The latest in a series of test satellites that has advanced the art of space-based navigation is being planned by the U.S. Air Force in a bid to make GPS more resilient in contested environments.                                                                       

The third Navigation Technology Satellite (NTS-3) is planned for launch in 2022 and will follow NTS-1 in 1974 and NTS-2 in 1977, which qualified the rubidium and cesium clocks that form the backbone of GPS.

Faced with the certainty that GPS will be degraded or denied in future major conflicts, the U.S. is exploring ways to make the signal more robust as well as developing alternatives to GPS.

According to a request for information (RFI) issued by the Air Force Research Laboratory (AFRL), NTS-3 will broadcast additional signals on the L1 frequency band, improve anti-jam performance, counter spoofing, and modify all layers of the signal to enhance resiliency and improve performance.

L1, centered at 1575.42 MHz, is the most used GPS frequency band, carrying the open C/A-code signal, the encrypted P/Y code, modernized military M code and L1C civil signal.

NTS-3 will also investigate ways to cyber-protect GPS, including assured-by-design software techniques to improve resiliency of the space and ground segment in a cyber-warfare environment. Other goals of the test satellite are to improve onboard detection and notification of GPS signal anomalies.

AFRL also plans to test advanced clock and ephemeris (satellite orbital data) correction technologies, as well as antenna configurations that ensure GPS availability and signal strength for terrestrial and space users.

On the ground, the lab plans to investigate alternative methods of reconstituting the GPS ground segment after an attack. AFRL will also test automated and “lights-out” operation of the ground segment to reduce operating costs.

The RFI calls for NTS-3 to reach technology readiness level 6 through ground testing no later than 2021, to support a launch in 2022. The satellite will be designed to operate for 1-3 years in orbit.