The NANOGrav 15 Year Data Set: Observing Program and Millisecond Pulsar Timing

NANOGrav has been undertaking a long-term, high precision millisecond pulsar timing program since 2004. Our program initially included 16 pulsars, and has gradually grown to 73 pulsars. Sources are spread throughout the sky above declination -47 degrees. Observations of a given pulsar are at approximately monthly cadence with duration of 20 to 30 minutes. Pulse time-of-arrival measurement precision is one microsecond or better for most pulsars, and precision of 100 ns or better is achieved in the best cases.

The NANOGrav 15-yr data set, incorporating data through 2020, includes observations of 68 pulsars, each observed for at least 2 years at Arecibo Observatory, the Green Bank Telescope and/or the Very Large Array. We used this data set to find evidence for a stochastic background of gravitational waves at nanohertz frequencies (as will be reported in other talks in this session).

Data collection has continued beyond 2020 using the Green Bank Telescope and the Very Large Array for monthly measurements and CHIME for daily measurements. We will continue to release data sets at regular intervals. In addition, we pool data from telescopes worldwide via the International Pulsar Timing Array (IPTA) collaboration.

In this talk, we will describe the observing program, the process of timing the pulsars, various ancillary studies made using these data sets, and prospects for new instrumentation for improved precision and observational efficiency.