1、 Op. ITU-R 99 1 OPINION ITU-R 99*Time scale based on pulsar timing (2003) ITU Radiocommunication Study Group 7, considering a) that observations of single and binary radio pulsars are important, both for astrophysics and also for precise timekeeping; b) that among the more than 1 000 pulsars observe
2、d so far, there are some that have very stable spin and orbital rotation periods, particularly millisecond pulsars; c) that the increase in the apparent spin rotation period with time of most pulsars is well known, and in some cases is as small as 1021s/s; d) that the time of arrival (TOA) of pulsar
3、 pulses to the solar system barycenter is measured with an accuracy of 1 s or better by modern techniques; e) that timing observations of millisecond pulsar B1937+21 over more than five years showed quasi-white noise TOA with an RMS level of 2 s (fractional stability 1.2 1014); f) that pulsar “life
4、times” are several million years and they offer a common time reference to all terrestrial observers; g) that the radio frequency band 1 400-1 427 Hz is allocated for radio astronomy observations (No. 5.340 of the Radio Regulations) and this band provides the optimum signal-to-noise ratio for pulsar
5、 timing measurements, is of the opinion 1 that long-term timing monitoring of very stable reference pulsars, such as B1937+21, J1640+22, J1713+07 and B1855+09, by the largest radio telescopes in the world should be encouraged; 2 that a time scale based upon reference pulsars should be established to provide a new astronomical time scale with high long-term stability. *This Opinion should be brought to the attention of the International Astronomical Union (IAU), the International Union of Radio Science (URSI) and the Consultative Committee for Time and Frequency (CCTF).
