Russia maybe using her Chayka radio navigation system to outflank GNSS jamming in the Ukraine theatre of operations.
Russia’s RSDN-10 Chayka system is like the erstwhile LORAN-C radio navigation architecture. LORAN used a global network of transmitters, mainly located on coastlines. It exploited an elegantly simple principle. All radio waves travel at 161,595 knots-per-second (299,274 kilometres-per-second), the speed of light. LORAN stations work in pairs. Maps showed where stations were located and the distance between them. Each station transmitted a single radio pulse every half second on a frequency of 100KHz. If a ship or aircraft was exactly midway between both LORAN transmitters, the pulses from each arrived at the same time. If the ship or aircraft was closer to one, it received pulses from the nearest transmitter slightly earlier than pulses from the farthest one. By calculating the time lag between these two pulses, you could calculate your position relative to the transmitters.
LORAN was used by ships and aircraft following its introduction during the Second World War. However, LORAN fell into disuse as GNSS (Global Navigation Satellites Systems) began to predominate in the 1990s. The Soviet Union developed its own version of LORAN called Chayka (Seagull). According to an article on the gpsworld.com website, a Chayka station in Bryansk, western Russia, and Simferopol in Crimea cover Ukraine. This is alongside a third station in Slonim, western Belarus. All three transmitters form part of the GRI-8000 Chayka chain covering European Russia providing reasonably precise navigation services. Open sources say these may have a range of up to 1,287 kilometres (800 miles).
The Threat
Despite falling into disuse, LORAN-C has enjoyed a new lease of life as E-LORAN (Enhanced-LORAN) as a result of GNSS vulnerabilities. GNSS is vulnerable to two main threats, Anti-Satellite (ASAT) weapons and GNSS signal jamming. ASAT weapons are surface-to-air or air-to-air missiles which can destroy a satellite in orbit. Four countries; India, the People’s Republic of China (PRC), Russia and the United States have successfully tested ASAT weapons over the past 20 years.
Meanwhile, GNSS jammers can be easily purchased online for civilian use although these devices may have a limited reach of tens of metres. Of more concern are military-grade systems designed to jam GNSS signals at the tactical or operational level. The Russian Army is a known user of such equipment. These include the RB-341V Leer-3 system deployed for operational GNSS jamming by Independent Electronic Warfare Brigades. The RB-341V is reinforced at the tactical level by the R-330Zh Zhitel jamming system. Both reportedly attack GNSS signals on wavebands of 1.1 gigahertz/GHz to 1.6GHz. Recent incidences of GNSS jamming have been blamed on Russia. These include alleged Russian jamming of GNSS signals in the Baltic in early March following Russia’s invasion of Ukraine on 24th February.
E-LORAN is a vastly modernised version of the original LORAN-C architecture. E-LORAN provides position accuracy either side of eight metres (26 feet) using the same frequency as LORAN. E-LORAN stations can transmit PNT (Position, Navigation and Timing) information at ranges of up to 1,000 nautical miles (1,162 kilometres). Both LORAN and E-LORAN signals are difficult to jam as they are around one million times more powerful than the circa 50-watt signals transmitted by GNSS constellations. E-LORAN stations are starting to proliferate. The Republic of Korea is implementing E-LORAN as a GNSS alternative as is China.
No doubt cognizant of both her own capabilities and the potential jamming threat to her GLONASS GNSS constellation Russia has been looking at GNSS alternatives. This included a planned modernisation of Chayka. US Congressional documents from 2014 stated that the Russian government had planned to upgrade Chayka to an E-LORAN equivalence. This cooperation focused on the United Kingdom and Russia collaborating on E-LORAN technology.
This process appears to have stalled following Russia’s first invasion of Ukraine in 2014. Russia’s ability to implement E-LORAN technologies now appear in doubt. Sanctions placed on the country resulting from the Ukraine invasion stop Russia acquiring E-LORAN assistance from the West. Nonetheless, this might not prevent Russia obtaining E-LORAN technology. Dana Goward, president of the Resilient Navigation and Timing foundation, says Moscow could potentially get this technology from the PRC. China has already made substantial inroads in the adoption of E-LORAN.
Chayka and Ukraine
Reports immediately prior to Russia’s invasion of Ukraine on 24th February said her armed forces were expected to rely heavily on Chayka alongside GLONASS. Clearly, the Russian military fully expected GNSS signals to be jammed. Whether or not Russian forces have experienced GNSS jamming is impossible to verify at this stage in the war. The Ukrainian Army has a GNSS jamming system in the form of its Proximus Bukovel-AD system. This can reportedly jam GNSS signals, including those from GLONASS, at ranges of up to 16km (ten miles). Hawkeye 360 revealed on 4th March that some localised GNSS jamming was detected by its signals collection satellites. This appeared to correlate with the southeast of the Ukraine theatre of operations, principally around the Donbass regions. GNSS interference was also detected in the northern theatre, notably around the Chernobyl nuclear plant captured by Russian forces on 25th February.
Mr. Goward says that the Chayka system is operational and transmitting. The three Chayka systems mentioned above could provide PNT information for Russian forces in Ukraine. The circa eight metre margin of error may be adequate for Russia’s military requirements. Jamming Chayka could be far more challenging than jamming GNSS transmissions given its circa 800 kilowatt signal strength. Moreover, the Chayka stations are several hundred kilometres from Ukraine’s borders. Ukrainian forces would not be able to get jamming equipment close enough to the transmitters for these to work.
For the Ukrainian armed forces, Russia’s use of Chayka maybe one advantage they can do little about. For the Russians, using Chayka could be a valuable way to pre-empt any GNSS attacks.
by Dr. Thomas Withington
