SIEMENS

It will take a little more time and patience before this new high-tech baby is born. Nevertheless, its “fathers” — scientists from DLR Gesellschaft für Raumfahrtanwendungen mbH (a space applications company) at the control center of the German Aerospace Center in Oberpfaffenhofen near Munich — keep glancing at a monitor that is already displaying the countdown to the blastoff of the first launcher late in 2011. That’s when the first two satellites of the new European satellite navigation system are scheduled to be launched into orbit from Kourou Space Center in French Guyana. To date, only two test satellites have been launched, in 2005 and 2008. This civilian system — both a competitor and an extension of the GPS (Global Positioning System), which is now 25 years old — was planned by the European Space Agency (ESA) and financed by the European Union. By 2014 at least 18 satellites are scheduled to be in orbit, thus making the system operational. Siemens scientists and engineers have been among those actively engaged with the new navigation technology. At Siemens Space in Vienna, for example, they have taken a close look at the heart of the satellite system — the atomic clocks used in generating the navigation signal. At another level, the Mobility Division in Erlangen is developing concepts for combining the signal with existing technologies to create entirely new solutions for the transportation industry.

All Systems Go. In Oberpfaffenhofen you can look down from a gallery through massive glass panes into the satellite control center. It is from here that the first satellites will be controlled in their orbits during tests. “We’ve already transmitted wireless commands to the first two satellites, which are being assembled in Italy and are nearly complete,” says Walter Päffgen, who heads the control center. “For instance, we’ve gotten the satellite to activate a control nozzle that adjusts its position.” Everything is ready for — and that’s true across the board, because the research to define the three orbits in which, eventually, 30 satellites of the European navigation system will ultimately circle the Earth, has been completed. The orbits will be located at an altitude of 23,200 kilometers (14,407.2 miles) and inclined 56 degrees with respect to the equator. This positioning will ensure that at least eight satellites will simultaneously provide users with information at any given time, anywhere, even at the Earth’s poles.

One of ’s major advantages is accuracy. This is the first navigation system to be equipped with a passive hydrogen maser clock, which has a deviation of one second per three million years. That’s important, as satellite navigation depends on chronological postage marks that are transmitted from satellites to the ground. The receiver — for instance, a car’s navigation device — compares its clock time with that of the satellite. The distance from the satellite can be computed from the time differential. Since the satellite knows exactly where it is in its orbit, the receiver system can derive its own position through simple calculations. At least four satellites are needed to provide unequivocal positional data: three for the spatial coordinates height, length, and width, and a fourth to correct for the inaccuracy of the recipient’s clock, since it is not an atomic clock.

“The atomic clocks — and the time signals they generate — are the heart of the satellite,” explains Hans Steiner of Siemens Space. “A deviation of ten nanoseconds would result in an inaccuracy of several meters on Earth.” Steiner and his team plan to ensure that each atomic clock functions flawlessly before its satellite is launched. To do this, they have developed a test system with a timing instrument that contains an atomic clock based on an active hydrogen maser that is ten times more accurate than the atomic clocks to be based on satellites. The testing device’s timing signal is compared with that of each satellite’s clock. “It’s essential to keep potential errors from developing in the first place,” explains Steiner.

With its one-meter accuracy, the system is of interest to Siemens Mobility, which is developing applications that would be inconceivable without satellite navigation technology. For example, the new technology would make it possible to mail test letters containing GPS receivers. The resulting data would let the Postal Service know how long a letter is delayed at different locations — which would highlight bottlenecks in its logistics system. This would be difficult to accomplish with the current GPS-based system because if a letter were opened or lost, the system would be hard pressed to detect where this happened. GPS is simply not as reliable. But that will change with . “The signal always contains additional information that indicates how accurate the received signal actually is,” explains Dieter Geiger of Siemens Mobility. This is an enormous advantage, because it makes the information stand up in court. If a valuable piece of mail were equipped with a receiver, it could later be proven — in court, if necessary — at what location the item had been lost. If the item were additionally equipped with sensors, it would even be possible to prove where it had been opened.

Another field in which Siemens Mobility has long been active is traffic management. “Here too we intend to use the capabilities of ,” says Geiger. One example is traffic light control systems. A traffic signal controller at an intersection could, for instance, automatically detect the traffic flow rate on each street and regulate its timing accordingly (for more, see article "Green Light for Vehicle-to-Infrastructure Communications"). This capability is currently supported by old-fashioned induction loops in the ground that count passing vehicles. If this technology were augmented by receivers, however, a bus, for instance, could relay its speed, direction and distance to the nearest traffic light with one-meter accuracy. The light would then stay green until the bus had passed. Unnecessary braking would be avoided and fuel would be saved.

These and other applications are being tested under realistic conditions in two Test and Development Centers — Siemens’ Test and Validation Center for rail systems in Wegberg- Wildenrath (see Pictures of the Future, Fall 2010, Trains on Trial) and at the Aldenhoven Test Center, which is operated by RWTH Aachen University. Both centers are testing transmitters that emit signals identical to those that will be emitted by satellites. At Siemens’ rail test center, engineers are investigating how receivers can be used to optimize train speeds and energy use. For example, in order to avoid delays, trains must travel along curves at a speed that makes optimal use of each curve’s radius, while minimizing the use of brakes on downhill sections.

Taking Weather into Account. It’s particularly difficult for a train’s engineer to stay exactly on schedule when tracks are slick with rain. But precise positioning data from satellites in conjunction with up-to-date weather data will enable the train’s speed to adapt more accurately to the situation, because exact information will be available regarding the track’s gradient and level of slippage due to moisture. As a result, train travel will become safer and more dependable.

At the Aldenhoven Test Center, where applications for road traffic are also being explored, scientists are looking for ways to improve safety. Since all vehicles at the facility are equipped with receivers, drivers can be alerted instantly to hazardous situations. For example, if a car moves dangerously close to another vehicle at an intersection, its navigation system triggers an alarm. Safety mechanisms in both cars are activated, seat belts tensioned, and brake pressure increased.

Siemens development engineers in Aldenhoven are also thinking a step ahead — to the approaching introduction of electric cars. ’s one-meter precision will enable drivers of electric vehicles to see which recharging stations are within their range and possibly even reserve a charging port. “Once is in orbit, many other applications will be found,” Geiger predicts. He is convinced that will open the door to the future of mobility.