The second in a series of explainer blogs by Merkhet Solutions Advisor Pat Diamond.
What the heck is this CPNT, Complementary Position Navigation and Time, stuff really? What are the threats we keep hearing about? Good questions both. In the first blog of this series, we talked about the reliance of critical infrastructure on GPS for positioning, timing and navigation. The risk this introduces is at the heart of this discussion. How real is the risk? Can we mitigate? Dramatic topics to be sure.
Let’s start with what is this PNT that needs a complementary system? PNT, Position where am I? Navigation, how do I get there? And then, Timing, which is the enabler used to answer the previous two questions. When a GNSS (Global Navigation Satellite System) receiver wants to figure out its location the most common method in architectures is based upon RF distributed systems, such as a constellation of satellites with each reporting its location in space is called multilateration. Sorry to dive into a bit of tech here, but multilateration uses the value of the multi-signal time difference of arrival math to figure out its location. Notice that time has crept into this process. Various terrestrial transmission sites as source, and again figuring out location, use a physical method called ranging. This process measures the flight time of an optical or electrical signal from receiver to source and back divided by two, again time creeps into this. What this is saying without so many words, time is used in lots of mathematical processes regarding locating or navigating around as an event measuring device. In reality what else is time good for? Time will be discussed in much more detail in a future version.
OK, so the GPS constellations of satellites each have precise atomic clocks on board so they can send their value of time to the receiver community. This value of time across the constellation has coordinated time value precision on the order of nanoseconds. These clocks are updated daily from ground stations connected to the United States Naval Observatory (USNO), which is the U.S. mandated source of Universally Coordinated Time (UTC).
There are really two GPS PNT impairments CPNT needs to be targeted towards. The easiest is mitigation of jamming and spoofing interruptions. In these cases, at least the basic GPS PNT technology is healthy just being locally impacted. The other and much more serious case is loss of GPS PNT at scale. By this, I mean GPS is gone, probably taken out by an anti-satellite attack by our adversaries. China and Russia have demonstrated anti-satellite kinetic capability.
The next section will focus on GPS PNT impacts that are interruptions and not an at scale issue. We will get to the at scale issue later in this series. Now on to CPNT. This acronym was created by the Department of Transportation to define the techniques and technologies they test to determine if these can provide some of the PNT solutions lost in jamming or spoofing. DOT has no plans or funding to implement any of these solutions to back up or mitigate a GPS PNT interruption. The plan is to build a gigantic database with reams of text describing each tested model to allow U.S. entities to review these and decide if they want to use any of them to solve their specific PNT problem. Personally, I don’t recognize this approach as compliance with Executive Order 13905, which directed the Department of Transportation to be responsible for civilian and industrial use of GPS PNT. But at the end of the day I was not asked to define what compliance with the order actually means. I guess this is better than the previous approach of “admiring” the PNT problem.
Just for fun, let’s postulate what the scope of the problem these CPNT capabilities will need to mitigate. First in fairness today, there is no known solution for the entire GPS PNT solution. I know there are LEO (Low Earth Orbit) satellite vendors that will take exception to my comment. Fine, they need to defend themselves to stay relevant in this solution market. The only LEO with mature technology offering a CPNT solution today is Iridium. This private company was started as Motorola in the 1990s to offer satellite telephones to users. After ownership changes and investment, it now offers satellite telephones and a proprietary CPNT capability, the performance of which I cannot speak to factually. Let’s wait for the DOT report to make up our minds. Bottom line today, show me! Only one can offer something the others cannot.
The first issue to realize is that the GPS PNT solution covers the entire United States, so in my mind a valid CPNT solution would do the same. One argument the technology pretenders use to justify their solutions is jamming and spoofing are local events generally, not CONUS wide. Fair enough, however, since these events can occur anywhere in the CONUS, in order for a mitigation solution to be viable it would also need to be CONUS wide, Darn, that makes this much harder to accomplish.
In fairness to the industrial and commercial participants in the PNT marketplace – and there are many of them – serving client bases in all industries where PNT is a component of that industry's business. Several of the industries noted below use local solutions for their time and location needs. Many of them buy point-of-use pseudo-PNT solutions in their locations since CONUS-wide or buying a service is too expensive.
For example, a user of robotic systems needs a means to control the motion of the robots, this is a PNT problem elegantly solved by creative PNT technology. Aviation is also a huge user of PNT technology and we are all better served and safer for it. Autonomous vehicles, think Waymo for example, use PNT to control their vehicles. Your DoorDash driver uses PNT to execute food order delivery. There are PNT technologies inside vehicles used to interconnect and facilitate functional attributes of your vehicles. There are PNT technologies used in power grids and mobile wireless networks to distribute “common time base” data to needing subsystems. And, time is the cornerstone to each of the noted cases above operating as expected. The BPS signal can be the time source for all of these examples of PNT usage.
Stay tuned for more on how BPS delivers precision time in my next blog.