LASER IN MILITARY APPLICATIONS
INTRODUCTION
1. In recent years the Laser has seen widespread use especially in the Ranging and Designation for Laser Guided Bombs and Missiles. The features of a Laser including its very narrow beamwidth, highly monochromatic and source brightness make it a very powerful tool for such operations where it has advantages over and complements conventional Radar.
AIM
2. The aim of this section is to explain the design and operation of military Laser systems. The following subjects will be covered:
a. Laser Rangefinders.
b. Target Designators.
c. Target Illuminators.
d. Laser Guidance / Tracking Systems.
e. Laser Communication Systems.
f. Laser Radar LADAR.
LASER RANGEFINDERS
3. A Laser rangefinder transmits an intense highly collimated beam of short pulses. The time taken for a single pulse to travel to the target and back is recorded. Because we know the sped of light, a simple calculation will provide us with the range to the Target. If c = speed of light and T = time taken back and forth then:
Range = cT / 2
4. Early Rangefinders were made from Ruby Lasers which were then replaced by Nd/YAG systems which had the advantage of being invisible, therefore could not be seen by the enemy, and less dangerous to the human eye. More recent Rangefinders use Carbon Dioxide which has better penetration in adverse weather conditions and has four times less eye hazard than Nd/YAG. This means that Rangefinding can safely be conducted in training exercises without the fear of causing unintentional eye damage. Most Rangefinders have operational ranges of 5 to 10 Km although some have ranges greater than this. The figure below shows the basic operation of a Laser Rangefinder in an airborne scenario although the same principal applies to any platform such as the man-portable system shown in figure.
TARGET DESIGNATION
5. The principle of Designation is that the target is illuminated by Laser beam and a detector in the host platform, or weapon system, homes in onto reflected light from the target. The Lasers very narrow beam width ensures very accurate and selective marking of the target at ranges of up to 10 Km. Unless the enemy has lots of Laser Warning Receivers (LWR’s) it will not know who is being targeted. In most modern systems once the returning laser signals have been acquired, automatic tracking of the signal takes place. All the operator has to do is to keep the target illuminated and the weapon should home to the correct target. Accurate targeting information is then supplied to the aircraft or weapon systems, navigation and weapon aiming systems. Examples of Targeting systems include Litening and TIALD targeting pods which both include a Laser Designator as well as various FLIR and visual TV cameras.
The basic principal of operation of a Laser Designator is shown in the figure below.
TARGET ILLUMINATION
6. Target illumination can be used to improve the performance of Image Intensifiers. Here the Designator is used in the same manner as a torch producing reflections off the target that are large enough to be picked up by the Image Intensifier.
LADAR (LASER RADAR)
7. A Laser Radar generates very narrow beam widths which greatly improves covertness and resistance to jamming.
8. Optical Radar (LIDAR) employs visible wavelengths.
Laser Radar (LADAR) generally refers to systems employing other wavelengths.
9. The characteristics of LADAR greatly improve target profiling, definition, signature and tracking accuracy.
10. When using wavelengths in the UV band the high frequencies induce target fluorescence which improves signature analysis.
11. LADAR systems are used in;
a. Atmospheric Ozone detection.
b. Submarine detection.
c. Rangefinding.
d. As a Missile Seeker head.
12. Low Cost Autonomous Attack System (LOCAAS) – utilises LADAR technology.The purpose of this development was to illustrate that an autonomous low cost attack munition could be integrated into an air vehicle powered by a miniature turbojet engine.This would be integrated on the F-22, F-22X and JSF aircraft or a UAV as an autonomous system.
13. The vehicle would consist of a Multi-Mode Warhead (expanding rod, fragmentation) coupled to a solid state radar (LADAR) seeker with Autonomous Target Recognition (ATR) and INS/GPS midcourse guidance in a manoeuvrable airframe.
14. The LADAR allows target aim point and warhead selection to be determined automatically.
15. Endurance 30 min; Range >100km; Cost $33K/unit.
INTRODUCTION
1. In recent years the Laser has seen widespread use especially in the Ranging and Designation for Laser Guided Bombs and Missiles. The features of a Laser including its very narrow beamwidth, highly monochromatic and source brightness make it a very powerful tool for such operations where it has advantages over and complements conventional Radar.
AIM
2. The aim of this section is to explain the design and operation of military Laser systems. The following subjects will be covered:
a. Laser Rangefinders.
b. Target Designators.
c. Target Illuminators.
d. Laser Guidance / Tracking Systems.
e. Laser Communication Systems.
f. Laser Radar LADAR.
LASER RANGEFINDERS
3. A Laser rangefinder transmits an intense highly collimated beam of short pulses. The time taken for a single pulse to travel to the target and back is recorded. Because we know the sped of light, a simple calculation will provide us with the range to the Target. If c = speed of light and T = time taken back and forth then:
Range = cT / 2
4. Early Rangefinders were made from Ruby Lasers which were then replaced by Nd/YAG systems which had the advantage of being invisible, therefore could not be seen by the enemy, and less dangerous to the human eye. More recent Rangefinders use Carbon Dioxide which has better penetration in adverse weather conditions and has four times less eye hazard than Nd/YAG. This means that Rangefinding can safely be conducted in training exercises without the fear of causing unintentional eye damage. Most Rangefinders have operational ranges of 5 to 10 Km although some have ranges greater than this. The figure below shows the basic operation of a Laser Rangefinder in an airborne scenario although the same principal applies to any platform such as the man-portable system shown in figure.
TARGET DESIGNATION
5. The principle of Designation is that the target is illuminated by Laser beam and a detector in the host platform, or weapon system, homes in onto reflected light from the target. The Lasers very narrow beam width ensures very accurate and selective marking of the target at ranges of up to 10 Km. Unless the enemy has lots of Laser Warning Receivers (LWR’s) it will not know who is being targeted. In most modern systems once the returning laser signals have been acquired, automatic tracking of the signal takes place. All the operator has to do is to keep the target illuminated and the weapon should home to the correct target. Accurate targeting information is then supplied to the aircraft or weapon systems, navigation and weapon aiming systems. Examples of Targeting systems include Litening and TIALD targeting pods which both include a Laser Designator as well as various FLIR and visual TV cameras.
The basic principal of operation of a Laser Designator is shown in the figure below.
TARGET ILLUMINATION
6. Target illumination can be used to improve the performance of Image Intensifiers. Here the Designator is used in the same manner as a torch producing reflections off the target that are large enough to be picked up by the Image Intensifier.
LADAR (LASER RADAR)
7. A Laser Radar generates very narrow beam widths which greatly improves covertness and resistance to jamming.
8. Optical Radar (LIDAR) employs visible wavelengths.
Laser Radar (LADAR) generally refers to systems employing other wavelengths.
9. The characteristics of LADAR greatly improve target profiling, definition, signature and tracking accuracy.
10. When using wavelengths in the UV band the high frequencies induce target fluorescence which improves signature analysis.
11. LADAR systems are used in;
a. Atmospheric Ozone detection.
b. Submarine detection.
c. Rangefinding.
d. As a Missile Seeker head.
12. Low Cost Autonomous Attack System (LOCAAS) – utilises LADAR technology.The purpose of this development was to illustrate that an autonomous low cost attack munition could be integrated into an air vehicle powered by a miniature turbojet engine.This would be integrated on the F-22, F-22X and JSF aircraft or a UAV as an autonomous system.
13. The vehicle would consist of a Multi-Mode Warhead (expanding rod, fragmentation) coupled to a solid state radar (LADAR) seeker with Autonomous Target Recognition (ATR) and INS/GPS midcourse guidance in a manoeuvrable airframe.
14. The LADAR allows target aim point and warhead selection to be determined automatically.
15. Endurance 30 min; Range >100km; Cost $33K/unit.
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