  We briefly review the covariant formulation of the Green-Schwarz superstring
by Berkovits, and describe how a detailed tree-level and one-loop analysis of
this model leads, for the first time, to a derivation of the low-energy
effective action of the heterotic superstring while keeping target-space
supersymmetry manifest. The resulting low-energy theory is old-minimal
supergravity coupled to tensor multiplet. The dilaton is part of the
compensator multiplet.
