Time and frequency transfer
Encyclopedia
Time and frequency transfer describes mechanisms for comparing measurements of time
and frequency
from one location to another. The technique is commonly used for creating and distributing standard time scales such as International Atomic Time
(TAI).
Examples of time and frequency transfer techniques include:
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....
and frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
from one location to another. The technique is commonly used for creating and distributing standard time scales such as International Atomic Time
International Atomic Time
International Atomic Time is a high-precision atomic coordinate time standard based on the notional passage of proper time on Earth's geoid...
(TAI).
Examples of time and frequency transfer techniques include:
- Simultaneous observation methods:
- Simultaneous carrierCarrier waveIn telecommunications, a carrier wave or carrier is a waveform that is modulated with an input signal for the purpose of conveying information. This carrier wave is usually a much higher frequency than the input signal...
phasePhase (waves)Phase in waves is the fraction of a wave cycle which has elapsed relative to an arbitrary point.-Formula:The phase of an oscillation or wave refers to a sinusoidal function such as the following:...
observation of GPS signals - Time transfer by simultaneous observation of TVTelevisionTelevision is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
transmissions - Time transfer by simultaneous observation of radio astronomyRadio astronomyRadio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The initial detection of radio waves from an astronomical object was made in the 1930s, when Karl Jansky observed radiation coming from the Milky Way. Subsequent observations have identified a number of...
signals
- Simultaneous carrier
- Two-way transfer methods:
- Two-Way Satellite Time and Frequency TransferTwo-Way Satellite Time and Frequency TransferTwo-way satellite time and frequency transfer is a high-precision long distance time and frequency transfer mechanism used between time bureaux to determine and distribute time and frequency standards....
- Two-Way Satellite Time and Frequency Transfer
- Network methods:
- Network Time ProtocolNetwork Time ProtocolThe Network Time Protocol is a protocol and software implementation for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. Originally designed by David L...
- Precision Time ProtocolPrecision Time ProtocolThe Precision Time Protocol is a protocol used to synchronize clocks throughout a computer network. On a local area network it achieves clock accuracy in the sub-microsecond range, making it suitable for measurement and control systems....
- Network Time Protocol