BEIJING, July 19 (Xinhua) -- Europe's Galileo satellite navigation system returned to service on Thursday a week after a mass outage.
Some fluctuations may still be experienced until further notice, said the European Global Navigation Satellite Systems Agency, adding that "the root causes of the major incident" will be identified by an independent inquiry board.
The system's navigation and timing features were down in the outage, with the search and rescue services functioning normally.
The Prague-based agency explained that the outage originated by an equipment malfunction in the Galileo ground infrastructure, affecting the calculation of time and orbit predictions.
Malfunction of ground infrastructure is better news than that of satellites, and is easier to fix, said Robert Wimmer-Schweingruber, a professor at the University of Kiel in Germany.
Similarly, Guglielmo Aglietti, director of the Surrey Space Center at the University of Surrey, noted that this outage won't delay the construction of the Galileo system.
Galileo has been in an "initial services" period since December 2016. During this "pilot" phase, the system's signals are used in combination with other satellite navigation systems, which allowed for the detection of technical issues before the system becomes fully operational.
Also, users could fall back on other satellite navigation systems like the GPS. For Galileo, experts viewed this "pilot" phase as an opportunity to expose problems.
In the full operational phase, Galileo should function independently of other satellite navigation systems.
Galileo system is one of the four space-based navigation networks operating globally, along with the U.S. Global Positioning System (GPS), Russia's GLONASS and China's Beidou.
Galileo system was launched in 2002, and the complete 30-satellite system is expected by 2020. According to former French President Jacques Chirac, the system was essential to keep Europe from becoming a "vassal" of the United States, which owns the GPS.
The 24-satellite GPS became fully operational in 1993, and today, it provides two levels of service: one is exclusively for U.S. Armed Forces, Federal Agencies and selected allied armed forces and governments, and the other available to all worldwide users.
A Russian equivalent to the GPS, GLONASS, is operated by the Russian Aerospace Force for both military and civilian use, providing real-time positioning and speed data for land, sea and airborne receivers worldwide.
Meanwhile, China is also nearing a completion of its BeiDou-3 system in 2020 to provide global services of all-time, all-weather and high-accuracy positioning, navigation and timing.
Previously, China has deployed Beidou-1 and Beidou-2 systems to provide services to the whole country and the Asia-Pacific region, respectively.
The BeiDou Navigation Satellite System, independently constructed and operated by China, currently has 38 in-orbit satellites including 18 BDS-2 and 20 BDS-3.
