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Flexible and Secure Access to Space
Michael Hadjtheodosiou was the Principal Investigator for a NASA Space Communications Project in Computing Information and Communication Technologies award. The project "Flexible and Secure Access for High Data Rate Space Communications" evaluated alternatives for more efficient and dynamic ways to communicate with NASA missions. The objective was to enable scientists to access data "anytime, anywhere" through the Internet. It focuses on issues such as dynamic multiple access techniques for an "on-demand" operational scenario and required modifications of the Ground Network that will enable more efficient access. It also looked at security, traffic analysis and QoS support issues.
Communication requirements for constellation missions and
Planetary Sensor Nets
This project addressed the communication requirements for constellation space missions and planetary senson networks. We developed the framework for studying the operational communication trade-offs for typical constellation missions. We developed a simple prototype dynamic routing algorithm for this type of mission. As an example, we studied Magnetospheric Multiscale Mission (MMS) in detail, developed fairly detailed simulation models for this mission and performed simulation and obtained some preliminary simulation results.Sensor networks employed in NASA exploration missions have to pay particular attention to energy, as energy depletion will render them useless. The harsh space environment and the large distances make the problem of designing energy efficiency in all aspects of the network a very challenging problem. We investigate energy efficiency issues in sensor networks at all levels, from hardware to application level. We will investigate energy efficient algorithms for maximizing throughput as well as optimizing other metrics such as mission lifetime.
Communications for the International Space Station (ISS)
As an interim solution to providing high-speed communication services from the ISS to the ground via commercial assets, NASA is considering, in the short term, the option to transmit commercial data from the ISS directly to existing commercial ground Ka-terminals . While utilizing these existing terminals could save costs, their properties may not be optimum, such as location, terrestrial link to Internet backbone, and available terminal time. Hence, NASA could consider building new terminals that would allow for optimum placement of the terminals and ensure priority service.
This project investigated the feasibility of using existing commercial fixed ground Ka-band terminals for ISS communications in the near future, and perform a trade-off analysis between this option versus building new ground terminals at optimally placed locations.
Broadband Support for Aeronautical Communications
The US airspace is reaching its capacity with the current Air Traffic Control System. The FAA has undertaken several initiatives to modernize the National Airspace System (NAS) to ensure the safety of the increasing number of flights. Next generation satellite systems offering global coverage and high capacity can be an alternative to the terrestrial communication systems and the challenges that need to be addressed in doing that will be the focus of this study.We studied the current NAS communication system and FAA modernization program, defining the communication requirements for a satellite-based solution to broadband aeronautical communications and designing an efficient and reliable transport layer protocol for aeronautical satellite networks that maintains high utilization of the satellite link and improve fairness among competing TCP connections.
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