NASA and ESA are collaborating to better explore our Moon with Lunar Pathfinder

At the ESA Ministerial Council meeting in Netherlands on June 15, 2022, NASA and ESA extended their space collaboration in several ways, including agreeing to cooperate on the Lunar Pathfinder orbiter mission, whose spacecraft is being built by UK’s Surrey Satellite Technology Ltd. (SSTL) with input from anchor customer ESA.

As part of the agreement, the Lunar Pathfinder spacecraft will be deployed into lunar orbit by 2025 by a Moon lander competitively selected by NASA under the agency’s CLPS program. Lunar Pathfinder will operate in a frozen elliptical orbit for at least 8 years and relay communications between Earth and robotic mission hardware on or around the Moon. This includes aiding missions on the Moon’s farside, where such a relay is required, and hardware on the poles, where Earth visibility is limited due to rocky terrain and our planet being low on the horizon. The latter will be especially useful for future rovers venturing into permanently shadowed regions, where line of sight to their landers or Earth can be quickly lost.

The Lunar Pathfinder will relay communications between Earth and robotic mission hardware at the Moon as a commercial service. Credit: SSTL

In return for NASA launching and deploying Pathfinder to lunar orbit, ESA will let NASA use Pathfinder to relay communications between Earth and its robotic hardware on the Moon, particularly for the agency’s CLPS missions on the farside.

Aligning incentives

This collaboration is a great move for both NASA and ESA. Because of Pathfinder’s availability, NASA doesn’t necessarily need to build or buy its own relay hardware for future farside missions while also gaining enhanced communications for its robotic polar missions taking place around the same time. In much the same vein, ESA intends to utilize Pathfinder’s communications for their multipurpose Large Logistics Lander (EL3) launching end of decade, whose capabilities include delivering cargo for astronauts, bringing lunar samples, and more. In fact, the Schrödinger crater is one of the proposed landing sites for an EL3 sample return mission.

On another note, the fact that NASA and ESA are willing to launch and deploy an important mission like Pathfinder using a ride-along CLPS lunar lander shows their confidence in the growing maturity of the program that can enable regular Moon landings at low costs.

For ESA, Lunar Pathfinder also represents the first step of their Moonlight ambitions to have a high-throughput lunar constellation that commercially provides communications and navigation services to robotic and crewed hardware at the Moon. In May 2021, ESA selected SSTL as one of the two companies leading a developmental study to demonstrate the feasibility of Moonlight.

In the meanwhile, both ESA and SSTL are hoping to find lunar hardware customers right now whose missions could benefit from Lunar Pathfinder by achieving higher data rates with lower cost communication systems. ESA intends for three to four more satellites to join Lunar Pathfinder by end of decade, and then progressively expand coverage to the entire Moon’s surface with more satellites and surface beacons to complete project Moonlight.

Extending GPS to the Moon

The Lunar Pathfinder mission also sports an intriguing experiment onboard, in which NASA and ESA are again collaborating. An ESA-provided NaviMoon receiver will be regularly oriented towards Earth by the spacecraft to demonstrate a GPS fix at the Moon using signals millions of times fainter than those used by our phones. Positioning fixes from the receiver will be compared with conventional radio ranging methods to know how well it works. A NASA-provided retroreflector onboard will be used to test laser ranging capabilities and aid said GPS-fix demonstration. If successful, such systems can reduce operational costs of future lunar missions. NASA itself will be testing a similar system on Firefly’s CLPS mission in 2024.

NASA and ESA collaborating on Lunar Pathfinder represents a third major vertical of collaboration between the two agencies in exploring our Moon, the other two being Europe’s contributions to NASA’s Artemis program in the form of the crewed Orion spacecraft’s critical service module and the NASA-led Gateway lunar station’s i-HAB habitation module as well as the ESPRIT communications & refueling module.

Here’s to many more such pieces of progress.

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