On September 23, a groundbreaking spacecraft, Space Weather Follow-On L1 (SWFO-L1), is set to launch with a critical mission: to maintain continuous surveillance of the sun and safeguard Earth from the impacts of space weather. This timely initiative comes as scientists express urgent concerns regarding the aging fleet of solar monitoring satellites, which are nearing the end of their operational lives. Richard Ullman, deputy director of the NOAA Office of Space Weather Observations, emphasized during a media press briefing on August 21 that the need for this new capability is pressing, stating, “We must replace this capability now.”
For decades, Earth has relied on a select group of satellites stationed approximately one million miles away from our planet, including NASA's Advanced Composition Explorer (ACE), which was launched in 1997, and NOAA's Deep Space Climate Observatory (DSCOVR), launched in 2015. These spacecraft have been essential in providing the first alerts about potentially disruptive space weather phenomena. However, many of these satellites are currently functioning well beyond their intended lifespans, leading to increased vulnerability.
Solar storms can have far-reaching consequences beyond creating beautiful auroras. When the sun ejects charged particles, they travel through space and collide with Earth's magnetic field. Known as coronal mass ejections (CMEs), these events can disrupt GPS signals, pose threats to astronauts, damage satellites, and, in severe cases, incapacitate power grids on Earth. The critical advantage these satellites provide is the advance warning they offer, enabling operators to prepare for incoming threats.
Satellites like ACE and DSCOVR are strategically positioned at a location called Lagrange Point 1 (L1), about 1 million miles (1.6 million kilometers) from Earth towards the sun. This vantage point allows them to observe the complex environment of space weather, including the solar wind. By measuring the solar wind's speed, density, and magnetic orientation, these satellites can provide warnings ranging from 15 minutes to an hour before a storm reaches Earth. As Irene Parker, acting assistant administrator of NOAA Satellites, noted, these warnings represent the first line of defense against the potentially damaging effects of space weather.
Currently, the responsibility of monitoring solar activity rests on a dwindling number of aging missions. NASA's ACE has been operational for nearly three decades, far surpassing its original five-year design life. Meanwhile, the joint NASA-NOAA DSCOVR mission, intended to succeed ACE, has faced reliability challenges. As of July 2025, DSCOVR is offline due to a software issue, with no clear timeline for restoration, according to NOAA communications with Space.com.
In the interim, NOAA's Space Weather Prediction Center (SWPC) is once again relying on ACE as the primary source of solar wind data, alongside data from ESA/NASA's Solar and Heliospheric Observatory (SOHO) and NOAA's GOES-19 satellite, which features the agency's first operational compact coronagraph. Space weather physicist Tamitha Skov expressed disappointment about DSCOVR, stating, “We were supposed to be able to retire ACE.” Even SOHO, launched in 1995 for research purposes, continues to provide valuable solar imagery and data long after its intended retirement.
The upcoming SWFO-L1 mission aims to reinforce the fragile space weather monitoring system. This new satellite will ensure that real-time solar wind monitoring continues seamlessly, even if ACE fails or DSCOVR remains offline. Once positioned at L1, SWFO-L1 will collect data on solar wind, magnetic fields, and high-energy particles emitted by the sun. This information will be transmitted in real-time to NOAA's Space Weather Prediction Center in Boulder, Colorado, where experts issue alerts and warnings to critical sectors, including airlines and power grid operators.
While SWFO-L1 cannot prevent an incoming solar threat, it provides the crucial time needed for preparation. Parker noted, “It can give us time to prepare,” emphasizing the importance of having reliable data to protect the nation's critical systems.
Unlike missions such as NASA's Parker Solar Probe or ESA's Solar Orbiter, which focus on advancing our understanding of solar physics, SWFO-L1 is designed with operational reliability in mind. Its primary goal is to ensure that there is always a vigilant eye on the sun, continuously feeding data into space weather models.
Shawn Dahl, a forecaster at the Space Weather Prediction Center, expressed enthusiasm about the impending launch, stating, “This is a giant leap forward for our forecast and decision support services.” The launch of SWFO-L1 on September 23 marks the beginning of a new chapter in space weather monitoring, a critical step towards building a more resilient future.
For scientists advocating for enhanced investments in space weather monitoring, the launch of SWFO-L1 is a pivotal moment. This mission is not merely about deploying a new satellite; it represents a commitment to protecting our technologies and infrastructure from the sun's most extreme events. Whether we depend on GPS navigation, satellite communications, or simply wish to enjoy the beauty of the auroras, SWFO-L1 ensures that the sun remains firmly in our sights.
