A reconnaissance satellite is an orbital vehicle that contains intelligence sensors. The most common form, for which there are commercial equivalents, uses photographic methods to collect imagery intelligence. A number of nations also have imaging radar satellites.
Less common are signals intelligence satellites, still deployed by several countries. The most unusual are dedicated measurement and signature intelligence collection satellites, such as the Defense Support Program, although the discipline of spectroscopic MASINT interacts with civilian earth resources observation satellites.
Their orbits vary with their mission. electro-optical MASINT Space-based Staring Infrared Sensors, which scan the globe for heat sources characteristic of missile launchers, use geosynchronous earth orbits. SIGINT satellites use low to medium orbits depending on the strength of the signal they are designed to capture. Close-look photographic satellites that are targeted on the northern Russian installations may use highly elliptical orbits to have as much low-altitude time as possible over the area of interest.