Constructing a Pulsar Timing Array

Arrival time data from a spatial array of millisecond pulsars can be used (1) to provide a time standard for long time scales, (2) to detect perturbations of the earth's orbit, and (3) to search for a cosmic background of gravitational radiation. A polynomial time series representation for these three effects is first developed that is appropriate for analysis of the present data with its limited degrees of freedom. A pulsar timing array program is then described that has been established at the National Radio Astronomy Observatory 43 m telescope with observations of PSR 1620 - 26, PSR 181 - 24, and PSR 1937 + 21. The results cover a 2 yr period beginning in July 1987. The influence of global parameters - clock, earth location, and effects of gravitational radiation is discussed in the context of the polynomial model.