Uses There are a wide variety of UGVs in use today. Predominantly these vehicles are used to replace humans in hazardous situations, such as handling explosives and in bomb disabling vehicles, where additional strength or smaller size is needed, or where humans cannot easily go. Military applications include surveillance, reconnaissance, and target acquisition. They are also used in industries such as agriculture, mining and construction. UGVs are highly effective in naval operations, they have great importance in the help of Marine Corps combat; they can additionally avail in logistics operations on to the land and afloat. UGVs are also being developed for peacekeeping operations, ground surveillance, gatekeeper/checkpoint operations, urban street presence and to enhance police and military raids in urban settings. UGVs can "draw first fire" from insurgents—reducing military and police casualties. Furthermore, UGVs are now being used in rescue and recovery mission and were first used to find survivors following 9/11 at Ground Zero. Space Applications NASA's Mars Exploration Rover project included two UGVs, Spirit and Opportunity, that performed beyond the original design parameters. This is attributed to redundant systems, careful handling, and long-term interface decision making. Opportunity (rover) and its twin, Spirit (rover), six-wheeled, solar powered ground vehicles, were launched in July 2003 and landed on opposite sides of Mars in January 2004. The Spirit rover operated nominally until it became trapped in deep sand in April 2009, lasting more than 20 times longer than expected. Opportunity, by comparison, was operational for more than 14 years beyond its intended lifespan of three months. Curiosity (rover) landed on Mars in September 2011, and its original two-year mission has since been extended indefinitely. Civilian and commercial applications Multiple civilian applications of UGVs are being implemented to automatic processes in manufacturing and production environments. They have also been developed as autonomous tour guides for the Carnegie Museum of Natural History and the Swiss National Exhibition Expo. Agriculture UGVs are one type of agricultural robot. Unmanned harvesting tractors can be operated around the clock making it possible to handle short windows for harvesting. UGVs are also used for spraying and thinning. They can also be used to monitor the health of crops and livestock. Manufacturing In the manufacturing environment, UGVs are used for transporting materials. They are often automated and referred to as AGVs. Aerospace companies use these vehicles for precision positioning and transporting heavy, bulky pieces between manufacturing stations, which are