The key lessons of this chapter:
- Radar (radio waves up to 100 GHz) is the only sensor that independently measures position, range and velocity at long range and in all weather — but it transmits actively and thereby gives itself away.
- Infrared detects passively on heat, with excellent angle measurement, but without range information and with strong weather dependence.
- Visible light provides the best identification but requires light and visibility.
- Laser fills the gaps: exact distance measurement and weapon guidance, at the cost of depending on line of sight.
| Sensor | Active/passive | Position | Range | Velocity | All weather |
|---|---|---|---|---|---|
| Radar | active | good | very good | very good (Doppler) | yes |
| Infrared | passive | very good | no | angular rate only | limited |
| EO (light) | passive | very good | no | angular rate only | no |
| Laser | active | n/a (pointed) | excellent | possible (Doppler) | limited |
Modern weapon systems therefore always combine several sensors. In the following chapters we dive into the technology of each sensor family, starting with the most important one: radar.