Current navigation systems are heavily reliant on GPS for both commercial and military applications. While GPS provides high accuracy, it is subject to denial in a contested environment. Under this effort, NAVSYS shall deliver an alternative navigation (ALTNAV) solution that utilizes signals of opportunity (SoOP) from a combination of commercial and military space systems. This will heavily leverage prior work performed by NAVSYS to deliver PNT as a Service (PNTaaS) under contract to DARPA, Air Force, and Navy customers. Under the Phase I effort, we shall design an ALTNAV solution using SoOP signals and Software Defined Radio (SDR) technology suitable for use on a hypersonic glide vehicle. We shall demonstrate the expected ALTNAV performance through simulation and develop a plan to build a prototype solution in Phase II. We shall work with industry partners to develop a transition plan to a solution suitable for the high-velocity and challenging environmental conditions associated with hypersonic flight or low earth orbit. Under the Phase I option, we shall use prototype hardware and signal simulators to demonstrate a proof of concept of the ALTNAV solution. Under Phase II, we shall build a prototype for live demonstration of the navigation solution using space SoOp broadcasts