Objective. The objective of this research project is to evaluate the feasibility of a new navigation system for aviation, using the signals from millisecond radio pulsars. Pulsars are fast rotating neutron stars emitting electromagnetic radiation, received anywhere in our solar system as a series of very stable fast periodic pulses with extremely precise periods, comparable to that of atomic clocks. Each pulsar has its own rotational period, between milliseconds to seconds with an accuracy comparable to that of atomic clocks. These pulses are emitted in a wide frequency range (from radio, to gamma and X-ray), and are received at regular intervals, corresponding to the beam emitted by the rotating neutron star, which can be compared with the light beam which is received by a light house. Furthermore, they have their own singular shape, which grants each pulsar an unique signature enabling its use as celestial beacons for navigation using time of arrival (TOA) estimates.
The usefulness of such a navigation system for aviation is that it overcomes GNSS vulnerabilities, such as jamming and spoofing, since the pulsar signal is wide-band. Furthermore, no satellites or ground transmitters are required, thus reducing the operational cost, when compared to the cost of launching and maintain the GNSS satellite constellations. In addition, more than a thousand pulsars are known and spread all over the galaxy, therefore, larger world coverage can be achieved than that of GNSS.
However, the system requirements for the signal processing, the antenna and the RF front-end are very challenging since the signal is received on Earth 60 dB below the noise level. Therefore, new algorithms for fast acquisition and tracking of the pulsar signal were explored, new antenna designs and its possible integration on an aircraft were evaluated and finally different RF front-end architectures were studied.
Developments. The INESC-ID research ream involved in this project was responsible for the study and evaluation of RF front-end which would suit for receiving this signal. Common architectures to receive the signal were studied to serve as a baseline (Low-IF receiver and a sub-sampling receiver), and a completely new receiver architecture using ultra wideband techniques was proposed. Developed based on the pulsar signal characteristics to provide the required digitized information for the navigation algorithms. The signal processing team at TU Delft, found that typical steps used on Radio Telescopes, were of no use for navigation purposes, allowing a drastic reduction on the required computational effort. These findings combined with several antenna solutions, which can be integrated on an aircraft proved that system is feasible and can be applied in aviation.
Team. PulsarPlane project was funded through the 7th Framework Programme and ends in May 2015. The consortium was composed by a strong participation of universities and research institutes, namely, TU Delft (from The Netherlands) , Sofia University (from Bulgaria), Twente University (from The Netherlands), Aalto University (from Finland) and INESC-ID (from Portugal). Furthermore the National Aerospace Laboratory, NLR (from the Netherlands) was also part of this consortium.