Air Force space experiment will seek to demonstrate multi-orbit satellite navigation

The Air Force Research Laboratory's NTS-3 will broadcast PNT signals from geostationary orbit to supplement GPS satellites in medium Earth orbit

COLORADO SPRINGS — The Navigation Technology Satellite-3 (NTS-3), an experiment funded by the Air Force Research Laboratory, will fly to a geostationary Earth orbit in 2023 and will be used to augment the positioning, navigation and timing (PNT) services currently provided by GPS satellites.

The concept of adding another layer of PNT could be significant as the Pentagon fears that signals from GPS satellites in medium Earth orbit (MEO) could be jammed or disrupted during a conflict. 

“We wanted to look at how you use a constellation that is truly a hybrid architecture,” Joanna Hinks, NTS-3 deputy program manager at AFRL, told reporters April 7 at the Space Symposium.

When NTS-3 was first conceived, “initially we looked at MEO,” she said. But later it was decided that GEO would be a better location for NTS-3 so researchers could assess the potential benefits of having a multi-orbit PNT architecture. 

“The idea here is that we already understand very well how navigation works from MEO,” Hinks said. 

Another goal for NTS-3 is to test software-defined radio technologies so signals can be reprogrammed to confuse and defeat jammers. A ground system being developed by Parsons Corp. would integrate GPS and NTS-3 signals and assess the network’s performance in a jamming environment. 

“Reprogrammable signals is one major emphasis,” said Hinks.  This is going to require a flexible ground system and user receivers “that can handle reprogrammability.”

The 1,250-kilogram satellite is being assembled at an L3Harris facility in Palm Bay, Florida. The company in 2018 won an $84 million contract from AFRL to build NTS-3. L3Harris is integrating a digital mission data unit on a Northrop Grumman ESPAStar bus.

The satellite is projected to launch on the USSF-106 mission planned by the U.S. Space Force. This would be the first national security mission to fly on United Launch Alliance’s new Vulcan Centaur rocket.

Once in orbit, NTS-3 would provide PNT services only over the United States “because of the ease of access and the ability to easily install receivers in in locations of interest,” Hinks said. 

Because NTS-3 will be in geostationary orbit, “it is persistently in view of one location,” she said. By comparison, GPS satellites in six orbital planes circle the Earth twice per day broadcasting PNT signals.

With a GEO satellite “you don’t need to worry that you’ve only got one or two satellites, and they’re going to be gone in a few hours and you won’t be able to see them,” said Hinks. “That’s one of the big things, but we are really just starting to lay the groundwork for how you could have a constellation that it’s not just in one orbit regime. That’s a big part of the experiment.”