Brunthaler, A., Reid, M. J., Menten, Karl M., Zheng, X. W., Bartkiewicz, A., Choi, Y. K., Dame, T., Hachisuka, K., Immer, K., Moellenbrock, G., Moscadelli, L., Rygl, K. L. J., Sanna, A., Sato, M., Wu, Y., Xu, Y., and Zhang, B. 2011. "The Bar and Spiral Structure Legacy (BeSSeL) survey: Mapping the Milky Way with VLBI astrometry." Astronomische Nachrichten 332:461. https://doi.org/10.1002/asna.201111560
Astrometric Very Long Baseline Interferometry (VLBI) observations of maser sources in the Milky Way are used to map the spiral structure of our galaxy and to determine fundamental parameters such as the rotation velocity (Θ_0) and curve and the distance to the Galactic center (R_0). Here, we present an update on our first results, implementing a recent change in the knowledge about the Solar motion. It seems unavoidable that the IAU recommended values for R_0 and Θ_0 need a substantial revision. In particular the combination of 8.5 kpc and 220 km s-1, can be ruled out with high confidence. Combining the maser data with the distance to the Galactic center from stellar orbits and the proper motion of Sgr A* gives best values of R_0 = 8.3 ± 0.23 kpc and Θ_0 = 239 or 246 ± 7 km s-1, for Solar motions of V_⊙ = 12.23 and 5.25 km s-1, respectively. Finally, we give an outlook to future observations in the Bar and Spiral Structure Legacy (BeSSeL) survey.