Featured Research

from universities, journals, and other organizations

Navigation satellites contend with stormy Sun

September 1, 2010
European Space Agency
Just as we grow used to satellite navigation in everyday life, media reports argue that a coming surge in solar activity could render satnav devices useless, perhaps even frying satellites themselves. Is it true? No.

This illustration shows a CME blasting off the Sun’s surface in the direction of Earth. This left portion is composed of an EIT 304 image superimposed on a LASCO C2 coronagraph. Two to four days later, the CME cloud is shown striking and beginning to be mostly deflected around the Earth’s magnetosphere. The blue paths emanating from the Earth’s poles represent some of its magnetic field lines. The magnetic cloud of plasma can extend to 30 million miles wide by the time it reaches earth. These storms, which occur frequently, can disrupt communications and navigational equipment, damage satellites, and even cause blackouts.

Just as we grow used to satellite navigation in everyday life, media reports argue that a coming surge in solar activity could render satnav devices useless, perhaps even frying satellites themselves. Is it true? No.

Related Articles

It is a fact that variations in the gigantic unshielded fusion reactor we call the Sun have effects that extend far out into the Solar System. And the solar activity follows a roughly 11-year 'sunspot cycle'. That means the next 'solar maximum' -- solar max for short -- is due in 2013, not long after ESA launches its first four operational Galileo satellites.

"These Galileo In-Orbit Validation (IOV) satellites will indeed go up during a period of enhanced solar activity," explains Bertram Arbesser-Rastburg, head of ESA's Electromagnetics and Space Environment division.

"But the solar max is hardly a surprise event. Astronomers counting sunspots have tracked the solar cycle for more than 250 years. All the indications are this solar max will not be especially energetic -- the last solar minimum has been unusually long and deep."

"So it's reassuring the Galileo satellites won't be faced with the worst of the worst on day one. But in any case, they have indeed been built to endure the worst of the worst: even then, they would not fail."

Satellites proofed against solar flares

The Sun has various potential impacts that satnav system designers must take account of. The first can indeed affect satellites themselves: electromagnetic radiation and charged particles from solar flares can disrupt satellite electronics, induce potentially harmful electrostatic charging and damage onboard materials.

All satellites run these risks but for satellite navigation constellations, the danger is severe. Placed at relatively high altitudes -- 22 000 km in the case of Europe's Galileo -- they pass through belts of charged particles funnelled by Earth's magnetic field.

The satellites are built with radiation-hardened components and shielding, and boast redundancy in key subsystems. Error detection and correction routines guard against charged particles randomly 'flipping' bits of computer memory.

Galileo satellites were designed with precise data on the radiation hazard they faced: in 2005 and 2008 a pair of test satellites, Galileo In Orbit Validation Element (GIOVE) -A and -B, were launched into the constellation's future orbit. The satellites were fitted with radiation monitors, still returning data to this day.

Our Sun influencing the ionosphere

The Sun also has a continuing influence on the outermost layers of Earth's atmosphere, with energetic solar radiation splitting scanty air molecules to form an electrically-charged 'ionosphere'. Radio pioneers used the ionosphere to reflect signals beyond Earth's horizon, but for satellite navigation it is more a hindrance than a help.

"Dynamic in nature -- especially around where the Sun is shining -- the ionosphere may cause noisy scintillations leading to ground receivers losing their satellite locks," added Arbesser-Rastburg.

"Depending on its local density or 'total electron count', the ionosphere can also delay a signal passing through it, amounting to a navigation error on the order of tens of metres."

Dual receivers receiving two different frequency signals can correct for most of this error, although such receivers tend to be too bulky for in-car or personal use. Smaller GPS systems rely on a regularly-updated error estimate broadcast in the satellite signals themselves.

Increasing certainty in stormy times

Benefiting from four decades of computer advances since the GPS system was designed, each Galileo receiver incorporates a sophisticated ionosphere-modelling plug-in for error estimation -- GPS makes use of a simplistic 2D 'eggshell' ionosphere model instead.

Added certainty is given by regional overlay systems: the Wide Area Augmentation System (WAAS) for North America and the European Geostationary Navigation Overlay Service (EGNOS) for Europe, with other systems in development.

"What EGNOS offers is an assurance of integrity for European users of GPS and later Galileo signals," explained Arbesser-Rastburg."As well as checking the correctness of satellite orbits and clocks, its pan-European network of ground stations measure small changes in the total electron content of the vertical ionosphere above them to deliver local corrections. This is vital when it comes to planned 'safety-of-life' uses such as civil aviation.

"In the worst case -- perhaps during a geomagnetic storm, when an incoming coronal mass ejection completely churns up the ionosphere -- the system might tell the user not to rely on it at all. But that would not be a total shutdown, just local unavailability on a scale of hundreds of kilometres, like getting caught up in an incident of bad weather -- except this would be space weather."

In parallel with rolling out Galileo, the Agency is also putting together a Space Situational Awareness programme, combining ground- and space-based assets to increase operational knowledge of space conditions. So while space weather is likely to affect the operational Galileo system in limited ways, more accurate forecasting will be there to mitigate these factors.

For more information, see the ESA Space Situational Awareness web site at: http://www.esa.int/ssa

Story Source:

The above story is based on materials provided by European Space Agency. Note: Materials may be edited for content and length.

Cite This Page:

European Space Agency. "Navigation satellites contend with stormy Sun." ScienceDaily. ScienceDaily, 1 September 2010. <www.sciencedaily.com/releases/2010/09/100901073403.htm>.
European Space Agency. (2010, September 1). Navigation satellites contend with stormy Sun. ScienceDaily. Retrieved March 27, 2015 from www.sciencedaily.com/releases/2010/09/100901073403.htm
European Space Agency. "Navigation satellites contend with stormy Sun." ScienceDaily. www.sciencedaily.com/releases/2010/09/100901073403.htm (accessed March 27, 2015).

Share This

More From ScienceDaily

More Space & Time News

Friday, March 27, 2015

Featured Research

from universities, journals, and other organizations

Featured Videos

from AP, Reuters, AFP, and other news services

Supermassive Blackhole Detector Ready for Business

Supermassive Blackhole Detector Ready for Business

Reuters - Innovations Video Online (Mar. 25, 2015) Construction of the world&apos;s largest and most powerful observatory designed to detect and analyze gamma rays has been completed in Mexico. Gamma ray particles are considered the most energetic in the universe and scientists hope to use the observatory to learn more about the supernovas and black holes that produce them. Ben Gruber reports. Video provided by Reuters
Powered by NewsLook.com
Rocket Blasts Off Carrying U.S. Air Force GPS Satellite

Rocket Blasts Off Carrying U.S. Air Force GPS Satellite

Reuters - News Video Online (Mar. 25, 2015) A U.S. Air Force GPS IIF-9 satellite launches aboard a United Launch Alliance Delta IV rocket into semi-synchronous orbit. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Opportunity's Marathon: The Mars Rover Just Keeps Going

Opportunity's Marathon: The Mars Rover Just Keeps Going

Newsy (Mar. 24, 2015) NASA&apos;s Opportunity Mars Rover finished a full marathon, making it the first human creation to do a full 26.2 miles on another planet. Video provided by Newsy
Powered by NewsLook.com
Twin Astronaut to Break NASA Record in Study

Twin Astronaut to Break NASA Record in Study

AP (Mar. 23, 2015) NASA astronaut Scott Kelly will be the first American to spend a year aboard the International Space Station in an experiment to test human endurance in space, while his twin brother&apos;s health is compared on Earth. (March 23) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.


Breaking News:

Strange & Offbeat Stories

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News


Free Subscriptions

Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile

Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?

Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins