GPS World, December 2014

SYSTEM THE Policy and system news and developments GPS Galileo GLONASS Beidou eLoran Operational on Eastern UK Coast Back up to Vulnerable GPS Signals Required for Busy Shipping Lanes T he General Lighthouse Authorities GLAs of the UK and Ireland announced October 31 the initial operational capability of UK maritime eLoran Seven differential reference stations now provide additional position navigation and timing PNT information via low frequency pulses to ships fitted with eLoran receivers The service will help ensure they can navigate safely in the event of GPS failure in one of the busiest shipping regions in the world with expected annual traffic of 200000 vessels by 2020 Ships carry 95 percent of UK trade accounting for its strongly expressed concerns regarding GPS vulnerability to jamming and spoofing and the leadership role it has taken in eLoran research and testing The UK is the first country in the world to deploy the technology along its coastline thronged with both passenger and cargo services Deployment involved replacing the existing radio receiver equipment in two prototype reference stations at Dover and Harwich and the creation of five new reference BRIDGE OF THE GALATEA a GLA vessel that carries a eLoran receiver and conducted tests of the new system stations in the Thames Humber Middlesbrough and Firth of Forth and Aberdeen in Scotland on the North Sea Galileo Roving High T he fifth Galileo navigation satellite one of two left in the wrong orbit in August made a series of November maneuvers as a prelude to its health being confirmed The aim was to raise the lowest point of its orbit its perigee to reduce the radiation exposure from the Van Allen radiation belts surrounding Earth as well as to put it into a more useful orbit for navigation purposes Should the two week operation prove successful the sixth Galileo satellite will follow the same route according to the European Space Agency ESA The Galileo pair launched together on a Soyuz rocket on August 22 ended up in an elongated orbit traveling out to 25900 kilometers km above Earth and back down to 13713 km The target orbit was a purely circular one at an altitude of 23222 km Also the orbits are angled relative to the Equator less than originally planned The two satellites have only enough fuel to lift their altitude by about 4000 km insufficient to correct their orbits entirely But the move will take the fifth satellite into a more circular orbit than before with a higher perigee of 17339 km See eLoran page 10 The new orbit will fly over the same location every 20 days said Daniel Navarro Reyes ESA Galileo mission analyst The standard Galileo repeat pattern is every 10 days so achieving this will synchronize the ground track with the rest of the Galileo satellites In addition from a user receiver point of view the revised orbit will reduce the variation in signal levels reduce the Doppler shift of the signal and increase the satellites visibility Navarro Reyes said For the satellite reducing its radiation exposure in the Van Allen radiation belts will protect it from further exposure to charged particles The orbit will also allow Galileos Earth Sensor to hold a stable direction for the satellites main antenna to point at Earth Right now when the satellite dips to its lowest point Earth appears so large that the sensor is unusable The satellite relies on gyroscopes alone degrading its attitude precision The recovery is being overseen from the Galileo Control Centre in Oberpfaffenhofen Germany with the assistance of ESAs Space Operations Centre ESOC in Darmstadt Germany Frances CNES space agency is providing additional ground stations so that contact can be maintained with the satellite as needed ESA said GPS World December 2014 www gpsworld com 8