The Solar Wind Plasma Sensor (SWiPS) onboard the Space Weather Follow On – Lagrange 1 (SWFO-L1) observatory, NOAA’s newest space weather mission, was successfully powered on six days after it launched on September 24, 2025. After completing several major post-launch tests, SWiPS began sending science data back to Earth on November 6. As the solar wind (a hot, ionized gas) flows outward from the sun and passes the spacecraft, this state-of-the-art instrument takes detailed, rapid measurements of the plasma. Based on this information, scientists can then calculate a number of properties of the wind, including its speed, density, temperature and pressure. These data are essential for accurate space weather forecasting.
Measuring the State of the Solar Wind
When a strong geomagnetic storm swept through Earth’s space environment on November 12, 2025 causing a range of technological disruptions, SWiPS measured the intensity of the incoming solar wind, a key driver of the ensuing disturbance. At the time, the dominant solar wind structure whipping up the storm was a coronal mass ejection (CME) which had erupted from the sun the previous day and was directed towards Earth. SWiPS measures the three-dimensional flow of ions in the solar wind thanks to its two “top hat” electrostatic analyzers.
Preliminary SWiPS measurements of the solar wind during a CME passage which was the key driver of a severe geomagnetic storm in the Earth’s environment on November 12, 2025. Top panel: measurements of solar wind ions (mainly protons and alpha particles) over a range of energies shown as an energy-time spectrogram. Four lower panels: preliminary estimates of the derived speed, density, temperature, and dynamic pressure for protons. During that phase of post-launch testing, SWiPS measured the solar wind for 12 hours each day. Image credit: NCEI, SWPC, and Southwest Research Institute.
The first panel of the figure above shows measurements from the central portion of the CME as it washed over the spacecraft and, shortly afterward, the Earth. The four subsequent panels show preliminary derived wind speed and other properties that are useful to space weather forecasters in understanding the space environment around Earth. The same data are essential in driving numerical prediction models such as those run 24/7 at NOAA’s Space Weather Prediction Center (SWPC).
Understanding the Drivers of Destructive Space Weather
CMEs are colossal structures, thousands of times the diameter of the Earth. When they reach our planet, they can drive powerful, long-lasting geomagnetic storms in the upper atmosphere. For example, the measurements shown above are part of a disturbance extending over several days, which also appeared in the first public data release for another SWFO-L1 instrument– the magnetometer (MAG).
These storms can affect a wide range of technological systems, from electrical charging of satellites to radio communication disruptions to outages in electric power grids on the ground. Thanks to SWPC’s monitoring and timely warnings, the impacts of the severe geomagnetic storm of November 12 (rated G4 on NOAA’s space weather scale) were significantly reduced.
Beyond operational forecasting, data from the new SWiPS instrument will be useful for science and modeling of the solar wind. High-resolution datasets (as shown in the second figure) will help researchers better distinguish the roles of different particle populations, such as protons and alpha particles, and study how they are accelerated and heated within the solar wind.
Upcoming Milestones and Data Releases
SWFO-L1 is expected to arrive at the Lagrange point 1 (L1) region in January 2026. Once it reaches its final orbital position, the observatory will be renamed SOLAR-1 (Space weather Observations at L1 to Advance Readiness – 1). After completing additional testing and validation, SOLAR-1 will begin operational service in spring 2026, and SWPC will begin incorporating SWiPS measurements, along with data from other instruments, for its official space weather watches and warnings.
All mission data will be archived at NOAA’s National Centers for Environmental Information (NCEI) with open and free access. Additional information on the instrument, data products, and science results will be shared on the SWFO Data and Science webpage.
Data from SWFO-L1 during the post-launch testing phase should be considered preliminary and non-operational.