PNT Technology: The Communication Between Satellites
The ability to discern the geographic location of a person, object, or signal is known as ‘positioning.’ The capacity to determine a route to the desired location from a current location is known as ‘navigation.’ To put it another way, it’s the ability to figure out how to get from point A to point B.
The capacity to compute the travel duration between sites and preserve precise time following time zone standards such as Coordinated Universal Time (UTC) or ‘Australian Central Standard Time’ is enabled by ‘timing,’ which connects ‘navigation’ and ‘Positioning.’
Satellite positioning, navigation, and timing (PNT) technology is one of the essential aspects of current technology systems and devices that we use daily.
Uses of PNT Technology
PNT’s most well-known offering (when paired with maps, weather, traffic statistics, and other information) is global navigation using Global Navigation Satellite Systems (GNSS) such as the U.S. Global Positioning System (GPS). Other GNSS-based applications provide critical support for emergency communications, water supply, and electrical power networks.
Entrepreneurs also use GNSS technology to create apps that improve the effectiveness and efficiency of space activities, including activities such as mining, agricultural, construction, and transportation industries.
When PNT is combined with map data and other information (such as weather or traffic data), the result is the most well-known and identifiable service — the current navigation system, also known as the global positioning system (GPS).
While PNT offers much more than just navigation, GPS is an important part of it. There are already more than two billion GPS users in the U.S.
The GPS space segment refers to a constellation of 24 satellites orbiting the Earth. The monitoring stations are set worldwide to monitor and maintain the satellites are referred to as the control segment.
The user sector includes innumerable military, governmental, commercial, and other organizations, as well as common citizens that rely on the GPS for different purposes.
To know more about the Satellite positioning, navigation and timing (PNT) technology click here.
Global Navigation Satellite Systems (GNSS)
GNSS systems are made up of a constellation of satellites that beam down positioning and timing data to GNSS receivers, which analyze the information to determine location. Military, governmental, commercial, and other organizations, including private citizens, rely on the data collected by the GNSS for a variety of purposes. The global navigation satellite system (GNSS) provides global service coverage.
There are several GNSS systems used across countries. A few of them are mentioned below.
· GPS (Global Positioning System) (U.S.)
· BeiDou (China)
· Galileo (Europe)
· GLONASS (Global Navigation Satellite System) (Russia)
· Regional Navigation Satellite System (RNSS)
RNSS, in contrast to GNSS, provides limited regional coverage.
Despite various countries’ desire to build their GNSS, all countries rely on GPS services provided by the U.S.
The following regional navigation satellite systems (RNSS) are now operational:
· Indian Regional Navigation Satellite
· Quasi-Zenith Satellite System (QZSS) (Japan): The service is used in conjunction with GPS for highly precise positioning by transmitting signals from Quasi-Zenith Satellites (QZS) having the same frequency and timing as GPS.
There are currently two forms of satellite positioning mistakes:
1) Faults induced by a less number of satellites
2) Ionospheric errors
1. Errors Caused by Less Number of Satellites
(a) Errors with multiple paths
Satellite signals do not arrive straight; instead, they are transmitted along many paths while reflected off mountains, buildings, and other obstacles. The reflected signals take some time to reach their destination. It results in a more distant computation, which harms satellite positioning accuracy.
(b) Errors in the satellite constellation cause inaccurate satellite location.
When satellites are equally scattered across a wide region in the high-altitude sky, it improves accuracy. Dilution of Precision (DoP) refers to the degree to which satellites are organized in a balanced manner in the sky. When satellites with low elevation angles are included, DOP improves the placements of satellites.
2. Errors in the Ionosphere
The most prevalent positioning mistake is caused by signal delays generated by the ionosphere. The ionosphere is a charged region of the high atmosphere that extends from 100 to 1,000 kilometers. The speed of satellite signals reduces as they pass through the ionosphere. Since satellite signals arrive late, an error occurs when the distance between the satellite and the user is computed as being longer than it should be.
(a) Using multi-frequency signals to reduce ionospheric errors
The ionosphere causes satellite signal speed delays that vary depending on the frequency of the satellite broadcasts. Due to this property, mistakes induced by ionosphere delays can be calculated and, in most cases, corrected by sending various frequencies of satellite signals from a single satellite. As a result, using satellites that can send signals at several different frequencies can reduce errors.
(b) Using single-frequency signals to reduce ionospheric errors
Due to the high cost of dual-frequency receivers, single-frequency receivers are projected to be widely used shortly.
With GPS, the entire world is approximated using a single formula. QZSS, on the other hand, generates and transmits two sorts of parameters: those for Southeast Asia and Oceania, and those for the region around Japan.
There are various global and regional navigating satellite systems. These systems use the newly advancing PNT technology for communication among the satellites. It provides with positioning, navigation, and timing of other satellites. Since the PNT technology is in the development stage, there are multiple errors to be rectified. But the facilities available to us are not affected by the progress along the way.
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