Caption: The Chang'e-6 returner landed safely carrying lunar samples from the far side of the moon Source/Xinhua News Agency (the same below)
html At 14:07 on June 25, the Chang'e-6 returner accurately landed in the predetermined area of Siziwang Banner in Inner Mongolia and was working normally. It marked the complete success of the Chang'e-6 mission of the lunar exploration project and achieved the world's first return of samples from the far side of the moon.Chang'e-6's lunar exploration journey went through the carrier launch section, the Earth-moon transfer section, the near-lunar braking section, the lunar flight section, the landing and descent section, the lunar surface working section, the lunar surface ascent section, rendezvous and docking and samples The transfer section, the lunar waiting section, the lunar-to-Earth transfer, the re-entry recovery section, etc. are known as one of the "most complex missions" in my country's aerospace history.
The road to breakthrough is "full of energy"
The tasks are interlocking and cannot be missed. In order to ensure that Chang'e-6 successfully "breaks through", the power supply "lineup" of Chang'e-6 is quite "luxurious", and its power supply method is also very complicated.
Chang'e-6 is composed of four major sections: the orbiter, returner, lander, and ascender. Among them, the orbiter, lander, and ascender are each equipped with solar cell wings. In order to ensure stable energy supply throughout the mission, the orbiter The solar wings of the lander have an angle adjustment function, while the lander's solar wings not only have an angle adjustment function, but also a deployment and retraction function. The ascender and orbiter are also equipped with lithium-ion battery packs respectively. From the earth to the moon, and then back to the earth, in order to go all out to cope with this challenging journey, at each exciting stage, the power supply will be adjusted according to the timing and the stage.
In order to improve the safety and reliability of the detector's power supply, and to further "reduce weight", Chang'e-6's four-vehicle team is composed of two teams: the orbiter and returner ("orbit return") combination and the lander and ascender ( "on") combination. Before the moon landing, during the joint flight of the four vehicles, the "orbit return" assembly and the "landing" assembly have the ability to provide two-way power supply. When either side encounters power shortage, the orbiter and lander can provide each other with a power supply capacity of no less than 300 watts. The
"mounting" assembly has a set of reasonable and orderly power supply divisions when performing important tasks such as moon landing, "digging", and ascent. Before the moon falls, the power supply task is handed over to the lander's solar wing during the light period and to the ascender's lithium-ion battery pack during the shadow period; when the moon falls, the ascender's lithium-ion battery pack assumes the responsibility of powering the assembly; "Dig. When "digging", the power supply is jointly supplied by the solar wing of the lander and the battery pack of the ascender; after the "digging" is completed, the ascender takes off from the lunar surface, the partnership between the two partners ends, and each of them supplies power independently.
Since the returner only carries a primary power supply, the orbiter assumes the task of providing long-term power supply to the returner. After the "orbit return" assembly separated, the returner was powered by a primary battery and returned to Earth. It carried not only lunar samples, but also the dreams of the other three "companions".
Caption: Animated simulation of the Chang'e-6 returner's imminent landing
Escorting the longest-lived satellite in deep space
After successfully completing the Chang'e-6 mission, the Queqiao-2 relay star will choose an opportunity to carry out a scientific exploration mission. The extreme ultraviolet camera it carries , the Array Neutral Atom Imager and the Earth-Moon Very Long Baseline Interferometry (VLBI) experimental system, which will collect scientific data from the moon and deep space.
"As a key link in the implementation of the fourth phase of the lunar exploration project, Queqiao-2 will operate in orbit for 8 years and is the longest-lived satellite in my country's deep space field." Queqiao-2 Relay Satellite from the 811th Institute of the Eighth Academy of China Aerospace Science and Technology Corporation Commander Xu Qifeng introduced that the Queqiao-2 relay satellite has chosen a special mission orbit, which brings problems such as extremely low temperature, long ground shadow, and high radiation, which have brought challenges to the developers of the 811th Institute of the Eighth Academy of Sciences, which is responsible for the development of the power subsystem. . The
relay satellite is in a frozen orbit around the moon. The space environment is very harsh. The satellite will experience two simultaneous shadows from the earth and the moon twice a year. The longest shadow period is nearly 5 hours. During this period, the battery will undergo a deep discharge of up to 90%. This is very important for The battery life is quite disadvantageous.In addition, when it is in the shadow period for a long time, the surface temperature of the satellite drops to minus 207°C, which is the lowest temperature encountered by the domestic satellite power supply so far. It will also have a great impact on the exposed solar wing outside the star. The developers faced the challenge head-on, improved the formula of lithium batteries, optimized the battery structure, tailor-made long-life lithium-ion battery cells that can store high state of charge for a long time, and carried out one-to-one ground simulation tests to test lithium-ion batteries. Battery performance. The team also proposed for the first time new technologies such as long-shadow charging final voltage upshift and temperature wake-up, which effectively extended the battery life on orbit; it also formulated a battery protection strategy of "over-discharge, overcharge, and short circuit" to ensure that the lithium battery will be in orbit for 8 years. Reliable to use.
In order to ensure that the solar wing installed outside the relay star module can maintain stable operation, the 811 research and development team carried out technical research in three aspects: components, raw materials and processes: for the first time, it selected a solar wing with better fatigue resistance and greater strength. The alloy material was used as the battery interconnection sheet, and a resistance welding process with a wider temperature alternating range was adopted to synthesize an extreme temperature resistant film adhesive, and a new solar cell chip patching process was developed based on the film adhesive.
"Navigating" the lunar exploration journey in real time
In the Chang'e-6 mission, my country's Very Long Baseline Interference (VLBI) orbit measurement subsystem plays an important role in earth-moon communications. It is like a pair of eyes, providing real-time navigation for Chang'e-6 No. "Navigation". The
vlbi measurement subsystem includes "four stations and one center", namely Shanghai Tianma Station, Beijing Miyun Station, Xinjiang Nanshan Station, Yunnan Kunming Station and Shanghai vlbi data processing center. The highest resolution can be equivalent to a machine with a diameter of 3200 kilometers. single aperture telescope.
"Since Chang'e 1, we have successfully applied real-time vlbi technology to the orbit determination of the lunar probe, forming the existing 'range and speed measurement + vlbi angle measurement' deep space high-precision orbit determination system." Chinese Academy of Sciences Shanghai Zheng Weimin, a researcher at the Observatory, said.
Caption: A group photo of some scientific researchers of the VLBI operation team after the successful return of Chang'e-6. Source/Provided by Shanghai Observatory.
The reporter learned that during the Chang'e-6 mission, the VLBI orbit measurement subsystem faced different difficulties and challenges than before: ground observation station The position of the detector is partially invisible during near-lunar braking and lunar-to-earth incident. It is not visible during the power descent section, lunar surface working section, and lunar surface ascent section. It requires the support of the Queqiao-2 relay satellite. Compared with the "Chang'e-5" mission, the requirements for timing and fixed-point landing are higher, and the propellant surplus is smaller; because the Chang'e-6 mission adopts a new retrograde orbit, the flight time around the moon is greatly increased, and the real-time mission period is longer. The extension from 23 days to 53 days is a great test for the stability of vlbi equipment and the continuous work of personnel.
Zheng Weimin introduced that during the implementation of Chang'e-6, the vlbi orbit measurement subsystem was mainly responsible for the real-time orbit determination of 9 of the 11 flight segments of the entire mission. "In the Chang'e-6 mission, the vlbi measurement subsystem can measure four It can conduct real-time orbit determination of the orbiter assembly, the separated orbiter and the ascender, and can also conduct real-time orbit determination of the Queqiao-2 relay satellite in a time-sharing manner, supporting measurement and control communications on the far side of the moon. In addition, it can also complete dual missions. The rapid switching of target observation and orbit determination ensures that the switching between the Chang'e-6 detector and the relay satellite can be completed within 50 minutes, and the subsequent switching time between the orbiter and the ascender will be even shorter."
Xinmin Evening News reporter Ye Wei Gaoyang
