We describe the specifications for an ultraviolet radiometer for measuring the F-region electron density gradients form the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC). We also present a technique for determining the two-dimensional structure of the ionosphere using the measured ionospheric gradients inferred from observation of the radiative recombination emission at 1356 Å in conjunction with occultations of Global Positioning System satellites observed from the COSMIC satellites. Our scheme uses a nadir viewing UV photometer to characterize the F-region gradients while obtaining altitude information about the F-region from the GPS occultation measurements. We present the results of simulations that demonstrate the applicability and accuracy of the technique and observational concept.