The Application of Laser Ranging Technology in Space -- JIOPTICS

With the development of space technology and aerospace industry. Space distance measurement has become an important research topic in the field of space. Traditional radar ranging is highly susceptible to interference from high-energy particles and electromagnetic waves in space, resulting in low measurement accuracy and inability to meet the requirements of high-precision measurement. The air in space is thin and the temperature changes dramatically, making it impossible to perform ultrasonic ranging. Therefore. Measuring spatial distance requires a ranging method that is suitable for the spatial environment, has strong anti-interference ability, and high measurement accuracy. Laser ranging technology is an automatic non-contact measurement method that is insensitive to electromagnetic interference, has strong anti-interference ability, and high measurement accuracy. Compared with general optical ranging technology, it has the advantages of convenient operation, simple system, and the ability to work both day and night. Compared with radar ranging, laser ranging has good anti-interference ability and high accuracy.

While repeating ranging, scanning the space with a fine laser beam to obtain information such as distance, angle, and velocity of the target is called LiDAR. Lidar can achieve many performance requirements that traditional radar cannot meet. Laser has a small divergence angle and concentrated energy. Capable of achieving extremely high detection sensitivity and resolution; Its extremely short wavelength allows for very small antenna and system sizes, which are incomparable to traditional radar. Compared with microwave radar, laser rangefinder has better directionality, smaller size, and lighter weight. Very suitable for space target distance measurement carried on spacecraft.

Laser ranging technology integrates multiple technologies such as laser technology, photon detection technology, and signal processing technology. High ranging accuracy. Large measurement range, high reliability, and able to meet the requirements of high-precision and long-range distance measurement for space targets. It has been widely applied in the field of spatial measurement.

Laser is a type of light that does not originally exist in nature and is emitted due to excitation, with characteristics such as good directionality, high brightness, good monochromaticity, and good coherence. The characteristics of laser are:

1. Good directionality - ordinary light sources (such as the sun, incandescent lamps, or fluorescent lamps) emit light in all directions, while the direction of laser emission can be limited to a solid angle of less than a few milliradians, which increases the illuminance in the direction of illumination by tens of millions of times. Laser collimation, guidance, and ranging utilize the characteristic of good directionality.

2. High brightness - Laser is the brightest light source of our time, and only the intense flash of a hydrogen bomb explosion can match it. The brightness of sunlight is approximately 103 watts/(cm2 · spherical degree), and the output brightness of a high-power laser is 7-14 orders of magnitude higher than that of sunlight. In this way, although the total energy of the laser may not be very large, due to the high concentration of energy, it is easy to generate high pressure and high temperatures of tens of thousands or even millions of degrees Celsius at a small point. Laser drilling, cutting, welding, and laser surgery utilize this feature.

3. Good monochromaticity - Light is an electromagnetic wave. The color of light depends on its wavelength. The light emitted by ordinary light sources usually contains various wavelengths and is a mixture of light of various colors. Sunlight includes visible light in seven colors: red, deng, yellow, green, cyan, blue, and purple, as well as invisible light such as infrared and ultraviolet. And the wavelength of a certain laser is only concentrated in a very narrow spectral band or frequency range. The wavelength of helium neon laser is 632.8 nanometers, and its wavelength variation range is less than one thousandth of a nanometer. Due to the good monochromaticity of laser, it provides extremely favorable means for precision instruments to measure and excite certain chemical reactions in scientific experiments.

4. Good coherence - Interference is an attribute of wave phenomena. Based on the high directionality and monochromaticity of laser, it is bound to have excellent coherence. In the early 1990s, several major companies in Europe and America successively produced commercially available semiconductor laser diodes, revolutionizing the practical application value of lasers. Other types of lasers are greatly limited in their application due to the complex mechanism of generating lasers, which results in their large volume, weight, and high power consumption. The emergence of semiconductor lasers has easily solved these problems. As the technology of semiconductor lasers further matures and prices gradually decrease, their application batches and fields continue to expand. From the current development speed, the application prospects are very promising. Semiconductor lasers have small size, light weight, high reliability, high conversion efficiency, low power consumption, simple driving power supply, direct modulation capability, simple structure, low price, safe use, and a wide range of application fields. Such as optical storage, laser printing, laser typesetting, laser ranging, barcode scanning, industrial detection, testing and measurement instruments, laser display, stage lighting and laser performance, laser level and various marking positioning, etc. The unique advantages of semiconductor lasers make them very suitable for military applications, such as field ranging, aiming of firearms, shooting simulation systems, blinding, submarine communication guidance, fuses, security, etc. Due to the use of regular electric bubble drivers, it is possible to configure some portable weapon devices. At present, semiconductor lasers that have been developed and put on the market have wavelengths of 370nto, 390r Shan, 405r Shan, 430nto, 480hm, 635r dish, 650hm, 670hm, 780hm, 808nm, 850hm, 980rm, 1310hm, 1550hm, etc. Among them, 1310hm and 1550hm are mainly used in the field of fiber optic communication. 405nm to 670nm is in the visible light band, 780nm to 1550hm is in the infrared light band, and 390nm to 370hm is in the ultraviolet light band. Laser is a high-intensity light source radiation device, and high-power lasers can be used to cut and weld metal materials. Therefore, lasers can cause serious harm to the human body, especially the eyes, and special care should be taken when using them. There is a unified classification and safety warning sign for lasers internationally. Lasers are divided into four categories (Classl-Class4). Class 1 lasers are safe for humans, Class 2 lasers cause minor harm to humans, and lasers above Class 3 lasers cause serious harm to humans. Special attention should be paid when using them to avoid direct eye contact.