With the growing jamming capabilities of Russia and China, the SASC (United States Senate Committee on Armed Services) has asked the US Department of Defense (DoD) to provide Combatant Commander’s alternate position, navigation and timing (PNT) systems to GPS within two years.
As per the Section 1601 of the 2021 National Defense Authorization Act (NDAA), SASC says, the two-year deadline is “consistent with” urgent needs voiced by commanders in the field. The DoD must:
- Prioritize and rank order the mission elements, platforms, and weapons systems most critical for the operational plans of the combatant commands;
- Mature, test, and produce for such prioritized mission elements sufficient equipment
- to generate resilient and survivable alternative positioning, navigation, and timing signals; and
- to process resilient survivable data provided by signals of opportunity and on-board sensor systems; and
- Integrate and deploy such equipment into the prioritized operational systems, platforms, and weapons systems.
Delayed from an April launch date in response to the spread of the novel coronavirus, the third GPS III satellite was launched into orbit June 30 on a SpaceX Falcon 9 rocket. In addition to being SpaceX’s first launch with the US Space Force as well as the new service’s third launch since its inception, this event saw the first successful booster recovery during a National Security Space Launch.
GPS Vulnerabilities
Earlier this year in April, the Space Force announced that it had accepted as operational Lockheed Martin’s latest anti-jam upgrade to the software system for the stopgap operational control system, called Ground Operational Control System, built to fill in until the full OCX is available (currently planned for 2023). However, there is difference of opinion amongst experts, many believe that improvements to GPS III are not enough — military coded GPS III signals will still be weak compared to the strength of the signals commonly used to disrupt them. The vast majority of GPS users and critical infrastructure will see no improvement at all. In November 2018 DoD has put out a PNT strategy document that acknowledges that GPS vulnerabilities are systemic to the nature of a satellite-based system, and calls for a “layered system” including terrestrial-based options and regional networks.
In the document SASC has not specified the explicit non-GPS technologies they have in mind that could provide backup PNT capabilities. Experts say that SASC is looking for solutions that would provide alternative signal sources (which could be from other satellites, including non-US GNSS systems) and for receivers that can process ‘data provided by signals of opportunity and on-board sensor systems.’ The later part could include using things like comms signals coming from other systems (think proliferated commercial LEO systems, for example) to triangulate one’s position. The Non-US Global Navigation Satellite Systems include Europe’s Galileo, Russia’s GLONASS and China’s newly completed Beidou constellations.
Race Against Time
DoD and the services do have a number of efforts underway to provide GPS back-up. These include the Army’s developing WarLoc that would use inertial guidance units embedded in soldiers’ boots; and DARPA’s Spatial, Temporal, and Orientation Information in Contested Environments (STOIC) program looking at three technical areas: 1) earth-fixed navigation using very low frequency (VLF) signals; 2) deployable optical clocks based on technology developed under the DARPA QuASAR program; and 3) precision time transfer and ranging over data links. But none these efforts is very far along.
The technologies that DoT has been testing are supposed to be ready or nearly ready (according to DoT’s May 3, 2019 Request for Information). However, experts say there is a big question as to whether or not any of them is any more ready than DoD’s efforts to be fielded within two-years.
