NASA GROUND COMMUNICATIONS

John Roeder NASA Headquarters

ABSTRACT

As part of the Communications Requirements and Constraints, NASA's two major Ground Data Networks were briefly described.

The NASA Communication Network, called NASCOM, is the worldwide operational telecommunications system which interconnects as the tracking and telemetry acquisition sites, launch areas, mission and project control centers, data capture facilities, and network control centers in support of space flight. Currently, the NASCOM network contains over 2 1/2 million circuit miles using satellite, terrestrial, and submarine cable leased links; more than 630 circuits connect 139 domestic and foreign sites. The network is engineered and controlled at the Goddard Space Flight Center (GSFC) with major switching centers in Australia, Spain, and at the Jet Propulsion Laboratory (JPL) in California.

All kinds of communications traffic is supported, from low rate digital data and voice to narrow and wide band analog and digital at rated up to tens of megabits. NASCOM is transitioning to an all digital network with wideband links which utilizes improved technology in the competitive market place.

For the Space Station era, NASCOM plans are set for higher data rate service (up to 300 Mbps) utilizing data packet switched technology (CCSDS standards). Increased use of fiber optics is expected in a much more diverse network topology.

The second major ground network, the Program Support Communications Network (PSCN), interconnects all NASA Centers and NASA contractor

locations for intercenter non-operation communications. The primary functions are to transport voice, video, data and facsimile information for intercenter coordination, and to provide user access to space science and applications data bases. Currently, the PSCN contains almost 400 thousand circuit miles using satellite and terrestrial links, supporting many teleconference rooms and high and low speed FAX stations and a packet switched at 35 locations. This network is engineered and managed at Marshall Space Flight Center (MSFC) .

Individual data rates covered are from 110 bps to 56 Kbps, 388 different types of computers and terminals are accommodated, and more than 3000 mail boxes are provided for NASA's TELEMAIL network. A computer networking subsystem allows resource sharing among the four aeronautics and space technology centers scientific mainframe computational centers.

For the Space Station era, PSCN plans address the significant increase in forecast requirements for science data distribution and access to the Numerical Aerodynamics Simulator, and increased use of the Video Teleconference System.

For communications in general, a recent NASA life cycle cost analysis predicts total data volume for NASA science missions to increase as much as two orders of magnitude, by the year 2000. Obviously, costs for telecommunications will not be allowed to keep pace, so creative concepts such as data compression and information reduction are sorely needed.

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