"I've designed this tracking device. You just set it to search for a moving object, like so. Hasn't got much of a range, but when you get within a certain distance, it will start to give off a signal."
Ash, regarding the tracking device (from Alien)
Tracking device

The tracking device.

The tracking device, also known as the portable tracker,[1] was a surveillance device designed and built by the synthetic Ash. As its name implies, it was capable of detecting movement and providing corresponding locating information for the user.

In June 2122, 2 of the devices were constructed by Ash for use by the crew of the USCSS Nostromo in their efforts to find and kill the fully grown Alien (which the crew believed to still be a Chestburster). After the crew discovered the size of the creature when Samuel Brett was killed by it, Arthur Dallas came up with a plan to flush the Alien from the Nostromo's ventilation shafts and into the ship's main airlock so that it could be expelled into space, while Ash and Joan Lambert tracked its position with the tracking devices. After the plan failed when Dallas was killed, the devices were left in the Nostromo's mess hall and were ultimately destroyed when the ship's self destruct system, activated by Ellen Ripley, detonated.


"What's it key on?"
"Micro changes in air density."
Ripley and Ash (from Alien)
TD detecting movement

The tracker's display showing movement.

The tracking device keyed on "micro changes in air density." When motion was detected within a certain distance, the device would begin to give of a signal and the source of the movement would be represented as a dot on the tracker's display. However, the range at which the device could detect movement was short. The tube on the front of the tracker had "ELECTRO MAG FIELD TRACE" written on it.


Dallas holding tracker

Dallas holding a tracking device sideways.

After a Chestburster erupted from Thomas Kane in 2122 aboard the USCSS Nostromo, two tracking devices were constructed by the Hyperdyne Systems 120-A/2 Synthetic Ash in an attempt to locate the creature.

After the destruction of the Nostromo, all known tracking devices were destroyed along with the ship.

Non-canon depictions[]

Alien novelization[]

Main article: Alien (novel)

In the novelization of Alien, the motion tracker is quite different to the version used on screen. It is far smaller, being only around the size of a communicator.[2] When movement is detected, a tiny red light below the main screen illuminates, it beeps querulously[3] and a crudely marked needle gauge set in the unit's face[4] displays distance.[3][5] The tracker is also capable of being silenced by touching a control, which Ash does when the crew are searching the ship and he detects Lambert or Dallas.[3]

Unlike the tracker seen in the film, Ripley notes that it looks like it was assembled in a factory, instead of something "hastily cobbled together in a commercial tug's science lab."[1]

Alien: The Illustrated Story[]

Main article: Alien: The Illustrated Story

In Alien: The Illustrated Story, Parker beheads Ash with a tracking device, not a fire extinguisher as in the film.

Aliens: Colonial Marines[]

Main article: Aliens: Colonial Marines (2013 video game)

In the 2013 video game Aliens: Colonial Marines DLC map "Nostromo", two unusable tracking devices are seen on the cafeteria table in the middle of the map.

Alien: Isolation[]

Main article: Alien: Isolation
Isolation TD

The tracking device in "Crew Expendable".

In the Alien: Isolation DLC "Crew Expendable", the tracking device can be used by the player. For gameplay reasons, the tracking device features a screen like on the main game's Motion Tracker, allowing the player to more easily see where the Alien is. Strangely, the circular device has been moved from the left side of the tracking device to the right, despite the screen also being added to the right side.

Behind the scenes[]


TD left

The left side of Bob Burns' tracker. Note the ice cube tray.[6]

The tracking device prop was built by Ron Cobb.[7] The main body of the prop is a Panasonic Ranger-505 (or more likely the National Commando 505, National being a brand used by Panasonic outside the United States and presumably in the United Kingdom, where the film was made) portable TV with various cosmetics added,[8] including an ice cube tray[9] (left side), a Stadium black plastic 7" gully cover (right side), a 45mm diameter Vernier dial (top), and cut down plastic speaker grills (right, left and back side).[8] The prop also features colored lights, a small television viewer, and a sound output to indicate detected movement.[7] The key used with the prop is from a 1970's Vauxhall car.[8]

At least two props of the tracker were made for Alien, with one currently owned by collector Bob Burns. However, Burns's tracker is not complete, missing "some of the knobs and switches", as well as the tube that started to the right of the gully cover and ran in front of the tracker, connecting with the front end of the handle. Strangely, a grill that does not appear in the film was added at an unknown time below the "probe" on the front of the tracker.[8]

Aliens Predator Collectible Card Game use[]

Sentry Gun Control

"Sentry Gun Control".[10]

In the Aliens/Predator Collectible Card Game, the card "Sentry Gun Control" (312) uses a picture of the tracking device, despite the controllers for the Sentry Guns in Aliens being GridCase laptops.


The tracking device was presumably the inspiration for the Motion Tacker seen in Alien's sequel, Aliens. Additionally, the ice cube tray on the tracking device inspired to use of an ice cube tray-like detail on the motion tracker in Alien: Isolation.


  • When the trackers are first introduced in the film, they emit a high-pitched humming when they register movement, as heard when they are first tested and when Ripley, Parker and Brett mistakenly detect Jones. However, when Dallas is in the air shafts, the devices instead issue a completely different beeping tone.




See also[]