This talk adds more detail to the proposed TianQin mission \cite{TQ}. The
response of TianQin to a binary source is an important problem for the
experiment. Here we present the detail of the response function of an equal-arm
Michelson interferometer to the gravitation waves of a binary source with a
circular orbit.Comment: To be published in the proceedings of the "XIIth International
Conference on Gravitation, Astrophysics and Cosmology", (Moscow, Russia,
2015), World Scientific, Singapor