COLA (Collision Avoidance Manoeuvre)

Collision avoidance — COLA in operations shorthand — is the end-to-end process of acting on a dangerous conjunction: evaluating the warning, deciding whether to move, designing the manoeuvre, and executing it. Screening systems compare each protected satellite against the catalogue days ahead; when a predicted approach breaches the operator's thresholds — typically a collision probability above about 1 in 10,000, or miss distances inside a protection volume — a manoeuvre plan is built. The burns themselves are tiny, often centimetres per second of delta-v: applied half an orbit or more before the encounter, a small along-track nudge shifts the satellite's arrival time at the crossing point, converting a possible hit into a clean miss measured in kilometres. The discipline's hard part is decision-making under uncertainty — probabilities swing as fresh tracking arrives, manoeuvring costs propellant and disrupts missions, and mega-constellation fleets now automate much of the loop, executing thousands of avoidance manoeuvres per year.