First 60 Starlink Satellites Launched
The first 60 Starlink satellites were launched from Cape Canaveral into low-Earth orbit by a Falcon 9 rocket. In the framework of the program of providing the population of the Earth with broadband Internet access, almost 12 thousand more satellites will join them in the future. It was possible to watch the launch of the rocket using the Internet broadcast on the YouTube channel of the Space X company.
In order to connect to the Internet via satellite communication, the user must have a transceiver – transceiver – and a satellite dish. Satellites placed in a geostationary orbit at an altitude of 36,000 km make it possible to transmit data even to remote places on the planet where there is no proper technical infrastructure. The altitude allows one satellite to cover almost an entire hemisphere, but creates a delay on the communication channel – the signal takes 500 ms to travel from the antenna to the satellite and back. In addition, to the poles, the signal quality is greatly reduced due to the increasing distance.
SpaceX Tests Big Falcon Rocket Second Stage Engine
For the first time, the idea of a global satellite Internet was announced by Elon Musk on November 11, 2014. According to the project, the company will create a constellation of 11,943 microsatellites. The orbital constellation will be split into three components. 7518 satellites will be located in circular orbits with an altitude of 340 km, 1584 satellites will be placed in a circular orbit with an altitude of 550 km. There will be 2,841 more satellites at an altitude of 1150 km.
An hour and two minutes after launch, the first 60 Starlink satellites separated from the second stage of the rocket and deployed at an altitude of 440 km. They then used inboard engines to reach an operating altitude of 550 km. The total payload mass of the Falcon 9 reaches 18.5 tons, while the total mass of the satellites was 13.62 tons.
Each satellite – a flat panel with phased array antennas – weighs about 227 kg. Hall-effect electrostatic motors run on krypton and allow you to adjust position in orbit, maintain altitude and deviate from orbit. The Startracker navigation system tracks the position of satellites, and the vehicles themselves can autonomously evade orbital debris. Satellites will be able to transmit data between themselves thanks to laser communication with a radiation frequency of more than 10 THz. At the end of each Starlink’s lifecycle, 95% of its structure will burn up in the Earth’s atmosphere.
Scientists from the Institute of Nuclear Physics. GI Budker SB RAS found information characteristics of a nonlinear dispersionless fiber-optic communication channel, and for the first time discovered an unusual law of growth of the capacity of such a channel with increasing input signal power. This made it possible to find the optimal way of coding information, which can increase the bandwidth of the communication channel, that is, increase the data transfer rate. The results of the work were published in the journal Physical Review E.
The simplest model of a fiber-optic communication channel has two parameters – nonlinearity and dispersion. In addition, in the transmission of information, interference occurs, which is called noise. For a given input signal power and noise power, these parameters determine the amount of information that can be transmitted over the channel per unit of time. Senior researchers of the INP SB RAS Alexei Reznichenko and Ivan Terekhov calculated the maximum throughput (channel capacity) in a dispersionless fiber-optic communication channel, that is, they found the statistics of the optimal signal coding method for a given pulse shape. To do this, scientists used the methods of quantum field theory, which are usually used in particle physics and condensed matter physics. It turned out that the mathematical apparatus used in these areas is applicable to theoretical research in information theory.
“Theoretical studies aimed at studying signal propagation through optical fiber are carried out at the INP SB RAS as part of a series of works devoted to the application of the nonlinear Schrödinger equation in fiber-optic systems. The work was carried out with the support of grants from the Russian Science Foundation and the Russian Foundation for Basic Research. The calculations we obtained for a dispersionless fiber-optic communication channel may be interesting for the telecommunications industry, since it also uses communication channels with zero average dispersion, ”says Aleksey Reznichenko, Senior Researcher of the INP SB RAS, Candidate of Physical and Mathematical Sciences.
The predictions obtained by the staff of the INP SB RAS for the communication channel capacity were confirmed in the course of computer calculations by the staff of the NSU and the Institute of Automation and Electrometry of the SB RAS on the computer cluster of the university. The research was based on two different methods of mathematical computer modeling.
“To check the analytical calculations, two independent computer experiments were carried out, based on different methods of numerical simulation.