Space weather events affect directly both manned and unmanned spaceflight missions. In order to determine the influence of such events, observations of the solar phenomena away from Earth and/or near Earth are mandatory. The Sun-Earth equilateral Lagrange point L5 (SEL5) is a perfect candidate for an observation post of the solar space weather mission due to the constant dynamical and environmental conditions a spacecraft would face in that position. For these reasons, SEL5 is selected for the ESA LAGRANGE Mission to be launched in 2023.
The Lagrange mission concept is overseen by the Space Situational Awareness Programme at ESA. On 2 February 2018, ESA signed technological contracts (Phase A) to be led by Airbus UK and OHB SE of Germany to design the spacecraft specifications and the instruments’ integration process. This mission concept proposes positioning two spacecraft in orbit at the L1 and L5 Lagrangian points, respectively, where gravitational forces interact to create a stable location to save propellant and from which to make observations. L1 is in the solar wind ‘upstream’ from Earth, so measurements at L1 provide information about the space weather coming toward Earth. In contrast, the L5 point provides a way to monitor coronal mass ejections (CMEs) from the ‘side’ in order to estimate their speed and direction.