Abstract
Surveillance operations are increasingly being used in various fields now. Radar is the technology used in most domestic, governmental, corporate, retail and residential security use and in the armed forces. Intelligence and military operations use it frequently. Search and rescue operations, scientific research, skip tracing and personal communications all utilize this surveillance technique (Petersen, 2007). Surveillance is essential for intelligence operations and is actually a part of the larger process of intelligence gathering. However it is equally important in wildlife conservation, weather forecasting, and security for residences and institutions. Where previously it was the prerogative of the offender to control the intrusive behavior, now it is the responsibility of the victim to ensure that he is not harmed. The power of surveillance was restricted to government agencies and some private ones (Petersen, 2007). The most extensively used surveillance techniques are visual, chemical and acoustic based and they are audio, radar and sonar. Aerial surveillance is widely used just as radar and infra-red applications. Biometric surveillance is growing. This paper has investigated into the history of radar, its development, uses and the various events which evolved into its present status. The significance of its use in the military has been detailed.
Radar
Radar is radio direction and ranging or radio detection and ranging. Microwave frequencies are involved mainly in this remote-sensing technique. It detects and interprets radio signals and can be passive or active. The objective of active radar radio signals is to intercept a moving object or a structure and interpret the reflected signals (Petersen, 2007). Radio wavelengths are long and occupy the lower end of the electromagnetic spectrum. They slow down when moving in particulate matter or water. Distance can be calculated by knowing the time and speed of the wave. Radio signals when emitted from the radio wave transmitter, move away till they hit an obstruction in their path. A beam of microwave energy would hit an approaching or withdrawing target. If the beam hits, a portion of the energy would be reflected and received by the radar unit which transmitted the original signal (Held, 2008). Some of the signal reflections from the obstruction reach back to the radar receiver. These returning ‘echoes’ reveal information about the obstruction target. If the obstruction is smooth, scattering of the reflections is minimal (Petersen, 2007). If it is rough, maximum scattering occurs and only a few return to the receiver. If the object is small, it may get missed. The properties of the reflected signals or the echoes like spectral reflectivity, polarization and time of arrival can be visualised, interpreted and displayed. Mathematical analysis provides information about size, shape, location and velocity of the object. If the radar is placed in a moving object, the calculations would contain these variations too. Radar signals may be hindered by rough weather, terrain, radar jamming or absorbing systems (Petersen, 2007).
Radar echoes are displayed in a number of ways. The radio receiver intercepts the incoming radio waves and converts them into electrical impulses which then are seen as displays. Ground-based target data are represented by special cathode ray tubes and computers for displaying the ‘blips’. Radar in aircraft and satellites use a radar imaging sensor to obtain digital or film images which look like traditional greyscale photographs (Petersen, 2007). The radar systems ranging from portable systems to large earth or marine stations are used on the ground or aircraft and satellites (Petersen, 2007).
History
The beginning of the 20th century saw the invention of radar for marine navigation in Germany. It was adopted for air navigation in 1936. The cathode-ray tube’s commercial availability also occurred simultaneously. Radar ranging and sonar ranging share a common history. The experience of the First World War, the development of the bombing theory in the interwar period and the thought that the bomber would always get through led to the concept of surveillance (Munns, 2001, p.406). Radar was employed regularly in military use in the Second World War. Its use has been described as ‘the real scientific hero of the Second World War’ over the atomic bomb by many authors. (Munns, 2001, p. 407). The use of radar enhanced when the transistor was invented in 1947. Radar is now essentially used in marine and air navigation and in aerial and planetary imaging (Petersen, 2007).
Development
In1842, Johann Christian Doppler developed the concept that was applied to invent the radar. He examined the way motion could compress sound waves and change the frequency of sound in relation to the perspective of the observer (Petersen, 2007). The same principle, the Doppler effect, was found relevant in other wavelike phenomena like light (Petersen, 2007). Other discoveries by inventors like Heinrich Hertz, a German physicist, led to the development of radar. The first use of radar was in the searchlights of vessels to illuminate objects and obstacles. However these were limited in use in rough weather conditions. Radio waves were developed by Christian Hulsmeyer to improve navigation. Telemobilscope was a radio device to prevent collisions in marine navigation.
This device was demonstrated in 1904 (Petersen, 2007). Hans Dominik, a science fiction writer and Richard Scherl developed the Strahlenzieler, a raw pointer, which used radio waves for detection. This invention was rejected in World War One. Nicola Tesla described the radar concepts in the ‘Electrical Experimenter’ in 1917. In 1922, Gugielmo Marconi described the use of radar for navigation. Till then, radar was used only for detection but did not provide the details of the obstruction. In 1926, Gregory Breit and Merle Antony Tuve discovered that a pulse modulated radio signal could be bounced off the ionosphere of the earth to detect the distance covered (Petersen, 2007). The experiment demonstrated that such a pulse bouncing a signal off a wave-reflecting object could allow calculation of the distance from an echo of the reflected signal. Radar technology was put to wider use in the 1930s. First, slow-moving ships were detected with radar. Later fast-moving aircraft were detected with radar. Display devices were not available in the early days of radar use.
Display devices developed Karl Ferdinand Braun, a German physicist, developed many technologies which turned out to be important in radio communications and radar systems (Petersen, 2007).
He invented a crystal rectifier which was used in earlier radios. In 1897, he designed the oscilloscope, a cathode-ray display system for displaying radar signals. Vladimir Kosma Zworykin patented the Iconoscope television tube which is a variation of cathode-ray tube in 1923. This new invention emitted beams from an electron tube. Display systems have now become an integral part of radar since the 1930s. Modern versions are used in vector displays and computerized raster displays (Petersen, 2007). Electron tubes are used to design transmitters, amplifiers, receivers and other electronic components.
Practical radar systems
A radio locator was designed to detect aircraft by Robert Watson-Watt in 1935.
Radio waves were used for direction finding, homing and ranging for commercial aircraft by 1937 (Petersen, 2007). A radar duplexer was invented by Leo Young along with an antenna for receiving and transmitting. A bettered version was used in the ship USS New York in 1939. It ushered in the era of strategic warfare and defence. This ship was used for training for sometime. The first electron-tube cavity magnetron was built by physicist Henry Boot and biophysicist John Randall. Radar accuracy significantly improved after this. High power magnetrons which could generate microwaves for radar paved the way for this accuracy (Petersen, 2007). Modern radar systems owe their present era efficiency to Zworykin’s cathode-ray tube and the transmission system of Boot and Randall.
Applications of Radar
Radar is used for military targeting, tracking and defense surveillance activities. Civilian monitoring of moving vessels is another common use. Tracking hazards, threats, environmental catastrophes and weather systems are using radar.
Short-range low-power systems are available for consumers (Petersen, 2007). Costlier medium-range and long-range tracking stations are found throughout the world and used for navigation, international surveillance and defence purposes. High-end radar systems are extremely costly
The use of radar in World War II led to the development of the radar gun, radar controlled camera and other devices (Held, 2008). Police officers operating the radar gun can detect a speeding vehicle and see its license plate a mile away or even see it in the mail as the photograph of the speeding vehicle will be taken if the driver overshoots the optimum speed.
The first radar unit was used by the US police in 1947 (Held, 2008). It was operated from a stationary police car. The X band radar is used in all weather conditions.
European countries used the Ku band with 13.45 GHz as traffic radar (Held, 2008). The K band radar has a wider beam than Ka and is narrower than the X band. Frequency hopping is possible in defeating overspeeding vehicles and detected by radar detectors using the Ka band.
Uses of radar in the Military
Movement, vessels, projectiles and unidentified objects are detected using the radar system. Commercial security systems and satellite warnings are all using radar to provide early warnings (Petersen, 2007). Radar provides information without interference from other signals. Long-range radar systems provide warnings of incoming missiles and aircraft. Artificial satellites are monitored by a joint program of the United States and Canada called SPADATS (Space Detection and Tracking system). Computer systems have automated much of the radar plotting. Movement over time can be illustrated using animation programs. Individual targets can be monitored using a number of stop-action frames quickly in succession (Petersen, 2007). Vehicle and troop movement could be tracked and relayed to stations in Hungary in the NATO Implementation Force in Bosnia and Herzegovina using Boeing aircraft with the J-STARS (Joint Surveillance Target Attack Radar System). When flying, the radar can detect and track up to 120 miles of terrain. A phased array radar antenna feeds information to the armed forces with large screen consoles (Petersen, 2007).
Early warning and defence systems using radar signals are a part of aircraft patrols and satellite links. Specific sighting and imaging are done with radar. Incoming sea-launched ballistic missiles are detected with the Pave Paws, an early warning phased radar system (Petersen, 2007). Radar monitoring and imaging allow data storage and analysis too. Earlier computer formats have been changed to high storage capacity hard drive and tape systems. The speed and size of display consoles have changed.
Projectile detection and guidance of incoming and outgoing missiles is possible with radar. The Iraqi Patriot missiles were guided by radar for precision and detected on the US side also by radar (Petersen, 2007). The path of a guided missile is determined using fire-control computers. Homing guidance is provided by the Missile Guidance Radar (MGR). The Missile Tracking Radar (MTR) is supplemented or replaced by the high power Continuous Wave Illuminator radar which is used together with the Target Tracking Radar (TTR). A multifunction-phased array device named AN/MPQ 53 radar set was used in Operation Desert Shield for detecting the MIM 104 Patriot tactical air defence system. A large number of incoming projectiles like enemy fire could be detected by radar. The AN/TPQ- 36 Fire Finder is used by the US Army for monitoring incoming projectiles like rockets and mortars (Petersen, 2007), understanding both location of firing and location of possible landing. AN/TPQ-27 Fire finding radars are also used.
Mine detection seems to be necessary in many places even though much progress has been seen in surveillance. Detecting mines may be dangerous for the person involved.
A long stick is employed for mine detection and definitely is not feasible at all as the dangers of the mine bursting still exist. Low-cost metal detectors could be used but plastic explosives would not be detected by them. Ground penetrating radar systems (GPR) have been used with some success (Petersen, 2007). The Micropower Impulse Radar (MIR) developed by the Lawrence Livermore National Laboratory has been used to detect mines. This detects plastic and metal mines embedded in 10 cm. of moist soil and 30 cm of dry soil. It provides three dimensional images of objects below the soil surface. Winter conditions may disturb the detection. Radar may be combined with infrared technology to get good detection. The systems may be vehicle mounted or aircraft mounted. This GPR technology is used for archaelogical purposes and crime scene investigation too (Petersen, 2007).
Other uses of radar
The radar on the DEW line which detects Russian planes flying over the North Pole ice cap to North America uses the continuous transmission radar system (Held, 2008). The radar gun which police use has the intermittent transmission technique. A third type works only in the presence of a moving vehicle.
The collision avoidance radar permits intervehicle communication and assists the driver in avoiding a collision by observing other cars or objects through millimeter wave radar and radar sensors using the range 36-94GHz for operation, far away from the range of police radar. The millimeter waves is the new technology used in radar, car radar and cloud radar, radiometry for concealed weapon detection, high speed wireless access, ultra high speed wireless local area networks and other communication systems (Xiao, 2008).
Unfavourable environments or noise do not affect the millimeter wave radar systems (Xiao, 2008).
The ability to see in the dark and peer into small structures is an important need.
Many security and diagnostic applications use the advantages of radar (Patersen, 2007).
Smaller, less expensive and more powerful devices are being made commercially for the purpose of many disciplines especially the medical field.
Applications in Research
Radar images have helped anthropologists to find out more about technology, features and habits of ancient civilizations in archaeology. Physical features, patterns and trend are visualised better with these radar applications (Petersen, 2007). Visual and radar aerial imaging helped to obtain information about the boundaries of the Great China Wall which had changed many times. Structures that were not seen with the naked eye were found in the Sahara Desert through radar imaging.
Earth monitoring and mapping have been done. Many aerial images of the earth are created with radar technologies. Weather mapping and space shuttle mapping have contributed a great deal of information about the earth (Petersen, 2007).
Human caused and natural environmental changes are being detected and monitored using radar as in the Space Radar Laboratory which has carried out many space shuttle missions (Petersen, 2007). Geographic rock formations, ocean currents, volcanoes and their activities, vegetation, ice, snow and wet lands have all been viewed and studied in detail. The data collected on the different space missions are shared with the international scientific community.
Side looking radar systems are used for detecting oil spills. Ground penetrating radar measures the depth of glaciers and ice floes (Petersen, 2007). The same technique is used for geophysical research. Radar happens to be an important tool for astrophysical research. Weather monitoring and forecasting require the radar technology. Air traffic controllers depend very much on it too.
References
- Held, G. (2008). “Communication Fundamentals” Chapter 2 in “Inter and Intra vehicle Communications”, Auerbach Publications
- Munns, D. (2001). “Magnetrons, Micropups and Me: Personal Histories of radar”.Survey Review, AAHPSSS
- Petersen, J.K. (2007). “Understanding Surveillance Technologies; Spy devices, privacy, history and applications”. Revised and expanded Second Ed, Auerbach Publications. Books 24×7
- Xiao, S., Zhou, M. and Zhang, Y. (2008). “Millimetre wave radar: Principles and Applications” Chapter 10 in Millimetre Wave Technology in Wireless PAN, LAN and MAN, Auerbach publications