Measurement uncertainty in pulsar timing array experiments

Highly precise monitoring of arrival times of pulses from pulsars will allow for gravitational-wave detection in the nano-Hertz regime in the near future. Due to the complex nature of such pulsar-timing experiments and to the large number of effects that can affect these data (starting with magnetospheric effects at the pulsars themselves but extending across the entire signal path down to the final gravitational-wave detection algorithm), any treatment of the measurement uncertainties relevant to such a gravitational-wave detection has been lacking and incomplete so far. In this review, we provide an exhaustive description of the currently known influences on measurement precision in pulsar-timing experiments in general and in gravitational-wave detection through pulsar-timing specifically. While some of these effects remain poorly understood and largely unquantified at present, we discuss both analytic and observational quantifications where available.