Communication in space: how it works

Shot from the film “Space Odyssey of 2001” (1968)

Imagine that you need to throw a grain of sand through the eye of a needle from a distance of 16,000 kilometers. Scientists were doing roughly the same thing, sending the Rosetta interplanetary station to the comet Churyumov-Gerasimenko in 2004. In 2015, the station and the comet were located at a distance of about 265.1 million km from the Earth. However, reliable communication allowed Rosetta not only to sit on a comet, but also to receive the most valuable scientific data.

Today, space communications is one of the most complex and promising areas of development of communication technologies. Orbiting satellites have already given us GPS, GLONASS, the most accurate global digital maps, the Internet and voice communications in the most remote areas of the Earth, but we look further. How does space communications work now and what awaits us in the future?

The Rosetta Path The



basis of the ground station infrastructure used during the Rosetta mission was the Intermediate Frequency Modem System (IFMS) , developed by BAE Systems. In addition to decrypting 350 gigabytes of data transmitted by the station, the system made it possible to accurately calculate the position of the spacecraft, acting as GPS for the solar system.

The IFMS system received and transmitted signals throughout the 10-year mission and accompanied the station about 800 million kilometers. IFMS allows you to measure speed with an accuracy of fractions of a millimeter per second, and the position of the spacecraft with accuracy within a meter at any point in the solar system.

IFMS modules are located at the ground stations of the European Space Agency (ESA), upgraded more than 20 years ago to better receive radio signals from spacecraft. Instead of analog processing - tuning to a signal, filtering and demodulation - a new (at that time) technology made it possible to convert the raw signal to digital form, from which the software extracted the necessary information.

After conversion, most of the subsequent signal processing is performed using PPVM microchips (user-programmable gate array, field-programmable gate array, FPGA). They consist of logical blocks that can be connected in parallel to perform calculations. This allowed us to develop complex algorithms to maintain a high level of noise reduction and stability of signals from space.

To Mars and vice versa Deep Space Network (DSN)


Terrestrial Antenna Network

Mostly satellites provide radio communications as repeaters, however, to communicate with interplanetary spacecraft, a more advanced system consisting of large antennas, ultra-powerful transmitters and ultra-sensitive receivers is required.

The data transmission channel to Earth is very narrow - for example, the DSS (Deep Space Stations) parabolic antenna near Madrid receives data at a speed of 720 Kb / s. Of course, the rover transmits only 500-3200 bits per second on the forward channel, but the main channel passes through the orbiting satellite of Mars - about 31 MB of data is received per day from the rover, plus more data received from the measuring sensors of the satellite itself.

Communication at a distance of 55 million kilometers is supported by the Deep Space Network, an international network of radio telescopes and communications. DSN is part of NASA. In Russia, for communication with distant spacecraft, they use the famous Oriental center for long-distance space communications, located near Ussuriysk.

Today DSN unites three ground bases located on three continents - in the USA, Spain and Australia. Stations are separated from each other by approximately 120 degrees of longitude, which allows them to partially overlap each other's coverage areas.

The Mars Odyssey satellite, the longest operating spacecraft ever sent to Mars, communicates with DSN using a high gain antenna at 8406 MHz. Reception of data from rovers is carried out on the UHF antenna.

“Roaming” in the Solar System


DSS-63

Mars is far from the only place in the Universe with which we need to keep in touch. For example, interplanetary probes were sent to Saturn and Titan, and Voyager-1 generally flew 20 billion kilometers from Earth.

The farther away interplanetary stations fly from us, the more difficult it is to pick up their radio signals. We cannot yet arrange orbiting satellites throughout the solar system, so we are forced to build huge parabolic antennas.

Take, for example, the Madrid long-range space communications complex. The main parabolic antenna of the DSS-63 complex has a mirror with a diameter of more than 70 meters and weighing 3.5 thousand tons. To track the probes, the antenna rotates on four ball bearings weighing one ton each.

The antenna not only receives the signal, but also transmits. And although the trajectory of the Earth’s movement and rotation has long been counted and recounted, finding a small object in space in order to accurately direct a huge antenna at it is a very difficult task.

To search for distant objects, radio triangulation is used. Two ground stations compare the exact angle at which the signal hits the antenna mirror at different time intervals, and thus the distance to the object and its location are calculated.

Long-range space communication centers



Development in the 50s The first Soviet intercontinental ballistic missile (ICBM) R-7, equipped with radio control, set its creators a difficult task - it was necessary to build a large network of measuring stations that could determine the speed and adjust the flight of the rocket.

To support the launches of the first satellites, the equipment originally created for ballistic missile tests was modernized and placed in research and measurement centers (NPCs). From them, the transfer of commands to spacecraft was carried out.

Dozens of NPCs were built in the country. Part of the measuring equipment was placed on special ships of the Navy. The ships participated in the tests of all types of Soviet ICBMs, artificial satellites and automatic interplanetary stations, provided all the developmental and regular near-Earth and lunar flights of Soviet space ships.

After the collapse of the USSR, ships of the measuring complex, with rare exceptions, were destroyed. However, other objects important for space communications have been preserved. For geographical reasons, the most important command and control centers were created in the Crimea (16th NPC - Western Center for Long-Range Space Communication) and in Primorsky Krai (15th NPC - Eastern Center for Long-Range Space Communication known as the Ussuriysk object ).

The Western Center in Yevpatoriya received and processed information from the first Luna automatic station, maintained communication with interplanetary stations of the Venus, Mars, and Echo series, and controlled the spacecraft in many other projects.


The main object of the Center is the ADU-1000 antenna with 8 parabolic mirrors 16 meters in diameter.

The Ussuriysk facility was created in 1965 as a result of the transfer of the Radio-electronic part of the military-space forces in the vicinity of the village of Galenki, 30 km northwest of Ussuriysk. In 1985, one of the largest antennas in the world was built - the RT-70 with a mirror diameter of 70 m (the same antenna is located in the Crimea).

RT-70 continues to operate and will be used in the most promising developments of the country - in the new Russian lunar program starting in 2019 (Luna-25 project), and for the world's only project of orbiting X-ray astronomy for the next 15 years, Spectrum-X-ray -Gamma".

Maximum speeds.


Operation of the Deep Space Optical Communication device.

There are now about 400 commercial communications satellites in Earth orbit, but in the near future there will be many more. ViaSat announced a joint project with Boeing to launch three new generation satellites, the throughput of which will be more than 1 Tbit / s - this is more than the throughput of all working satellites combined for 2017.

ViaSat plans to provide Internet access at a speed of 100 Mbit / s around the world at a frequency of 20 GHz, using phased array antennas, as well as multi-position data transmission systems.

SpaceX plans to start launching more than 12,000 communications satellites (30 times the size of all flying today!), Which will operate at frequencies of 10.7-18 GHz and 26.5-40 GHz, already in 2019.

As you can imagine, you need to provide control over the entire orbital constellation of satellites in such a way as to prevent collisions of vehicles. In addition, projects to create communication channels with all the artificial objects of the solar system are being considered. All these requirements force engineers to accelerate the deployment of new channels.

Interplanetary telecommunications in the radio spectrum since 1960 increased by eight orders of magnitude in bandwidth, but we still lack the speed to transmit high-definition images and video, not to mention communication with thousands of objects at the same time. One of the promising ways to solve the problem is laser communication.

The first space laser communication was tested by Russian scientistson the ISS on January 25, 2013. In the same year, a two-way laser communication system between the Moon and the Earth was tested on the Lunar Atmosphere and Dust Environment Explorer. It was possible to achieve a data transfer rate of 622 Mbit / s from the device to the ground station, and 20 Mbit / s from the ground station to the device, located at a distance of 385,000 km from the Earth.

The Laser Communications Project (LASERCOM) in the future will be able to solve the issue of communications in near-Earth space, the solar system and, possibly, in interstellar missions.

Laser communication in deep space will be tested during the mission "Psyche". The probe starts in 2022, and in 2026 it will reach the metal asteroid 16 Psyche. Special equipment Deep Space Optical Communications will be installed on board the probe.(DSOC) to transfer more data. DSOC should increase the productivity and communication efficiency of spacecraft 10-100 times compared with conventional means, without increasing the mass, volume, power and spectrum.

The use of laser communications is expected to lead to revolutionary changes in future space missions.