The Motion Tracker is a simple surveillance device originally designed for use by search-and-rescue rescue and police services. Essentially, it is a high-powered ultrasound scanner that uses doppler-shift discrimination to filter out moving objects from its stationary background.
A moving object is shown on the tracker's display as a series of contours of probable loci, with the range and bearing given to the target. Motion trackers are often employed for perimeter surveillance, able to monitor movements of small animal-sized targets up to a range of 1000 metres in open country. The greatest advantage of the motion tracker is its ability to scan through objects; however, intervening terrain can cut this detection range quite drastically and in built-up areas the presence of walls and partitions can reduce the range to less than 20 metres.
Motion tracker operators must become familiar with their limitations. First, they are active sensors, emitting thousands of high-energy ultrasound bursts every second, and can be easily located by enemy fire. Secondly, the tracker range gate function is calibrated to reject small or slight movements (such as bugs crawling, plants waving in the wind etc.), so that very slow-moving objects can infiltrate a tracker's detection cone (as guerrillas did on many occasions during the Arcturan War). Thirdly, trackers are vulnerable to spoofing by ultrasound jammers, or 'jumping jack' decoy devices. As a result, most commanders prefer to employ motion trackers only in support of other surveillance techniques.
Colonial Marines are fitted with technology that renders them "immune" to the motion trackers carried by the USCM, thereby preventing false detection of friendly personnel, although this technology is apparently liable to malfunction on occasion. Later variants of USCM standard armor include integrated motion trackers, thereby leaving a Marine's hands free to ready their weapon.
Behind the scenesEdit
The motion tracker has become an integral part of the Alien universe, particularly with respect to the Colonial Marines. As such, it has featured in numerous video games featuring the USCM, although in most of these appearances, owing to gameplay mechanics, the motion tracker is incorporated into the player's HUD and requires no interaction to use. One exception to this is Aliens: Colonial Marines, which features the motion tracker as a separate item that must be equipped to use just as in Aliens (although an audible warning is played to alert the player when it may be needed even when the motion tracker is holstered). Also as in Aliens, the player cannot use their weapon at the same time as the motion tracker.
- Aliens/novel (First Appearance)
- Aliens vs. Predator (video game) (integrated into armor)
- Aliens: Colonial Marines (video game)