Why the Euclid space mission orbits an invisible point 1.5 million kilometres away
Launched in July 2023, the ESA’s Euclid mission travels to a unique location in space called Lagrange point 2. This invisible oasis of forces allows the telescope to remain thermally stable while keeping the Sun, Earth, and Moon behind it, providing a clear, uninterrupted view of the dark universe.
The Euclid mission, launched on 1 July 2023 via a SpaceX Falcon 9, is designed to investigate dark matter and dark energy, which constitute 95% of our universe. To achieve the high stability required for its long-exposure observations, the telescope was sent to Lagrange point 2 (L2). This position is located approximately 1.5 million kilometres from Earth, sitting in the opposite direction from the Sun. By positioning itself here, Euclid maintains a permanent, stable thermal environment, as the Sun, Earth, and Moon are perpetually blocked from its line of sight.
Euclid does not sit perfectly still at L2; instead, it follows a large halo orbit. The radius of this path varies between 400 000 and 800 000 kilometres from the centre of the point. This specific orbit is chosen because it is highly fuel-efficient. Because the launch was near-perfect, Euclid required only a tiny correction manoeuvre to settle into this trajectory. The mission is expected to spend six years in this orbit, completing revolutions while the Moon circles the Earth six times.
The mission's name honors the ancient Greek mathematician Euclid of Alexandria, who flourished around 300 BCE. While little is known of his life, his seminal work, the Elements, served as the foundation for Western mathematics for over 2000 years. Just as the ancient Euclid built a rigorous logical framework from fundamental axioms, the modern Euclid mission seeks to build a clearer understanding of the fundamental, yet mysterious, components of our cosmos.
Source: Euclid | Launch to ‘L2’
