The Citation Research Aircraft is a jet manufactured by Cessna and modified by the University of North Dakota for conducting atmospheric research. The basic instrument package includes measurements of aircraft speed and position, along with atmospheric state parameters, such as temperature, relative humidity and winds. However, research projects typically involve deployment of very advanced instruments to conduct specific scientific measurements, such as hydrometeor concentration, size and mass. Most projects are in the field of cloud physics; however, the platform has done projects to study electric fields, atmospheric chemistry and weather modification. In addition, the aircraft conducts flight testing of new instruments designed for commercial aircraft. The detailed measurements provided by the aircraft's instruments help to understand remote sensing observations made by surface and satellite platforms. Atmospheric observations made by the aircraft provide new insights into many important processes, such as precipitation formation and effects of air pollution.