Vigil, formerly known as Lagrange, is a future space weather mission under development by the European Space Agency (ESA). The mission will provide the ESA Space Weather Office with instruments able to monitor the Sun, its solar corona, and interplanetary medium between the Sun and Earth, to provide early warnings of increased solar activity, to identify and mitigate potential threats to society and infrastructure, as well as to allow 4 to 5 days space weather forecasts. To this purpose the Vigil mission will place for the first time a spacecraft at Sun-Earth Lagrange point 5 (L5) from where it would get a 'side' view of the Sun, observing regions of solar activity on the solar surface before they turn and face Earth.
Objectives Monitoring space weather includes events such as solar flares, coronal mass ejections, geomagnetic storms, solar proton events, etc. The Sun-Earth L5 location provides opportunities for space weather forecasting by monitoring the Sun beyond the Eastern solar limb not visible from Earth, thus increasing the forecast lead time of potentially hazardous solar phenomena including solar flares, fast solar wind streams. The Vigil mission will improve the assessment of Coronal Mass Ejection (CME) motion and density, speed/energy, arrival time and impact on Earth to support protection of the critical infrastructure on ground and in space. The mission will also perform in-situ observations of the solar wind bulk velocity, density, and temperature as well as the Interplanetary magnetic field (IMF) at L5, to provide enhanced detection and forecasting of high-speed solar wind streams and corotating interaction regions. Vigil mission objectives can be grouped in two main categories:
Nowcasting with the aim to provide an early warning about solar flares and the onset of a Coronal Mass Ejections (CMEs). Thanks to the side view from SEL5, the Vigil mission will also be able improve the accuracy of the predicted arrival CME arrival time on Earth by 2 to 4 hours compared to the current capabilities; this will be achieved by monitoring the entire space between Sun and Earth allowing mid-course tracking of CME and in general solar wind features as they travel towards Earth. Forecasting up to 4 to 5 days of the developing solar activity thanks to the monitoring of active region development beyond the East limb no visible from Earth. In-situ measurements in Sun-Earth L5 will allow monitoring of high-speed solar wind streams and magnetic field several days in advance before they reach the Earth.
Project history As part of the Space Situational Awareness Programme (SSA), ESA initiated in 2015 the assessment of two missions to enhance space weather monitoring. These missions were initially meant to utilize the positioning of satellites at the Sun-Earth Lagrangian L1 and L5 points. Eventually, in the frame of the cooperation on space-based space weather observations between the European Space Agency (ESA) and the United States National Oceanic and Atmospheric Administration (NOAA) National Environmental Satellite Data and Information Service (NESDIS) the following was agreed:
NOAA/NESDIS will launch a Space Weather Follow On (SWFO) Mission to Lagrange Point L1 for continuity of operational space weather observations and to reduce the risk of a measurement gap in the current coronal mass ejection (CME) imagery and in-situ solar wind measurements. ESA will launch a mission to Lagrange Point L5 to provide capability for solar and space environment monitoring away from the Sun-Earth line. In the scope of this agreement the two agencies will share data and provide each other with instruments to be embarked on the respective platforms. Then a new opportunity arose: ISRO had plans to start a new solar observatory in low earth orbit. ESA convinced ISRO to expand the mission to a larger satellite bus, more instruments, and operate it at Lagrange Point L1. The Indian Space agency hesitated because it never had operated a spacecraft at L1 before. ESA supported the necessary software upgrade with trajectories of real ESA spacecraft. The Indian spacecraft operating system showed very similar results and was then certified to operate spacecraft at the Lagrange Points. In exchange for sharing data, ESA provides ESTRACK service for Aditya-L1, which started in 2023. The space segment of the Vigil mission completed the first part of Preliminary Definition (Phase B1) in June 2022. On 21 November 2022, ESA issued a Request for Quotation to Airbus Defence and Space Ltd. for the design, development and verification (Phase B2, C and D) of the Vigil Space Segment. The Phase B2 activities started in April 2024, with the Preliminary Design Review planned for Q1 2026 and the Critical Design Review in Q1 2028. In October 2025, ESA and the South Korean KASA signed a joint statement of intent about potential future sharing of data from Vigil and the KASA's upcoming solar probe mission to the Sun-Earth Lagrange point L4. ESOC in Darmstadt will be Missions Operation Centre. The development of the Ground Segment, including the Mission Operation Centre and Payload Data Centre, will start in 2027 (TBC), although a series of preparatory activities are currently on going.
Mission timeline Vigil is scheduled to be launched in 2031, followed by 3 years of cruise to L5. The mission aims to start quasi-nominal operation as soon as the spacecraft has reached the mid course point on its way to L5 (30deg separation from Earth with respect to Sun). Nominally from L5 for 4.5 years, with a possibility of extension up to 5 additional years. The robust design is for a lifespan of more than 20 year. The orbit around L5 is stable and can be maintained for decades with no or very little fuel consumption. The expectation is that it can get a similar lifespan as SOHO.
Trajectory
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