M55 GUARD DOG Sentry Gun

The is a UNSC Sentry Gun.

Description
The is a remote Sentry Gun used by the UNSC. The unit weighs 18.9 kg and can be assembled by a single marine in 140 seconds. The unit consists of a single, self contained barrel assembly, ammunition drum, sensor systems, the barrel and breech assembly, the magazine and the fire control computer and a collapsing, motorised tripod. A radio datalink connects the sentry the UNSC War Net, where in it can be interfaced by a single Marine, A.I. or routed to a remote computer, when accessed by the correct password. Once in place, the sentry gun may be programmed to sweep wide arcs up to 360 degrees, though it is subject to terrain and emplacement restrictions, though Marine Corp doctrine is to place several sentries to cover smaller, interlocking fields of fire in a narrow band in front of it. The mounts a 9x4.5mm machine gun with a drum of 700 rounds. The weapon fires at 1200 rounds per minute and uses a electronically cooled, titanium-chrome cold hammer forged barrel and carbon fibre inserts.

The sentry gun's main sensor array is mounted above the barrel, aligned to cover a forward cone in front of the weapon. The sensor suite consists of a cooled infra-red detector, full colour day/night optics, a two stage passive infra-red/ultrasonic motion tracker and a LIDAR. If a target’s visual or thermal profile is recognised, the fire control system may be set just to monitor those specific targets using infra-red or optical. However, the system is usually set to multi-spectral mode, where the sentry's fire control system correlates received data from the different sensors to obtain a complete target profile. If the sentry is set to 'auto-remote', it will interrogate all targets in its sensor cone, using an Identification Friend Foe transponder. All UNSC and other AUR aligned personnel carry an IFF transponder in their communication gear which sends back a coded radio signal when interrogated. If the IFF return is positive, the weapon will let them pass, otherwise it will open fire. If the system is set to 'manual override' or 'semi-automatic', this information is flashed back to the command console, where the system operator can decide whether or not to fire. If the returned IFF is incorrect, it can act as a beacon for the turret.

The stabilized tripod automatically adjusts the boresight along the Y-Axis. The sentry gun's fire control computer limits the number of rounds expelled based upon the the target profile so that  ammunition is conserved for longer operations.