Mission Design for Deep Space Constellation Deployed on Asteroid Flyby Cyclers

The U.S. Decadal Survey highlights the critical role of rapid-response flyby missions in planetary defense, enabling timely characterization of hazardous near-Earth objects (NEOs) and supporting mitigation strategies. A traditional mission architecture is to send a spacecraft as soon as a target object is discovered; however, this approach requires a dedicated launch vehicle capable of rapid response, which is hampered by technical and logistical hurdles for some countries, including Japan. As an alternative, we propose a mission architecture in which multiple small spacecraft are pre-deployed into deep space on Earth-resonant flyby orbits. This allows for opportunistic flybys of NEOs as they are discovered, enabling routine monthly encounters across a constellation of ~10 spacecraft. Our numerical simulations demonstrate the feasibility of reaching hazardous asteroids using this approach. To maximize science return during the brief flybys, we are developing high-fidelity proximity-operations concepts, including closed-loop relative navigation that fuses computer vision measurements with advanced filtering and a camera-simulation pipeline that informs our sensor selection and maneuver plan. Our architecture offers a practical, accessible path to continuous NEO reconnaissance and a stronger planetary defense posture.