The typhoon is a cloud in the traditional eye satellite 'eye', but the 'California' camera carried by China's first geosynchronous orbit remote sensing satellite with high scores on the 4th can see the structure of the typhoon center and its evolution mechanism, which makes China's The typhoon is forecasting to enter the 'accurate' era.
A few days ago, Gaofen No. 4 worked closely with other 'small partners' and performed well in the task of Typhoon 'Maria' of the 8th this year near the monitoring center, and continued to keep an eye on 'Maria'. , obtained its satellite imagery and related data.
How does the 'Clitun' of the satellite be 'refined'? What is the core mirror of the core of the 'eyeball'? What is the most advanced space mirror in the world? What are the main research directions in the future? The reporter of Science and Technology Daily went to the founder of the satellite 'California'. The earliest research institute of space optical remote sensor, China Aerospace Science and Technology Group Co., Ltd., 508 Institute of Wuyuan, interviewed Wang Xiaoyong and space mirror lens in China. Tune expert Wang Hao.
Light weight, strong stiffness, no deformation
'Lens' is demanding on materials
The Hubble telescope is a famous space telescope that realizes the dream of astronomers to see the universe. How do the inhabitants of the earth see what is happening on the earth? This requires a space telescope looking at the earth. Its scientific name Called the remote sensing observation system.
In essence, the space telescope and the telescope on the ground have basically the same principle. But the earth is wrapped in the atmosphere, and the atmospheric disturbance in the space from the ground is large, which directly leads to invisibility or even 'seeing the eye'. After the satellite launch technology matures, people put the telescope 'Hit' into space to see the universe and the earth, everyone is amazed at the clarity of the image in space, human exploration of space, the ability to monitor the Earth is also greatly enhanced.
However, the space environment is not a small test for space telescope materials, especially the space mirror of the core components of the telescope. Can it withstand this harsh environment?
Wang Xiaoyong told reporters that the space mirror material currently has glass, silicon carbide ceramics, tantalum and a variety of composite materials. The general glass material can not meet the needs of space telescopes, because the thermal environment in space is very bad, the material requirements are very low. Swelling, almost zero expansion. So developed a glass-ceramic with a coefficient of expansion less than 1 × 10-6, and ultra-low expansion quartz glass (ULE) invented in the United States, the latter used in Hubble On the main mirror of the space telescope.
By satellite, the 'big mirror' is hit to the scheduled orbit. One requirement is that the 'large mirror' can't be too heavy, so people try to solve the problem of material lightweighting, such as making lightweight holes on the back of the glass-ceramic, honeycomb-shaped, minus Regained the original 15% -10%.
The mechanical environment of the satellite launching is very bad, which is equivalent to a heavy weight pressed on the 'big mirror', and the whole process is shaken and bumped. The 'big mirror' must be strong enough to be easily deformed by external disturbances. Two important parameters of coefficient and stiffness become the basic requirements of optical materials.
Later, it was found that silicon carbide ceramics not only have a low thermal deformation coefficient, but also have much higher stiffness than glass materials, and the weight is very light, so ceramics has become an important optical mirror material. Wang Xiaoyong said: '508 high-resolution satellite 2 and China The largest commercial satellite, the Gaojing No. 1 camera, uses mirrors of silicon carbide material.
In recent years, the fourth metal crucible in the periodic table has been widely used in mirror materials with strong advantages. The main material of the James Webb space telescope that the United States is expected to launch in 2020 is metal crucible. This material is at 40K (zero). At 233 degrees Celsius, the expansion coefficient is zero at low temperature, which is very suitable for the James Webb telescope working at this temperature. The infrared camera on China's CMB Resources No. 1 satellite also took the lead in using metal enamel. This camera poured 508 Wisdom and strength.
'The materials used in the world are basically used in China. We are further developing lighter composite fiber materials and high-strength, high-rigidity porous structural materials. 508 precision optical manufacturing centers have accumulated a lot of experience in recent years. ' Wang Xiaoyong said.
Optical processing, precision adjustment
Create a super 'eye of the eye' important link
'Material is one aspect. The optical processing and precision adjustment of space mirrors is another important aspect of the birth of 'Eye of the Space'. ' Wang Wei told reporters that unlike the ordinary eyeball, the eye of the 'eye of space' has reached the eye. Meter level, surface accuracy requires a few nanometers. After milling, grinding, finishing and coating, and other processes, after a comprehensive test of mechanical energy, light, sound, electrochemistry, chemistry and other energy, Complete, efficient, high quality 'eyeball' announced birth.
'In recent years, we have carried out detailed process tests and key technological breakthroughs, which not only greatly improved the efficiency of the use of high-precision equipment, but also broke through the inherent limits of the equipment in some technical indicators. We have developed a number of high-precision optical components. For example, the Ф800mm wedge standard lens for the standard mirror of large-caliber interferometer, the lens processing precision reaches 3 nanometers, and has passed the third-party verification, reaching the highest level in the country, equivalent to the microscopic surface in the range of 4.3 square kilometers. The degree of undulation is controlled within the diameter of the hair. ' Wang Xiaoyong explained.
After the 'eyeball' is perfectly formed, how can it work with other components? Then, it must be optically assembled and adjusted, that is, according to the kinematics principle, through appropriate correction and adjustment processes and testing methods, after cleaning, connection, inspection, Adjustment, tightening, testing, etc., put the 'eyeball' and related components in the correct position, and finally let them work systematically and meet the design requirements.
In recent years, in the face of 'eye of the eye' product variety, the development cycle is tight, personalized customization, technical indicators to the international advanced level and so on, we carry out a number of optical system adjustment and testing technology research, overcome the computer More than ten key technologies, such as auxiliary assembly, have formed the core competitiveness of optical assembly and autonomy. 'Wang Wei said, 'A function of detecting the effect of the adjustment is called the quality factor, which is the actual value and the theoretical value of the adjustment quality. Ratio, the higher the value, the better the effect of the adjustment, the current 508 camera adjustment effect up to 0.95, while the domestic 0.9 is already leading.
Folding or LEGO construction, expanding the fairing
Increase caliber and increase resolution into a global trend
Wang Xiaoyong introduced that the larger the aperture of the optical mirror, the smaller the diffraction effect, which means that the stronger the convergence of light, the higher the resolution. From a global perspective, the development trend of the aperture of the space mirror is getting bigger and bigger. However, the space mirror that launches the sky through the rocket, in addition to not too heavy, should also pay attention to its size, otherwise it will not be able to put into the rocket 4.5 m fairing.
'The large-diameter mirrors will be developed in the future by folding or in-orbit reloading. The former is to divide the mirror into multiple pieces, and when it reaches the track, it opens like an umbrella; the latter is like building blocks in space. Build a mirror. This is the first path for the development of a new generation of mirrors in the world. 508 is also doing research and development in this area. ' Wang Wei said.
However, increasing the caliber and increasing the resolution will inevitably lead to more difficult development. For example, the folded large-diameter mirror is opened in space. How to ensure that its surface undulation is the same as before launching? How to detect in space What is the undulation of the shape? 'Large mirror' cut into several pieces, and then how to fit together with high precision? If you assemble like a building block, rely on what instrument To control? These are still unsolved problems.
'At present, the launch lens is adjusted to launch into space. In the future, the mirror will be adjusted in space. ' Wang Xiaoyong said that there is strong vibration during the launch, and the small relative position change is still within the acceptance range. The relative position of the large-diameter mirror It will change the order of millimeters, which means that the accuracy is 106 times worse. On the ground, the adjustment mirror has a large factory and many people, and the folding mirror is slowly corrected back to the highest precision after it is unfolded.
The other path is to expand the fairing space to carry large-diameter mirrors. Currently, the United States is conducting related research. 'The large-caliber mirror is launched into space. Because the weight loss rebounds up to millimeters, the mirror fails. The larger the mirror, the greater the influence of gravity deformation, and the difficulty of manufacturing is also increasing. 'Wang Xiaoyong said that the two technical routes are controversial, but they are all being tested.
