IONOSPHERE EFFECTS ON GPS/RF COMMUNICATION, ELECTRIC, METAL NETWORKS AND SPACECRAFTS OSMAN AKGÜN

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1 IONOSPHERE EFFECTS ON GPS/RF COMMUNICATION, ELECTRIC, METAL NETWORKS AND SPACECRAFTS OSMAN AKGÜN

2 IONOSPHERE

3 IONOSPHERE EFFECTS

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5 POSSIBLE EFFECTS GPS errors Atomic oxygen attack Spacecraft charging HF communication errors GIC Induced currents

6 GPS ERRORS The ionosphere is that part of the upper atmosphere where free electrons occur in sufficient density to have an appreciable influence on the propagation of radio frequency electromagnetic waves. - The ionosphere introduces a variable time delay in the propagation of signals from the satellite to the receiver, which affects positioning. - The delay calculation requires modeling the electron density along the pass of the signal. - Radio bursts - Scintillation can prevent signal lock

7 GPS ERRORS Models of the ionosphere to compute corrections Empirical climatological models: Klobuchar Coefficients Physics based numerical models: CTIPe, TIE-GCM Data assimilation schemes: WAAS, US-TEC, GAIM Models can provide specification and forecast

8 GPS ERRORS Typical Error in Meters (per satellites) Satellite Clocks Orbit Errors Ionosphere Troposphere Receiver Noise Multipath Standard GPS Differential GPS The ionosphere is the largest source of error for Standard GPS and second largest for Differential GPS

9 ATOMIC OXYGEN ATTACK Atomic oxygen, formed in Earth s thermosphere, interacts readily with many materials on spacecraft flying in low Earth orbit (LEO). All hydrocarbon based polymers and graphite are easily oxidized upon the impact of ~4.5 ev atomic oxygen as the spacecraft ram into the residual atmosphere. The resulting interactions can change the morphology and reduce the thickness of these materials. Directed atomic oxygen erosion will result in the development of textured surfaces on all materials with volatile oxidation products.

10 SPACECRAFT CHARGING

11 RF TRANSMISSION

12 INDUCED CURRENTS A time-varying magnetic field external to the Earth induces electric currents in the conducting ground. These currents create a secondary (internal) magnetic field. As a consequence of Faraday's law of induction, an electric field at the surface of the Earth is induced associated with time variations of the magnetic field. The surface electric field causes electrical currents, known as geomagnetically induced currents (GIC), to flow in any conducting structure, for example, a power or pipeline grid grounded in the Earth. This electric field, measured in V/km, acts as a voltage source across networks. Examples of conducting networks are electrical power transmission grids, oil and gas pipelines, non-fiber optic undersea communication cables, non-fiber optic telephone and telegraph networks and railways. GIC are often described as being quasi direct current (DC), although the variation frequency of GIC is governed by the time variation of the electric field. For GIC to be a hazard to technology, the current has to be of a magnitude and occurrence frequency that makes the equipment susceptible to either immediate or cumulative damage. The size of the GIC in any network is governed by the electrical properties and the topology of the network. The largest magnetospheric-ionospheric current variations, resulting in the largest external magnetic field variations, occur during geomagnetic storms and it is then that the largest GIC occur. Since the largest magnetic field variations are observed at higher magnetic latitudes, GIC have been regularly measured in Canadian, Finnish and Scandinavian power grids and pipelines since the 1970s. GIC of tens to hundreds of amperes have been recorded. GIC can cause problems, such as increased corrosion of pipeline steel and damaged high-voltage power transformers. GIC are one possible consequence of geomagnetic storms, which may also affect geophysical exploration surveys and oil and gas drilling operations.

13 Space weather effects Many of the space weather effects on communication and navigation are a consequence of the response of the upper atmosphere: solar flares, coronal mass ejections solar proton events

14 Space weather effects

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19 SOLAR PROTON EVENT EFFECTS A Solar proton event occurs when protons emitted by the Sun become accelerated to very high energies during a solar flare accompanied by a coronal mass ejection or in interplanetary space by the shocks associated with coronal mass ejections. Protons are finally guided by the interplanetary magnetic field lines. Energetic proton storms can electrically charge spacecraft to levels that can damage electronic components. Solid state memory can be altered. Energetic solar protons are a significant radiation hazard to spacecraft and astronauts. They can cause spacecraft to lose their orientation. Flashes and streaks of light occur when energetic protons strike the sensitive optical electronics in spacecraft and can also destroy the efficiency of the solar panels. Significant proton radiation exposure can be experienced by astronauts who are outside a protective shield in the space.

20 REFERENCES The Effects of Earth's Upper Atmosphere on Radio Signals, Radio Communications In the Digital Age, Harris Corporation, RF Communications Division Thomas J. Bogdan, Space Weather Effects on GPS, Director, Space Weather Prediction Center, USA Ionospheric Perturbations, HF Propagation Tutorial, Natural Hazards, SPACE WEATHER,