Chronos Technology has launched the CTL8200 eLoran GPS UTC Timing Receiver, a combination eLoran and GPS Timing Receiver which enables users to undertake continuous simultaneous real-time evaluation and analysis of UTC as derived from both the GPS constellation of satellites and selected eLoran stations.
The CTL8200 automatically calibrates its own eLoran UTC using GPS UTC on first installation. Thereafter it outputs a UTC-aligned 1pps that is independent of GPS and immune to disruption of GPS by interference, jamming or spoofing of the GPS signal. Moreover, since the eLoran signal is inherently resilient to the failure or downtime of any individual LORAN station, the eLoran signal can be used to determine whether the GPS signal is being spoofed.
The CTL8200 will be an ideal test bed for organisations wishing to conduct long term evaluation of the health and UTC alignment of the various European eLoran timing signals. In addition it enables GPS vulnerability research in the presence of Interference, jamming and spoofing signals.
On 31 May 2007, the General Lighthouse Authorities of the UK and Ireland (GLA), supported by the UK Department for Transport (DfT), awarded a 15-year contract to provide a state-of-the-art enhanced LORAN (eLoran) service to improve the safety of mariners in the UK and Western Europe. The first eLoran transmitter in the UK is situated at Anthorn radio station in Cumbria, UK. The GLA also partnered Chronos on the GAARDIAN and SENTINEL projects.
Each Loran station is equipped with a suite of specialized equipment to generate the precise timing signals that modulate the transmitting equipment. The signals are synchronised to UTC, using up to three commercial caesium atomic clocks adjusted to follow UTC (Brest) by a Control Centre in France which monitors the signals.
eLoran transmitters are on land. Their signals propagate as ground-waves over the Earth. The speed of propagation depends on the electrical conductivity of the surface over which they travel. It is greatest over sea-water, slightly less over farmland and least over mountainous terrain. The total delay of the signal reaching a timing receiver, with respect to propagation through space, may be several microseconds. This delay, which is highly stable, can be estimated using a computer model. More commonly it is measured when the receiver is installed by comparing the UTC value derived from eLoran with that from GPS and then applying an adjustment to bring them into synchronisation. For the very highest eLoran timing accuracy this adjustment can be kept under continuous review, removing any small variations due to seasonal freezing of the ground or weather systems.
Prof. Charles Curry, Managing Director of Chronos Technology said “The receiver is an enhanced development from the GAARDIAN and SENTINEL research projects using sensors with the latest eLoran receiver technology from UrsaNav, Inc. all incorporated within a single 1U 19” chassis. It represents the first step towards a truly resilient Positioning, Navigation and Timing (PNT) solution that can deliver ‘Resilient PNT’ using two dissimilar technologies, neither of which is impacted by the same interference or jamming.”
