Lunar Pathfinder relay satellite, ESA¶
Blue Ghost Mission 2 · manifested · partner payload
A small communications relay satellite for lunar orbit, built by Surrey Satellite Technology Ltd (SSTL) with ESA as anchor customer. It talks to landers and orbiters on S-band (and UHF, per NASA's 2023 release) and to Earth on X-band. It also carries an ESA GNSS receiver (NaviMoon), a NASA laser retroreflector array to check the receiver's position fixes, and an ESA radiation monitor. Firefly's Elytra orbiter releases it into lunar orbit; it does not land.
PI: not in public sources (a commercial satellite; SSTL's project director named in 2023: Sophie Bywater)
Built by: Surrey Satellite Technology Ltd (SSTL), United Kingdom, with ESA. NASA Goddard furnished the laser retroreflector array (built by KBR), under the Space Communications and Navigation (SCaN) program. (company)
| Technology | lunar communications relay satellite, with navigation experiments |
| Moon Base need | FN-C-101 L, #0101 (Partly NASA's link. NASA's Moon Base Phases page lists Blue Ghost Mission 2 among the Phase One assets and says the User Terminal will demonstrate relay communications through Lunar Pathfinder. The ties to function FN-C-101 L (surface-to-Earth communications) and, for the NaviMoon and retroreflector tests, to gap #0101 (positioning and timing) are the study's reading. Lunar Pathfinder is a single small relay, not the 'second orbital relay constellation' of the Phase 1 target; it is a first step to ESA's Moonlight network.) |
| Route onto CLPS | partner; An ESA–NASA arrangement, not a NASA payload call. ESA signed a collaboration agreement with SSTL and Goonhilly Earth Station in April 2018. NASA and ESA signed a memorandum of understanding in June 2022 and a joint plan in 2023: NASA delivers Lunar Pathfinder to lunar orbit through CLPS, and in return gets relay services for its lunar payloads. NASA put it in Firefly's task order CS-3 (14 March 2023).; 2022-06 |
| Timeline | first funding 2018 (ESA collaboration agreement with SSTL and Goonhilly); first flight test not in public sources; selected 2022-06 (NASA–ESA memorandum of understanding); CS-3 task order to Firefly 2023-03-14; launch Not yet launched. ESA's service page: no earlier than November 2026. Wikipedia (revision of 23 Aug 2026): no earlier than 2027. ESA said 2025 in 2022.; landing not in public sources |
| On the Moon | not yet flown |
| FO | none |
Flights before the Moon¶
- earlier lunar mission: Lunar Reconnaissance Orbiter's laser retroreflector array (LRO, in lunar orbit), not in public sources. The parent design of the NASA retroreflector array that rides on Lunar Pathfinder; the new array is larger (48 cubes against 12). A part's predecessor, not a flight of Lunar Pathfinder. No flight of the satellite or of ESA's NaviMoon receiver is in the sources read.
"the LRA was produced for NASA by KBR, based on a previous LRA already flying on NASA’s Lunar Reconnaissance Orbiter (LRO)"
— ESA - NASA laser reflector for ESA satnav on Lunar Pathfinder, ESA news, Nov 2022
Heritage hardware¶
- flown design (retroreflector): The NASA laser retroreflector array is based on the one flying on the Lunar Reconnaissance Orbiter, but larger: 48 corner cubes of 4 cm against LRO's 12 of 3 cm.
"the LRA was produced for NASA by KBR, based on a previous LRA already flying on NASA’s Lunar Reconnaissance Orbiter (LRO)"
— ESA - NASA laser reflector for ESA satnav on Lunar Pathfinder, ESA news, Nov 2022
- ground test models: SSTL tested a structural model in 2024 and a satellite risk reduction model (trial solar array deployment). The proto-flight model was about half through assembly, integration and test when ESA's service page was written (it mentions tests in December 2025).
"After successful mechanical tests on the Structural Model of Lunar Pathfinder in 2024"
— Lunar Pathfinder - BSGN"The Lunar Pathfinder Proto-Flight Model is currently under Assembly, Integration and Test process (now ~50% completed)."
— Lunar Pathfinder - BSGN
Funding before the lunar flight¶
- ESA, through a commercial lunar mission support services partnership with SSTL; ESA is the anchor customer for its services. No amount in the sources read. (ESA (commercial partnership); from 2018): amount not in public sources
"ESA is supporting the development of Lunar Pathfinder through a commercial Lunar mission support services partnership with SSTL. ESA is the anchor customer for Lunar Pathfinder services"
— ESA - Firefly to take Lunar Pathfinder to the Moon, ESA news, March 2023
- NASA: the laser retroreflector array (Goddard, SCaN oversight, built by KBR), and delivery to lunar orbit inside CLPS task order CS-3. The CS-3 price covers all three payloads and can't be split. Not development money for the satellite itself. (NASA SCaN (retroreflector); NASA CLPS (delivery); 2022 (retroreflector delivered); 2023 (CS-3)): amount not in public sources
"NASA delivered the first flight hardware for the Lunar Pathfinder mission to ESA (European Space Agency), which [formally accepted]"
— NASA Delivers First Flight Hardware to ESA for Lunar Pathfinder - NASA, NASA image article, 2 Dec 2022
How it got onto CLPS¶
"ESA and NASA have signed a Memorandum of Understanding in June 2022 and a Joint Management Implementation Plan in 2023."
— Lunar Pathfinder - BSGN"NASA is supporting the delivery of the Lunar Pathfinder spacecraft in lunar orbit in exchange for an access to the Lunar Pathfinder lunar relay communication services towards its lunar payloads"
— Lunar Pathfinder - BSGN"The move follows ESA’s collaboration agreement with UK partners Surrey Satellite Technology Ltd and Goonhilly Earth Station for support in lunar services, signed in April 2018."
— ESA - A pathway for communicating at the Moon, ESA news, October 2019"ESA collaborated with NASA for delivery through the CLPS initiative."
— NASA Picks Firefly Aerospace for Robotic Delivery to Far Side of Moon - NASA, release of 14 Mar 2023
On the Moon¶
To be released into lunar orbit by Firefly's Elytra; not a surface payload. Planned: an elliptical frozen orbit that favors the South Pole, relay service for LuSEE-Night and others, and a test campaign comparing GNSS fixes with laser ranging.
"Once in lunar orbit, Elytra will deploy Blue Ghost and the European Space Agency’s Lunar Pathfinder satellite."
— Blue Ghost + Elytra: Lunar Far Side"Lunar Pathfinder will orbit in a highly elliptical ‘Lunar Frozen Orbit’, designed to optimise coverage over the Moon’s South Pole"
— ESA - NASA laser reflector for ESA satnav on Lunar Pathfinder, ESA news, Nov 2022
FO's role¶
Grade: none. No FO project, flight or report names Lunar Pathfinder, SSTL (Surrey), NaviMoon or the retroreflector array; the study searched the 430 FO TechPort records, FO's reports and FO's pages. A European satellite built and tested in the UK. The study's earlier traceback grade (none found) stands.
"the deployment of the Lunar Pathfinder orbiter built by Surrey Satellite Technology Ltd."
— earlier finding of this study (not a public source)
Who built it¶
"ESA’s Lunar Pathfinder is designed and developed by Surrey Satellite Technology Limited."
— NASA Picks Firefly Aerospace for Robotic Delivery to Far Side of Moon - NASA"The retroreflector array is designed and manufactured by Kellogg Brown & Root (KBR), a science and engineering solutions company."
— NASA Delivers First Flight Hardware to ESA for Lunar Pathfinder - NASA, NASA image article, 2 Dec 2022"furnished the Lunar Pathfinder mission with the retroreflector array with oversight from the Space Communications and Navigation (SCaN) Program"
— NASA Delivers First Flight Hardware to ESA for Lunar Pathfinder - NASA, NASA image article"Sophie Bywater, Project Director at SSTL"
— ESA - Firefly to take Lunar Pathfinder to the Moon, ESA news, March 2023"will provide communication services to lunar missions via S-band and UHF links to lunar assets on the surface and in orbit around the Moon and an X-band link to Earth"
— NASA Picks Firefly Aerospace for Robotic Delivery to Far Side of Moon - NASA
Moon Base need¶
"Blue Ghost will carry a NASA-developed User Terminal that will communicate through the Lunar Pathfinder satellite, demonstrating relay communications that could help provide reliable connections for future spacecraft operating around and on the Moon."
— Moon Base Phases - NASA, Phase One, Blue Ghost Mission 2"Provide communications and data exchange between the lunar surface and Earth."
— Moon to Mars knowledge base: Moon Base Phase 1 functional gaps, Communications and PNT, FN-C-101 L"Deployment of a second orbital relay constellation with surface imaging capabilities"
— Moon to Mars knowledge base: Moon Base Phase 1 functional gaps, Communications and PNT, capability targets"The Lunar Pathfinder services will be a mission enabler for polar and far-side missions, which, without direct line of sight of the Earth, would otherwise have to procure their own communications relay spacecraft."
— Lunar Pathfinder - BSGN"using a navigation infrastructure such as an orbital constellation"
— Moon to Mars knowledge base: ESDMD #0101: Positioning, Navigation, and Timing for Lunar Surface Extreme Environments, summary
Open questions¶
- SSTL's platform heritage for Lunar Pathfinder (which earlier SSTL satellites it draws on): not in the pages read.
- ESA's development cost and NASA's cost for the retroreflector array: not in public sources read; USAspending was not reachable on 4 October 2026.
- Did the NaviMoon receiver or the radiation monitor fly before? Not in the pages read.