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Chang 'e-2, the second satellite to orbit the moon in China's lunar exploration program, is also
Chinese lunar exploration project
Phase II technology lead star, originally
Chang 'e 1
It is named after the ancient Chinese mythological figure Chang 'e.
Chang 'e-2 blasted off from the Xichang Satellite Launch Center on Oct. 1, 2010
[1-2]
; On October 6, 2010, Chang 'e-2 was captured by the moon and placed into orbit around the moon
[3]
; On August 25, 2011, Chang 'e-2 entered the orbit of Lagrange L2
[4]
; On December 15, 2012, the Chang 'e-2 project was announced to be over
[4]
.
The complete success of the Chang 'e-2 mission marked a breakthrough in the field of deep space exploration and China has mastered a large number of new core and key technologies with independent intellectual property rights, laying a solid technical foundation for the subsequent implementation of the "landing" and "returning" of the second phase of the lunar exploration project and the next phase of deep space exploration such as Mars. China has taken another important step in the process from a major space power to a major space power
[5]
.
- Chinese name
- Chang 'e-2
- Foreign name
- Chang'e 2
- Launch time
- October 1, 2010
- Home country
- China
- Launch site
- Xichang Satellite Launch Center
- Honor received
- State Science and Technology Progress Award Special prize
- Chief designer
- Huang Jiangchuan [6]
- Launch rocket
- Long March 3C carrier rocket [1]
On December 17, 2007, the Chang 'e 1 backup planet was named Chang 'e 2
[7]
.
On June 24, 2008, the special study on Chang 'e-2 satellite was held. In July, the second round of overall plan demonstration of Chang 'e-2 was completed; In October, Chang 'e-2 was approved by The State Council. In 2008, the whole program of Chang 'e-2 was designed, which mainly carried out top-level planning, technical status cleaning and review, general specification formulation and other development work, mission orbit design, large-scale system indirect port coordination, sub-system technical specification formulation, X-band transponder and other new product technology research and special test work
[7]
.
In 2009, the first prototype of Chang 'e-2's stand-alone, technical test and payload subsystems was completed. Speed to height ratio compensation for the determination of orbit accuracy requirements, 15 km orbit flight system guarantee and other special coordination and all special tests completed; Complete the development, final assembly, AIT stage electrical performance test and software /FPGA drop welding work; Quality review and review were carried out in orbit design and space single particle effect protection, and technical special studies such as "orbit design, flight program, Iridescent imaging, surveillance camera/UV imaging" were supplemented.
June 2010, Chang 'e-2 quality review and factory review completed; Chang 'e-2 arrived on July 10
Xichang Satellite Launch Center
[8]
.
Chang 'e-2 launch
|
date
|
time
|
Flight time
|
incident
|
|---|---|---|---|
|
October 1, 2010
|
11:00
|
/
|
Officially entered the launch process, held the last meteorological "conference"
|
|
13:30
|
/
|
Weather reports came in, and the rocket was cryogenically fueled with liquid hydrogen
|
|
|
17:00
|
/
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Entering the prefire system, the ground begins to power the system
|
|
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18:20
|
/
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Tower No. 2 rotating platform from the top down to expand step by step
|
|
|
18:45
|
/
|
The last crew leaves launch tower 2
|
|
|
18:58:27
|
/
|
The rocket switches from ground power to battery power inside the system
|
|
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18:58:57
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/
|
60 seconds on the clock for fire and launch
|
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18:59:57
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/
|
Ignite
|
|
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19:00:00
|
/
|
Take off
|
|
|
19:02:07
|
127.4992 seconds
|
Booster separation
|
|
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19:02:23
|
143.4972 seconds
|
Primary and secondary separation
|
|
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19:04:15
|
255.4117 seconds
|
Throw off the fairing
|
|
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19:05:24
|
324.7087 seconds
|
Secondary tertiary separation
|
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Three-stage primary shutdown
|
|||
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Three stage secondary ignition
|
|||
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Three-stage secondary shutdown
|
|||
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Final speed correction shutdown
|
|||
|
19:25:33
|
1533 seconds
|
Separation of star and arrow
|
|
|
Reference materials:
[1-2]
|
|||
On October 6, 2010, Chang 'e-2 was captured by the moon for the first time
Monthly braking
It enters an elliptical orbit around the moon with a period of about 12 hours
[3]
.
In April 2011, the design life of Chang 'e-2 expired, and the established engineering objectives and scientific tasks were completed
[4]
.
Photo of Asteroid 4179 1 (Exposure time: 7 ms) [10]
On August 25, 2011, Chang 'e-2 entered the orbit of Lagrange L2
[4]
.
On June 1, 2012, Chang 'e-2 entered a controlled transfer orbit to an asteroid
[4]
.
On December 13, 2012, Chang 'e-2 rendezvoused with asteroid 4179 (Toutatis) and captured images of the asteroid, completing the first international close-up optical survey of asteroid 4179.
On December 15, 2012, Chang 'e-2 flew into deep space about 7 million kilometers away from the Earth and passed by the asteroid Toutatis, marking the success of Chang 'e-2 further expansion experiment, and the Chang 'e-2 project was announced
[4]
.
On January 5, 2013, Chang 'e-2 reached a distance of 10 million kilometers from the Earth.
On February 28, 2013, Chang 'e-2 reached a distance of 20 million kilometers from Earth.
On July 14, 2013, Chang 'e-2 reached a distance of 50 million kilometers from Earth
[11]
.
On November 26, 2013, Chang 'e-2 reached a distance of 61 million kilometers from Earth
[12]
.
In mid-2014, Chang 'e-2 passed 100 million kilometers from Earth
[13]
.
The Chang 'e-2 mission is divided into seven phases: pre-launch preparation phase, active phase, phase modulation orbit phase, Earth-moon transfer phase, lunar capture phase, lunar working state establishment phase and lunar orbit operation phase.
|
Serial number
|
Start time
|
Flight plan
|
|---|---|---|
|
1
|
October 1, 2010
|
Launch into space
|
|
2
|
October 2, 2010
|
Earth-moon transition
|
|
3
|
October 6, 2010
|
Lunar capture
|
|
4
|
October 6, 2010
|
Circumlunar exploration
|
|
5
|
April 14, 2011
|
Further exploration of lunar orbit
|
|
6
|
June 9, 2011
|
Lunar transition to Lagrange L2
|
|
7
|
August 25, 2011
|
Solar-terrestrial Lagrange L2 point detection
|
1. Obtain three-dimensional images of the lunar surface with a resolution of better than 10 meters, which provides a basis for the subsequent landing area optimization, and provides original data for the division of geomorphic unit fine structure, fracture and ring structure on the lunar surface
[14]
.
2, to detect the composition of lunar materials, to detect the content and distribution characteristics of silicon, magnesium, aluminum, calcium, titanium, potassium, thorium, uranium and other elements on the lunar surface, and to obtain the distribution map of elements with higher spatial resolution and detection accuracy
[14]
.
3. Probe lunar soil characteristics. The microwave radiation characteristics of the lunar surface were measured by microwave detection technology, the microwave radiation brightness and temperature data were obtained, and the lunar soil thickness was estimated
[14]
.
4. Probe the Earth-moon and near-moon space environment. During Chang 'e-2's orbit, it is the peak year of solar activity, which is the best exploration period for the detection and study of solar high-energy particle events, solar wind and its impact on the lunar environment. The flux, composition and energy spectrum of interplanetary solar energetic particles and solar wind ions are obtained by solar energetic particle detector and solar wind ion detector, and the interaction between solar activity and Earth-moon space and the near-moon space environment can be studied. The acquisition of Earth-moon space environmental data can provide environmental scientific data for the follow-up missions of China's lunar exploration project
[14]
.
-
"Fast, close, precise and many"
|
keyword
|
Characteristic description
|
|---|---|
|
fast
|
The Chang 'e-2 satellite was sent directly into orbit around the moon by a carrier rocket, without passing through a transitional orbit, which is more efficient.
|
|
nearly
|
Chang 'e-2's orbit around the moon was lowered to 100 kilometers, and its closest point was only 15 kilometers, to get a closer look at the moon.
|
|
fine
|
The measurement accuracy of Chang 'e-2 has been improved, and the camera resolution is 10 meters at 100 kilometers orbit and 1.5 meters at 15 kilometers orbit, which is a high resolution.
|
|
more
|
Chang 'e-2 conducted many experiments, such as deep space exploration, landing camera test and other projects.
|
|
Reference materials:
[15]
|
|
-
Flight control is complex
Chang 'e-2 needs to go through 100 km ×100 km and 100 km ×15 km test orbit around the moon, which needs to undergo many complex orbit and attitude maneuvers, and has high requirements for satellite orbit control
[16]
.
-
Complex space environment
During its lifetime, Chang 'e-2 will undergo two lunar eclipses, each with an effective shadow duration of about three hours. During this period, the satellite cannot obtain light energy, and the temperature of the satellite will decrease rapidly, which requires high requirements for satellite energy, temperature, and the whole planet working mode
[16]
.
-
The three-body combination control mode is complex
During Chang 'e-2's orbit around the moon, the star should be oriented to the moon, the solar wing should be oriented to the sun, and the directional antenna should be oriented to the earth, so the attitude control of the satellite body, solar wing and antenna is required
[16]
.
-
There are many new and improved equipments
In addition to the six payloads of Chang 'e-1, Chang 'e-2 satellite also adds a technical test subsystem, including X-band transponder, landing camera and other engineering payloads, so the type of intelligent terminal of the satellite system is complex, and there are special requirements for satellite information collection, storage, compression, coding and other processing modes
[16]
.
|
item
|
Technical requirement
|
|---|---|
|
Satellite weight
|
≤2480 kg
|
|
Satellite dry weight
|
≤1175 kg
|
|
Working track
|
100 km x 100 km
|
|
Test track
|
100 km x 15 km
|
|
Satellite lifetime
|
6 months
|
|
Structure body size
|
2000 mm x 1720 mm x 2200 mm
|
|
Accuracy of attitude control towards the moon
|
≤±1 degree (3σ)
|
|
Attitude control stability towards the moon
|
≤0.005 degrees/second
|
|
Propulsion mode
|
Two-component unified propulsion system
|
|
Power supply output
|
1466 watts
|
|
Angle of incidence
|
45 degree Angle of incidence
|
|
Measurement and control system
|
USB+VLBI
|
|
Telemetry code rate
|
512 bits per second /1024 bits per second (after coding)
|
|
Remote code rate
|
125 bits per second
|
|
Encoding mode
|
Convolutional encoding /LDPC encoding
|
|
Data transmission modulation mode
|
BPSK
|
|
Data to code rate
|
6 megabits per second
|
|
Reference materials:
[17]
|
|
Chang 'e-2 uses the Dongfanghong 3 satellite platform, with a total mass of 2350 kg, a design life of one year, and a size of 2000 mm ×1720 mm ×2200 mm, inheriting the mature technology and products of Earth satellites such as Resource No. 1 and No. 2 for adaptive transformation.
The Chang 'e-2 satellite has a total of 10 sub-systems, which can be divided into two parts: service system and payload. Service systems include: structure, thermal control, guidance/navigation and control (GNC), propulsion, power supply and distribution, data management, measurement and control data transmission, directional antenna and technical testing. Load subsystem by
CCD stereo camera
,
Microwave detector
,
Solar energetic Particle Detector
Such as a variety of load composition.
Chang 'e-2 operation
LDPC
Coding function, compared with convolutional coding gain of about 2.5 dB; The engineering load data transmission channel is increased, and the minimum multi-file code rate of 23.4375 kilobits per second is designed, which can support the data transmission from 20 million kilometers to the ground.
-
summary
Chang 'e-2 carries scientific instruments
-
APS camera
Chang 'e-2 is equipped with four APS cameras as the main equipment of the technical test subsystem, and the new technology of the camera is tested and verified. It mainly includes several key technologies, such as APS in-orbit imaging technology, high system integration technology, automatic exposure technology, high rate compression technology, and space environment adaptive imaging design
[10]
.
-
CCD stereo camera
Chang 'e-2 is equipped with a TDI-CCD camera, and adopts the principle of multiple linear CCD to expose the same target multiple times, which can meet the requirements of camera exposure control for resolution improvement, and can obtain ultra-high resolution images with a local resolution of better than 1.5 meters in the near-monthly arc
[18]
.
-
Solar energetic Particle Detector
Chang 'e-2 is equipped with a solar high-energy particle detector, which can obtain the flux, composition, energy spectrum and time-space variation characteristics of interplanetary solar high-energy particles and solar wind ions, and is used to study the interaction between solar activities and the Earth-moon space and the near-moon space environment, and provide environmental scientific data for subsequent lunar exploration projects
[19]
.
-
X-ray, gamma ray spectrometer
Chang 'e-2 is carrying
Gamma ray spectrometer
, which is used to detect crystals
Lanthanum bromide
New materials, the detection sensitivity increased by more than 1 times; The X-ray spectrometer carried by Chang 'e-2 can detect the content and distribution characteristics of nine elements on the lunar surface, including silicon, magnesium, aluminum, calcium, titanium, potassium, thorium and uranium, and obtain the distribution map of elements with higher spatial resolution and detection accuracy
[19]
.
1. During the operation of Chang 'e-2, all orbital and maneuvering flight control technologies before the power descent in the subsequent landing mission were designed and verified
Earth-moon transfer orbit
For the first time, X-band measurement and control was used to conduct high-resolution imaging of the Chang 'e-3 landing area.
2. In view of the uneven gravity field of the moon and the highly fluctuating terrain environment, it broke through key technologies such as the moon's freezing orbit design, satellite autonomous inertial alignment, and maneuvering orbit splicing, successfully realized the 100 km circular orbit and 100 km ×15 km orbit flight for the first time, and realized the main engine ignition and orbit change without measurement and control conditions on the far side of the moon. The accuracy of satellite orbit control is up to 0.02%.
3, In the international lunar exploration, Chang 'e-2 for the first time to use time delay integral (
TDI
Two kinds of velocity to height ratio compensation imaging methods assisted by ground line frequency data injection and altiometry data were designed, and the whole moon stereo image with a resolution of 7 meters was obtained. The local image with a resolution of 1.3 meters was obtained, which reached the international advanced level.
4. Innovated and developed the first X-band high-sensitivity digital measurement and control transponder based on the unified carrier system, achieving a number of breakthroughs in spaceborne measurement and control technology in the field of deep space exploration. The on-orbit test verified the X-band deep space TT&C system and technology. Breakthrough in differential unidirectional ranging (DOR) interferometry, X-band digital transponder and ground S/X dual-band measurement and control equipment development and other key technologies, speed measurement accuracy reached 1 mm/s, ranging accuracy reached 1 meter, the realization of 7.8125 bits per second of extremely low code rate remote control.
5. Break through the micro-intelligent design technology, and realize the monitoring imaging of the Earth-moon space flight process for the first time. For the first time, dynamic images of key links such as solar wing deployment, antenna deployment/rotation, and main engine ignition were obtained in real time.
6. It was first used in the space segment of aerospace engineering
LDPC
The main indexes of encoding and decoding, encoding gain and efficiency are better than the international (CCSDS) standard.
7. The long-life technology of the high-pressure gas path of the propulsion system was verified on-orbit for the first time, laying a dynamic foundation for high-intensity (time span of more than half a year, more than 10 times) orbital maneuvering and subsequent L2 point and asteroid detection tests.
8. For the first time, the detection sensor and load integration technology were broken through, and the satellite-ground large loop navigation test was completed with the imaging sensor.
9. In the complex environment of Earth-moon and Sun-Earth double trisomes, aiming at the difficulties such as the complex perturbation of the solar and Earth gravitational translational points, the absence of analytical solutions in orbit design, and the long distance of measurement and control, the manifold design of nonlinear system and low-energy transfer orbit control technology have been overcome, and the orbit design, flight control and long-distance measurement and control communication of the flight from lunar orbit to L2 point have been realized. For the first time in the world, China has flown from lunar orbit to the Japan-Earth Lagrange L2 point of exploration, and carried out scientific exploration of the Earth's far magnetic tail ion energy spectrum, solar flares and cosmic gamma-ray bursts, making China the third country after the United States and Europe to carry out space exploration of L2 point.
10. Breaking through the deep space orbit and measurement and control communication technology 10 million kilometers away from the earth, achieving the first interplanetary flight. Based on the strong constraints of energy, distance and time, as well as the physical characteristics of the target, a potential asteroid target selection strategy is proposed, and the approach flyby detection method and the high-speed converging apodiation gaze imaging technique are designed and realized for the first time in the world. The world's first successful flyby of asteroid 4179 Toutatis and the acquisition of 3-meter resolution optical color images.
11. Innovative utilization
The Lagrange point
Under the constraints of satellite propellant, satellite-earth communication distance, and the progress of large antenna on the ground, the transfer from the Lagrange point to a small body has been realized for the first time in the world.
12, through innovative design, comprehensive verification, careful implementation, make full use of the remaining resources of the satellite, give full play to the potential of the satellite, from the moon to L2 and then to Toutatis, to achieve multi-target and multi-mission exploration with international characteristics and standards, and achieve outstanding results of "good, fast and save".
13. Through the transformation and application of previous research results, special observations from multiple stations at home and abroad have been carried out to achieve the target asteroid orbit determination and prediction, and the accuracy has reached the international advanced level
[20]
.
|
Serial number
|
experiment
|
|---|---|
|
1
|
Breakthrough in the launch technology of launch vehicles that directly launch satellites to Earth-moon transfer orbit
|
|
2
|
The X-band deep space TT&C technology was tested, and the deep space TT&C system was initially verified
|
|
3
|
Verify the 100 km lunar orbit acquisition technology and accumulate more space environment data near the month
|
|
4
|
Verification of maneuvering and rapid orbit determination technology for 100 km ×15 km elliptical orbit around the moon
|
|
5
|
Low density check code telemetry channel coding, high speed data transmission, landing camera and other technologies were tested
|
|
6
|
A high-resolution imaging experiment was carried out on the landing area of Iridescent Bay on the moon pre-selected for the Chang 'e-3 mission
|
|
7
|
Transfer and test from lunar orbit to Sun-Earth L2 point
|
|
Reference materials:
[14]
|
|
|
Award time
|
Award name
|
Awards received
|
issuer
|
|---|---|---|---|
|
The year 2012
|
Chang 'e-2 project
|
State Science and Technology Progress Award
Special prize
|
/
|
|
Reference materials:
[21]
|
|||
The complete success of the Chang 'e-2 mission marked a breakthrough in the field of deep space exploration and China has mastered a large number of new core and key technologies with independent intellectual property rights, laying a solid technical foundation for the subsequent implementation of the "landing" and "returning" of the second phase of the lunar exploration project and the next phase of deep space exploration such as Mars. China has taken another important step in the process from a major space power to a major space power
[5]
.
(Academician of the Chinese Academy of Sciences, representative of the research and development unit of the lunar exploration project Chang 'e-2 mission, chief designer of the launch vehicle
Jiang Jie
Review)
Sinus iridum
Chang 'e-2's controlled and accurate entry into the orbit of the Sun-Earth Lagrange L2 point is the first time that China has carried out the design and control of the Lagrange point transfer orbit, and achieved 1.5 million kilometers of long-distance measurement and control communication. This marks China becoming the third country in the world to visit the solar-terrestrial Lagrange L2 point, and the first country in the world to reach the point from lunar orbit
[23]
.
(Commentary by People's Daily)
