Looking from space for nuclear detonations

Sandia’s GBD mission is appealing to Gomez and the rest of the Sandia team because it deals with space. “I think we’re all fascinated by space,” said Gomez, deputy project manager for the generation that will fly on GPSIII. “And the treaty verification work is meaningful to a lot of folks.”

Detection was a natural extension for the labs that designed the early stockpile. They understood the physics and engineering of the weapons and the detectable optical, electromagnetic pulse and X-ray signals they produce. “Those are the three that make it to space and what the GBD tries to detect,” Gomez said. Sandia develops the optical sensors; Los Alamos National Laboratory is responsible for electromagnetic pulse and X-ray sensors.

It takes about two years to build, test and integrate GBD hardware into a satellite system, Gomez said.

Five subsystems — what the teams call “boxes” — of sensors and instruments make up a GBD: three from Sandia and two from Los Alamos.

Sandia integrates system
Sandia integrates it all into an overall system and performs seemingly endless tests. When a satellite launches, everything aboard faces extreme temperatures, vibration, and shock. Sandia’s testing and computer models help determine how the rigors of launch and deployment will affect the GBD.

Teams assemble boxes from printed circuit boards, wiring harnesses and other mechanical hardware, conducting electrical and thermal testing on individual modules and pieces before assembly into the box. They follow with integration, electrical, functional, thermal and vibration tests for each box. The five completed boxes together become a GBD system or payload. The entire system is then subjected to integration, functional, electrical, thermal-vacuum and other tests before it’s shipped to the space vehicle contractor. Further electrical testing is done at the contractor site.

“Teams that build the hardware here develop a test plan suited for their subsystem and do that testing. Then we integrate the payload as the five boxes and do additional testing,” Gomez said. “At every level of integration, whether it’s the box level or a whole system at the vehicle level, you add to the testing to make sure that at every integration point the payload is operating.”

That’s especially important because the hardware can’t be repaired in space.

“Some things you can fix through software but you depend on building something that has high reliability,” Gomez said. McKenney added, “We have a very good track record for that. I think we can say that our payloads have substantially exceeded their design life.”

About thirty satellites and their detectors, representing several generations, remain in operation, some well past their design life, Gomez and McKenney said. The satellite generation before IIF was designed for 7.5 years, IIF was designed for twelve years, and GPSIII and Prime will be designed for fifteen years.

Payload must last as long as satellite
GPS drives us because we want our payload to last as long as the bird does,” McKenney said.

Sandia teams work where the payloads go as they move toward launch. Gomez described the process for IIF: Once testing showed the GBD met requirements, Sandia shipped its payload to the satellite contractor, Boeing in El Segundo, California, for more tests. Sandia notes that Sandia employees at the Boeing site provided GBD components for Boeing to install. Then the satellite went through months of additional tests, aided by the on-site Sandia team. Some 60 to 90 days before launch, Boeing shipped the satellite to Cape Canaveral, where ground crews aided by Sandia also did tests. Days after launch, a Sandia team arrived at Schriever Air Force Base, Colorado, for about a month of early orbit testing before the system was handed over to the Air Force to operate.

Even that is not the end. “We have a group that examines telemetry coming down from our payloads so we can monitor the state of health,” McKenney said. Developers use that information to improve next-generation technology. Under an agreement with the Air Force, Sandia also develops ground station components that support the Nuclear Detonation Detection System and integrate data from all the satellites.

As project lead, Gomez worked with the program office headed by McKenney, subsystem managers, team leaders and colleagues at Los Alamos to ensure GBD development and delivery stayed on schedule. “It’s very much about schedule because our payload is integrated on a satellite that the Air Force is paying a subcontractor to build,” he said. “We have equipment that bolts onto that satellite so we need to be there and we need to be there with a product that works.”

He smiled and quoted a 2015 tweet from astronaut Scott Kelly that’s been informally adopted by members of Sandia’s satellite group: “Space is hard.”