Impactor Spacecraft Encounter Sequence Design for the Deep Impact Mission

On July 4, 2005, another first in space exploration was achieved. NASA’s Deep Impact spacecraft (s/c) released a small, 350 kg Impactor s/c designed to target comet Tempel 1, estimated to be 14 km x 5 km x 5 km in size at the time of release. With a closing speed of approximately 10.3 km/s, the Impactor s/c autonomously guided itself to impact and captured 40 cm resolution images, the highest resolution images ever of the surface of a cometary nucleus, just moments before the collision. The objective of the Impactor s/c was to impact in an illuminated area viewable from the Flyby s/c. This paper describes the Impactor encounter sequence design, execution and contingency planning that contributed to the successful outcome in which all objectives were met.