  In this work computation of the renormalised mass at two loop order for the
NS sector of heterotic string theory is attempted. We first implement the
vertical integration prescription for choosing a section avoiding the spurious
poles due to the presence of a required number of picture changing operators.
As a result the relevant amplitude on genus 2 Riemann surface can be written as
a boundary term. We then identify the 1PI region of the moduli space having
chosen a gluing compatible local coordinates around the external punctures. We
also identify the relevant integrands and the relevant region of integration
for the modular parameters at the boundary.
