Determining the position of a rocket to within a few centimetres throughout its flight. That is what a team from the universities of Eindhoven and Nijmegen want to achieve during an experimental rocket launch in Sweden between 11 and 14 March. With their method - up to ten times more accurate than GPS - rockets could possibly be better steered to land in the right place again.
In the long run, the method could possibly also be used to track down lost objects at sea, such as the remains of a plane wreck or lost containers like those that recently washed ashore on the Wadden Islands
The part of the Rexus rocket in which PR3 Space's experiment is mounted. Photo: PR3 Space
Experiment PR3 Space participates in the European Rexus programme, an initiative of the Swedish, German and European (ESA) space agencies in which two rockets take to the air each year, each carrying around four to five experiments by student teams from different countries. The rocket will be launched between 11 and 14 March in Esrange, near Kiruna in northern Sweden, stay in the air for about 15 minutes and reach an altitude of eighty to one hundred kilometres. PR3 Space plans to conduct two experiments during the flight: accurate positioning and radiation measurement using phone cameras.
Accurate by a few centimetres
The new positioning method uses radio interferometry. This involves three antennas emitting radio signals from the rocket, each at slightly different frequencies. These signals are picked up on the ground by five ground stations around the launch base. "Based on the phase difference between the arriving signals, we can recognise the location of the rocket," explains researcher Hamid Pourshaghaghi. The rocket's location is measured 1,000 times per second, determining it to within a few centimetres.
Tracking lost objects
"Accurate positioning of rockets is technically difficult because of the rocket's high speed - up to 1,500 metres per second - and passing through multiple layers of atmosphere," says project leader Mark Wijtvliet. "For space organisations, this experiment is interesting, because in this kind of experimental flight it is important to be able to adjust the rocket in time, so that the rocket lands in the desired spot again." He thinks the method could be used for tracking all kinds of objects and people in the future. "Especially at sea, our method can help find lost objects."
