  We derive boundary state of superstring in the open string channel. It
describes the superconformal field theory of open string emission and
absorption by D-brane. We define the boundary state by conformal mappings from
upper half plane with operators inserted at two points corresponding to the
corners of semi-infinite strip. We obtain explicit oscillator forms
analytically for the fermion and superconformal ghost sectors. For the fermion
sector we compare this with numerical result obtained by using naive boundary
condition.
