Skysweeper was an anti-aircraft gun

Anti-aircraft warfare

NATO defines air defence as "all measures designed to nullify or reduce the effectiveness of hostile air action." They include ground and air based weapon systems, associated sensor systems, command and control arrangements and passive measures. It may be to protect naval, ground and air forces...

 deployed in the early 1950s by both the U.S. Army

United States Army

The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...

 and U.S. Air Force

United States Air Force

The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...

. It was the first such gun to combine a gun laying

Gun laying

Gun laying is the process of aiming an artillery piece, such as a gun, howitzer or mortar on land or at sea against surface or air targets. It may be laying for direct fire, where the gun is aimed similarly to a rifle, or indirect fire, where firing data is calculated and applied to the sights...

 radar, M10 analog computer (director)

Director (military)

A director, also called an auxiliary predictor, is a mechanical or electronic computer that continuously calculates trigonometric firing solutions for use against a moving target, and transmits targeting data to direct the weapon firing crew....

, and an autoloader

Autoloader

An autoloader or auto-loader is a mechanical aid or replacement for the personnel that load ordnance into crew-served weapons, such as tanks and artillery...

 on a single carriage.
Anti-aircraft guns naturally fall into several categories, each for a different altitude

Altitude

Altitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...

 and speed

Speed

In kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as...

 requirement. High-altitude targets require very large guns to get the needed power into the shell to reach those altitudes, but at the same time have the advantage of not needing to move very fast because at that range the change in angle of the target was small—consider the seemingly slow motion of an airliner

Airliner

An airliner is a large fixed-wing aircraft for transporting passengers and cargo. Such aircraft are operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is typically defined as an aircraft intended for carrying multiple passengers in commercial...

 at cruise altitude.