5.3 Space-Time Reference Based on Newtonian Mechanics
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stands for the UTC maintained by the U.S. Naval Observatory in Washington D.C.;
UTC (APL) stands for the UTC maintained by the Applied Physics Laboratory in
Maryland, the United States; UTC (SU) stands for the UTC maintained by the Institute of Metrology for Time and Space in Moscow, Russia; UTC (PTB) stands for the
UTC maintained by the Federal Physical Institute (Physikalisch-Technische Bundesanstalt), the national metrology institute with scientific and technical service tasks,
in Braunschweig and Berlin, Germany. The TAI can be provided in the form of “paper
clock”, while the UTC is broadcasted by the time service stations to meet the needs of
national economic construction and scientific research applications. Therefore, the
UTC (k) everywhere is achieved by the atomic clocks, which would be a physical
atomic clock or a group of atomic clocks controlled by computers, and its signals
are outputted by the computers.
5.3.2.8 Navigation Satellite Time
The navigation satellite system is the space-based radio navigation and time transmission system, and thus the generation, measurement and maintenance of time
information is one of its core tasks. The navigation satellite time is with the atomic
time as the timescale, selecting the corresponding UTC (k) as the time origin, and
realized and maintained by the atomic clocks at the ground control stations together
with those of the onboard navigation satellites. The GPS Time (GPST) is based
on the UTC (USNO) time maintained by the U.S. Naval Observatory, and its time
maintenance is achieved together by the atomic clocks deployed at the master control
stations, monitor stations and on-orbit satellites. The origin of the GPST is at 0:00
UTC (USNO) on January 6, 1980, and its timescale is length of a second of the TAI.
The GPST is a continuous time system without the leap seconds, which is expressed
by the GPS weeks and second counts of a week. There is a constant deviation of
19 s between the GPST and TAI. Besides the leap seconds, the GPS ground control
stations keep the system difference between the GPST and UTC (USNO) within 1
μs, which can be corrected by using the corresponding parameters of the navigation message. The GLONASS Time (GLST) is based on the UTC (SU) maintained
by the Institute of Metrology for Time and Space in Moscow, achieved together by
the atomic clocks deployed at the GLONASS system control center, TT&C stations,
monitor stations, Laser ranging stations and time synchronization stations. The GLST
is a time system with synchronous leap seconds, with the system difference of 3 h
and less than 1 μs between the GLST and UTC (SU) and without the leap second
differences between the two. The BeiDou Navigation Satellite System Time (BDT)
is continuous timing system based on the second length of the SI units, and its initial
epoch is at 0:00:0.0 UTC on January 1, 2006, which is expressed by the BeiDou weeks
and second counts of a week. The BDT is connected with the international UTC time
through the UTC (NTSC) maintained by National Time Service Center of China, and
the deviation between the BDT and UTC is kept within 100 ns (module 1 s). The
Galileo Navigation Satellite System Time (GST) is generated and maintained by
the two active hydrogen atomic clocks and four cesium atomic clocks installed at
291
stands for the UTC maintained by the U.S. Naval Observatory in Washington D.C.;
UTC (APL) stands for the UTC maintained by the Applied Physics Laboratory in
Maryland, the United States; UTC (SU) stands for the UTC maintained by the Institute of Metrology for Time and Space in Moscow, Russia; UTC (PTB) stands for the
UTC maintained by the Federal Physical Institute (Physikalisch-Technische Bundesanstalt), the national metrology institute with scientific and technical service tasks,
in Braunschweig and Berlin, Germany. The TAI can be provided in the form of “paper
clock”, while the UTC is broadcasted by the time service stations to meet the needs of
national economic construction and scientific research applications. Therefore, the
UTC (k) everywhere is achieved by the atomic clocks, which would be a physical
atomic clock or a group of atomic clocks controlled by computers, and its signals
are outputted by the computers.
5.3.2.8 Navigation Satellite Time
The navigation satellite system is the space-based radio navigation and time transmission system, and thus the generation, measurement and maintenance of time
information is one of its core tasks. The navigation satellite time is with the atomic
time as the timescale, selecting the corresponding UTC (k) as the time origin, and
realized and maintained by the atomic clocks at the ground control stations together
with those of the onboard navigation satellites. The GPS Time (GPST) is based
on the UTC (USNO) time maintained by the U.S. Naval Observatory, and its time
maintenance is achieved together by the atomic clocks deployed at the master control
stations, monitor stations and on-orbit satellites. The origin of the GPST is at 0:00
UTC (USNO) on January 6, 1980, and its timescale is length of a second of the TAI.
The GPST is a continuous time system without the leap seconds, which is expressed
by the GPS weeks and second counts of a week. There is a constant deviation of
19 s between the GPST and TAI. Besides the leap seconds, the GPS ground control
stations keep the system difference between the GPST and UTC (USNO) within 1
μs, which can be corrected by using the corresponding parameters of the navigation message. The GLONASS Time (GLST) is based on the UTC (SU) maintained
by the Institute of Metrology for Time and Space in Moscow, achieved together by
the atomic clocks deployed at the GLONASS system control center, TT&C stations,
monitor stations, Laser ranging stations and time synchronization stations. The GLST
is a time system with synchronous leap seconds, with the system difference of 3 h
and less than 1 μs between the GLST and UTC (SU) and without the leap second
differences between the two. The BeiDou Navigation Satellite System Time (BDT)
is continuous timing system based on the second length of the SI units, and its initial
epoch is at 0:00:0.0 UTC on January 1, 2006, which is expressed by the BeiDou weeks
and second counts of a week. The BDT is connected with the international UTC time
through the UTC (NTSC) maintained by National Time Service Center of China, and
the deviation between the BDT and UTC is kept within 100 ns (module 1 s). The
Galileo Navigation Satellite System Time (GST) is generated and maintained by
the two active hydrogen atomic clocks and four cesium atomic clocks installed at