SUDS: The Advent of a Dynamic Space Communications Era

Just as modern phones give us the nearly constant ability to communicate anytime, anywhere, without scheduling our texts and phone calls in advance, satellites and other spacecraft are also headed in this direction. SUDS is the first step in developing the quicker, simpler and highly adaptable communications systems of the future.

The Exploration and Space Communications division’s vision for the future of space communications is delineated by the conceptual Space Mobile Network (SMN), which calls for easy-to-access, reliable and flexible space data return. The Space Mobile Network User Demonstration Satellite (SUDS) will test and improve early software applications for some of the SMN concepts, enabling automated data return scheduling protocols and generally versatile communications services.

For instance, one SMN concept, user initiated services (UIS), will transform scheduling processes: Rather than requiring users on the ground to interpret spacecraft data and trajectory in order to ask networks for data return services in advance, UIS would allow the spacecraft themselves to request downlink passes as needed. SUDS will include one of the first-ever space applications of UIS.

Graphic illustrating user-initiated services

The illustration above depicts a user spacecraft using user-initiated services over a direct-to-Earth communications link. The user requests communications services, and the receiving ground station uses its UIS server to check whether other ground stations are available to accommodate. After the request goes through, the user may downlink data at an available station. 

The Goddard team has developed a simulator to test UIS software prototypes and the performance of several candidate UIS protocol designs; simulations will examine expected wait times for users receiving communications services and compatibility of UIS software and automation processes with network capabilities, both for now and in the future as technology develops.

SUDS is the product of an agreement between Goddard Space Flight Center and the U.S. Naval Academy, which offers an engineering capstone class that builds one to two CubeSats, or miniature satellites typically conducive to cost-effective technology demonstrations, each year. Goddard developed SMN software to fly as an experimental communications payload on the CubeSat, using the opportunity to test and demonstrate SMN concepts at a low cost.

Due to the limited power and other constraints of CubeSats, SUDS will conduct its initial demonstration of UIS and another SMN concept that mitigates delays in critical data delivery, delay tolerant networking, using a direct-to-Earth connection with Near Earth Network (NEN) ground stations. The Goddard team is also investigating ways to emulate a link between the spacecraft and a Tracking and Data Relay Satellite to determine how the software would perform if used with Goddard’s other global communications asset, the Space Network.

The SMN software could be reproduced and given to a variety of users and service providers. The Goddard team plans to provide UIS technology to any mission that would like to use it for demonstration purposes. As the software matures over the course of several demonstrations, the team will also expand the application of the software to other communications networks, both in government and industry.

By Harry Shaw and Seema Vithlani