In an interview, the general designer of the Tracking, Telemetry, Command and Communication System of the China Manned Space Engineering Qian Weiping said that, if we say the core mission of the Shenzhou-9 is to realize the rendezvous and docking and withdraw, then the core of the core task is the fight management and control, and everyone is paying close attention to the "flight control."
The Tracking, Telemetry, Command and Communication System is facing three major tests
Reporter: Compared to the Shenzhou-8 mission, in which, "the flight control is the emphasis, key point and difficult point," what has changed in the Shenzhou-9 mission?
Qian: In the Shenzhou-9 mission, the "flight control" or the Tracking, Telemetry, Command and Communication System is still the difficult point and highlight. During the hand-control rendezvous and docking course, the astronaut must manually complete such steps as the translation motion and docking, and all these steps must be done with help of the "flight control."
During the automatic rendezvous and docking course, the remote control needs to guide the spacecraft to gradually move from a place 30,000 kilometers from the Tiangong-1 to a place 52 kilometers below it and several orbital transfers must be completed. It is the most challenging and core part.
This time, astronauts came out of the spacecraft and enter the Tiangong-1, realizing the human's visit in an on-orbit spacecraft for the first time. They also did relevant experiments in the on-orbit spacecraft. All these cannot be done without the effective guarantee from the Tracking, Telemetry, Command and Communication System.
Reporter: In this mission, astronauts will stay a long period on the orbit. Does it have stricter requirements on the system?
Qian: The fact that astronauts will stay on the orbit for a long period indeed has stricter requirements on our system and the requirements are mainly in three areas.
First, the tracking, telemetry, command and communication support must be more reliable. It must be able to guarantee the smoothness of the sky-earth information channel so that information on conditions of the spacecraft and astronauts could be got correctly and timely. It must be able to guarantee the correctness of information processing and display of the flight control center so that the commands will be right and effective.
Second, the rapid emergency responding system must be more reliable and effective. After astronauts enter the orbit, rapid emergency responding modes have increased greatly. For example, cases like fire accident and pressure loss all need the ground to precisely judge malfunctions, rapidly make countermeasures and effectively implement them.
Third, instant communication between astronauts and the group must be more reliable and effective. During the flight on the orbit, the ground and astronauts must communicate with each other widely, the system must provide a reliable information channel and the flight control must have a special supporting team so that the on-orbit astronauts' requirements will be met. It needs a lot of preparations on the ground before the mission.
Two major difficulties to overcome in manual rendezvous and docking
Reporter: The manual rendezvous and docking will take place in a few days. What is the biggest difficulty in it?
Qian: The difficulty of the manual rendezvous and docking, in regard of flight control, is the close coordination between the astronauts and the ground system, as well as timely and effective professional support. For this reason, the system has specially established a professional support team on the ground to provide the astronauts with real time support for manual rendezvous and docking. By design, in case of abnormal situation during manual docking, it will switch to the automated control system to continue with the task.
Reporter: Which technology is more reliable, the automated docking or the manual docking? Do the different docking methods have the same requirements on the Tracking, Telemetry, Command and Communication System?
Qian: Automated docking and manual docking are two implementation methods of docking. From an international point of view, Russia primarily uses the automatic docking system, and the United States, primarily the manual docking system. In my opinion, the manual docking system has higher requirements on the system.
Ground continuous communications support from 47 minutes to 54 minutes
Reporter: In the manual docking process, the system provides continuous tracking, telemetry, command, and communication coverage for up to 54 minutes. What are the adjustments compared with the 47 minutes during which the astronaut was out of the capsule at the time of the Shenzhou-7 mission?
Qian: During the rendezvous and docking, the system needs to conduct multiple times of control over the spacecraft. Every minute of tracking, telemetry, command, and communication is extremely valuable. We will arrange the decision-making point in the monitoring area of the domestic earth stations, from Kashgar to Weinan, Qingdao, and the Yuanwang Space Tracking Ship, so that the arrangement can be more flexible. It is actually quite hard for the system to guarantee 54 minutes of continuous tracking, telemetry, command, and communication coverage. It took much effort for the Shenzhou-7 to achieve 47 minutes. In order to increase to 54 minutes, Yuanwang-6 Space Tracking Ship needs to transit for more than 2,000 nautical miles just to increase coverage time.
Reporter: Why do you spend so much just to increase these few minutes?
Qian: In the critical moment of the docking of the spacecraft with Tiangong-1, every minute of ground tracking, telemetry, command, and communication support is particularly valuable.
First, the ground segment is of special significance for the reliability of the entire mission. During the rendezvous and docking process, the tracking, telemetry, command, and communication and communication system has to conduct multiple times of spaceship control. In case of loss of control or instability of the spacecraft attitude or other unexpected circumstances, it is difficult for the relay satellite to provide effective tracking, telemetry, command, and communication support.
Second, the duration of effective tracking, monitoring and communication support has extraordinary significance during the implementation of key actions. Why is 47-minutes not enough and 54-minutes required? If you were a participant in Shenzhou-7 mission you would fully understand, that every minute is precious. One to two minutes of tracking, telemetry, command, and communication support at the docking spot 300 meters and 140 meters away from the Tiangong-1 will be greatly helpful to the psychological state of the operating and decision-making personnel.
