| Vigil | |
| Names List: | Formerly known as Lagrange |
| Image Alt: | Vigil Mission Patch |
| Mission Type: | Space Weather nowcast/forecast |
| Operator: | European Space Agency |
| Cospar Id: | TBD |
| Satcat: | TBD |
| Website: | https://www.esa.int/Space_Safety/Vigil |
| Mission Duration: | Cruise phase: 3 yearsOperations: 4.5 yearsExtension: up to 5 years |
| Launch Mass: | 2,500 kg (limit) |
| Dry Mass: | ~1,100 kg |
| Payload Mass: | ~150 kg (before system margins) |
| Power: | Spacecraft ~1000 W; Payload ~200 W |
| Launch Date: | 2031 (planned) |
| Launch Rocket: | Ariane 62 |
| Launch Site: | Guiana Space Centre |
| Launch Contractor: | Arianespace |
| Orbit Reference: | Sun-Earth L5 |
| Orbit Regime: | Lissajous orbit |
Vigil,[1] formerly known as Lagrange,[2] is a space weather mission developed by the European Space Agency. 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 ground, airborne and space based infrastructure as well as to allow 4 to 5 days space weather forecasts.[3] 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.
Monitoring space weather includes events such as solar flares, coronal mass ejections, geomagnetic storms, solar proton events, etc.[4] 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 co-rotating interaction regions.
As part of the Space Situational Awareness Programme (SSA),[5] 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:
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.
The space segment of the Vigil mission completed the first part of Preliminary Definition (Phase B1)[6] 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.[7] The formal start of the activities is planned before the end of 2023.
The status of the Ground Segment is ... [to be completed].
Vigil is scheduled to be launched in 2031,[8] followed by 3 years of cruise to L5. The mission aims to operate nominally for 4.5 years, with a possibility of extension up to 5 additional years.
Vigil mission objectives can be grouped in two main categories:
The Platform supplies all service-related functions required to support the proper operation and data collection of the Vigil Payload Suite. The key feature of spacecraft concept for an operational mission like Vigil is a robust avionics architecture able to remain operational during the most extreme space weather events seen in the last 100 years. The Failure Detection Isolation and Recover (FDIR) will be designed to enhance the autonomy of the spacecraft, thus reducing the risk of service interruption requiring ground intervention.
The Mission Data downlink is via X-band at an average data rate of ~1 Mbps (~86 Gbits per day) with 24/7 coverage provided by ESTRACK supplemented by additional commercial stations.
The mass at launch is projected close to 2500 kg. To reach SEL5 the proposed design will rely on a bi-propellant Chemical Propulsion System equipped with a 450 N main engine.
Payload Suite will include:
In the frame of the inter-agency cooperation between ESA and NASA, Vigil will offer the possibility to accommodate an additional instrument NASA instrument of opportunity (NIO).[9]
The remote sensing instruments will allow to estimate size, mass, speed, and direction of CMEs.
In-situ instruments can be used to monitor the Stream Interaction Regions (SIR)[11] and Co-rotating Interaction Regions (CIR) up to 4–5 days in advance before their arrival at Earth.
The Ground Segment, consists of:
The Launcher service is baselined as Ariane 6.2 by Arianespace from the Guiana Space Centre. The launcher will be in dual-launch configuration for injection in GTO. The Spacecraft will be launched as secondary passenger with a commercial customer bound for geostationary orbit in a dual-launch with Ariane 6.4. This transfer option makes use of the Sun-Earth L1/L2 connection and the Weak Stability Boundary effects near L2 to reach L5.
After release of the Spacecraft into GTO, it will perform a series of 3 Apogee Raising Manoeuvres (ARM) to make its way towards L1 within a period of 14 days, planned to minimise the transitions through the Van Allen belts.
From L1 the Spacecraft will be placed on a zero to low-cost transfer trajectory towards L2 from which it will then leave towards SEL5. Deep Space Manoeuvres (DSM), preceded and followed by correction manoeuvres, will be executed as needed.
When the Spacecraft reaches L5, a braking manoeuvre to insert the spacecraft into the final orbit will be executed. Different options are investigated, resulting in a split of such manoeuvre in two burns.
The cruise to L5 can take up to 3 years. To increase the use of the Vigil spacecraft, the mission will enter in a pre-operational phase once the halfway through the journey L5.
Alternatives include the use of Ariane 6.2 for direct injection in SEL5, Ariane 6.4 or Falcon 9 provided by SpaceX.