## Collision Avoidance

Once a high-risk conjunction event is identified, various avoidance scenarios are generated. An acceptable maneuver plan must produce an orbit change that reduces the collision risk, while still meeting various operational constraints. Common operational constraints include restrictions on: maneuver magnitude, maneuver direction, and the time of day when the maneuver can be executed. Often times, avoidance planning methods do not specifically target or even directly consider more than a single conjunction event at a time. SpaceNavâ€™s approach to collision avoidance is to create a maneuver sequence that reduces the total collision risk for one or more conjunction events.SpaceNavâ€™s collision avoidance software consists of the following tools:

*1. Maneuver Trade Space Utility*

The Maneuver Trade Space Utility generates a series of new trajectories spanning a set of user selected maneuver times and maneuver sizes. For each perturbed state, new points of closest approach are identified and a collision probability calculation is made. Contours of equal probability show regions of maneuver times and magnitudes that effectively mitigate the collision risk

*2. Optimal Collision Avoidance*

The Optimal Collision Avoidance Utility produces an optimal avoidance maneuver that mitigates the risk posed by multiple conjunction events by utilizing a derivative-free optimization (DFO) technique. The DFO algorithm varies both maneuver time and magnitude in order to produce a maneuver plan that reduces the total collision probability to a specified value. Operational constraints are applied by forming penalty functions that are added to the original cost function.