Linking up: Connecting Artemis crew, ground and spacecraft

Uplink capabilities on moon rocket’s Exploration Upper Stage will enable teams to complete mission-critical tasks

October 19, 2023 in Space, Defense

What is EUS? The EUS-enabled Space Launch System (SLS) rocket is the foundational capability for future deep space missions.

Starting with Artemis IV, the Exploration Upper Stage (EUS) will replace the Interim Cryogenic Propulsion Stage (ICPS) on NASA’s SLS rocket as it evolves to its Block 1B configuration, allowing NASA to send both astronauts and large payloads to the deep space destinations in a single mission. It’s expected to carry 40% more payload than the initial Block I configuration that features ICPS as the upper stage.

What makes EUS different? EUS implements innovative capabilities to enable NASA’s Moon to Mars objectives.

“EUS is designed from the ground up for its mission,” said James Savage, Boeing’s EUS chief engineer. “We are designing EUS for missions that require more capability and payload, which leads us to prioritize safety and functionality in the development and build process.”

One example of a new functionality leveraged by EUS is its “uplink” capability. While EUS can complete mission tasks autonomously, the upper stage can also be commanded by the ground crews or the human capsule via the uplink capability.

“For instance, when EUS is functioning in proximity operations – or in other words when the spacecraft has separated from EUS but is still within proximity – the crew in the spacecraft can command EUS to perform certain actions to help them with the task at hand, like extracting payloads from EUS,” Savage explained.

Why is this important? The uplink capability is one of the ways EUS enables significantly improved deep-space performance. In the event of an anomaly during the mission, the uplink capability allows the ground crew on Earth or the astronauts in the crew capsule to step in and command EUS to take the actions necessary to complete the mission objectives. This allows for additional possibilities for nominal mission planning and ensures the mission can safely carry on amidst the variable conditions or situations experienced in space.

“The uplink capability is a truly unique functionality that EUS brings to the table by giving astronauts what they need to execute a mission in a safe and highly capable way,” reflected Sarah Weis, SLS B1B Deputy Program Manager.


NASA’s Space Launch System (SLS) rocket – the nation’s next-generation, human-rated rocket – will enable NASA’s Artemis program and will carry people and cargo to the moon, Mars and beyond. Boeing was selected by NASA to design, develop, test and produce the core stages, upper stages, and avionics suite for the SLS fleet of rockets. The first SLS rocket – featuring the Boeing-built Core Stage – successfully launched at 1:47 AM ET on November 16, 2022, as part of the Artemis I Mission. Production is currently underway for the Boeing-built core stages, upper stages (including Exploration Upper Stage) and avionics for future Artemis missions. Read more about SLS.