Space optics isUpper atmosphereNeutralization Atmosphere Outer space is an applied discipline branch that uses optical equipment to observe and study space and the earth (see optical remote sensing for earth observation).The transition from ground to space observation to space to earth and celestial body observation, thus getting rid of the constraints brought by the atmosphere, is a major scientific progress.For space (celestial body) observation and research, we mainly use different wavebands and different types of optical equipment to receive data fromcelestial bodiesTo detect their existence, determine their location, study their structure, and explore their movement and evolution laws.
If the history of space optics was launched in the 1940sSounding rocketAnd sending balloons, but itsdevelopmentIt is very eye-catching.stay1946utilizeV-2 rocketEmission spectrograph detects ultraviolet rays from space;1957The Soviet Union launched its first man-made satellite.The launch of artificial satellites marks the arrival of the space age.Since then, space optics has begun a period of vigorous development.Since the 1960s, the United States has launched a series of orbital solar observatories (OSO) that continue to observe the whole sun,Soviet UnionA series of astronomical satellites (mainly the "Forecaster" satellite series) have been launched, and the European Space Agency has also launched the Ted-1A (TD-1A) satellite.
However, most of the optical equipment they carry work in the ultraviolet and X-ray bands.From the mid-1960s to the early 1970s, the United States launched three orbital observatories (OAOs), of which OAO-3 was equipped with a Cassegrain type ultraviolet with a diameter of 91 cmtelescopeThe operating wave band is 1000~4000 A, and the spatial resolution is 5 angular seconds.1973The United States launched a manned sky laboratoryApollo telescope mount It is a group of optical equipment for observing the sun. Its emission has brought the observation of the sun from space to a new stage.U.S.A1978The second high-energy observatory (HEAO) launched, which is equipped with a large grazing X-ray telescope,caliber0.6 m, focal length of 3.4 m, resolution of 1~2 angular seconds.There are also four replaceable detectors: high-resolution imager, crystal spectrometer, imaging proportional counterSolid spectrometer。On January 26, 1983, the world's firstInfrared astronomical satelliteIt was successfully launched. This satellite was jointly developed by the Netherlands, the United States and the United Kingdom. It is equipped with an infrared telescope with an aperture of 60 cm. Its sensitivity is higher than that of the same kind usedinstrumentMuch higher.
Research object
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The observation of the sun is mainly to study the structure of the sun
Specifically, for Earth observation, instruments are mainly used to detect and record through visible light and infrared atmospheric windowsa bank of clouds、atmosphere, land andoceanTo study their status and changing rules.staycivilResources exploration (including mineral resources, agriculture, forestry and fishery)meteorological, geography, surveying and mapping, and geologymilitaryFor reconnaissance, space defense and other services;yesspace(Celestial objects) observation and research, for example, the observation of the sun is mainly to study the structure, dynamic process, chemical composition of the sun and long-term and rapid changes in solar activity;Observe the ultraviolet line spectrum, albedo and scattering of planets and comets in the solar system and stars in the Milky Way to determine their atmospheric composition and establish their atmospheric models.
The transition from ground to space observation to space to earth and celestial body observation, so as to get rid of various restrictions brought by the atmosphere, isscienceA major development on the.As we all know, there is a dense atmosphere around the earth, which has restricted people's observation and research of the sky from the ground and low space for many years.The sun is powerfulRadiatorIts maximum radiance is at the wavelength of 0.47 μ m, and 46% of the radiant energy is in the visible spectrum range of 0.40~0.70 μ m.When sunlight passes through the atmosphere, its energy is attenuated due to various effects of the atmosphere. The short wave part of the sunlight projected to the ground is cut off at 0.3 μ m, making it more difficult for X-ray and gamma rays to reach the ground. In the infrared band, the longer the wavelength, the stronger the absorption.At the same time, even the visible light of 3000~7000 A in the atmospheric window and the solar light in the near infrared bands are also affected by atmospheric refraction and turbulence, resulting in a significant decline in the spatial resolution of optical instruments.
The observation and research in space have transcended the barrier of atmosphere and realized visible lightinfrared、ultraviolet rays、X-rayandGamma rayAll electromagnetic wave band detection improves the measurement accuracy.For example, it is estimated that the United StatesSpace telescopeThe aperture is only 2.4 meters, and its resolution is ten times higher than that of the Haier telescope with the aperture of 5 meters on the ground;In addition, all day longSky patrolObservation.
Measuring instrument
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Sketch Map
In general, the space optical systems used in the infrared band are mainlyInfrared telescope。For example, the infrared telescope installed on the first infrared astronomical satellite above uses a fairly compact Cassegrain optical system with double mirrors. The mirrors and supports are made of beryllium alloy with light weight and high strength.The aperture of the primary mirror is 60 cm, the focal ratio is f/10, the secondary mirror is supported by the ring of the light shield of the primary mirror, and the detector is a focal plane assembly.The whole system (including the light shield, anti reflection plate and internal heat shield) is placed in a cooling vacuum system.Cooling systemFor differentpartsUsing different cooling temperaturesPreamplifier, field mirror and filter cooled to 3K, optical system cooled to 10KSunshadeCool to 16K.It is said that its sensitivity is 100 times higher than that of similar instruments used.
The space observation equipment used in the ultraviolet band mainly includes the solar farUltraviolet grazing telescope, Far ultravioletSolar monochromator, far ultraviolet spectrometer - solar monochrome spectrometer, ultraviolet line spectrometer, ultraviolet broadband photometer, etc.They use detectors similar to visible light observation instruments, including photographic emulsionPhotomultiplier tubeAnd image intensifier.Gas ionization chamber andProportional counter。
The instruments used in the X-ray band mainly includeX-ray telescope, solar X-ray spectrometer, solar X-ray monochromator and various types of X-ray detectors.American SkylabS-056 X-ray telescopeThe total length is 253.7 cm, the diameter is 40.3 cm, and the weight is 104.3 kg. The main telescope structure is composed of two dimensional wave tubes.The front tube is installed with a quartz grazing incidence X-ray reflector assembly, and the rear tube is installed with a camera mechanism and a film cassette.Optical system with grazing incidence of X-rayPrinciple of total reflectionThe design consists of a concave grazing incidence paraboloid followed by a concave hyperboloid.The focal length is 190.3 cm, the light collecting area is 14.8 square cm, and the grazing incidence angle is 0.916 degrees.The inner diameter of the reflector at the intersection of the two reflectors is 24.4 cm, the effective field of view is 38 minutes, and the effective focal ratio isf/44。The telescope works with all X-rays above 6 AwavelengthWithin the range, it has high sensitivity and spatial and temporal resolution.
equipment
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spatial light modulator It is a kind of device that can load information on one-dimensional or two-dimensional optical data field, so as to effectively use the inherent speed, parallelism and interconnection ability of light.
Such devices can change the amplitude or intensity, phase, polarization state and wavelength of spatial light distribution, or convert incoherent light into coherent light under the control of time-dependent electric driving signals or other signals.Because of itsnatureIt can be used as the construction unit or key device in real-time optical information processing, optical computing, optical neural network and other systems.
Spatial light modulator can be divided into reflection type and transmission type according to different readout modes of readout light;But according to the inputcontrol signalOfmodeThe difference can be divided into optical addressing (oa slm) and electrical addressing (ea slm).
application
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Space laser communication refers to the use of laser beams as information carriers in space?It includes atmospheric space, low orbit, medium orbit, geosynchronous orbit, interstellar, and space communications.Compared with microwave space communication, laser space communication has a significantly shorter wavelength than microwave space communication, and has a high degree of coherence and spatial orientation, which determines that space laser communication has communicationcapacityLargeweightLightpower wasteAnd small size, high confidentiality, low construction and maintenance costs.
1. Large communication capacity: the frequency of laser is 3-4 orders of magnitude higher than that of microwave (its corresponding optical frequency is 1013-1017 Hz)?As a communication carrier, it has a larger utilization frequency band.Optical fiber communication technologyIt can be transplanted into space communication. The data rate of each beam of optical fiber communication can reach more than 20Gb/s, and the wavelength division multiplexing technology can be used to increase the communication capacity dozens of times.Therefore, in terms of communication capacity, optical communication ratiomicrowave communication It has great advantages.
2. Low power consumption: the divergence angle of the laser is very small, the energy is highly concentrated, and it falls on the telescope antenna of the receiverpower density High, the transmission power of the transmitter can be greatly reduced, and the power consumption is relatively low.This is suitable for space communication with high energy cost.
Space Optics Laboratory, Chinese Academy of Sciences
3. Small size and light weight: due to the high energy utilization rate of space laser communication, the weight of transmitter and its power supply system is reduced;Due to the short wavelength of the laser, under the same requirements of divergence angle and receiving field angle,launchAnd receivetelescopeOfcaliberCan be reduced.Get rid of the huge dish antenna of the microwave system, and reduce the weight and volume.
4. High confidentiality?The laser has a high degree of directionality, the beam is thin, and the divergence angle of the laser is usually in milliradian, which makes the laser communication have a high degree of confidentiality, and can effectively improve the ability to resist interference and eavesdropping.
5. Laser space communication has low construction cost and maintenancefunds。
expectation
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The development of space optical system is to pursue necessary precision and spectral, temporal and spatial resolution, which is closely related to new technologies, new devices and information transmission and processing technologies.The development trend is to develop multiple linear arraysCCD imagingSelf tracing large imaging system of devices and large two-dimensional array focal plane detector, development of data control technology, improvement of satellite and grounddata processing, shorten processingtimeAnd cost reduction;Use X-ray astrophysical equipment to expand the ability of high-energy astronomical observation;The Sun Earth Observatory is used to study the sun Earth environment in more detail.
