While raising or lowering an orbit is relatively cheap, rotating the orbital plane — changing inclination — is enormously expensive.
While raising or lowering an orbit is relatively cheap, rotating the orbital plane — changing inclination — is enormously expensive. Understanding why explains both why missions plan inclinations so carefully at launch, and why seeing one in tracking data is significant.
A plane change requires a velocity burn perpendicular to the current orbital velocity — not adding to it, but redirecting it.
Despite the cost, there are scenarios where plane changes are unavoidable or deliberately chosen.
In TLE data, an inclination change produces a distinctive signature across multiple fields simultaneously.
When a tracked object shows a confirmed inclination shift, it's one of the strongest signals in SSA: it proves active propulsion, it implies significant fuel expenditure, and it often signals a deliberate mission change worth paying close attention to.