Europe’s Galileo sat­nav iden­ti­fies prob­lems be­hind fail­ing clocks

Kuwait Times - - TECHNOLOGY -


In­ves­ti­ga­tors have un­cov­ered the prob­lems be­hind the fail­ure of atomic clocks on­board satel­lites be­long­ing to the be­lea­guered Galileo sat­nav sys­tem, the Euro­pean Com­mis­sion said Mon­day. For months, the Euro­pean Space Agen­cy­which runs the pro­gram-has been in­ves­ti­gat­ing the rea­sons be­hind fail­ing clocks on­board some of the 18 nav­i­ga­tion satel­lites it has launched for Galileo, Europe’s al­ter­na­tive to Amer­ica’s GPS sys­tem.

Each Galileo satel­lite has four ul­tra­ac­cu­rate atomic time­keep­ers, two that use ru­bid­ium and two hy­dro­gen maser. But a satel­lite needs just one work­ing clock for the sat­nav to work-the rest are spares. Three ru­bid­ium and six hy­dro­gen maser clocks were not work­ing, with one satel­lite sport­ing two failed time­keep­ers. “The main causes of the mal­func­tions have been iden­ti­fied and mea­sures have been put in place to re­duce the pos­si­bil­ity of fur­ther mal­func­tions of the satel­lites al­ready in space,” com­mis­sion spokes­woman Lu­cia Caudet said.

ESA found af­ter an in­ves­ti­ga­tion that its ru­bid­ium clocks had a faulty com­po­nent that could cause a short cir­cuit, ac­cord­ing to Euro­pean sources. The in­ves­ti­ga­tion also found that op­er­a­tions in­volv­ing hy­dro­gen maser clocks need to be con­trolled and closely mon­i­tored, the same sources said. The agency has taken mea­sures to cor­rect both sets of prob­lems, the sources added, with the agency set to re­place the faulty com­po­nent in ru­bid­ium clocks on satel­lites not yet in or­bit and im­prove hy­dro­gen maser clocks as well.

“The sup­ply of the first Galileo ser­vices has not and will not be af­fected by the mal­func­tion­ing of the atomic clocks or by other cor­rec­tive mea­sures,” Caudet said, and that the mal­func­tions have not af­fected ser­vice per­for­mance.

Most ac­cu­rate clocks ever

The Galileo sys­tem went live in De­cem­ber last year, pro­vid­ing ini­tial ser­vices with a weak sig­nal, hav­ing taken 17 years at more than triple the orig­i­nal bud­get. The civil­ian-con­trolled ser­vice is seen as strate­gi­cally im­por­tant for Europe, which re­lies on two mil­i­tary-run ri­vals-GPS and Rus­sia’s GLONASS. ESA boasts that Galileo has the most ac­cu­rate atomic clocks ever used for ge­olo­cal­i­sa­tion. Sim­i­lar to tra­di­tional clocks re­ly­ing on the tick of a pen­du­lum, atomic time­keep­ers also count reg­u­lar os­cil­la­tions, in this case switches be­tween en­ergy states of atoms stim­u­lated by heat or light.

But Galileo has ex­pe­ri­enced many set­backs, in­clud­ing the place­ment of two satel­lites in the wrong or­bit. In Jan­uary, ESA di­rec­tor gen­eral Jan Wo­erner an­nounced that the sys­tem had suf­fered a set­back with its atomic clocks. The EU Com­mis­sion ex­pects Galileo to be fully op­er­a­tional by 2020. ESA signed a con­tract in late June with a Ger­man-Bri­tish con­sor­tium to build eight more satel­lites for Galileo, which will even­tu­ally com­prise 30 or­biters. Twen­ty­four will be op­er­a­tional, in three or­bital planes, with the rest stand­ing by as spares, in or­bit and on the ground.

Once fully de­ployed, Galileo aims to pin­point a lo­ca­tion on Earth to within a me­ter­com­pared to sev­eral me­ters for GPS and GLONASS. Clients of a pay­ing ser­vice will be able to re­ceive even more ac­cu­rate read­ings-down to cen­time­ters. Such ac­cu­racy will be very use­ful in search-and-res­cue op­er­a­tions. All new cars sold in Europe by 2018 will be fit­ted with Galileo for nav­i­ga­tion and emer­gency calls. Its high-pre­ci­sion clocks will also boost syn­chro­niza­tion of bank­ing and fi­nan­cial trans­ac­tion, telecom­mu­ni­ca­tions and en­ergy smart­grids, mak­ing them more ef­fi­cient. It should also boost the safety of driver­less cars. —AFP

KOUROU: This file photo shows the Ari­ane 5 rocket with a pay­load of four Galileo satel­lites lift­ing off from ESA’s Euro­pean Space­port in Kourou, French Guiana. —AFP

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