  An important tool for the development of the next generation of extremely
large telescopes (ELTs) is a robust Systems Engineering (SE) methodology. GMACS
is a first-generation multi-object spectrograph that will work at visible
wavelengths on the Giant Magellan Telescope (GMT). In this paper, we discuss
the application of SE to the design of next-generation instruments for
ground-based astronomy and present the ongoing development of SE products for
the GMACS spectrograph, currently in its Conceptual Design phase. SE provides
the means to assist in the management of complex projects, and in the case of
GMACS, to ensure its operational success, maximizing the scientific potential
of GMT.
