Some weeks before the Global session, Bure and Pico Veleta conducted a two-station fringe test to verify if the fringe loss problem at Pico Veleta in October 2007 had been solved, and if the rennovated EFOS-10 maser was working fine. The excellent test fringes showed that both observatories were fully operational.
Since its installation in a thermally controlled rack, the EFOS-38 hydrogen maser on the Plateau de Bure is sufficiently stabilized to study its long-term drift in detail. The analysis of more than 5 months of maser-GPS difference logfiles revealed a tiny but regular drift acceleration of 42.6 picosec/day, an effect which is expected due to the slow atom-by-atom erosion of the maser resonance cavity wall coating during normal operation.
In a re-tuning of EFOS-38 on August 16th, we have taken this acceleration into account to aim for a minimum maser-GPS drift on Plateau de Bure during the forthcoming October GMVA session.