Gravitational lens system B0218+357: constraints on lens model and
  Hubble constant
  The possibility to use observations of lensed relativistic jets on very small
angular scales to construct proper models of spiral lens galaxies and to
independently determine the Hubble constant is considered. On the example of
the system B0218+357 it is shown that there exists a great choice of model
parameters adequately reproducing its observed large-scale properties but
leading to a significant spread in the Hubble constant. The jet image position
angle is suggested as an additional parameter that allows the range of models
under consideration to be limited. It is shown that the models for which the
jet image position angles differ by at least 40 deg can be distinguished
between themselves during observations on very small angular scales.
Observations with the space interferometer RadioAstron-Earth is proposed to
determine the jet orientation.
