The Guidance, Navigation, and Control Lead basically is in charge of all of the components to make sure the spacecraft is pointed where the scientists want it to be pointed.

Mathematical modelers use mathematics to create models that demonstrate complex processes or solve problems. Many mathematical modelers use their skills to create and animate 3D representations of their processes with the assistance of software technology. 

Check out how Dr. James Smith, Research Scientist at Biospheric Sciences Branch at NASA Goddard Space Flight Center researches changes in the Biosphere using remote sensing techniques.