Speaking of "Magpie Bridge", most people will think of the love story of the Cowherd and the Weaver Girl. In order for the Cowherd and the Weaver Girl to meet, magpies from all over the country used their bodies to build a bridge - the Magpie Bridge, and the Cowherd and the Weaver Girl met on the Magpie Bridge.
Four years ago, at 5:28 on May 21, 2018, the Long March 4C carrier rocket carried the "Queqiao" relay satellite into space. The "Queqiao" relay satellite orbits the Earth-Moon Lagrange L2 point, about 65,000 kilometers away from the moon. It has become the world's first satellite to orbit this point, providing ground for the Chang'e-4 lunar probe. Monthly relay measurement and control communications.
At present, the "Queqiao" relay satellite is operating stably in orbit, and the equipment of each subsystem is in good working condition. We look forward to it returning more detection data and achieving more fruitful scientific results.
How does the "Queqiao" relay satellite keep the Earth permanently connected to Guanghan Palace Chang'e-4?
How does the "Queqiao" relay satellite keep Chang'e-4 permanently connected?
01
"Queqiao" Earth-Moon Communication
Let The back of the moon is no longer "no service area" with the earth
Due to the tidal locking between the earth and the moon, the moon's rotation period and revolution period are exactly the same. For millions of years, humans can only see the moon's " "Front face", before Chang'e 4 softly landed on the back of the moon, the back of the moon was like a little girl waiting to be married, never showing off to others easily.
This is because once the spacecraft lands on the back of the moon, the signal will be blocked by the moon. Without the "contact person" in the middle, the earth and the spacecraft cannot get in touch. It is like two people " shouting across the mountain " unable to hear each other. . At this time, the "Queqiao" relay satellite can play the role of a passer. After
"Magpie Bridge" opened its 4.2-meter "giant umbrella", it meant that the largest-diameter space communication antenna in the history of human deep space probe began to work normally in more than 400,000 kilometers of interstellar communication links.
html In 14 years, letters were sent from the earth to the moon, so that the back of the moon and the earth are no longer "without service areas".02
Laser corner reflector
Sets up a communication distance of more than 400,000 kilometers
In addition to the "giant umbrella", the "Queqiao" relay satellite also has an ultra-high-definition "reflector" - a laser corner reflector. The laser beam emitted by the Earth Observation Station can accurately find the "Magpie Bridge" flying at high speed more than 400,000 kilometers away, and calculate the distance between the star and the earth through the time difference between sending and receiving. This is the longest distance laser ranging test in human history.
The "Queqiao" relay satellite is not big, and its entire "weight" is only 448 kilograms.
Although it looks inconspicuous on the outside, the "lining" has "connotation". With a communication distance of more than 400,000 kilometers, "Magpie Bridge" builds the longest "bridge" in the world. Speaking of "Queqiao", it is easy to think of the "Tianlian-1" relay satellite with mature technology. 11 years ago, the first " Tianlian-1 " was successfully launched. In the past 11 years, the four "Skylink-1" relay satellites launched successively have been operating in a network, successfully achieving 100% global coverage of medium- and low-orbit spacecraft.
Compared with "Tianlian-1", the "Queqiao" relay satellite has one biggest difference - "Tianlian-1" adopts a transparent forwarding method for data, that is, it does not process the data and maintains the "original taste"; The "Queqiao" relay satellite belongs to "regenerative forwarding", that is, the data is first "decoded", "deformatted", "multiplexed" and "encoded" before being sent. It can be seen that the "Queqiao" relay satellite has been fully upgraded.
03
is running in the Halo orbit.
"sees" both the earth and the moon.
The "Queqiao" relay satellite is running in the Halo orbit, flying around the Earth-Moon Lagrange L2 point. The Earth-Moon L2 point is located on the Earth-Moon line. On the extended line is one of the gravitational balance points between the Earth and the Moon. The "Queqiao" relay satellite is the world's first satellite operating at this location.
At this point, it can see the earth and the back of the moon at the same time, and can always maintain communication with the Chang'e-4 lander and rover that landed on the back of the moon, and at the same time establish contact with the ground station to achieve the required relay communications.At the same time, near the Earth-Moon translation point, the gravitational pull between the Earth and the Moon is relatively balanced. When the relay satellite flies here, it is easier to maintain a relatively stable operating state. The mission orbit shape of
is different from the elliptical orbit of earth satellite , but a three-dimensional irregular curve, and the orbit control is very complicated. The "Queqiao" relay satellite will perform quasi-periodic motion around the L2 point, maintain orbital stability through regular orbit control, and achieve relay communication coverage for the Chang'e-4 lander and rover.
04
Fiber optic gyroscope Inertial measurement unit
Get rid of the need to use the earth, the sun and other celestial bodies to locate
Halo orbit is also called "halo orbit", which means solar halo and lunar halo . The orbit shape is a non-coplanar three-dimensional irregular curve. The difficulty and complexity of the control of " halo track " are "really dizzying."
"Queqiao" relay satellite is like a naughty child. As long as you don't pay attention to it for a period of time, it may "run away from home." In order to keep an eye on this naughty "child", the flight control "parents" on the ground specially customized a The fiber optic gyro inertial measurement unit with high intelligence level, all-weather, all-day and all-airspace operation capabilities has completely got rid of the previous constraints of needing to rely on the earth, the sun and other celestial bodies for positioning, and greatly improved its orbit control capabilities.
In order to meet the challenge of frequent attitude adjustments of the spacecraft in complex orbits, experts also designed two modes: speed incremental shutdown and time shutdown, and accurately designed the engine pulse width before orbit control shutdown.
At the same time, "Queqiao" has the ability to control the speed with an accuracy error of no more than 0.02m/s during high-speed on-orbit flight at 1000m/s. It can be said that "it can stably do micro-carving while running at high speed." This ability to be "independently controllable and accurate to the last detail" lays the foundation for the safe, long-term and stable on-orbit operation of relay satellites.
05
Equipped with multiple "mobile phones"
Multiple safe backup remote control commands to ensure uninterrupted communication
Building a communication link that travels through more than 400,000 kilometers of "interstellar space" and connects the earth and the moon will test not only the scientific and reasonable design, but also the Stable and reliable working conditions are required. The design of multi-safety backup telemetry and remote control commands is an innovative move made by technicians from the Xi'an Branch of the Fifth Academy of Aerospace Science and Technology Group in response to the unique working environment of "Queqiao". It is like equipping "Queqiao" with multiple "mobile phones" through multiple backups.
Ground staff can call these "mobile phones" at the same time and issue the same telemetry instructions to avoid problems such as signal interruption and inaccurate information transmission caused by long distances or other unknown factors. In addition, the S-band digital deep space transponder equipped by "Queqiao" is my country's first digital deep space transponder. It not only has the function of self-correction of erroneous data, but also has strong sensitivity and signal capture capabilities, which will further improve the stable operation of the spacecraft. The last "safety lock".
06
uses special materials
to cope with the severe cold test of minus 230 degrees Celsius
The "Queqiao" relay satellite will experience a period of days without light in the vast space. When there is no sun, the temperature in the shadow area is about minus 200 degrees Celsius, the coldest The place will reach minus 230 degrees Celsius. Under such severe cold, the whole body of the antenna must be "frozen". These antennas need to undergo severe tests in space. In order to prevent it from being "frozen" in an "ice cellar"-like environment, during the development process, in addition to using special materials, scientific and technological personnel also conducted a large number of tests in extreme environments, effectively ensuring that these antennas can cope with harsh environments. test.
Coordinator: Yi Fuhong Yang Cunhai
Comprehensive Xinhua News Agency , CCTV
IC photo
