Signal (AFS) used for navigation, was made available alongside LNIS v5 as a draft for public comment.

LNIS is accompanied by a suite of Applicable Documents covering specific technical areas: AD-1 (LSIS, Augmented Forward Signal and message structure), AD-2 (measurement schema and parameters), AD-3 (detailed message definitions), AD-4 (location services for users), AD-5 (Lunar Reference System and Lunar Time System), and AD-7 (LunaSAR search-and-rescue service definitions). Together these documents form the complete standards architecture for LunaNet communications and navigation interoperability.

For a provider to qualify as a LunaNet Service Provider for the Lunar Augmented Navigation Service (LANS), LNIS requires adoption of the common AFS signal and message structure, meeting signal-in-space error requirements, and meeting power-at-surface requirements so users on or near the lunar surface receive adequate signal strength. This approach allows navigation signals from different providers to be combined in a multi-constellation fashion analogous to GPS and Galileo on Earth.

Coverage and relay orbits

NASA's Lunar Relay Services Requirements Document (SRD) defines three service volumes for relay coverage. Service Volume III (SV3) encompasses the entire lunar surface at all latitudes and extends to altitudes of at least 200 km, corresponding to global lunar surface coverage for communications and PNT. Within SV3, relay services are required to provide Ka-band return data services, S-band forward and return data services, and point-to-point PNT link services at specified coverage percentages.

LunaNet does not mandate a specific relay orbit; the SRD states that LCRNS orbits are defined by the service provider. Relay constellations must meet the interoperability and service-volume performance requirements of the SRD and LNIS, but providers are free to select orbits — such as near-rectilinear halo orbits (NRHO), elliptical lunar frozen orbits (ELFOs), or polar orbits — that satisfy coverage requirements. The navigation side of LunaNet has a published baseline of eight navigation satellites in two stable ELFOs.

For early Artemis-era operations, relay and PNT services are expected to concentrate on the South Pole region. ESA's Moonlight initial service concept targets a minimum of approximately 15 hours of continuous PNT service at the South Pole every 24 hours, with position accuracy goals of roughly 100 m for orbiters, 50 m for landing, and 10 m for surface operations (3 m with post-processing). The long-term architecture targets full global lunar surface coverage, with the mature LunaNet network sized to ensure any point on the lunar surface lies within the service volume of at least several relay satellites.

Surface users connect to orbital relays via S-band and Ka-band proximity links, with optical links also under consideration. Local surface-to-surface connectivity is envisaged using Wi-Fi (2.4/5 GHz) and 3GPP LTE/5G (Release 16 and later) networks, backhauled through orbital relay nodes.

International partners

LunaNet is explicitly an international framework. NASA, ESA, and JAXA are named as the three founding LunaNet Partners and jointly develop the LNIS standards through dedicated working groups. The architecture and specification are designed to allow additional agencies and commercial operators to join as LunaNet Service Providers.

ESA's contribution is the Moonlight Lunar Communications and Navigation Services (LCNS) programme. Moonlight is designed to comply with LNIS v5 and maximize interoperability with LunaNet. ESA's LCNS prime contractor is Telespazio, under a €123 million contract signed in November 2024, with support from the UK Space Agency and the Italian Space Agency (ASI). Thales Alenia Space holds the satellite manufacturing contract for four LCNS spacecraft. Viasat is responsible for the end-to-end lunar orbiting satellite communications service. ESA targets an Moonlight IOC around 2028 and full operational capability around 2030.

Japan's contribution is the Lunar Navigation Satellite System (LNSS), which provides lunar navigation satellite services and acts as a communications relay using X-band and Ka-band, with optical links also under consideration. ArkEdge Space has been selected as contractor. A LNSS demonstration mission is scheduled in 2028, planned jointly with ESA, and intended to be the first lunar PNT experiment conducted in the actual lunar environment. LNSS is explicitly designed to comply with LunaNet interoperability specifications, so that receivers at the lunar south pole can receive signals from LCRNS, Moonlight, and LNSS as a unified network.

Lunar Pathfinder, an S-band communications relay satellite built by Surrey Satellite Technology Ltd for ESA and developed in partnership with NASA, is designed to comply with a subset of LNIS v5. It will also demonstrate GPS and Galileo signal reception in lunar orbit, bridging Earth GNSS and LunaNet lunar PNT services. As of the research notes, Lunar Pathfinder was planned for launch on Firefly's Blue Ghost lander in December 2025, with an exploitation phase running from Q1 2026 to Q3 2034.