Serhat Altunc

A concept for an Agile Mission Development Facility for CubeSat and suborbital missions

This paper introduces the Agile Mission Development Facility (AMDF), a concept for a new mission development platform at NASA Wallops that will develop a specific kind of Earth observing missions based on networks of small assets (CubeSats, UAVs and balloons) in a timeframe of weeks to months. To achieve this reduced development time, the AMDF will use a new catalog-based and platform-based approach to mission design that emphasizes commonality at the subsystem or assembly level and the use of COTS components when possible. This will necessarily constrain the range of performance achievable by these missions, since only a few alternatives will be available for each subsystem. Only missions whose objectives can be achieved through a combination of the available modules will be considered. In addition to providing a high-level description of the AMDF architecture, this paper describes the process by which this platform consisting of a few standard modules will be optimally designed to maximize the range of attainable performance while keeping short development times. Particular emphasis is put on the communications module that will enable cross-links between nanosatellites, UAVs, balloons, and ground assets. Importantly, the AMDF focuses on a different customer segment than other similar NASA facilities such as the IDC at GSFC or Team X at JPL. AMDF Missions are not meant to compete with larger NASA missions in terms of performance, operational risk or mission assurance, but rather they intend to be complementary. In particular, the very short development time and multi-asset character of these systems will enable a completely new class of missions that can effectively respond to a rapidly changing phenomenon of opportunity, such as a hurricane, a volcano or a geopolitical event of interest for which a larger mission would be inappropriate. Additionally, they can be used to accelerate technology infusion for future larger missions, as long as the new technology satisfies a certain set of interface requirements. The AMDF will maximize reuse of existing design, integration and testing software and hardware infrastructure at NASA Wallops as well as other NASA centers. All potentially relevant stakeholders, such as NASA Goddard, Headquarters, JPL, Ames, the Aerospace Corp., Applied Physics Lab, and universities with nanosatellite programs will be involved and considered in the AMDF development process. This paper focuses on the description of the design aspects of the AMDF, as this is where most of the novelty lies. Integration, testing, launching and operations are only briefly discussed. A description of the system architecture of the AMDF is given using model-based systems engineering tools (SysML). An example application mission to measure ecological changes in the Jefferson and Washington National Forests is also discussed to illustrate the new kinds of missions that this facility could enable.

Transparent reflectarray antenna printed on solar cells

This paper presents an integrating of highly transparent X band reflectarray on the cover glass of solar panels. Two types of element geometries are studied, and optimal unit cell element, effect of the solar cell on the antenna, feed consideration, and final design data are presented. The overall transparency and aperture efficiency of the design are more than 90% and 40% respectively, making it a promising solution as a high gain conformal satellite antenna.

Direction finding using an antenna with direction dependent impulse response

Wideband antennas may be designed to have an impulse response that is direction dependent. This property can be used for angle-of-arrival estimation using a single fixed antenna, without the need for an array or antenna rotation. The method is demonstrated using a simple candelabra-shaped monopole operating in the 1-3 GHz range. A known transmitted pulse and high signal-to-noise ratio are needed, and the method is not as accurate or robust as conventional methods. However, it can add direction finding capability to a wideband communication system without additional hardware requirements.