How do satellite-based cameras, infrared sensors, and radar contribute to military reconnaissance?

Satellite-based cameras, infrared sensors, and radar are essential components of military reconnaissance, providing critical data for medium- and long-term warning by observing tactical preparations and identifying new military capabilities.1

• Satellite-based Cameras: These systems collect high-resolution imagery using photographic film or television-type signals. They are vital for mapping and monitoring activities on the ground, though their effectiveness depends on achieving high resolution over large distances, which requires large, heavy telescopic optics.1
• Infrared Sensors: These sensors detect thermal energy, allowing for the identification of "hot spots" such as missile exhausts, jet engines, and motor-vehicle engines. Because they detect radiation rather than reflected light, they can operate in total darkness and are highly sensitive to signals, often outperforming image intensifiers in range.2
• Radar: Unlike optical sensors, radar can operate at night and penetrate cloud cover that would otherwise obscure imagery. While conventional radar is limited by resolution and power requirements, specialized systems like side-looking radar provide higher resolution for surface target recognition. In space, radar is used to locate patterns of activity, while ground-based and airborne radar systems are fundamental for tracking aircraft and monitoring large areas.134

These technologies collectively enhance situational awareness, though they must overcome challenges like terrain clutter and the physical limitations of orbital altitudes.134