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Session C7: Military PNT Equipment: M-Code Receiver Testing

Testing Rapid M-Code Integration with Legacy Avionics on Operational Flight Platforms Using a GPS Transcoder
Andrew Halverson, Dan Dresher, Northrop Grumman Mission Systems; Cole Hedden, Josh Stevenson, UDRI; Dave Prentice, Mark Smearcheck, Air Force Research Laboratory/RYWN; Mike ”5ive” Senseney, and Jeff ”Predator” Engelker, AFLCMC;
Location: Ballroom D
Date/Time: Tuesday, Jun. 3, 4:05 p.m.

The modernized military GPS signal, or M-Code, has been in development since the 1990s and first broadcast in 2005. The benefits over GPS P(Y) code include jammer resistance, improved anti-spoof, and spot beam capability for higher receive power in select regions. However, fielding on operational flight platforms has been limited. Here, we present a proof of concept to field M-Code reception on flight platforms using a GPS transcoder, with minimal modification of the existing Selective Availability Anti-spoofing Module (SAASM) P(Y) code receivers. While somewhat of a stop-gap solution, this method may lead to significant cost and schedule savings for M-code integration.
The core of the proof of concept is a GPS transcoder. This is a GPS simulator which accepts a Position, Velocity, and Time (PVT) solution in serial NMEA format from any type of navigation source (in this case an M-code receiver), then outputs a basic civilian GPS L1 C/A signal representing exactly the signal, ephemeris, and almanac expected for that PVT solution.
The solution is installed between the original antenna electronics and GPS receiver on any platform, enabling it to receive M-Code GPS. The solution is flexible, additionally capable of receiving GNSS and smoothing with a high rate Inertial Navigation Unit (INU). Data was collected using AFRL’s Vampire MIL-STD-1553 bus analysis tool which enabled quick post processing of the data and the ability to replay the data in real-time for further analysis. Initial test results from a static and tow test on the first platform have shown close matches between the unmodified legacy system’s GPS reception and the system with the solution installed. This includes strong (> 40 dB-Hz) C/N0, figure of merit (FOM) of 1, and > 6 satellites acquired.
In this presentation, we will present results and findings from multiple ground and flight tests, including the effects of flight dynamics on the ability of the M-code receiver and GPS transcoder to seamlessly mesh with the legacy receivers. We will also present plans for future demonstrations and options for legacy platforms to integrate M-code.

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