Space and satellite communications
What is space communication?
Space communication is the transmission of information between terrestrial points and space aircraft (SPACECRAFT), or between several spacecraft. The most common way of transmitting information through outer space is radio communication.
Types of CLA:
AIS (Automatic Interplanetary Station)
Like any other types of communication, space communication depends on many factors, but to a greater extent, due to the long range of communication and, as a result, operation with low power levels of the received signals. On the one hand, it requires special equipment, including powerful and large-sized antennas, sensitive receiving devices capable of separating noise, highly efficient systems for detecting, isolating and registering radio signals.On the other hand, the power of on-board radio transmitters on the spacecraft is very limited, since the spacecraft launched into space should have as little weight as possible.
Due to the fact that there is an ionosphere between the earth's surface and orbit, which has an absorbing and reflecting effect on medium-long radio waves, such communication should be carried out using short—wave signals (for space communications, the optimal range is 1.5 — 30 centimeters).
Types of space connections:
Earth—KLA and KLA—Earth communication (communication for transmitting the necessary information between the Earth station and the spacecraft or astronauts on board)
KLA — KLA communication (communication between two spacecraft for various purposes, for example, signal relay between two satellites)
Ground — to—Ground (in which the device acts as a repeater, transmitting a signal between ground stations at a considerable distance. This is how satellite communications work.)
The history of the development of space communications
The precursor of the satellite communication method can be called the article «Extraterrestrial repeaters» in 1945, written by the English writer and inventor Arthur C. Clarke. It proposed a simple idea — to raise the antenna to the maximum height. In low-Earth orbit, this «extraterrestrial repeater» would receive signals from ground sources and transmit them further beyond the horizon. The signal quality also increases, and the number of receiving stations is not limited.
Arthur Charles Clarke 1917 — 2008
Soon, with the development of science, Arthur C. Clarke's prediction began to come true and the technology was implemented in reality. For example, the first spacecraft whose signal was received is the world's first artificial Earth satellite PS-1 (the simplest Satellite -1) or simply Sputnik-1, launched by the USSR on October 4, 1957.
PS-1
On Sputnik-1, 2 vibrator antennas were installed crosswise, consisting of 2 shoulder pins for the VHF band (2.4 m) and HF band (2.9 m), alternately emitting a signal, installed so as to ensure the most uniform radiation in all directions, which is due to the fact that the satellite was not oriented. The satellite's power supply was non-renewable and was provided by a set of silver-zinc batteries that made up 60% of the total mass of the device and worked for 21 days after launch.
The success of the PS-1 mission was the beginning of the space race — the rivalry between the USSR and the United States in the technological field of space exploration. During this race, they came to be considered space powers.
Reacting to the launch of the Soviet satellite, the US Congress in 1958 created the NASA organization (National Aeronautics and SpaceAdministration), which launched the passive reflecting satellite Echo-1 into space in 1960, and then, in the same year, the first experimental active transmitting satellite-repeater Courier-1B, which was also the first satellite which was powered by solar panels.
Echo-1
The satellite did not have any transceiver equipment, it was a sphere made of a thin polyester film that acts as a reflector. The diameter in the decomposed state was 30.5 meters, and the approximate weight was 76 kg. Echo-1 entered the dense layers of the Earth's atmosphere and collapsed on May 25, 1968.
Courier-1B
There were 3 satellites of this series in total: Courier-1A, Courier-1B and Courier-1C. The first satellite, Courier-1A, was lost as a result of an unsuccessful launch, which ended in an explosion 2.5 minutes after launch. Courier 1B was successfully launched into low Earth orbit and stopped responding 17 days after the launch of the mission, although it is still in orbit. The third satellite was built, but it was never launched.
The first two-way space communication, and concurrently the first communication with a person in orbit, was conducted on April 12, 1961. Yuri Gagarin maintained telephone and telegraphic communication with the Earth on meter and decameter waves during the flight around the earth. Specifically for this purpose, the Zarya space communication system, manually controlled by operators (not to be confused with the reusable Soviet spacecraft of the same name) and the Vesna KV communication system duplicating it, which was used for communication during the flights of the Vostok, Voskhod and the first Soyuz spacecraft, were created.
Yuri Alekseevich Gagarin 1934 -1968
Installation of the Zarya space communication system
The farthest space links
Radio waves, like any other electromagnetic waves, travel at the speed of light. For this reason, there is no delay in transmission on Earth and in close orbit, but communication with remote terminals occurs with a delay. For example, the response from the spacecraft on the surface or orbit of Mars reaches the Earth in 6 minutes, and the further away, the longer the delay. Also, the further away the object is, the lower the level of the received signal, since the power of the received signal decreases proportionally to the square of the distance, therefore, in order to capture such weak space signals (from spacecraft launched from earth or natural cosmic radiation), it is necessary to build especially large reflective antennas, and even complexes of such antennas.
RT-70 Radio Telescope
The most distant connections are with research vehicles of the AMC class, sent for the purpose of studying to other planets and their orbits. The world's first AMS was launched by the USSR in early 1959. «Luna-1», also received the name «Dream» in the world press.
Luna-1
The first station to reach the second space speed, it was supposed to make a hard landing, crashing on the surface of the Moon, but passed close (at a distance of 5-6 thousand kilometers), after which, going beyond the sphere of gravity, it became the first artificial satellite of the sun. The result was a huge technological breakthrough, but the main goal, the flight from one celestial body to another, was never achieved.
In the second half of the same year, another device of the same series, the Luna-2 station, which had minor structural differences, reached the surface of the moon for the first time, leaving a fixed dust cloud and presumably forming a crater with a diameter of 15 to 130 meters.
At the moment, the most distant connections with the AMS are those with the Voyager 1 and Voyager 2 spacecraft launched in 1977 by NASA, the most remote and the second most distant AMS from earth, respectively (More than 21.1 billion km and 17.5 billion km from Earth).
The Voyager probe
Both Voyagers have the same design. There are 2 antennas on each of them: directional (with a 3.66 m reflector) and non-directional. Scientific instruments mounted on special external rods (Various spectrometers, detectors, magnetometers and radio emission receivers). Since solar panels would be useless due to their great distance from the Sun, three RTGS (a radioisotropic thermoelectric Generator), also mounted on a rod, provide power.
The most record—breaking long-distance communications with people in space, at this point in time, are Earth-Moon communications, with the astronauts of the Apollo program, which began in 1961 and ended in 1972. In total, there were 6 successful landing flights and 1 emergency flight of the Apollo 13 mission, during which the landing on the surface was disrupted, but the astronauts managed to return to earth by performing a maneuver with a flyby of the Moon from the reverse side. During the entire program, 12 people went beyond the orbital module on the surface of the earth's natural satellite, the first of whom were Neil Armstrong and Buzz Aldrin in 1969 as part of the Apollo 11 mission.
After the closure of the program, no human flights to the moon were conducted.
Neil Alden Armstrong 1930 — 2012
Edwin Eugene Aldrin Jr. (Buzz Aldrin)
Space communication in our time
Right now, there are approximately 9,000 satellites in orbit around our planet, for various purposes, communication with which we use everywhere. GPS navigation, surveillance, scientific research, weather forecasting, TV broadcasting, data transmission of Internet services, etc. Approximately 60% of them are inactive, i.e. space debris. This is partly due to the fact that the ways to remove a failed device from orbit are too resource-intensive and a new one is simply launched to replace it.
Among them there are amateur radio satellites, through which, having the equipment, it is possible to communicate on some bands, it is also necessary to take into account the frequency shift caused by the Doppler effect.
There are currently 2 active space stations in space. The Chinese Tiangong Station and the ISS (International Space Station).
The International Space Station
The station orbits the earth every 90 minutes. If desired, you can listen to the ISS service signals, use it as a repeater, or even, if circumstances are right, contact the crew. From a technical point of view, any amateur radio operator with the right equipment can do this. The receiving frequency of the station is 145.825 MHz. The first QSO from the ISS was conducted in 2000.