IMO Tracking requires continuing for at least how many out of how many consecutive sweeps?

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Tracking relies on proving a target’s continued presence over a practical window, not just a single successful sweep. To keep a radar track valid, you must see the target being tracked in at least five of the next ten consecutive sweeps. This half-of-the-window rule helps distinguish genuine targets from brief clutter, false echoes, or momentary misses due to maneuvering or sensor issues. If the target fails to reach that five-in-ten threshold, the system drops the track so you don’t carry forward unreliable information.

Other thresholds would either be too permissive or too strict for typical radar returns. For example, three in eight is a looser standard and could allow spurious tracks through, while seven in twelve or four in nine impose different proportions that aren’t the established balance used here. Five in ten is the standard, easy to remember, and provides a reliable compromise between stability and responsiveness.