Ionospheric Remote Sensing with GNSS

Yaoli Peng ,W A Scales

doi:10.3390/encyclopedia1040094

Abstract

The Global Navigation Satellite System (GNSS) plays a pivotal role in our modern positioning, navigation and timing (PNT) technologies. GNSS satellites fly at altitudes of approximately 20,000 km or higher. This altitude is above an ionized layer of the Earth’s upper atmosphere, the so called “ionosphere”. Before reaching a typical GNSS receiver on the ground, GNSS satellite signals penetrate through the Earth’s ionosphere. The ionosphere is a plasma medium consisting of free charged particles that can slow down, attenuate, refract, or scatter the GNSS signals. Ionospheric density structures (also known as irregularities) can cause GNSS signal scintillations (phase and intensity fluctuations). These ionospheric impacts on GNSS signals can be utilized to observe and study physical processes in the ionosphere and is referred to ionospheric remote sensing. This entry introduces some fundamentals of ionospheric remote sensing using GNSS.

Highlights

To determine the unknown location (x, y, z) of a Global Navigation Satellite System (GNSS) receiver as shown in Figure 1, for simplicity let us assume the locations of three beacon GNSS satellites in the sky are known beforehand
Under the influence of the nearly vertical geomagnetic field as well as the horizontal variation of plasma density and electric fields driven by plasma instabilities, various multi-scale (∼10−2 to 105 m) ionospheric structures lead to phenomena such as aurora, sub-auroral polarization streams (SAPS), as well as polar tongues of ionization (TOI)
Fundamental physics and engineering of GNSS and ionospheric remote sensing are introduced in this entry

Summary

GNSS Introduction

Satellite System (GNSS) forms a ubiquitous technological infrastructure in modern society. This set of four equations, involving reception of at least four GNSS satellite signals, forms the underlying algorithm to solve a simple static positioning problem in the 3D space including the receiver clock bias. There are four operational GNSS constellations: USA’s Global Positioning System (GPS), Russia’s Global’naya Navigatsionnaya Sputnikovaya Sistema (GLONASS), European Union’s Galileo, and China’s BeiDou Navigation Satellite System (BDS, formerly known as COMPASS). 24 operational GLONASS satellites are located within three different MEO orbital planes with an altitude of ∼19,100 km, which indicates GLONASS satellites’ orbital period is ∼11 h 15 min. The other two GLONASS satellites transmit an additional frequency band, G3, with a center frequency of 1201 + n × 0.4375 MHz. The details of GLONASS signal structure can be found in their. The latest status of the Beidou constellation can be found at the Test and Assessment Research Center of China Satellite Navigation Office website [9]

GNSS Observables and Ranging Errors

Ionospheric Characteristics and Phenomena

Ionospheric Remote Sensing

Conclusions and Prospects