Read the text and do the task below.

Sensors are the eyes of a weapons system.

In the past the human eye and brain have constituted the primary military sensor system. A soldier on the battlefield would:

• look over the battlefield for possible enemy action (surveillance);
• note any significant object or motion (acquisition);
• determine if the object was a legitimate
• target (discrimination);
• follow the enemy motion (tracking);
• Aim his rifle (weapon direction), fire;
• look to see if he had killed the target (kill assessment); and
• if not, reacquire the target (retargeting), aim, and shoot again.

Ballistic missile defense entails these same functions of target surveillance, acquisition, discrimination, tracking, weapon direction, kill assessment, and retargeting. BMD sensors, however, must have capabilities of resolution, range, spectral response, speed, and data storage and manipulation far beyond those of the human eye-brain system.

Three types of sensors might satisfy portions of these BMD requirements: passive, active, and interactive. Passive sensors rely on natural radiation emitted by or reflected from the target. Active sensors, such as radars, illuminate the target with radiation and detect the reflected signal. “Interactive sensors” (a term unique to the SDI) would use a strong beam of energy or cloud of dust-like particles to perturb targets in some measurable way (without necessarily disabling it) so that RVs could be discriminated from decoys. For example, the cloud might slow down light decoys much more than heavy RV s, or penetrating particle beams might create a burst of neutrons or gamma rays from RVs but not from balloons.

Passive Sensors

How Passive Sensors Work. Passive sensors detect military targets either by measuring their natural emission, or by detecting natural light reflected from the targets. A typical sensor is similar to an ordinary camera. An optical element (the lens) forms an image, and alight sensitive surface records that image (the film). In BMD infrared sensors, the optical lens would be replaced by a system of reflecting mirrors and the camera film by an array of discrete optical detectors in the focal plane which convert the optical image into electronic signals for immediate computer processing. Many detectors are required to record a detailed image. In a sense each detector substitutes for one grain of photographic film. Some sensors use a stationary two-dimensional “staring” array of detectors, in direct analogy to photographic film. Others mechanically scan the image across an array of detectors that may be either two-dimensional or linear.

Active Sensors

How Active Sensors Work. Active sensors illuminate the target with radiation and monitor reflected energy. In general, active sensors have the advantage of adequate illumination under all conditions: they do not have to rely on radiation from the target or favorable natural lighting conditions. They suffer the disadvantage, under some circumstances, of being susceptible to jamming or spoofing: the opponent can monitor the illumination beam and retransmit a modified beam at the same frequency to overpower or confuse the receiver. At the very least, the illumination beam can alert the enemy that he is under surveillance or attack. This might be a concern for surveillance and tracking of defense suppression weapons such as direct-ascent or orbiting ASATs. Microwave radar, an active sensor used so successfully in tracking aircraft, might support some phases of BMD, particularly for terminal defense. These ground-based radars might use advanced data processing techniques to generate pseudo-images of RVs to distinguish between RVs and decoys, as described below. Conventional microwave radar has two serious limitations for most space-based BMD functions: limited resolution and large power requirements. Because of the large antennae, large power requirements, and survivability issues, microwave radar is not a prime candidate for BMD space applications. However, the SDIO still believes that micro-wave radar might be included in future BMD systems. SDI researchers are also investigating laser radar or ‘ladar” for applications such as measuring the range to a target and discriminating RVs from decoys. In principle, ladar is equivalent to radar with much shorter (optical or infrared) wavelengths. With shorter wavelength, ladars generally would give better resolution with less power and weight. Ladars cannot operate in all weather conditions on earth. They are therefore better suited for space applications.

Interactive Sensors

How Interactive Discriminators Work. In interactive discrimination, a sensor system would perturb each target and then measure its reaction to determine if it were a decoy or an RV. For example, a dust cloud of sufficient density and uniformity could be placed in front of a group of objects. The resulting collisions would slow down light decoys more than heavy RVs. A ladar would monitor the change of velocity of all objects, thereby identifying real RVs.

1. Do you agree with the writer’s comment: “Sensors are the eyes...”. Justify your choice.

2. How do passive sensors detect military targets?

3. Reflecting mirrors are never used in the ballistic missile sensors, are they?

4. What are the main disadvantages of active sensors?

5. Microwave radars have no disadvantages, have they?

6. Decipher “ladar”. What applications can it be used for?

7. They can work in all weather conditions on earth, can’t they?

8.  The interactive sensor system can never discriminate a decoy from an RV, can it?

 

Word list

illuminate направлять луч, волну

discrimination - различение; установление различия;

legitimate [lıʹdʒıtımeıt] - законный

kill assessment - определение степени поражения (цели)

BMD (ballistic missile defense) - воен. противоракетная оборона,

spectral response - спектральная чувствительность

RV (reentry vehicl e) - головная часть, ГЧ (ракеты); боеголовка;

3. Read the text and answer the questions below:

Sensors

When an electromagnetic source, such as radio or radar, is used to guide the missile, an antenna and receiver are installed in the missile to form what is known as a SENSOR. The sensor section picks up, or senses, the guidance instructions. Missiles that are guided by other means use different sensor elements. But the missile control sections, which follow the sensor section, are basically similar for all types of guidance. In some respects, the sensor unit is the most important section of the guidance system because it detects the form of energy being used to guide the missile. If the sensor unit fails, there can be no guidance.

The kind of sensor that is used will be determined by such factors as maximum operating range, operating conditions, the kind of information needed, the accuracy required, viewing angle and weight and size of the sensor, and the type of target and its speed.

Acoustic sensors called hydrophones are often used in torpedo guidance systems. Essentially, a hydrophone is a microphone that works underwater. It picks up the vibrations of ships' propellers, and the torpedo can "home" on this noise. Acoustic sensors are not well suited for airborne missiles.

Heat, or infrared sensors use an active element called a THERMOCOUPLE, or an element known as a BOLOMETER. Either sensor may be used with a lens and reflector system.

Sensors that respond to light use an active element called a PHOTOELECTRIC cell. Another light-sensing system uses a television camera to pick up information and send it back to the launching site by means of a TV transmitter in the missile.

Electromagnetic sensors use radio or radar antennas as active elements. The phase of guidance determines the location of the antenna in the missile structure. For initial and midcourse guidance the antenna is normally streamlined into the tail of the missile. For final phase guidance the sensor may be located in the nose of the missile.

All of these sensors have advantages and disadvantages. Some are well suited for final phase applications and totally unsuited for initial and midcourse guidance.

1. What is the most important part of a guidance system?

2. Can acoustic sensors be used for airborne missiles?

3. Can a TV camera be used as a part of a sensing system?

4. Where is a sensor installed in a missile structure?

 

4. Look through the text and answer the questions below:

The Sky Spotter

Electro-optical sensors are the most important component of ballistic missile defense. The term "electro-optical sensor" covers a wide range of sensor technologies and applications. At their root, electro-optical (E/O) sensors are electronic detectors that convert light, or a change in light, into an electronic signal, which is analyzed to trigger preset responses. The capability of any E/O sensor stems from the balancing of two fundamental limits: the combination of resolution and sensitivity, and pixilation. Resolution means how small an object can be usefully seen. Sensitivity means how dim the signal can be before it is overwhelmed by environmental noise. Pixelation refers to sampling of the sensor image.

Advances to E/O sensors have the potential to improve response time for multi-source information fusion, survivability, and reliability in missile defense applications.

The Sky Spotter is an advanced passive early warning electro optical (EO) system sensor for real-time airspace monitoring, early detection and accurate tracking of aerial objects, including drones, aircraft, etc. It features advanced algorithms for automation, image processing and artificial intelligence.

The Sky Spotter’s detection sensors are reinforced with multispectral investigation sensors which are pointed at the target by early detection. Operators can manage up to 4 sensors simultaneously, each with two channels. Originally developed to counter small drones, Sky Spotter can track aircraft and pinpoint their location. The Sky Spotter provides passive sensing, detection, tracking and identification of aerial targets. It remains unaffected by classic radar challenges: multipath, clutter, background. It enables multiple targets to engage, track and manage multiple targets simultaneously.

While airspace surveillance in both civil and military worlds relies almost totally on radar, advances in threat technology have rendered legacy radars less dependable than they once were. Jamming and defense suppression attacks can disrupt or deny large areas of coverage, while low-RCS (radar cross section) targets and those flying low and slow are increasingly difficult to detect.

To address these issues Rafael has developed a passive, unjammable airspace surveillance electro-optical system that uses medium- and short-wave infrared sensors alongside visible light sensors to provide complete coverage over a designated area, ranging from a radius of one kilometer out to many tens of kilometers. The employment of highly sensitive EO sensors removes the complications of radar surveillance, such as background clutter, multipath anomalies, and the inability to spot targets such as small drones.

Sky Spotter comprises a wide field-of-view staring sensor which maintains constant watch, its imagery being processed to automatically provide a sense-and-warn function and to lock-and-track multiple targets simultaneously. The number of staring sensors can be scaled to ensure full coverage in a networked environment.

When a suspect object is automatically detected by these sensors the system cues an investigating sensor with a much narrower field of view. Imagery from this sensor can be used for investigation purposes to determine what the target is, and can theoretically eliminate the need to needlessly send manned interceptors to investigate blips on a radar screen that often turn out to be harmless.

1. How do electro-optical sensors work?

2. How have the Sky Spotter’s detection sensors been improved?

3. Have there been any new developments in the Rafael electro-optical system?

4. What are the Sky Spotter sensors?