In the category of making lemonade when life hands you space lemons: > Begin forwarded message: > > From: GPS World <[email protected]> > Date: November 9, 2015 at 12:32:27 PM MST > Subject: [New post] Galileo Satellites Set for Year-Long Einstein Experiment > > New post on GPS World > > <http://gpsworld.com/?author=7> > Galileo Satellites Set for Year-Long Einstein Experiment > <http://gpsworld.com/galileo-satellites-set-for-year-long-einstein-experiment/>by > GPS World staff <http://gpsworld.com/?author=7> > News from the European Space Agency > > > > <http://gpsworld.com/wp-content/uploads/2015/11/Albert_Einstein_node_full_image_2.jpg> > Albert Einstein > > Europe’s fifth and sixth Galileo satellites — subject to complex salvage > maneuvers following their launch last year into incorrect orbits — will help > to perform an ambitious year-long test of Einstein’s most famous theory. > > Galileos 5 and 6 were launched together by a Soyuz rocket on August 22, 2014. > But the faulty upper stage stranded them in elongated orbits > <http://gpsworld.com/esa-releases-diagrams-showing-galileo-5-and-6-orbit/> > that blocked their use for navigation. > > ESA’s specialists moved into action and oversaw a demanding set of maneuvers > to raise the low points of their orbits and make them more circular. “The > satellites can now reliably operate their navigation payloads continuously, > and the European Commission, with the support of ESA, is assessing their > eventual operational use,” explained ESA’s senior satnav advisor Javier > Ventura-Traveset. “In the meantime, the satellites have accidentally become > extremely useful scientifically, as tools to test Einstein’s General Theory > of Relativity by measuring more accurately than ever before the way that > gravity affects the passing of time.” > > > > <http://gpsworld.com/wp-content/uploads/2015/03/Corrected_orbits-Galileo5.jpg> > The original (in red) and corrected (in blue) orbits of the fifth and sixth > Galileo satellites, along with that of the first four satellites (green). > > Although the satellites’ orbits have been adjusted, they remain elliptical, > with each satellite climbing and falling some 8500 km twice per day. It is > those regular shifts in height, and therefore gravity levels, that are > valuable to researchers. > > Albert Einstein predicted a century ago that time would pass more slowly > close to a massive object. It has been verified experimentally, most > significantly in 1976 when a hydrogen maser atomic clock on Gravity Probe A > was launched 10,000 km into space, confirming the prediction to within 140 > parts in a million. > > > > <http://gpsworld.com/wp-content/uploads/2015/11/Passive_hydrogen_maser_node_full_image_2.jpg> > Passive hydrogen maser atomic clock of the type flown on Galileo, accurate to > one second in three million years. (Photo: ESA) > > Atomic clocks on navigation satellites have to take into account they run > faster in orbit than on the ground — a few tenths of a microsecond per day, > which would give us navigation errors of around 10 km per day. > > “Now, for the first time since Gravity Probe A, we have the opportunity to > improve the precision and confirm Einstein’s theory to a higher degree,” > comments Javier. > > This new effort takes advantage of the passive hydrogen maser atomic clock > aboard each Galileo, the elongated orbits creating varying time dilation, and > the continuous monitoring thanks to the global network of ground stations. > > > > <http://gpsworld.com/wp-content/uploads/2015/11/Gravity_Probe_A_node_full_image_2.jpg> > he Gravity Probe A payload of 1976, flown in a highly elliptic single orbit > to measure the ‘gravitational redshift’ of Einstein’s Theory of General > Relativity more accurately than ever before, seen with its designers Robert > Vessot and Martin Levine of the Smithsonian Astrophysical Observatory. The > experiment compared a hydrogen maser clock on Earth with its replica in space > as it ascended to about 10 000 km, and confirmed theoretical expectations to > an accuracy of 0.02%. > > “Moreover, while the Gravity Probe A experiment involved a single orbit of > Earth, we will be able to monitor hundreds of orbits over the course of a > year,” explained Javier. “This opens up the prospect of gradually refining > our measurements by identifying and removing systematic errors. Eliminating > those errors is actually one of the big challenges. For that we count on the > support of Europe’s best experts plus precise tracking from the International > Global Navigation Satellite System Service, along with tracking to centimeter > accuracy by laser.” > > The results are expected in about one year, projected to quadruple the > accuracy on the Gravity Probe A results. > > The two teams devising the experiments are Germany's ZARM Center of Applied > Space Technology and Microgravity <https://www.zarm.uni-bremen.de/>, and > France's SYRTE Systèmes de Référence Temps-Espace > <https://syrte.obspm.fr/spip/?lang=fr>, both specialists in fundamental > physics research. > > ESA’s forthcoming Atomic Clock Ensemble in Space experiment, planned to fly > on the International Space Station in 2017, will go on to test Einstein’s > theory down to 2–3 parts per million. > > GPS World staff <http://gpsworld.com/?author=7> | November 9, 2015 at 2:32 pm > | Tags: Albert Einstein > <http://gpsworld.com/?taxonomy=post_tag&term=albert-einstein>, European Space > Agency <http://gpsworld.com/?taxonomy=post_tag&term=european-space-agency>, > Galileo 5 <http://gpsworld.com/?taxonomy=post_tag&term=galileo-5>, Galileo 6 > <http://gpsworld.com/?taxonomy=post_tag&term=galileo-6>, theory of relativity > <http://gpsworld.com/?taxonomy=post_tag&term=theory-of-relativity> | > Categories: GNSS <http://gpsworld.com/?taxonomy=category&term=gnss>, Latest > News <http://gpsworld.com/?taxonomy=category&term=latest-news> | URL: > http://wp.me/p2Jsnp-aSv <http://wp.me/p2Jsnp-aSv> > Comment > <http://gpsworld.com/galileo-satellites-set-for-year-long-einstein-experiment/#respond> > See all comments > <http://gpsworld.com/galileo-satellites-set-for-year-long-einstein-experiment/#comments> > > Unsubscribe > <https://subscribe.wordpress.com/?key=88b2d9e057141a250afc6ac237ed1940&email=seaman%40noao.edu&b=fDd29C3nUSDnyXF%2CogMJ-pR.d%26-pptYd5m%25%2BQv%2BumN05%2BKacqq> > to no longer receive posts from GPS World. > Change your email settings at Manage Subscriptions > <https://subscribe.wordpress.com/?key=88b2d9e057141a250afc6ac237ed1940&email=seaman%40noao.edu>. > > Trouble clicking? Copy and paste this URL into your browser: > http://gpsworld.com/galileo-satellites-set-for-year-long-einstein-experiment/ > <http://gpsworld.com/galileo-satellites-set-for-year-long-einstein-experiment/> >
_______________________________________________ LEAPSECS mailing list [email protected] https://pairlist6.pair.net/mailman/listinfo/leapsecs
