Space communications architecture. GS, ground station.
Long description of figure.
The Space Communications Testbed (SCT) is one of the defining projects of the Space Exploration Initiative that was awarded in April 2005. The SCT team is composed of ViaSat/Comsat (prime contractor) with Glenn Research Center, Goddard Space Flight Center, Langley Research Center, and the Jet Propulsion Laboratory as participating NASA centers.
The SCT is an integrated communications testbed focused on detailed testing of advanced space and ground communication networks, technologies, and client applications that are essential for future space exploration. Missions will utilize the testbed from development to operations for defining and validating mission requirements, testing communication schedules and patterns,testing and validating mission protocols, and verifying operational software. The testbed will function in an end-to-end environment where communications can occur continuously and seamlessly from a base station on the Moon to a computer connected to the Internet on Earth and, potentially, hopping through a series of relay satellites, as shown in the diagram. Customized, user-defined scenarios will specify the entities of the system, such as satellite and ground stations, and their properties, such as antennas and data rates.
SCT is divided into two phases. Phase I, a 1-year effort (April 2005 to 2006), will define a proof-of-concept system that NASA will use and evaluate. Phase II, a 3-year effort (2006 to 2009), will consist of system development and testing. In phase I, Glenn has the following responsibilities:
(1) Lunar Relay Satellite system development--The Lunar Relay Satellite is a satellite constellation system that will orbit the Moon. It will communicate with land entities on the Moon and satellite entities in space and will have cross-linking capabilities between individual satellites in the system. Orbital characteristics were based on the results of the Space Communications Architecture Working Group.
(2) Link emulator development--The link emulator provides bit-error-rate characteristics, link delays, data rates, and data loss. In phase II, the development will include aspects such as Doppler shift. The link emulator will use a technique called virtual large-area networks (LANs) to emulate multiple antennas on a satellite or ground station. Internally to the emulator, the connections will be dynamically bridged in an on-demand fashion. The number of connections to the emulator will be based on the number of ports available.
(3) Protocol tradeoff study--This year Glenn studied, tested, and evaluated a number of publicly and commercially available space-based protocols. The Glenn SCT team conducted a static analysis by evaluating code and documentation for parameters, such as the features and highlights of the protocol, assessment of the technology readiness level, the amount and thoroughness of protocol testing, and an identification of any known issues with the protocol. In addition, the team will conduct a dynamic test through the Protocol Research Evaluation Environment Testbed. The handbook from the protocol tradeoff study will serve as an operations guide for protocol integration in the SCT.
(4) Monitor and controller--The monitor and controller provide an interface for the main SCT controller located at ViaSat, to direct, manage, and control Glenn’s regional testbed. Glenn’s monitor and controller is responsible for configuring entities, starting and stopping the emulation, and providing health monitoring and statistics of the test-bed. It will report warnings and errors to the main testbed at ViaSat.
Find out more about Glenn’s Satellite Networks & Architectures Branch: http://ctd.grc.nasa.gov/organization/branches/snab/snab.html
Glenn contact:
Richard A. Slywczak, 216-433-3493, Richard.A.Slywczak@nasa.gov
Author:
Richard A.Slywczak
Headquarters program office:
Exploration Systems
Programs/Projects:
CEV, Life Support & Habitation, NGLT, RTF, Vehicle Systems, Satellite Missions
Last updated: October 17, 2006
Responsible NASA Official:
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216-433-8258
Point of contact for NASA Glenn's Research & Technology reports:
Cynthia.L.Dreibelbis@nasa.gov
216-433-2912
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Web page curator:
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