frontline: missile wars: excerpts: technology: faith or reason | PBS: "How long does the boost phase last? It varies. One of the countermeasures against a boost-phase system is something that's known as a quick-burn system, in which you minimize the amount of time that that very hot plume -- thousands of degrees -- is visible, because we have sensors that will pinpoint it. But it lasts long enough for us to believe we can track the missile with great accuracy."