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Era when it's hard to get lost

How did the world change. Do you remember Antoine de Saint-Exupery’s wonderful novel “Night Flight” in its lyricism? In the story, the postal plane was lost due to the cyclone in space, and in the final it is not clear whether it crashed or managed to make an emergency landing, and where it happened. Now a generation is growing up, who will be surprised at the very possibility of getting lost, because navigators have surrounded them all their lives. And the situation “somewhere someone is in trouble, and no one knows about it” gradually disappears too. A plane crash will be recorded very quickly through many channels. A prudent tourist will bring along a device the size of a smartphone and be able to call for help in case of problems. And in cars, systems are introduced that are able to automatically recognize an accident and call rescuers on their own,even if the driver and passengers are not able to do this.


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Less than ten years after the events of the “Night Flight”, radio compasses began to appear more and more on airplanes - an antenna in the form of a ring made it possible to find out the direction to the radio signal source - a special station or even an ordinary broadcasting station.


Lockheed Electra, the radio compass antenna in the form of a ring is clearly visible from above, photo Christian Bramkapmp / aitliners.net

Failure of equipment or insufficient qualification for working with equipment could become factors as dramatic as in “Night Flight”, the disappearance of the famous pilot Amelia Earhart - on Howland Island, the intermediate target of a round-the-world flight, heard her plane and received radio messages about attempts to find the atoll and fuel running out. The remains of Amelia Earhart, navigator Frederick Noonan and the plane have not been found so far.

The antenna in the form of a ring also had an unpleasant property - it showed the direction to the signal source, but could not say whether the plane was approaching it or, conversely, was moving away. Because of this, during the Second World War, the entire crew of the B-24 “Lady Be Good” bomber died - they flew a beacon and retired to the desert. When the aircraft ran out of fuel, they jumped with a parachute and tried to reach the base, not knowing that it was seven hundred kilometers. Ironically, the plane planned and made a relatively soft landing on the sand. Fifteen years later, he was found in the desert. The radio station through which one could call for help remained intact.


B-24 bomber, antenna ring in a black drop-shaped cowl at the top

But in general, the radio compass turned out to be a very useful device - you could fly along the air corridors between the beacons, and if there were several beacons in the hearing zone, you could determine your position with good accuracy - the intersection of bearings (directions to the beacon) from the transmitters indicated on the map gives the point at which the plane is located. Despite all the achievements of satellite navigation, beacons are still used in aircraft navigation.


Radio navigation map of the area around St. Petersburg, village Ivanovo.rf

Fixed corridors above stationary beacons are great for civil aviation, but the military will have to act on enemy territory where the enemy will not help with radio beacons, and the goal for bombers can change every day. Already at the beginning of World War II, the Germans used increasingly sophisticated radio navigation systems to direct their bombers at London.


Knickebein system, bombers fly in one beam and drop bombs when they cross the second, illustration by Dahnielson / wikimedia.org

The British responded with radio interference, disrupting the normal operation of the systems with their signals. A separate irony is that Reginald Victor Jones, who led this fight, adored the rallies and probably enjoyed the fact that he received the resources of a whole country to deceive the German pilots. As a result, the Luftwaffe was driven by electronic warfare so much that they lost all faith in radio guidance systems for bombers.

After the war in civil aviation for short range, the VOR / DME system became standard, allowing you to determine both distance and direction to the beacon. Military systems work on a similar principle - the western TACAN and the Soviet / Russian RSBN. An airplane transmitter sends a request that is relayed by a ground station. The response delay time determines the distance between the aircraft and the station. To determine the direction of the beacon, other antennas are used: one rotates, and its signal runs around the horizon in a circle. The other emits an omnidirectional signal at a time when the first antenna emits in the north direction. By the time difference between the reception of the first and second signals on the plane, you can determine which side it is relative to the station.


Antenna combining VOR / DME and TACAN,source

For long distances, the OMEGA, LORAN, Seagull, and RSDN systems used a different principle. Suppose there are three radio transmitters at a great distance from each other, synchronously emitting a signal. Due to the fact that the speed of light is finite, the signals will not reach the aircraft at the same time. They don’t know the distance to any station on the plane, but they know the difference in the time of receiving the signal and, therefore, the difference in the distances to the stations. Knowing the difference in distance between the two stations gives a hyperbole. Three stations allow you to build two hyperbolas, the intersection of which gives two possible points at which the aircraft can be. For example, if we know that it is 480 km closer to Moscow than to St. Petersburg, then we can be both in the Dnieper (former Dnepropetrovsk) and in Ufa. And if we are 50 km further to Moscow than to Omsk, then we can be in Ufa or Perm.The combination of conditions will give Ufa, from which I am writing this text.


Illustration Cosmia Nebula / wikimedia.org

This principle is called “hyperbolic navigation” and was first used in the Gee English system to direct British bombers to German cities. The main difficulty is the synchronization of ground-based transmitters that are remote over long distances, but with the advent of atomic clocks, the problem was generally solved in the 1960s. To ensure operation over long distances, long waves were used, so the antenna systems were very high.


Antenna of the OMEGA system in Japan, once the tallest building in the country, photo of the Ministry of Land, Infrastructure, Transport and Tourism of Japan / wikimedia.org

The beginning of the space age aroused interest in satellite navigation. Employees of the Johns Hopkins University's Applied Physics Laboratory, William Guyr and George Weifenbach, receiving signals from the first satellite, found that they could calculate its orbit by measuring the Doppler shift of its signal. The Doppler effect - a change in the frequency of a signal from a moving source - when the satellite was approaching the laboratory, it increased, when it moved away - it decreased.



Knowing the satellite’s orbit, it was possible to solve the inverse problem - to determine its position by the Doppler shift of the satellite signal. So the Transit navigation system was born. The first satellite was tried to put into orbit in 1959 (unsuccessfully), the second was launched in April 1960 and in the same year the first tests were successfully carried out. The system was commissioned in 1964.


The Transit 5-A satellite at the United States National Aeronautics and Astronautics Museum

Five satellites in five planes in polar orbits with a height of 1,100 km gave global coverage. Usually in space there were ten satellites, one spare for each plane. The task of determining one's position was non-trivial, required a large number of mathematical calculations and, for greater accuracy, required the immobility of the carrier. For example, for American submarines it was necessary to develop a special computer AN / UYK-1, sealed and made in such a form factor that it could be dragged into the hatch.


Computer advertising from the manufacturer

Since the satellite’s orbit changed over time, it transmitted not only the current time, but also elements of its orbit, which were downloaded from communication stations twice a day. The ground stations near the poles, knowing their position, constantly measured the orbits of the satellites and sent them the parameters of the orbits, which were then used to solve the inverse problem for users of the system.

But all the difficulties paid off with the acquired opportunities - the submarine advanced the antenna for only two minutes, caught satellite signals and could determine its location with an accuracy of 100 meters. Soon, the Transit system was made available for civilian use, and it not only helped many sailors, but also made it possible to solve rather unusual problems, for example, by averaging many measurements, the height of Mount Everest was adjusted.

In the USSR, the Cyclone navigation and communications system was created with the civil version of the Cicada, operating on a similar principle and consisting of 6 satellites. Transit stopped working in 1996, the last satellite of the Cyclone system went into orbit in 2010.

Of course, Transit and its analogues were not without drawbacks - just five satellites meant that in the equator area the satellite would have to wait several hours, at mid-latitudes the expectation was reduced to 1-2 hours. And the accuracy of 100 meters quickly wanted to improve. Already in 1973, the United States began the project of a new GPS navigation system, the first prototype of which went into orbit in 1978. The new system used a modification of the approach you already knew.

Remember hyperbolic navigation? GPS and analogs implement the same principle. All satellites broadcast the exact time and parameters of their orbit. Due to the fact that the speed of light is finite, time stamps do not come to the user at the same time. The user does not have an atomic clock synchronized with the satellites, so he only knows the difference between the readings, but this is enough. A signal from three satellites allows you to build two hyperboloid in space, the intersection of which will give a hyperbole that touches the surface of the globe at two points, one will be the correct location, and the second will be so incorrect that it will be easy to discard.


Illustration of the Munich Technical University

If you add a fourth satellite, then the three hyperboloid intersect at one point and will also determine the height above the surface. And each additional satellite will give new hyperboloids, which will increase accuracy. 24 satellites in three planes provide round-the-clock system availability.

Other modern navigation systems work on a similar principle: Russian GLONASS, European Galileo. The Chinese Beidou has the same principle, but the satellites are located in orbits of different heights. And the most dramatic story is, without a doubt, the Russian GLONASS.

The development of the system was started in 1976, and the first device went into orbit in 1982. First, small series were launched - 10, 9, 12 satellites, and since 1988 full-fledged deployment of the group began in a large series in which 56 satellites were produced.


"Cosmonautics News", 1999, No. 2

In the early 90s, 12 working satellites already allowed limited use of the system, and full deployment was completed in 1995. Alas, amid economic problems, the group began to degrade. The relatively short lifespan of the devices and rare launches - after 1995 there were one launch with three satellites in 1998 and 2000, led to the fact that in 2001 there were only 6 operational devices. But from the beginning of the zero, a revival of the group began. In 2003, the first second-generation vehicle, the GLONASS-M, went into orbit, the most important difference of which was the increased lifetime.


GLONASS-M, photo by Bin im Garten / wikimedia.org

The applied technical solutions were successful, and today the oldest of the working satellites were launched in 2007 and exceeded the warranty period by half. But today, the constellation faces a new challenge. It was originally planned that the second generation will be replaced by the third, “GLONASS-K”, which will switch to an unpressurized platform that promises even greater durability. But the satellites used imported components, which became inaccessible after the complication of the political situation in 2014. And in the end, it was decided to switch to a modified type, “GLONASS-K2”, using domestic components. Now the constellation is going through a dramatic stage, when the second-generation satellites that are out of order will have to be replaced by those already manufactured and stored, and the production of a new modification is being launched in parallel.


GLONASS-K2, image USSR BOY / wikimedia.org

So far, things are going well - the GLONASS-M reserve is almost over - the penultimate device will go into orbit in March, the last of which is most likely this year. “GLONASS-K” has 9 in stock, of which one is due to fly in May. And the first “-K2” can be launched as early as 2021.

For civilian users, even the worst-case scenarios are no problem - four global navigation systems mean that navigators will always see satellites and be able to determine their position. And not only navigation systems can help in a variety of cases. In Europe from 2018 and the Russian Federation from 2015, it is mandatory for new cars to install a system that recognizes an accident and automatically transfers a call to emergency services - eCall and ERA-GLONASS.

Both systems are compatible and work on the same principle: the sensors in the car record the fact of an accident - the deployment of airbags, deformation of the body, etc., determine the degree of accident and the coordinates of the incident using satellite navigation systems and send a message to the rescue services via cellular networks. According to information at the end of 2019, more than 4.6 million vehicles were equipped with ERA-GLONASS in Russia, about 36 thousand calls were recorded per year, 17 thousand of them in automatic mode. According to experts, the system saves 3-4 thousand people a year.

This is what the ERA-GLONASS device manufactured by NPP ITELMA looks like:

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More than 30% of all Russian cars are equipped with devices assembled in ITELMA. ERA-GLONASS systems go through a full cycle at the enterprise: we create architecture, develop software, make a prototype, test it and after successful tests we integrate the module into the car before it leaves the factory conveyor.

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The Telematics Directorate is responsible for the development of ERA-GLONASS emergency response systems and IoT-based projects at the enterprise, it offers several vacancies for programmers and developers .


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About ITELMA
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