China long-range space communications system

In my last article on the launch of a promising new spacecraft , I was asked a question about the Chinese long-range space communications system.

Thinking, I decided to put it in a separate article. Moreover, there is no other area in which the development of the cosmonautics of the People’s Republic of China would not be visible so well.

From the simple moon satellite Chang'e-1, launched at the end of 2007, for which it did not have its normal means, to the preparations for launching a full-fledged Martian station with a rover and a very complex station for delivering lunar soil to Earth. Among the AMS, the last station has no equal at all. Yes, the soil was delivered to Earth by Soviet stations of the E-8-5 series, but they were much simpler in design and had simpler capabilities.

All these achievements would not be available if the Chinese long-distance space communications system had not systematically developed over the past years.

Before describing the Chinese system, I would like to devote a couple of words to what the antennas of the deep space communication system (DSS) are all about.

If there are a very, very large number of types of radio telescopes, then DKS is much more conservative. This is determined by stringent requirements for them. If many ordinary radio telescopes are designed to observe the starry sky, then the BCS is required to track planets, the moon or interplanetary stations against the background of this sky, which can have a fairly high angular velocity.

Moreover, he must accompany these stations for a long time. Ideally, all the time when the station will be in the radio visibility zone. Including when the station just left the local horizon or will soon come over for it. When working with several stations, you need the ability to quickly redirect the antenna to another point in the sky.

On the technical side, this retargeting is not very simple, these antennas are very large. Dozens of meters. In addition, they have a so-called filled aperture (full coverage) to collect the signal from the entire surface of the mirror and maximize it.

In theory, for communication in the orbit of the moon, you can use a smaller diameter, but even there, "size matters." A larger antenna will provide greater energy, and hence the speed of information transfer.

And the last one. If the overwhelming number of radio telescopes are receivers, then in our case, you need to have a transmitter of sufficiently high power on the antenna. Actually, this is one of the key differences. There are many full-circle large-diameter radio telescopes; only a few units are equipped with transmitters. Most often, just related to space communication systems.

You can look at two classic representatives of such systems: the American DSS-14 and our RT-70. Both are 70 meters each.



And for an example of the complexity of using conventional radio telescopes, I want to make out the Chinese FAST (commissioned in 2016), which for some reason is sometimes attributed to the Chinese system of long-distance space communications.



This is the world's largest 500-meter filled aperture radio telescope, which means it should be a record in sensitivity.

That's just the way it is motionless, it can only "comfortably" observe objects above it. Moving the irradiator over the mirror, you can slightly shift the observation point, but it will not work to point to a station located near the horizon. In addition, this is only a receiver, the transmitters, as far as I know, have not been mounted on it and are not planned yet.

In an emergency, it can be used to search for an emergency station with a weak transmitter, but it cannot be used as a standard communication system with interplanetary stations.

Now, after a little theoretical preparation, we will be transported to 2007 and follow the development of the Chinese BCS system.

The beginning of

October 24, 2007, the first Chinese lunar station Chang'e-1 went into space. Chinese capabilities were then quite modest.

To determine the trajectory of the station, radio telescopes were involved. The largest of them was near Beijing at the Miyun Radio Observatory. This observatory was founded in the 60s and for many years its working tool was a line of twenty-eight nine-meter mirrors, the so-called MSRT (Miyun Synthesis Radio Telescope).



But in 2002, the construction of the largest at that time Chinese 50-meter radio telescope began there.

Start of construction and final result. In the background you can see the MSRT antennas.



Here is a satellite image. In addition to the systems described, you can also notice a 30-meter stationary radio telescope, about which I could not find information.



This 50-meter antenna was used to receive scientific data from the station. Also, together with the new 40-meter radio telescope in Kunming, she organized the base of the interferometer, with which it was possible to determine the trajectory of the apparatus.

I repeat, these were only radio telescopes. They were not suitable for communication. With transmitting stations, China then was much more difficult. For these purposes, 18-meter antennas were built in Kashi and Qingdao, but cooperation with the European Space Agency (ESA) has become a great help.

In exchange for scientific information from Chang'e-1, ESA provided 15-meter antennas for its stations in Spain and French Guiana, as well as a new 35-meter antenna for the New North Station in Australia. To ensure operation, the Beijing Control Center was connected to the European Satellite Operations Center in Darmstadt. At European stations, which usually operate in telecontrol mode, during the key elements of the Chang'e-1 mission, there were attendants on duty to quickly overcome any emergency situation.

The key signals when approaching the station to the moon were given by the Spanish station, and the signal from the station was received by the Australian one. When the station entered the orbit of the moon’s satellite, all three stations carried out continuous monitoring. The Chinese stations were then "caught up"

The first reception of information from Chang'e-1 at the Chinese station.



System deployment

The next Chinese station, Chang'e-2, was launched three years later. And during this time, a lot has happened. First of all, China has decided on the structure of its long-range space communications system. It was necessary. Not only extended lunar plans were officially announced, but also stations heading to Mars and Venus. I did not want to contact ESA every time. Two districts were chosen as the base of their BCS system, one in the Kashi region in western China, and the other in the Jiamusi region in the north-east of the country. It was there that transceiver antennas began to be built. In Kashi - 35 meters, in Jiamusi - 64 meters. Radio telescopes in other areas were planned to be used to determine the trajectory of the apparatus.

This scheme will help to better understand their location.



Transmitting antennas are highlighted in red, and some Chinese radio telescopes in blue. According to this scheme, the main idea of ​​choosing a place is also visible. As far as possible to remove the BCS stations from each other in order to maximize the time of work with the station. Unfortunately, full coverage from China could not be anyway. The gap was from 8 to 10 hours a day. And China began to negotiate with the countries of South America over the construction of a space communications center there.

The construction of these stations was completed in 2012. And already in October 2012, the Chinese center for long-distance space communications began working with the Chang'e-2 apparatus.

Appearance of the 35-meter antenna of the station in Kashi.





It is from the satellite



Zhang Zhuo is one of the engineers at this center. In the background is one of the control rooms.



In this picture, engineer Zhang Lei is already there and either the room is higher from another angle or another room. By the way, if you compare with the pictures of the station, you can understand where it is located.



An even greater achievement was the construction of a station in Jiamusi. And, interestingly, before the construction they called it a diameter of 64 meters, and after construction it was already 66 meters.

Here it is during construction.



Here it is after the



satellite. In stock, for some reason, only a snapshot of 2011. During the construction of the station



Here, apparently, the center staff. You can evaluate the scale of the structure.



There are a couple of shots from the control room. They are comrades Cai Boyu and Yue Shilei. The room, judging by the equipment racks in the background and the inscriptions above them, is the same.





Station diagram



But even after the commissioning of these antennas, cooperation with ESA did not stop. Stations in Spain, French Guiana, and Australia were still involved with the Chang'e-2 and Chang'e-3 stations. Moreover, in 2013, a long-term cooperation agreement was signed.

The head of ESA's International Relations Department, Karl Bergquist, commented on this:“ESA and China recently signed a Mutual Support Agreement, which stipulated that ESA could support the Chinese mission through our long-distance communications network. But the opposite is also possible, that is, ESA will ask China to use Chinese long-distance antennas for some ESA mission. So far this has not happened, but I am sure that this will happen in the next few years. This is a sign of the close ties that exist between ESA and the leaders of the Chinese space program. ”

The final touch

The last station of the Chinese long-range space communications system was built in Argentina. The negotiations mentioned above ended successfully.

In 2017, large-scale work began on the construction of a 35-meter antenna in the Argentinean province of Neuquen





In October 2017, the station was commissioned by



the Control Center.



After the commissioning of this station, China now has the opportunity of round-the-clock monitoring of interplanetary stations all 365 days a year, without any breaks in the schedule. This is a very serious achievement. The Soviet Union, for example, did not manage to create such a system.

Summarizing the above, we can say that since 2007, China has come a very long way and its terrestrial space communications system is fully ready for the next space launches. And we will definitely hear about it in future launches to the Moon, Mars and Venus.