ESA Vigil

''ESA Vigil'', formerly known as ''Lagrange'', is a planned solar weather mission by the European Space Agency. It envisions two spacecraft to be positioned at Lagrangian points L₁ and L₅.Design call for 'solar sentinel' mission
Jonathan Amos, ''BBC News''. 2 February 2018.Monitoring space weather
European Space Agency (ESA). 4 December 2017. Monitoring would help predict arrival times at the Earth and any potential effect on infrastructure. The ''Vigil'' spacecraft are anticipated to launch in the mid 2020s.

On 17 May 2021, ESA began soliciting design concept studies from various European industrial and scientific consortiums for the mission. A final design will be selected after approximately 18 months, in late 2022. Simultaneously, the ESA announced the No-Name Mission contest to replace the placeholder ''Lagrange'' name. The winning name, ''Vigil'', was announced on 10 February 2022.

Overview

To ensure an effective capability to monitor potentially dangerous solar events, ESA initiated a study of two potential future space weather satellites called ''Lagrange''. 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. UK's Rutherford Appleton Laboratory and Mullard Space Science Laboratory will assess the requirements of the science payload.

This mission concept proposed 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.

The SOHO mission already collects data at L1, but it is not able to deliver a constant data stream of sensor data around the clock like weather satellites do, which is needed for space weather forecasts. SOHO also is expected to end its service around 2025 due to a lack of fuel. There is however the Aditya-L1 mission of ISRO that fits the profile of the L1 mission very well and is scheduled to start in 2024. ESA has agreed to provide support by ESTRACK for this mission, and ISRO will exchange data with ESA to use it for space weather predictions.

Objectives

The preliminary mission objectives are:
*the spacecraft at L1 is to provide observations of the solar wind speed, density, temperature and dynamic pressure, charged particle environment and the direction and strength of the interplanetary magnetic field.
*The spacecraft at L1 would also monitor the solar disk and solar corona and measure solar energetic particles that may be associated with solar flares and the onset of coronal mass ejections.
*The spacecraft at L5 would complement measurements made from L1 by providing a side-view of the propagation of plasma clouds emitted by the Sun toward Earth.
*The spacecraft at L5 would monitor of the solar disk and corona and carry out measurements of the interplanetary medium.

Payload

To achieve these objectives, the satellites at the L1 and L5 positions have to carry different types of remote-sensing and ''in-situ'' instruments. The suggested optical instruments take heritage from ESA and NASA science missions like SOHO, STEREO and Solar Orbiter, but the instruments would be optimized for operational space weather monitoring. The notional science payload may require:
;Optical instruments
* Coronagraph – for onset and characterisation of coronal mass ejections (CMEs).
*Heliospheric imager (HI) – A wide-angle visible-light imaging system for the detection of coronal mass ejection events directed toward Earth.
*Magnetograph - would scan a selected solar spectrum to generate 3D maps of the magnetic field.
*EUV imager – Imaging of the complex solar corona (the Sun's atmosphere) will support monitoring of the magnetic complexity and activity in the corona and location of the flaring active regions.
*X-ray flux monitor – Detection of solar flares and quantification of the flare energy.

;''In situ'' instruments
*Magnetometer – Measurement of the interplanetary magnetic field.
*Plasma analyser – To measure angular velocity components of the solar wind approaching the Earth and estimates of geomagnetic storm strength.
*Radiation monitor – Monitoring radiation storms ( Solar particle event) is crucial, as these can disrupt and damage spacecraft, aircraft and ground systems.
*Medium energy particle spectrometer – This can monitor clouds of medium-to-low energy ions approaching the Earth.

References

{{ESA projects

Proposed space probes
2020s in spaceflight
Missions to the Sun
European Space Agency space probes
Solar space observatories
Solar telescopes