How we beat 2019 PDC to NYC by 2 years, within 2 years, 2 years ago

For the Planetary Defense Conference Exercise 2019, we set out to find ways to obtain the earliest possible characterization of the incoming (fictitious!) asteroid, 2019 PDC. After a partially successful deflection, a 'small' fragment was still bound for impact. The location was only known two weeks before impact - the time left for the evacuation of the larger New York City metropolitan region. With experience in Near-Earth Object (NEO) exploration mission design, solar sail and solar-electric propulsion (SEP) technology for small spacecraft, agile responsive design and integration, and from previous PDC Exercises, the importance of earliest possible information on impact location and energy was obvious. NEO in-situ exploration can provide invaluable information not just for deflection actions but also for planetary science and resource utilization. This is only possible with space missions closely approaching the asteroid. Expecting a solar sail mission flying in the 2020s could be re-directed, a unique feature of solar sailing, we searched for multiple rendezvous missions at initial sail technology characteristic accelerations of =2 years, within