Artemis II glossary: Terms to know as astronauts approach moon

From 'translunar injection' to 'sphere of influence,' here are the key terms to understand the Artemis II lunar mission.

Apr. 3, 2026 at 3:23pm

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A bold, highly structured abstract painting in soft, flat colors depicting sweeping geometric arcs, concentric planetary circles, and precise celestial spirals, conceptually representing the technical complexity of the Artemis II mission as the spacecraft travels to the moon.An abstract visualization of the Artemis II spacecraft's intricate journey to the moon, capturing the complex orbital mechanics and scientific forces at play.San Diego Today

As the Artemis II astronauts journey to the moon, there are many technical space terms that the public may not be familiar with. This article provides definitions for some of the key jargon, including 'translunar injection,' 'sphere of influence,' and more, to help readers better understand the mission as it unfolds.

Why it matters

The Artemis II mission marks the first time in over 50 years that humans will venture beyond Earth's orbit and approach the moon. Understanding the specialized terminology used to describe the various stages and maneuvers of the mission will allow the public to follow along and appreciate the technical complexity of this historic spaceflight.

The details

The Artemis II astronauts - NASA's Reid Wiseman, Christina Koch, and Victor Glover, along with the Canadian Space Agency's Jeremy Hansen - launched from Florida on April 3, 2026 and are now officially moonbound. In the coming days, they will become the first humans to see the far side of the moon that was never witnessed by the Apollo astronauts. Along the way, they will test critical systems and hardware to pave the way for future Artemis missions that aim to establish a lunar base and eventually send astronauts to Mars.

  • The Artemis II astronauts launched from Florida on April 3, 2026.
  • On April 5, 2026, the Orion spacecraft completed a pivotal 'translunar injection' maneuver to send it beyond Earth's orbit toward the moon.
  • The Artemis II astronauts are expected to make a water landing in the Pacific Ocean near San Diego, California on April 10, 2026 after their four-day journey back to Earth.

The players

Reid Wiseman

A NASA astronaut who is part of the Artemis II crew.

Christina Koch

A NASA astronaut who is part of the Artemis II crew and will become the first woman to venture within the vicinity of the moon.

Victor Glover

A NASA astronaut who is part of the Artemis II crew and will become the first Black man to venture within the vicinity of the moon.

Jeremy Hansen

A Canadian Space Agency astronaut who is part of the Artemis II crew and will be making his first spaceflight.

NASA

The U.S. space agency leading the Artemis program, which aims to return humans to the moon and eventually send astronauts to Mars.

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What they’re saying

“The Artemis II mission is far from a reprise of its Apollo program, as the series of missions are aimed to set up a moon base toward the lunar south pole ahead of the first crewed expeditions to Mars.”

— Eric Lagatta, Space Connect reporter

What’s next

After completing their lunar flyby, the Artemis II astronauts will make a four-day journey back to Earth, using the planet's gravity to 'slingshot' the Orion spacecraft home without the need for much propulsion or fuel. The capsule is expected to make a water landing in the Pacific Ocean near San Diego, California on April 10, 2026.

The takeaway

The Artemis II mission represents a major milestone in humanity's return to the moon, with the astronauts set to become the first to see the far side of the lunar surface. By understanding the specialized terminology used to describe the various stages of the mission, the public can better appreciate the technical complexity of this historic spaceflight and follow along as the Artemis program lays the groundwork for future lunar exploration and even potential missions to Mars.