Space situational awareness is knowing what is in orbit and what it is doing: detecting and cataloguing objects, predicting close approaches, spotting manoeuvres, break-ups and re-entries. It is the information layer that keeps an increasingly crowded orbital environment operable.
Understanding SSA
From photons to warnings
The SSA pipeline runs: sensors collect angles, ranges and Doppler; correlation matches each track to a catalogued object (or flags an unknown); orbit determination fits an updated state with uncertainty; propagation projects everything forward; and screening hunts for close approaches, publishing conjunction data messages to the operators involved. Each stage fights the same enemy — uncertainty growth between observations — which is why sensor diversity and revisit rate define catalogue quality.
The scaling challenge
The tracked population has multiplied within a decade — driven by mega-constellation deployment, better sensors finding smaller debris, and fragmentation events. Screening workload grows roughly with the square of the population, and human-in-the-loop processes are giving way to automated warning triage and even autonomous avoidance manoeuvres. The open questions are as much governance as engineering: common standards, liability, and who coordinates when two operators' satellites converge.