US Continues 60-Year Space Mission to Detect Nuclear Blasts

A 60-year-old mission to monitor Earth from space for nuclear detonations is advancing with new technology developed by Sandia and Los Alamos national laboratories. The final sensor system of the current generation was launched in May 2025, while the first units of a more advanced series are already being prepared for a 2027 deployment, ensuring continuous global surveillance.

This long-running national security program, known as the Global Burst Detection system, operates from a constellation of U.S. global positioning satellites orbiting approximately 12,550 miles above the planet. The system provides real-time data to the U.S. military and government, acting as a critical tool for monitoring nuclear treaty compliance and identifying potential threats.

A Continuous Watch from Orbit

For more than 60 years, the United States has maintained a constant watch from space for signs of a nuclear explosion. This capability is provided by the Global Burst Detection (GBD) system, a sophisticated suite of sensors integrated into the nation's GPS satellite network.

The GBD system is the space-based component of the larger U.S. Nuclear Detonation Detection System. Its primary function is to identify and report on nuclear events occurring in the atmosphere or in near-space. The network of sensors is designed to detect specific signals associated with a nuclear blast, including X-rays, optical flashes, and electromagnetic pulses.

The mission requires continuous technological advancement to counter evolving threats and maintain reliability. Teams of scientists and engineers at Sandia and Los Alamos work on a decade-long timeline to design, build, and test new generations of sensor technology.

Transition to a New Generation of Sensors

A significant milestone was reached in May 2025 with the launch of the final GBD system in the current IIIA series. This launch, which took place from Cape Canaveral, completed the deployment of the existing block of eight systems. Following the launch, teams from Sandia, Los Alamos, and the U.S. Space Force began calibrating the new system in June to integrate it into the operational satellite network.

Even as the final IIIA unit became operational, work on its successor was well underway. In 2024, the national laboratories delivered the first two flight systems for the next generation of detectors, designated IIIF. These units were sent to Lockheed Martin for integration onto new GPS satellites.

The development of the IIIF system was a 12-year collaborative effort between Sandia and Los Alamos. Over the next decade, the laboratories plan to deliver and launch additional IIIF systems to upgrade and sustain the nation's space-based detection capabilities.

Advanced Technology for a Harsh Environment

Operating in space presents extreme challenges. The GBD sensor payloads are designed to function reliably for over 15 years despite exposure to radiation, extreme temperature swings, and the vacuum of space. To ensure this longevity, the systems undergo an exhaustive series of qualification tests on the ground.

Funded by the National Nuclear Security Administration (NNSA), the testing regimen at Sandia National Laboratories simulates the harshest conditions the equipment will face. These tests include:

• Vibration and Shock Tests: To ensure the system can survive the violent forces of a rocket launch.
• Thermal Vacuum Tests: To verify performance in the airless, fluctuating temperature environment of orbit.
• Prompt X-ray Tests: To confirm the electronics can withstand the intense radiation of a nearby nuclear event without failing.

A key innovation in the new IIIF series is the Spectral Imaging Geolocation Hyper-Temporal Sensor (SIGHTS). This technology originated from foundational research at Sandia more than a decade ago. SIGHTS is a high-density optical sensor with the ability to capture tens of thousands of frames per second. This rapid imaging capability allows the system to better distinguish the unique signature of a nuclear flash from other natural phenomena, such as lightning, significantly reducing the chance of false alarms.

A Decades-Long Laboratory Collaboration

The enduring success of the Global Burst Detection mission is built on the partnership between Sandia and Los Alamos national laboratories. Under the program structure, both labs design and produce five key subsystems. Sandia is then responsible for integrating these components into a single, complete detection payload before it is delivered for satellite installation.

Officials from both laboratories highlighted the importance of this sustained effort following the recent launch.

"The launch of the final IIIA series Global Burst Detector marks an important milestone in our efforts to enhance nuclear detection capabilities," said Andrew Stuart, a Sandia manager. "The collaboration between Sandia National Laboratories and Los Alamos National Laboratory has been key to developing this advanced system, which will significantly contribute to our national security."

The mission requires a long-term perspective, with teams constantly working on technology that may not fly for another decade. This forward-looking approach ensures the U.S. maintains an uninterrupted surveillance capability.

"The May launch is a testament to the decades of effort that it takes to maintain uninterrupted national security space capability," stated Marc Kippen, program manager for Space Systems and Science at Los Alamos. "Los Alamos National Laboratory is proud to contribute to this important and enduring mission."

With the new IIIF systems preparing for launch, this critical national security mission is positioned to continue its silent watch over the planet for decades to come.