A tethered, moored or captive balloon is a balloon that is restrained by one or more tethers attached to the ground so it cannot float freely. The base of the tether is wound around the drum of a winch, which may be fixed or mounted on a vehicle, and is used to raise and lower the balloon.
A balloon is a form of aerostat, along with the powered free-flying airship, although the American GAO has used the term "aerostat" to describe a tethered balloon in contrast to the powered airship.
Surveillance aircraft or observation aircraft are aircraft used for aerial surveillance. They are primarily operated by military forces and government agencies in roles including intelligence gathering, maritime patrol, battlefield and airspace surveillance, observation (e.g. artillery spotting), and law enforcement.
Surveillance aircraft usually carry limited defensive armament, if any. They do not require high-performance capability or stealth characteristics and may be modified civilian aircraft. Surveillance aircraft have also included moored balloons (e.g. TARS) and unmanned aerial vehicles (UAVs).