As we delve deeper into our solar system, new technology is constantly needed to make this new era of space exploration possible and sustainable. Current navigation methods of the European Space Tracking (ESTRACK) network and the ground-based Deep Space Network (DSN) has a limit on the number of deep space maneuvers they can support as, only a small number of spacecraft can be tracked at a time. Apart from being costly, ESTRACK and DSN are also limited by the fact that they need to be in contact with the craft for the system to work. For a mission at the outer planets, this introduces a time delay of several hours and the delay increases dramatically for missions outside the solar system.
A specific type of dead star called a pulsar emits radiation in the form of X-rays, as well as other types of electromagnetic waves. These pulses of radiation occur with the regularity and precision of an atomic clock for so-called ‘millisecond pulsars’. Using this characteristic of pulsars, the University of Leicester together with the National Physical Laboratory (NPL) have published a paper that shows that pulsars can be used much like GPS in space. The initial results obtained an accuracy of 2km along a particular direction in space.
Dr John Pye, the Space Research Centre Manager at the University of Leicester notes that pulsar-based navigation has been a concept only up to now. Detailed simulations published in the Experimental Astronomy shows that by using data such as a craft’s distance from the Sun and pulsar positions, a spacecraft’s location in space in the direction of a specific pulsar can be calculated independently. The study was done for a European Space Agency as a feasibility study of the concept of pulsar-based navigation.
Using a small X-ray telescope on board the craft, the method uses X-rays emitted from pulsars to calculate the position of a craft in space in 3D. An accuracy of 30 km at the distance of Neptune has been achieved by using a small X-ray telescope on board the craft. The X-ray telescope was designed and developed by the University of Leicester. Although larger X-ray telescopes would allow higher accuracies, the team concentrated on technology that could be small and light enough to be integrated as part of a practical spacecraft subsystem in the future.
The NPL analyzed the position, velocity and timing of known pulsars to generate a list of usable pulsars and measurements that can be used for triangulation with current technology. NPL’s long heritage in atomic clocks has allowed them to develop their timing analysis capability over many years.
If an advanced atomic clock is also built into the spacecraft subsystems, the system can operate autonomously with no need to contact Earth for months or even years. The new space GPS system will already be part of a mission to Mercury in 2018.
The paper,”Towards practical autonomous deep-space navigation using X-Ray pulsar timing”, was published in the journal of Experimental Astronomy.