Deci hertz Laser Interferometer can determine the position of the Coalescing Binary Neutron Stars within an arc minute a week before the final merging event to Black Hole

It may be possible to construct a laser interferometer gravitational wave antenna in space with $h_{rms}\sim {10}^{-23}$ at $f\sim 0.1\mathrm{H}\mathrm{z}$ in $\sim 2020$. This deci hertz antenna may be called DECIGO/BBO,which stand for DECi hertz Interferometer Gravitational wave Observatory and Big Bang Observer, respectively. The analysis of 1-10 years observational data of the coalescing binary neutron stars or black holes at the distance of $\sim$ 300Mpc will give us the spatial position within $\sim$ an arc minute and the time of the coalescence within $\sim 0.1$ sec beforehand. With the knowledge of the accurate position and the time of final merging event, the follow up simultaneous observation using high frequency ($f\sim 100\mathrm{H}\mathrm{z}$) gravitational wave antennae as well as electro-magnetic wave antennae from the radio frequency to the ultra high energy gamma ray will reveal the physics in the enigmatic event of the coalescence and the formation of the black hole.