When keeping track of enemies, airborne instruments typically collect these different types of information:
IMINT Imagery Intelligence Still and video cameras as well as other sensors on satellites and aircraft create images of Earth’s surface. The instruments can passively detect radiation in visible, infrared, even ultraviolet ranges of the spectrum or actively illuminate targets and capture the reflection. Because the RQ-170 is intended to be stealthy, its suite of imagery collection devices is almost certainly passive. (Radar and other active illuminators are the equivalents of shining flashlights in the dark, allowing sensors on the ground to detect an airplane’s presence.)
SIGINT Signals Intelligence Antennas also collect a range of electromagnetic radiation, including cellphone conversations, text messages, two-way radio conversations, automated telemetry (for example: regularly transmitted diagnostic data on a fuel pipeline), Wi-Fi signals, and other forms of wireless data. This raw data goes to a processing facility, where systems decrypt (if necessary), analyze, and prepare a deliverable intelligence “product.” Not all SIGINT collectors look like flying cellphone towers; some, like the F-22 Raptor, have antennas embedded in their skin.
MASINT Measurement and Signature Intelligence A senior military intelligence officer calls MASINT “the least known and understood, but arguably the most reliable form of intelligence, and one of the most important.” Some sensors detect uniquely identifying spatial and temporal intervals and timing patterns in electronic transmissions; others detect uniquely identifying chemical and elemental signatures of substances and materials; still others collect data that enable analysts to identify a target by the way it moves.