The system consists of three main components: the Command Launch Unit, the Launch Tube Assembly and the missile itself. Each missile contains 250
microprocessors.
Command launch unit The gunner carries a reusable
command launch unit (CLU, pronounced "clue"), which is the targeting component of the two-part system. The CLU has three views, which are used to find, target, and fire the missile and may be used separately from the missile as a portable
thermal sight. Infantry personnel are no longer required to stay in constant contact with
armored personnel carriers and
tanks with thermal sights. This makes them more flexible and able to perceive threats they would not otherwise be able to detect. In 2006, a contract was awarded to Toyon Research Corporation to begin development of an upgrade to the CLU, enabling the transmission of target image and
GPS location data to other units.
Day field of view The first view is a 4× magnification day view. It is mainly used to scan areas in visible light during daylight operation. It is also used to scan immediately before sunrise and after sunset, when it is difficult to focus the thermal image due to the natural rapid heating or cooling of the environment.
Wide field of view The second view is the 4× magnification night view, a
wide field of view (WFOV) which shows the gunner a thermal representation of the area viewed. This is the primary view used, due to its ability to detect
infrared radiation and find both troops and vehicles otherwise too well hidden to detect. The screen shows a "green scale" view which can be adjusted in both contrast and brightness. The inside of the CLU is cooled by a small
refrigeration unit attached to the sight. This greatly increases the sensitivity of the thermal imaging capability, since the temperature inside the sight is much lower than that of the objects it detects. Due to the sensitivity this causes, the gunner is able to "focus" the CLU to show a detailed image of the area being viewed, by showing temperature differences of only a few degrees. The gunner operates this view with the use of two hand stations similar to the
control stick found in modern
cockpits. It is from this view that the gunner focuses the image and determines the area that gives the best heat signature on which to lock the missile.
Narrow field of view The third field of view is a 12× thermal sight, used to better identify the target vehicle. Once the CLU has been focused in WFOV, the gunner may switch to a
narrow field of view (NFOV) for target recognition before activating the
seeker FOV. Once the best target area is chosen, the gunner presses one of the two triggers and is automatically switched to the fourth view, the
seeker FOV, which is a 9x magnification thermal view. This process is similar to the automatic zoom feature on most modern cameras. This view is available along with the previously mentioned views, all of which may be accessed with the press of a button. However, it is not as commonly used as a high-magnification view, because it takes longer to scan a wide area. This view allows the gunner to further aim the missile and set the guidance system housed inside it. It is when in this view that information is passed from the CLU, through the connection electronics of the launch tube assembly, and into the missile's guidance system. If the gunner decides not to fire the missile immediately, they can cycle back to the other views without firing. When the gunner is satisfied with the target picture, a second trigger is pulled to establish a "lock". The missile launches after a short delay.
Lightweight CLU The US Army developed a new CLU as an improvement over the Block I version. The new CLU is 70% smaller, 40% lighter and has a 50% battery life increase. Features of the lightweight CLU are: a long-wave
infrared (IR)
thermographic camera; a high-definition display with improved resolution; integrated handgrips; a five-megapixel color camera; a laser point that can be seen visibly or through IR; a far target locator using GPS, a laser rangefinder, a heading sensor, and modernized electronics. Compared to the Block I Command Launch Unit (CLU), the Lightweight CLU will double target identification range and increase system engagement range from 2.5 kilometers (km) to 4 km. The Javelin Joint Venture received its first low-rate production contract for the LW CLU in June 2022. 200 units will be delivered before full-rate production is expected to initiate in 2023, which will increase the production rate to 600 per year. First delivery is slated for 2025.
Launch tube assembly Both the gunner and the ammunition bearer carry the Launch Tube Assembly, a disposable tube that houses the missile and protects the missile from harsh environments. The tube has built-in electronics and a locking hinge system that makes attachment and detachment of the missile to and from the Command Launch Unit a quick and simple process.
Missile Warhead The Javelin missile's tandem warhead is a
high-explosive anti-tank (HEAT) type. The Javelin F-model was planned to begin deliveries in early 2020.
Propulsion , April 2022,
Fort CarsonMost rocket launchers require a large clear area behind the gunner to prevent injury from backblast. To address this shortcoming without increasing recoil to an unacceptable level, the Javelin system uses a
soft launch mechanism. A small launch motor using conventional rocket
propellant ejects the missile from the launcher, but stops burning before the missile clears the tube. The flight motor is ignited after a delay to allow sufficient clearance from the operator. To save weight, the two motors are integrated with a
burst disc between them. It is designed to tolerate the pressure of the launch motor from one side, but to easily rupture from the other when the flight motor ignites. The motors use a common nozzle. The flight motor's exhaust flows through the expended launch motor. Because the launch motor casing remains in place, an unusual ring-shaped igniter is used to start it. A normal igniter would be blown out of the back of the missile when the flight motor ignited and could injure the operator. Since the launch motor uses a standard NATO propellant, the presence of lead beta-resorcylate as a burn rate modifier causes an amount of
lead and
lead oxide to be present in the exhaust. Gunners are asked to hold their breath after firing for their safety. In the event that the launch motor malfunctions and the launch tube is overpressurized—for example, if the rocket gets stuck—the Javelin missile includes a pressure release system to prevent the launcher from exploding. The launch motor is held in place by a set of
shear pins, which fracture if the pressure rises too high. They allow the motor to be pushed out of the back of the tube.
Seeker As a
fire-and-forget missile, after launch the missile has to be able to track and destroy its target without assistance from the gunner. This is done by coupling an onboard imaging IR system, separate from CLU imaging system, with an onboard tracking system. The gunner uses the CLU's IR system to find and identify the target, then switches to the missile's independent IR system to set a track box around the target and establish a lock. The gunner places brackets around the image for locking. The seeker stays focused on the target's image, continuing to track it as the target moves or the missile's flight path alters, or attack angles change. The seeker consists of three main components:
focal plane array image sensor, cooling and calibration, and stabilization.
Focal plane array (FPA) The seeker assembly is encased in a dome that is transparent to long-wave
infrared radiation. The IR radiation passes through the dome and then through lenses that focus the energy. The IR energy is reflected by mirrors on to the FPA. The seeker is a two-dimensional staring FPA of 64×64
MerCad (HgCdTe) detector elements. The FPA processes the signals from the detectors and relays a signal to the missile's tracker. The staring array is a photo-voltaic device where the incident photons stimulate electrons and are stored, pixel by pixel, in
readout integrated circuits attached at the rear of the detector. These electrons are converted to voltages that are multiplexed out of the ROIC on a frame-by-frame basis.
Cooling/calibration To function effectively, the FPA must be cooled and calibrated. In other applications, a CLU's IR detectors are cooled using a
Dewar flask and a closed-cycle
Stirling engine, but there is insufficient space in the missile for a similar solution. Prior to launch, a cooler mounted on the outside of the launch tube activates the electrical systems in the missile, and supplies cold gas from a
Joule-Thomson expander to the missile detector assembly, while the missile is still in the launch tube. When the missile is fired, this external connection is broken and coolant gas is supplied internally by an onboard
argon gas bottle. The gas is held in a small bottle at high pressure and contains enough coolant for the duration of the flight of approximately 19 seconds. The seeker is calibrated using a
chopper wheel. This device is a fan of six blades: five black blades with low IR emissivity and one semi-reflective blade. These blades spin in front of the seeker optics in a synchronized fashion such that the FPA is continually provided with points of reference in addition to viewing the scene. These reference points allow the FPA to reduce noise introduced by response variations in the detector elements.
Stabilization The platform on which the seeker is mounted must be stabilized with respect to the motion of the missile body, and the seeker must be moved to stay aligned with the target. The stabilization system must cope with rapid acceleration, up/down and lateral movements. This is done by a
gimbal system,
accelerometers,
spinning-mass gyros (or
MEMS), and motors to drive changes in position of the platform. The system is basically an
autopilot. Information from the gyros is fed to the guidance electronics, which drive a torque motor attached to the seeker platform to keep the seeker aligned with the target. The wires that connect the seeker with the rest of the missile are carefully designed to avoid inducing motion or drag on the seeker platform.
Tracker The tracker is key to guidance/control for an eventual hit. The signals from each of the 4,096 detector elements (64×64 pixel array) in the seeker are passed to the FPA
readout integrated circuits which reads then creates a
video frame that is sent to the tracker system for processing. By comparing the individual frames, the tracker determines the need to correct so as to keep the missile on target. The tracker must be able to determine which portion of the image represents the target. The target is initially defined by the gunner, who places a configurable frame around it. The tracker then uses
algorithms to compare that region of the frame based on image, geometric, and movement data to the new image frames being sent from the seeker, similar to
pattern recognition algorithms. At the end of each frame, the reference is updated. The tracker is able to keep track of the target even though the seeker's point of view can change radically in the course of flight. The missile is equipped with four movable tail fins and eight fixed wings at mid-body. To guide the missile, the tracker locates the target in the current frame and compares this position with the aim point. If this position is off center, the tracker computes a correction and passes it to the
guidance system, which makes the appropriate adjustments to the four movable tail fins. This is an
autopilot. To guide the missile, the system has sensors that check that the fins are positioned as requested. If not, the deviation is sent back to the controller for further adjustment. This is a
closed-loop controller. There are three stages in the flight managed by the tracker: 1) an initial phase just after launch; 2) a mid-flight phase that lasts for most of the flight; and 3) a terminal phase in which the tracker selects the most effective point of impact. With guidance algorithms, the autopilot uses data from the seeker and tracker, to determine when to transition the missile from one phase of flight to another. Depending on whether the missile is in top attack or direct attack mode, the profile of the flight can change significantly. The top attack mode requires the missile to climb sharply after launch and cruise at high altitude, then dive on the top of the target (curveball). In direct attack mode (fastball), the missile cruises at a lower altitude directly at the target. The flight path takes into account the range to the target, calculated by the guidance unit. ==Training==