Satellites and Services - Satellite Applications

Navigation Using Satellites

a) Compare and contrast between GPS and GLONASS

GPS (Global Positioning System) and GLONASS (Global Navigation Satellite System) are two of the most widely used global navigation satellite systems in the world. Both systems are designed to provide accurate and reliable positioning and timing services to users around the globe, but there are some differences between the two systems.

One of the main differences between GPS and GLONASS is the number of satellites in their respective constellations. GPS has a constellation of 24 satellites in orbit around the Earth, while GLONASS has a constellation of 27 satellites. Having more satellites in a constellation can provide better coverage and accuracy, as there are more satellites available to provide signals to users on the ground.

Another difference between GPS and GLONASS is the frequencies they use to transmit signals. GPS uses L1 (1575.42 MHz) and L2 (1227.6 MHz) frequencies to transmit signals, while GLONASS uses G1 (1602 MHz) and G2 (1246 MHz) frequencies. The use of different frequencies can affect the accuracy and reliability of the navigation signals, depending on the surrounding environment.

A key advantage of GLONASS over GPS is that it provides better coverage at high latitudes, such as in the Arctic and Antarctic regions. This is because GLONASS satellites are positioned in orbits that are more inclined to the Earth's equator than GPS satellites, which allows them to provide better coverage at high latitudes.

However, GPS is generally considered to provide better accuracy and reliability than GLONASS in most parts of the world. This is due in part to the fact that GPS has been in operation for a longer period of time, and has had more time to refine and improve its technology. In addition, GPS has a more advanced receiver technology and a higher signal-to-noise ratio, which allows it to provide better accuracy in challenging environments such as urban canyons or under heavy foliage.

Overall, both GPS and GLONASS are important global navigation satellite systems that provide critical services to users around the world. While there are some differences between the two systems in terms of coverage, accuracy, and reliability, both systems are important tools for navigation and positioning. Many modern devices, such as smartphones and tablets, are designed to be compatible with both GPS and GLONASS, allowing users to benefit from the strengths of both systems.

b) A review of BeiDou system and IRNSS satellite navigation systems

BeiDou Navigation Satellite System (BDS) and Indian Regional Navigation Satellite System (IRNSS) are two regional satellite navigation systems developed by China and India, respectively.

One of the main differences between BeiDou and IRNSS is the number of satellites in their respective constellations. BeiDou currently has a constellation of 35 satellites, while IRNSS has a constellation of 9 satellites. Having more satellites in a constellation can provide better coverage and accuracy, as there are more satellites available to provide signals to users on the ground.

Another difference between BeiDou and IRNSS is the frequencies they use to transmit signals. BeiDou uses B1, B2, and B3 frequencies to transmit signals, while IRNSS uses L5 and S-band frequencies. The use of different frequencies can affect the accuracy and reliability of the navigation signals, depending on the surrounding environment.

A key advantage of IRNSS over BeiDou is that it provides better coverage of the Indian subcontinent, which is the primary service area for the system. This is because the satellites in the IRNSS constellation are positioned in orbits that are specifically designed to provide coverage of the Indian region.

Overall, both BeiDou and IRNSS are important regional satellite navigation systems that provide critical services to users in their respective service areas. While there are some differences between the two systems in terms of coverage, accuracy, and reliability, both systems are important tools for navigation and positioning in their respective regions.

Note: B1, B2, B3, L5 and S band of frequencies

B1, B2, and B3 are the frequency bands used by the BeiDou Navigation Satellite System (BDS), a global navigation satellite system developed by China.

B1 is centered at 1.5611 GHz and has a bandwidth of 16 MHz, and is used for civilian applications.

B2 is centered at 1.20714 GHz and has a bandwidth of 10 MHz, and is used for military applications.

B3 is centered at 1.26852 GHz and has a bandwidth of 10 MHz, and is used for both civilian and military applications.

L5 and S-band are frequency bands used by various satellite navigation systems, including GPS and IRNSS.

L5 is centered at 1.17645 GHz and has a bandwidth of 24 MHz. It is used for both civilian and military applications, and is intended to provide improved accuracy and reliability compared to the other GPS frequencies.

S-band is a range of frequencies from 2 to 4 GHz, and is used for a variety of communication and navigation applications. In the context of satellite navigation systems, S-band is typically used for both uplink and downlink communication between the satellite and the user. In the case of IRNSS, S-band is used for navigation signals.