236
4 Navigations from Ground to Space
Frequency Division Multiple Access (FDMA) technique is used to identify the
different GLONASS satellite signals, and each GLONASS satellite transmits
the navigation signals within its given frequency band. All GLONASS satellites transmit the same code as their standard-precision signals on a different
frequency using a 15-channel FDMA spanning either side from 1602.0 MHz,
known as the L1 band. The L2 band signals use the same FDMA as the L1 band
signals, but transmit spanning the center frequency 1246 MHz. Since 2008, new
CDMA signals have been researched for use with the follow-on GLONASS
satellite series, considering the interoperability with other navigation satellite
systems.
In the wake of the achievement of full GLONASS constellation in 1995, the
replenished satellites could not be launched in time to the constellation due to the
Russian financial difficulty. As a result, the constellation had only six operational
satellites in 2001, reaching its lowest point. With the Russian economy recovery
and state finances improvement, the GLONASS system’s restoration was made one
of the government’s top priorities. For this purpose, the Federal Targeted Program,
“Global Navigation System 2002−2011”, was launched by the Russian Government
Decision No. 587. Meanwhile, responsibility of the program was transferred from
the Russian Ministry of Defense to the Russian Federal Space Agency, commonly
known as Roscosmos. In December 2003, the second-generation GLONASS satellite, GLONASS-M, was launched for the first time, with a weight of 1415 kg and
a design lifetime of 7 years. In the original GLONASS design, only the obfuscated high-precision signal was broadcasted in the L2 band, but starting with the
GLONASS-M, an additional civil reference signal L2OF was broadcasted with an
identical standard-precision code of the L1OF signal, and a new signal L3OC was
also added in the GLONASS-M series launched since 2014. In May 2007, all restrictions of the GLONASS system were lifted by the Russian government, and thus
the positioning accuracy, formerly military-only signal with a precision of 10 m,
has since then been freely available to civilian users. In June 2008, the GLONASS
constellation was composed of 16 satellites, 12 of which were fully operational at
the time. The Russia’s aim of finishing the constellation in 2010 suffered a setback
as a December 2010 launch of three GLONASS-M satellites failed. Following the
mishap, the Roscosmos activated two reserve satellites, and decided to make the first
improved GLONASS-K satellite, as a part of the operational constellation instead of
mainly for testing as was originally planned. The GLONASS-K is with a mass of 935
kg and a design life of 10 years, and broadcasts the new civil signal, designated L3
centered at 1202.025 MHz, using the CDMA to ease interoperability with the GPS
and Galileo. The three satellites were launched together into the orbits in February
2011, which would bring a total of satellites in the GLONASS constellation to 23
and achieve almost complete worldwide coverage.
Although the GLONASS constellation had reached a global coverage, its commercialization, especially development of the user segment, had been lacking compared
to the GPS system. For example, the first commercial Russian-made GLONASS
navigation device for cars, Glospace SGK-70, was introduced in 2007, but it was
4 Navigations from Ground to Space
Frequency Division Multiple Access (FDMA) technique is used to identify the
different GLONASS satellite signals, and each GLONASS satellite transmits
the navigation signals within its given frequency band. All GLONASS satellites transmit the same code as their standard-precision signals on a different
frequency using a 15-channel FDMA spanning either side from 1602.0 MHz,
known as the L1 band. The L2 band signals use the same FDMA as the L1 band
signals, but transmit spanning the center frequency 1246 MHz. Since 2008, new
CDMA signals have been researched for use with the follow-on GLONASS
satellite series, considering the interoperability with other navigation satellite
systems.
In the wake of the achievement of full GLONASS constellation in 1995, the
replenished satellites could not be launched in time to the constellation due to the
Russian financial difficulty. As a result, the constellation had only six operational
satellites in 2001, reaching its lowest point. With the Russian economy recovery
and state finances improvement, the GLONASS system’s restoration was made one
of the government’s top priorities. For this purpose, the Federal Targeted Program,
“Global Navigation System 2002−2011”, was launched by the Russian Government
Decision No. 587. Meanwhile, responsibility of the program was transferred from
the Russian Ministry of Defense to the Russian Federal Space Agency, commonly
known as Roscosmos. In December 2003, the second-generation GLONASS satellite, GLONASS-M, was launched for the first time, with a weight of 1415 kg and
a design lifetime of 7 years. In the original GLONASS design, only the obfuscated high-precision signal was broadcasted in the L2 band, but starting with the
GLONASS-M, an additional civil reference signal L2OF was broadcasted with an
identical standard-precision code of the L1OF signal, and a new signal L3OC was
also added in the GLONASS-M series launched since 2014. In May 2007, all restrictions of the GLONASS system were lifted by the Russian government, and thus
the positioning accuracy, formerly military-only signal with a precision of 10 m,
has since then been freely available to civilian users. In June 2008, the GLONASS
constellation was composed of 16 satellites, 12 of which were fully operational at
the time. The Russia’s aim of finishing the constellation in 2010 suffered a setback
as a December 2010 launch of three GLONASS-M satellites failed. Following the
mishap, the Roscosmos activated two reserve satellites, and decided to make the first
improved GLONASS-K satellite, as a part of the operational constellation instead of
mainly for testing as was originally planned. The GLONASS-K is with a mass of 935
kg and a design life of 10 years, and broadcasts the new civil signal, designated L3
centered at 1202.025 MHz, using the CDMA to ease interoperability with the GPS
and Galileo. The three satellites were launched together into the orbits in February
2011, which would bring a total of satellites in the GLONASS constellation to 23
and achieve almost complete worldwide coverage.
Although the GLONASS constellation had reached a global coverage, its commercialization, especially development of the user segment, had been lacking compared
to the GPS system. For example, the first commercial Russian-made GLONASS
navigation device for cars, Glospace SGK-70, was introduced in 2007, but it was