The Defense Advanced Research Projects Agency (DARPA) is soliciting innovative proposals to develop radiofrequency (RF) system architectures that employ and maintain optical timing precision in form factors and ruggedness traceable to compact mobile land, air, and space-based defense platforms. Proposals to the Radiofrequency (RF) Architectures Applying Photonic Timing and Routing (RAAPTR) program should investigate innovative approaches that enable revolutionary advances in vibration-hardened, ultra-low phase noise photonic oscillators; vibration-hardened, low phase noise ancillary analog and mixed-signal components; and high-performance analog and digital subsystem architectures that apply RAAPTR components to defense-relevant use cases and mission capabilities. Specifically excluded is research that advances non-optical methods of microwave generation or that results in evolutionary improvements to the existing state of practice. A Controlled Unclassified Information (CUI) addendum provides additional details on the RAAPTR program. Please see Attachment A of this Program Solicitation (PS) for instructions on how to request the CUI Addendum. The Proposer must request the CUI Addendum by the deadline stated in the Overview section.