Since our recent discovery of double spin resonances in the Co-underdoped NaFeAs superconductor, two different theoretical approaches have been proposed to interpret its origin. We propose to carry out an inelastic neutron scattering experiment on a detwinned NaFe0.985Co0.015As crystal under uniaxial pressure at IN8, to study the wavevector dependence of the two resonance modes at (Pi, 0) and (0, Pi). Important clues on the origin of double resonances and the nature of superconducting gap anisotropy can be expected from the planned experiment.