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The return capsule of China's Chang'e-5 probe touched down on its preset landing site in Siziwang Banner of the Inner Mongolia Autonomous Region at 01:59 a.m. on December 17, bringing back the country's first samples collected from the moon. The successful landing marks the completion of the Chang'e-5 mission, and also a successful conclusion of China's current three-step lunar exploration program of orbiting and landing, and bringing back samples.
The series of products with high performance, high precision and high reliability developed and produced by CASIC provides full support for the Chang'e-5 mission in orbiting and landing, and bringing back samples.
Instrumentation Radars "Take" the Return Capsule of Chang'e-5 Probe Home
The two instrumentation radars developed by CASIC successfully completed the tracking measurement in the return of the Chang'e-5 return capsule to Earth. They mainly performed high-precision measurement in the return process of the return capsule, sent back measured data to the command and control center in real time, and provided effective target landing point data to guide search and recovery at the frontline.
As an important part in Phase III of China's lunar exploration program, these two radars are mainly used to complete tracking measurement of various return capsules and orbit measurement in space launch. The radar far away from the landing area is mainly used for tracking measurement from the blackout zone to the ground, while the other one closer to the landing area mainly for tracking measurement from the return capsule to the ground after a signal is sent.
When the return capsule returns to the atmosphere, it creates intense friction with the surrounding air, forming a high-temperature and high-pressure ionized gas layer. This gas layer is wrapped around the surface of the return capsule just like a scabbard, to isolate the communication between the return capsule and the ground TT&C station. As a result, a blackout zone is formed. Such a dangerous phenomenon will cause deviation of the return capsule from the preselected landing area, delay search and recovery of the return capsule, and endanger the flight safety in severe cases. Moreover, it may even endanger the life of astronauts in the return capsule.
To realize radar tracking measurement in blackout zone and escort for the return capsule to return to Earth, the radar developers have made great efforts based on more than ten years' experience in the return missions of Shenzhou spacecraft, including careful analysis on guidance data before the recovery of Chang'e-5, full communication with the users, cooperation with the users to make adequate planning for the tracking measurement in blackout zone in the return mission, as well as adequate preparation to avoid stealth of the return capsule to the radar in blackout zone.
The radar found and captured the target immediately after the return capsule of Chang'e-5 moved into its field of view. In the whole mission, the radar tracked the target stably, sent back measured data to the center in real time and predicted the landing point of the return capsule, laying a solid foundation for the immediate search and recovery after the return capsule touched down safely. In May 2020, the radar contributed to the successful recovery of the return capsule of the new-generation manned spacecraft and a cargo return capsule for test, gaining experience in tracking measurement in blackout zone for the return of the Chang'e-5 return capsule to Earth.
The other radar is the tracking radar serving the final stage of the recovery mission. It performs target measurement after parachute deployment of the return capsule.
The landing section is a track section where the return capsule moves to the end of the return track and makes a soft landing by means of landing system or gliding flight. At this stage, parachutes play an important role in ensuring the landing safety of return capsule, while they are greatly affected by wind. At this stage, neither common radars can perform accurate measurement, nor optical equipment can perform round-the-clock and all-weather detection due to weather and light. Instead, this radar can realize high-precision positioning of the return capsule by means of passive positioning system from parachute deployment to landing, and work round the clock and all weather, fully guaranteeing the last step in the recovery task. In its first participation in the manned space mission, this instrumentation radar provides timely and accurate data information to guide the landing point prediction and the search and recovery of the return capsule.
Three Core Components Escort for Chang'e-5 in the Whole Journey
In the Chang'e-5 mission, the high-precision accelerometers mainly undertook the translational acceleration measurement of the probe in the stages of earth-moon transfer, lunar flight, rendezvous and docking in lunar orbit and moon-earth transfer, ensuring smooth and accurate maneuvering control over the probe during the orbital flight and the rendezvous and docking.
During the lunar landing of Chang'e-5, the gamma shutdown sensor measured the distance between Chang'e-5 and the lunar surface, and issued a brake command at a critical moment to make Chang'e "trippingly" land on the moon, realizing the "soft landing" of the probe.
As a key part in rendezvous and docking in lunar orbit and transfer of lunar samples, the microwave radar for rendezvous and docking in lunar orbit accurately measured the relative positions and attitudes of the orbiter and the ascender of Chang'e-5 probe, and realized two-way air-to-air communication, guiding the orbiter and the ascender to realize rendezvous and docking in lunar orbit and ensuring the safe transfer of lunar samples.
"Customized Design" Ensures Successful Unfurling of the Bright Five-star Red Flag on the Lunar Surface
Chang'e-5 probe landed successfully on the moon with a bright five-starred red flag slowly unfurled from the probe on the lunar surface.
As a landmark in this lunar exploration mission, the flag presentation system plays an important role. It must unlock and unfold independently with high reliability and high safety and is installed outside the lander. Considering harsh space environment, it needs to be of light and miniaturized design and meet extremely strict requirements on weight. While meeting the above-mentioned functional requirements, the system also needs to extend from the probe at the time of unfolding and provide a larger flag size and a good shooting angle, so as to allow the panoramic camera to take rich-element and well-scaled flag images.
To solve the technical difficulties of extreme space environment adaptability outside the capsule, unlocking and unfolding with high reliability and safety, and lightweight and miniaturization, the development team pooled wisdom to make breakthroughs, and carried out a large number of environmental tests, life tests, verification tests and reliability analysis, ensuring successful completion of the mission.
Crystal Components Stabilize the Pulse of this Accurate Lunar Exploration
The frequency signal of Chang'e-5 is like the pulse of human body, and the pulse stability is the prerequisite of the probe's stable and normal operation. Hundreds of autonomously controllable crystal components developed and produced by CASIC act as the heart of electronic equipment of Chang'e-5, stabilizing the pulse of Chang'e during the flight. Crystal oscillator, quartz resonator and other crystal components provide stable and reliable frequency signals in the stages of launch, TT&C, on-orbit flight, sampling and return of the mission.
High-performance clock crystal oscillator is a "meritorious" product that has been widely used in China's lunar exploration program. In the Chang'e-5 mission, it became an all-rounder again, acting as not only the communication equipment of the "forward-looking eyes" and the "attentive ears", and the control system for controlling precise landing of Chang'e-5, but also the optoelectronic equipment for taking images of the "Moon Palace", and the control system for controlling sampling and return of Chang'e-5. It was busy everywhere, fully ensuring the control and sampling of Chang'e-5 in distant space, and as well as the return of the probe to Earth.
With accurate frequency, the shock-resistant temperature compensated crystal oscillators (TCXOs) were all in the "key positions" of the Chang'e-5 probe to provide accurate signals for the beacon of Chang'e-5 probe. With the capability of withstanding strong shocks, these TCXOs provided accurate signals for the final positioning, ensuring the safe return of Chang'e-5 to Earth.
Key Components Escort for "Chang'e" during Lunar Exploration
The customized connection unlocking device plays an important role in the stages of lunar landing and bringing back samples in the Chang'e-5 mission. The ascender connection unlocking device is used for the connection and unlocking between the ascender and the lander of Chang'e-5, and the returner connection unlocking device for the connection and unlocking between the orbiter and the returner. The release push rod mechanism functions in electrical connector release and mechanical unlocking between the returner and the orbiter before the reentry of Chang'e-5. The precision gear transmission mechanism plays a pivotal role during detection, investigation, sample collection and transfer of Chang'e-5 probe on the lunar surface.
Self-locking valves, filler and drain valves, temperature control valves and other supporting high-reliability products of the temperature control system of Chang'e-5 probe are used to maintain a suitable and constant temperature environment for all kinds of instruments in the probe. Featuring fast response and high reliability, various special solenoid valves used in the attitude control system play a pivotal role in attitude control, ensuring accurate attitude adjustment of Chang'e-5 in the stages of orbital transfer, landing and bringing back samples.
The simulation, analysis and evaluation system developed for the lunar exploration mission provides quantitative analysis and evaluation means for the TT&C system of Chang'e-5, strongly supporting the design, analysis and evaluation of the TT&C scheme. In the Chang'e-5 mission, more than 7,800 connectors and relays are used for signal transmission, control, and ON/OFF in related systems, acting as the "nerve center" of the electrical signal transmission system. The zinc-silver storage battery pack equipped for the Chang'e-5 return capsule provides stable power supply for all equipment in the capsule. Tens of thousands of high-strength and high-performance fastener makes the body of Chang'e-5 just as strong as iron.
