The Planetary Ephemeris Program: Capability, Comparison, and Open Source Availability

We describe for the first time in scientific literature the Planetary Ephemeris Program (PEP), an open-source general-purpose astrometric data-analysis program. We discuss, in particular, the implementation of pulsar timing analysis, which was recently upgraded in PEP to handle more options. This implementation was done independently of other pulsar programs, with minor exceptions that we discuss. We illustrate the implementation of this capability by comparing the postfit residuals from the analyses of time-of-arrival observations by both PEP and Tempo2. The comparison shows substantial agreement: 22 ns rms differences for 1065 pulse time-of-arrival measurements for the millisecond pulsar in a binary system, PSR J1909-3744 (pulse period 2.947108 ms; full width half maximum of pulse 43 mu s), for epochs in the interval from 2002 December to 2011 February.