The Distance to Exoplanet Systems with Imaging and Spectral Measurement

Abstract: The distance $D$ to an exoplanet system with imaging and spectral measurement can be obtained by using the orbit as a ruler. The measurement of the Distance to a typical exoplanet system with imaging
and spectral measurement can be accurate to $\delta D/D\sim 0.2$, if the orbital velocity of the planet can be accurate to $\sim 3 {\ \rm km/s}$.