气层前后, 这个说法是错的。天基红外系统可以探测到从点火，助推段，中段，再入段各个阶段的导弹。

The SBIRS architecture has been allocated four missions:
– missile warning: detection of missiles during launch and boost,
– missile defence: support to missile defence by tracking targets from initial boost
phase to re-entry; the data will be relayed to missile defence platforms,
– technical intelligence: valuable data for missile characterisation, phenomenology
and other target data will be provided,
– battle space characterisation: assessment of battle damage and tracking
IR-intensive events to improve battle field situational awareness.