Space Weather Follow On-Lagrange 1 (SWFO-L1) is a future spacecraft mission planned to monitor signs of solar storms, which may pose harm to Earth's telecommunication network. The spacecraft will be operated by the National Oceanic and Atmospheric Administration (NOAA), with a nominal launch scheduled for October 2024. It is planned to be placed at the Sun–Earth L1 Lagrange point, a location between the Earth and the Sun. This will allow SWFO-L1 to continuously watch the solar wind and energetic particles heading for Earth. SWFO-L1 is an ESPA Class Spacecraft, sized for launch on an Evolved Expendable Launch Vehicle Secondary Payload Adapter (ESPA) Grande ring in addition to the rocket's primary payload. The spacecraft's Solar Wind Instrument Suite (SWIS) which includes three instruments will monitor solar wind, and the Compact Coronagraph (CCOR) will monitor the Sun's surroundings to image coronal mass ejection (CME). A CME is a large outburst of plasma sent from the Sun towards interplanetary space.
Together with space weather observation capabilities on the Earth-orbiting GOES-U satellite, SWFO-L1 constitutes the space segment of NOAA's Space Weather Follow-On (SWFO) program. The aim of the SWFO program is to ensure the robust continuity of space-based measurement of the critical space weather environment. All of the spacecraft located in L1 which are currently monitoring CMEs and the solar wind have operated beyond their design lifetime. The Advanced Composition Explorer (ACE) is expected to consume its remaining propellant around 2024. Deep Space Climate Observatory (DSCOVR), NOAA's primary solar wind monitor, was launched in 2015 with a five year design lifetime. The European Space Agency-NASA Solar and Heliospheric Observatory (SOHO) will cease operation before the mid-2020s. SWFO-L1's SWIS instruments will replace ACE's and DSCOVR's monitoring of solar wind, energetic particles and the interplanetary magnetic field while CCOR will replace SOHO's LASCO (Large Angle and Spectrometric Coronagraph) imaging of CMEs.
Space Weather Follow On-Lagrange 1 is planned to be launched as a secondary payload on the rocket carrying NASA's Interstellar Mapping and Acceleration Probe (IMAP) spacecraft. The launch service provider has yet to be selected. As of 2019, the launch is scheduled for October 2024.