NEAR EARTH SPACE ENVIRONMENT, EMERGING SPACE WEATHER MARKET IN EUROPE AND TURKEY: AN IMPLICATION FOR AEROSPACE APPLICATIONS Yurdanur Tulunay* and Khashayar Khazraei† Middle East Technical University Aerospace Engineering Department 06531 Ankara, Turkey
ABSTRACT Space weather is a new subject that is not yet widely understood and appreciated. Space weather processes can include changes in the interplanetary magnetic field, coronal mass ejections from the sun and disturbances in the Earth's magnetic field. The effects can range from damage to satellites to disruption of power grids on Earth. In this paper some remarks are given on emerging markets related to space weather. However, protection or shielding for severe space weather events is too costly and/or technically not feasible within technical budgets. Thus, the only protection to minimize the risk is timely space weather forecast. Data-driven approaches such as the Neural Network (NN) based modelling are shown to be promising for such cases.
satellite to sattelite radio systems in many different ways. Command, control and communication systems involving ionospheric as well as transionospheric propagation may be disrupted; global positioning networks comprised and surveillance (both optical and radar based) systems affected. The increasing need for new communication services, especially those involving ionospheric HF communications, satellite communications and navigational systems, imposes increasing demands for the continous monitoring of space weather, ionospheric and the development of an improved understanding of the propagation effects across a wide frequency spectrum. There is an on-going requirement to develop and improve means to predict reglar behaviour, to minimise the disturbing effects over a wide range of propagation conditions and to mitigate the deleterious effects on radio systems ([4]; [5]).
INTRODUCTION Space weather, conditions and processes occuring in space, which have the potential to affect the near Earth environment; space weather processes can include changes in the interplanetary magnetic filed, coronal mass ejections form the sun and disturbances in the Earth's magnetic field (NASA Dictionary of Terms). As stated above, space weather is driven by solar activity, when massive explosions, known as coronal mass ejections, carry magnetic clouds containing billions of tons of material hurtling into space. When the magnetic clouds reach the Earth they can cause geomagnetic storms which contribute to severe space conditions. The weather in space has a huge impact on telecommunications, navigation systems, electric power networks and spacecraft controls. Space weather storms can generate harmful electric surges in power grids, interupt radio communications systems and damage Earth-orbiting satelites. Complex temporal and spatial changes within the Earth’s ionosphere can limit and degrade the performance of terrestrial, earth to satellite and * †
Quoting from Siscoe ([12]), “To be able to talk about the network of space-vulnerable, technological entities upon which humankind is becoming increasingly dependent, I suggest referring to it as the cyberelectrosphere. The cyberelectrosphere is defined as the global totality of all space-vulnerable, electrically enabled technological systems. If we could see the network comprised of this totality by itself –see the satellite links, the cable links, the navigation and positioning links, the electric power grids, and the radio links – the image would resemble a picture out of Grey’s Anatomy showing the central nervous system or the circulation system. Here the sensory, information and energy transfer network does not belong to the human body [body] to an abstract, interconnected global entity, the cyberelectrosphere. Figure 1 attempts to show how the cyberelectrosphere emerges from an interaction between three subjects: society, science and space weather. Before science, the overlap of society and space weather in the form of low-latitude auroras that accompany space storms gave rise to omens and wonders.
Yurdanur Tulunay, Email:
[email protected] Khashayar Khazraei (Corresponding Author), Email:
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The overlap of space weather and science has given rise to the fields of space physics and aeronomy. The overlap of science and society has engendered modern technological society, those components of which that are vulnerable to space-weather disturbances form the cyberelectrosphere at the center of the triquetra.”
due to the destruction of base stations or due to the extremely heavy demand which locks the services. In particular, especially in such cases HF is a reliable service. However, it is known that HF which uses Earth’s ionosphere is susceptible to space weather (e.g. [11]). Corrosion of Pipelines Cathodic protection currents must be adaptively adjusted according to the space weather conditions so that geomagnetically induced currents (GIC) do not cause excessive corrosion. Even though high strength polymers are in consideration for pipelines, existing metal pipelines will certainly be in operation for considerable lengths of time until their economic life ends. Electric Power-line Disruption
Figure 1 A triquetra illustrating how the intersection of society, science, and space weather gives rise to the cyberelectrosphere ([12]).
At the moment, except for a few cases, the products of space weather research and development activities do not find customers easily. One of the reasons for this situation is the lack of awareness of the effects of space weather on terrestrial or Earth bound systems. Therefore, education and outreach activities in the space weather field are vital in creating a healthy environment of space weather markets. This will provide value added services driving motivation for the end user and last but not the least a portal financial support for space weather service providers ([2]). Some Examples of Services Open to Space Weather Effects ([1]; [6]) Telecommunication Radio communications and navigation: ionospheric perturbations caused by space weather events adversely affect Space to Space, Earth to Space and Earth to Earth telecommunications, including 330MHz HF and over the horizon HF radar systems, and various satellite navigation systems. Disasters like earthquakes, floods, etcetera, can be managed satisfactorily if reliable communication channels are provided. It has also been experienced in various disasters including the Turkish 1999 earthquake that especially during the first hours of the disaster, GSM channels are not effective either
GIC are driven by the geo-electric field associated with a magnetic disturbance in electric power transmission grids, communication cables and railway equipment. GICs flowing through electric power lines and transformer ground paths may cause severe excess loading, possibly even resulting in a complete breakdown of electric power services. GSM Services The quality of GSM mobile telephone services are adversely affected by space weather conditions. Global Positioning System (GPS) Based Services GPS based services, such as automatic toll calculation, based on vehicle tracking, transport systems for goods and military systems may suffer severely due to a decrease in positional accuracy caused by space weather events. Satellite dependent communication and GPS systems are also susceptible to space weather. Among its other effects it gives rise to ionospheric scintillations which in turn cause significant errors in navigation and positioning on Earth. Such errors no doubt cause vital adverse effects in rescue operations (e.g. [17]). Surveys Based on Magnetic Measurements Various geological and other types of surveys based on accurate geomagnetic field measurements are perturbed because of the space weather conditions.
Hazards for Airplane, Crew and Passengers There are failures and upsets in aircraft electronics, communication and navigation problems during space weather storms. Cosmic ray exposures bring severe health risks from radiation effects, especially during long distance, high altitude flights. Imposed Effects on Spacecrafts Space weather events impose many effects and disturbances on spacecrafts such as: surface charging, deep dielectric or bulk charging, Single Event Upset (SEU) due to galactic cosmic rays and Solar Proton Events (SEP), spacecraft drag (< 1000 km), total dose effects, solar radio frequency interferences and telemetry scintillation, space debris, spacecraft orientation deviation, photonics noise, materials degradation, meteorite impact. Climatic and Meteorological Effects Space weather affects the atmospheric circulation, precipitation and Ozone depletion. Risk for Astronauts Radiation in space is one of the main concerns for astronauts. Activities of astronauts, such as space walks, are planned by considering the space weather forecasts.
Community with one of its missions as developing internationally recognised NESE standards. In June 1994, first documentary titled as Natural Orbital Environment Guidelines for Use in Aerospace Vehicle Development was published by Anderson, B.J. (Ed.) in NASA Technical Manual. Between 1999 and 2001, there were many feasibility studies on the subject of space weather undertaken by European Space Agency (ESA). Between 2003 and 2005, ESA has also been active in investigating the need within Europe for increased space weather activities and it has run the Space Weather Applications Pilot Project which seeks to expand the results of the feasibility studies and further develop the community of informed space weather service users in Europe. ESA has started some Service Development Activities (SDA) each focusing on a wide range of space weather user domains such as solar monitoring and warnings, spacecraft hazards, operational airline risks and etcetera. Since 1999, there is a Space Weather Working Team (SWWT) that still continues to advise ESA on the progress of space weather activities within Europe. Figure 2 shows where the Near Earth Space lies within the branches of space sciences and technology.
Satellite Design Space weather effects constitute major hazards to satellites in orbit. The space weather effects range from simple disturbances to total failure. The financial magnitude of its effect is estimated to be around one billion Euros insurance claims within 10 year period. Therefore, space weather related anomalies must be taken into account during both the conceptual and practical design phases of satellites and their instruments. Developments’ Overture In 1993 the U.S. National Aeronautics and Space Administration (NASA) recognised the importance of the field of Near Earth Space Environment (NESE) by forming a national program to coordinate actual efforts in this area. The International Organization for Standardization (ISO) under charter from the United Nations (UN) formed a Space System Technological
Figure 2 Departments of Space Sciences and Technology (ESF-SSC, 1990) Since 1970, there were many Near Earth Space activities in Turkey; the ones which are relevant to ionospheric radio wave propagation can be listed as: i)
By using the Ariel 3 and Ariel 4 satellite electron density, VLF data the morphology of the upper atmosphere at about 550 km was investigated widely.
ii)
The Mid-Latitude Electron Density Trough was shown to be the ionospheric projection of the magnetospheric plasmapause by using Ariel 3, Ariel 4, OGO 4, ISEE 1, KYOKKO satellite data. Some modeling work of the Trough was xiii) performed in parallel.
iii) The possible influence of the Interplanetary Magnetic Field (IMF) Bz polarity reversals on ionospheric foF2 data in relation to quantification of the ionospheric variability was investigated. iv) The total electron content (TEC) over Ankara longitudes was computed by using the ATS 6 satellite Faraday rotation signals. v) A High Frequency (HF) Fading Experiment was conducted between United Kingdom and Turkey. vi) As part of the COST 238: PRIME Action the Polish make KOS Vertical Ionosonde was deployed at the Kandilli Observatory of the Boğaziçi University. vii) Within the COST 251: IITS Action data driven modeling approach was introduced and neural network based models were constructed for forecasting foF2 one to twenty four hours in advance for single stations and one hour in advance for multi stations. Neural network based models were also constructed to forecast foF2 one hour in advance during IMF Bz polarity reversals and to model the effect of Mid-Latitude Ionospheric Trough on foF2 values ([13]).
be carried out in collaboration with International Telecommunication Union, Commission R. The same station will be set up at the Fırat University in Elazığ, Turkey ([11]). A NATO-RTO project on the Surface Boundary Layer Refractive Index Measurements in Greece, Turkey and UK Relevant to Optical and Microwave Frequencies in Aerospace Operations.
xiv) At the Department of Meteorology and the Department of Physics of a few Turkish universities, some works on the Earth’s magnetosheath, magnetotail, solar windmagnetosphere-ionosphere coupling, magnetohydrodynamics, and plasma physics research related to Space Physics have been conducted. xv) There are a few electric and electronic engineering departments where theoretical electromagnetic and propagation research have been conducted. METHOD
viii) With the support of the State Planning Office (DPT), the orbit of TÜRKSAT 1B satellite was modeled by using numerical and data driven techniques, and a software package was obtained ([14]).
One way to mitigate the risk of severe space weather events is timely space weather forecast. Natural processes such as the NES are highly complex, nonlinear and time varying. Therefore mathematical modeling is usually very difficult or impossible. Data-driven approaches such as the Neural Network (NN) based modelling are shown to be promising for such cases. The only basic requirement is the availability of representative data. Since 1990 a group at METU have adopted a method of data driven modelling by using NNs ([8]). Some of the case studies are introduced below:
ix) An HF propagation experiment in Ankara and Elazığ was conducted during the last total solar eclipse of the century, 11 August 1999 ([11]).
i) NN based orbit prediction for a geostationary satellite ([3]; [10])
x) SPECIAL I and II, the European Science Foundation (ESF) Network on Earth Weather and Space Weather was one of the other European Union (EU) activities in the Near Earth Space discipline that Turkish scientists took part.
Man made satellites are good examples of complex systems. Keeping the satellite in its predetermined orbit requires the control of its atttitude control actuators remotely.
xi) Solar, geomagnetic field, seismic and geophysical observations have been conducted at the Kandilli Observatory of the Boğaziçi University. xii) An HF channel characterization project supported by the Turkish State Planning Organization is being conducted at the Middle East Technical University in Ankara. As part of this activity, an HF transmission experiment will be conducted by setting up an International Telecommunication Union (ITU)-Compliant HF Field Strength Monitoring Terminal. The work will
The classical simulation technique employed by Sakaci ([15]) was by means of numerical and analytical methods. Later, Kutay ([14]) trained his data driven model with some synthetic data generated by Sakaci’s model and predicted the orbital parameters of the TÜRKSAT 1B satellite. Table i-1 shows the errors in the estimation of the orbital parameters of a, e, and i. Figures i-1, i-2 and i-3 illustrate the variation of the orbital parameters for a period of 14 days.
MET UAEE1
1990 respectively, for the same months. RMS errors related to this model for three ionospheric stations are shown in Table ii-1.
AT KNN
42164500
a , Semi-major axis (m)
42164000 42163500 42163000
Table ii-1 RMS errors for the forecast of foF2 one hour in advance, in MHz.
42162500 42162000
Station\Month
42161500
Sept. 1990
Dec. 1990
Poiters
0.12566
0.12304
Slough
0.13319
0.11353
Uppsala
0.15652
0.13719
42161000 42160500 0
100
200
300
400
500
600
700
time (number of the sampling periods)
Figure i-1 Variation of the semi-major axis in 14 days calculated by METUAEE1 and estimated by ATKNN MET UAEE1
AT KNN
2.50E-04
The Influence of the Mid Latitude electron density Trough on High Frequency (HF) communication is discussed in other studies ([11]).
e , Eccentricity
2.00E-04
iii) Forecasting GPS TEC During High Solar Activity ([7]; [9])
1.50E-04
1.00E-04
5.00E-05
0.00E+00 0
100
200
300
400
500
600
700
time (number of the sampling periods)
Figure i-2 Variation of the eccentricity in 14 days calculated by METUAEE1 and estimated by ATKNN MET UAEE1
AT KNN
8.00E-02 7.50E-02
Total Electron Content (TEC) data evaluated from GPS between measurements from 2000 to 2001 at Chilbolton (51.8 N, 1.26 W) receiving station for April and May are used for the training, test and validation the METUNN. An additional validation has been performed on an independent validation data set by using the TEC values at Halisham (50.9 N, 0.3 E) receiving station for selected months in 2002. Errors and forecast of TEC one-hour ahead results are shown in Table iii-1 and Figure iii-1, respectively.
i , Inclination (deg)
7.00E-02 6.50E-02
Table iii-1 Error Table
6.00E-02 5.50E-02 5.00E-02 4.50E-02 4.00E-02
RMS Error (el/sqm * 1016)
1.87544
Normalized error
0.07259
3.50E-02 3.00E-02 0
100
200
300
400
500
600
700
time (number of the sampling periods)
1016)
1.22433
Cross Correlation Coefficient
0.98495
Absolute error (el/sqm *
Figure i-3 Variation of the inclination in 14 days calculated by METUAEE1 and estimated by ATKNN Table i-1 The rms errors, the normalized rms errors and the correlation coefficients in the estimation of a, e and i. o.p. a e i
rms error 21.28 m 3.24*10-6 2.09*10-3 deg
Norm. rms error 5.05*10-7 2.17*10-2 3.54*10-2
Corrl. Coeff. 0.9996837 0.9970946 0.9892513
ii) Temporal and Spatial Forecasting of Ionospheric Critical Frequency foF2 Values up to 24 Hours in Advance ([13]; [16]) Forecasting of foF2 is important for the telecommunication system planner, users and other groups of interests. Input data for training, test and validation sets are from the years 1979, 1968 and
Figure iii-1 Observed (red, lower curve), 1h ahead forecast (blue, mid curve), monthly median (black, upper curve) of TEC for 18-22 April 2002.
iv) Neural Network Based Solar Flux Forecasting
References
To sustain our objectives, which are to develop the science underpinning space weather applications as well as exploring methods for providing a comprehensive range of space weather services to a variety of users based on modeling and monitoring the Sun-Earth system, there has been a decision made to concentrate our efforts on ‘Neural Network Based Forecasting of the Probable Radio Wave Propagation Interferences by Solar Radio Flares (SRF)’.
[1] Tulunay, Y., Tulunay, E., Some Remarks on Emerging Space Weather Markets and Turkish Case, (in press) Adv. Geosci., 2005.
Noise from the sun, especially from the solar storms, is the largest source of non-anthropogenic noise in the 1-20 GHz frequency band, the lower frequency range of which is used for modern wireless communications. Considering the rapid growth around the world in wireless communications at GHz frequencies in the last decade and continuing to date calls for studies of solar noise levels at such frequencies ([6]), we decided to use the data provided by the Trieste Observatory of solar fluxes measured at 2695 MHz (2.695 GHz) to train the METU Neural Network and use it to forecast the values of these solar fluxes in specific time-intervals. Table iv-1 Errors for the Forecast of SFU 1 h. in advance Mean Square Error (MSE)
186.5673
Root Mean Square Error (RMSE)
13.65896
Cross Correlation Coefficient
0.591853
[2] Tulunay, Y., Effect of Upper Atmosphere on Terrestrial and Earth Communications: Near Earth Space Dimension in Turkey Since 1960’s Concerning Ionospheric Radio Propagation, 2 nd URSI-Türkiye’2004 Congress, Ankara, 8-10 September 2004. [3] Tulunay, Y., Tulunay E., Senalp, E. T., The Neural Network Technique-1: A General Exposition, Advances in Space Research, 33/6 , p:983-987, 2004. [4] Zolesi, B., Cander, L. R., COST 271 Action – Effects of the Upper Atmosphere on Terrestrial and Earth-space communications: introduction, edited by B. Zolesi, L. R. Cander, Annals of Geophysics, Supplement to 47(2/3), p: 915-925, 2004. [5] Zolesi, B., Cander, L. R., COST 296 Action – Mitigation of Ionospheric Effects on Radio Systems (MIERS), Proposers of a New EU Action, 2004. [6] Lanzerotti, L. J., Gary, D. E., Thomson, D. J., Maclennan, C. G., Solar Radio Burst Event (6 April 2001) and Noise in Wireless Communications Systems, Bell Labs Technical Journal 7(1), p:159163, 2002. [7] Senalp, E. T., Tulunay, E., Tulunay, Y., Neural Network Based Forcasting of the Total Electron Content Values, 1st URSI-Türkiye’2002 Congress, p:407-410, Istanbul, 18-20 September 2002. [8] Tulunay, E., Tulunay, Y., Kutay, A. T., Senalp, E. T., Neural Network Based Approaches for Some Non-Linear Processes, 1st URSI-Türkiye’2002 Congress, p:403-406, Istanbul, 18-20 September 2002. [9] Tulunay, E., Senalp, E. T., Cander, L. R., Tulunay, Y., Ciraolo, Forecasting GPS TEC During High Solar Activity by NN Technique, COST 271 Workshop, Faro, Portugal, 1-5 October 2002. [10] Kutay, A. T., Tulunay, Y.,Tulunay E., Tekinalp O., Neural Network Based Orbit Prediction for a Geostationary Satellite, The 2nd IFAC DECOM-TT Workshop on Automatic Systems for Developing the Infrastructure in Developing Countries, p:207-218, Lake Ohrid, Republic of Macedonia, 21-23 May 2001.
Figure iv-1 Horizontal axis refers to the normalized obtained values; vertical axis refers to the normalized measured values. One hour ahead forecast of solar fluxes at 2695 MHz.
[11] Tulunay, Y., Tulunay, E., Senalp, E. T., An Attempt to Model the Influence of the Trough on HF Communication by using Neural Network, Radio Science, 36(5), p:1027-1041, 2001.
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