There is a current effort at the CIMSS/SSEC/UW-Madison to develop an accurate and efficient clear sky forward model for GIFTS (and other high spectral resolution sensors) with the various features required for atmospheric profile and radiance data assimilation in a NWP context. This includes development and validation of the underlying line-by-line absorption and radiative transfer models, efficient and representative parameterization of the line-by-line results, and development of analytical jacobians and adjoints of the parameterized model. This paper discusses our ongoing progress on the forward and adjoint model for the GIFTS satellite. Special attention is given on how to evaluate the models.