  Future space borne gravitational wave detectors will require a precise
definition of calibration signals to ensure the achievement of their design
sensitivity. The careful design of the test signals plays a key role in the
correct understanding and characterisation of these instruments. In that sense,
methods achieving optimal experiment designs must be considered as
complementary to the parameter estimation methods being used to determine the
parameters describing the system. The relevance of experiment design is
particularly significant for the LISA Pathfinder mission, which will spend most
of its operation time performing experiments to characterise key technologies
for future space borne gravitational wave observatories. Here we propose a
framework to derive the optimal signals ---in terms of minimum parameter
uncertainty--- to be injected to these instruments during its calibration
phase. We compare our results with an alternative numerical algorithm which
achieves an optimal input signal by iteratively improving an initial guess. We
show agreement of both approaches when applied to the LISA Pathfinder case.
