Time Transfer With GPS Multi-Channel Motorola Oncore Receiver Using CCDS Standards

摘要

Most of the standard receivers used for the common-view time transfer are of the single-channel, single-frequency, Coarse/Acquisition code type. They all are built according to the 'NBS standard' prototype from the early 1980's. The uncertainty of the common-view time comparisons varies between 2-3 ns RMS for the best of them. The new generation of the unexpensive, multi-channel C/A code receivers which are now available seems to make the old standard obsolete. One of the interesting new solutions, proposed for the time transfer, is the 8-channel Motorola VP Oncore receiver combined with a time- interval counter and a microcomputer (Gifford et al., 1996), (Lewandowski et al., 1996). Such a measurement system was tested for several months at the Time Section of the Bureau International des Poids et Mesures (BIPM) in Sevres, yelding very interesting results (Lewandowski et al., 1997). To maintain the compatibility with the old 'NBS type' receivers, still in use at the majority of time laboratories, and to make use of the Motorola multi-channel capabilities, special software driving the receiver and the counter was developed at BIPM in 1997. The results of tests in time transfer between BIPM in Se'vres and AOS in Borowiec (Astrogeodynamical Observatory in Borowiec, Poland) at the baseline of about 1200 km give the uncertainty of results in the range of 1-2 ns RMS when applying recommendations of CCDS (Allan, Thomas, 1993).