Timing Devices

In Satellite Laser Ranging (SLR), there are two types of timing measurements, the time (epoch) of laser fire and the roundtrip Time Of Flight (TOF) of the optical pulse. The minimum timing related hardware required for these measurements is a master clock/oscillator, a GPS receiver, and a TOF unit.

Below are some frequently used terminology in timing:

Terminology:

ACCURACY – the deviation of a measurement from a standard. [Example: range bias]

PRECISION – the deviation of a set of measurements about their mean. [Example: single shot RMS]

RESOLUTION – the minimum differential measurement which can be made. [Example: granularity of a TOF device]

STABILITY – a measure of the constancy of some quantity over time. [Example: range bias stability]

JITTER – the random displacement of a signal from its absolute location. [Example: counter jitter]

LINEARITY – the relative accuracy between measurements. [Example: counter linearity]

ALLAN DEVIATION – non-classical statistic used to estimate stability. [Example: frequency stability]

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