NASAs science, exploration, operations, and technology organizations are identifying a growing number of potential applications for very small spacecraft. Such spacecraft can accomplish missions at a fraction of the cost of larger conventional spacecraft and can be developed quickly and more responsively. In order to expand and enhance the utility of small spacecraft, technology advances are needed in all subsystem areas and in particular: propulsion, power, thermal control, communications, and radiation tolerance. Certain other SBIR topics also address technology development for spacecraft subsystems and instruments that apply to small spacecraft. However, this topic will focus on development of integrated small spacecraft for applications to be described under specific subtopics. Small spacecraft, for the purpose of this solicitation, are defined as those with a mass of 180 kilograms or less and capable of being launched into space as an auxiliary or secondary payload. Small spacecraft are not limited to Earth orbiting satellites but might also include interplanetary spacecraft, planetary re-entry vehicles, and landing craft. A cubesat is a special category of small spacecraft. One cubesat unit (1U) has dimensions of 10 by 10 by 11 centimeters. Cubesats have typically been built in 1U, 1.5U, 2U, or 3U and 6U sizes.