During the many long voyages ships carry out each year, crews have become increasingly reliant on electronic positioning systems to help them fix their location and have subsequently reduced their use of celestial navigation on board. In fact, in a recent survey conducted by UKHO, only 35% of mariners surveyed said they actively practice celestial navigation on board each week. Without these key skills crews are becoming subject to increased risk at sea, particularly from the potential failure of GNSS systems and various types of high frequency radio communications.
What are the risks?
There are a number of reasons why these systems can go down. One of the hardest to predict is an outage caused by a space weather event. For example, a solar flare on the Sun can generate a substantial burst of X-ray radiation and a stream of charged particles that can potentially disrupt both high frequency signals used for communications as well as those used by GNSS systems for positioning. These disruptions can last a few hours for a small flare to a matter of days for a very large event, increasing the risk posed to mariners. Solar flares are also extremely difficult to predict and the radiation they emit can reach the Earth in a matter of minutes, giving authorities little or no time to warn ships before radio communications and GNSS signals are compromised. In addition to the risks posed by space weather, GNSS jamming and spoofing are also becoming an increasing risk due to the ease with which the necessary technology can be obtained by criminal groups and terrorists.
The ADMIRALTY Nautical Almanac supports mariners in the completion of mandatory gyro checks
How do you reduce the risks posed by space weather and jamming?
There are efforts to reduce the risk posed by these events, with agencies such as NOAA’s Space Weather Prediction Centre and the UK’s Met Office monitoring the Sun and the space environment surrounding the Earth with a handful of satellites. These organisations also produce forecasts covering a few days of the likely activity on the Sun, as well as the resulting effects on the Earth’s atmosphere and the nearby space environment. New generations of satellites for both GNSS and monitoring of Sun/Earth interactions are being built to mitigate risks posed by space weather phenomena and reduce outages.
However, despite these developments, one of the best ways to reduce risks is to ensure that routine celestial navigation checks are carried out on board. Having reached its 250th edition, the ADMIRALTY Nautical Almanac continues to be used by a large number of maritime organisations to meet this goal by providing mariners with the astronomical information needed to complete mandatory gyro checks and fix positions with a sextant. The publication, which is created in collaboration with the United States Naval Observatory, is used by many nautical colleges for celestial navigation training as well as the Royal Navy for carrying out routine checks. The publication has also been included within the ADMIRALTY e-NP range, making it easier for mariners to locate the information they need when carrying out routine and emergency checks through quick information searches.
By using this resource to carry out routine celestial checks alongside electronic positioning systems on board, mariners can ensure correct positions are maintained whilst benefiting from the efficiencies new digital technologies bring.
Find out more about the ADMIRALTY Nautical Almanac >
Find out more about e-Nautical Publications >