The Department of Energy's Atmospheric Radiation Measurement (ARM) Unmanned Aerospace Vehicle (UAV) program

The U.S. Department of Energy has established an unmanned aerospace vehicle (UAV) measurement program. The purpose of this paper is to describe the ev olution of the program since its inception, review the progress of the prog ram, summarize the measurement capabilities developed under the program, il lustrate key results from the various UAV campaigns carried out to date, an d provide a sense of the future direction of the program. The Atmospheric R adiation Measurement (ARM)-UAV program has demonstrated how measurements fr om unmanned aircraft platforms operating under the various constraints impo sed by different science experiments can contribute to our understanding of cloud and radiative processes. The program was first introduced in 1991 an d has evolved in the form of four phases of activity each culminating in on e or more flight campaigns. A total of 8 flight campaigns produced over 140 h of science flights using three different UAV platforms. The UAV platform s and their capabilities are described as are the various phases of the pro gram development. Examples of data collected from various campaigns highlig ht the powerful nature of the observing system developed under the auspices of the ARM-UAV program and confirm the viability of the UAV platform for t he kinds of research of interest to ARM and the clouds and radiation commun ity as a whole. The specific examples include applications of the data in t he study of radiative transfer through clouds, the evaluation of cloud para meterizations, and the development and evaluation of cloud remote sensing m ethods. A number of notable and novel achievements of the program are also highlighted.