The NASA (Ground) Communications System (NASCOM) manages terrestrial communications between ground stations, mission control centers, and other elements of spacecraft ground segments. Established in 1964, NASCOM provides worldwide, near real-time, transmission of commands, telemetry, voice, and television signals. It is managed out of NASA's Goddard Space Flight Center in Greenbelt, Maryland.
The NASCOM network comprises microwave links, undersea communications cables, land lines, and network centers at Goddard and around the world.
History
Early development
Prior to the advent of NASCOM, the Minitrack network—used to track the flights of Sputnik, Vanguard, Explorer, and other early spacecraft—largely relied on military-supplied teletype lines which were limited to about 30 bits per second. Scientific data from the Vanguard missions was recorded at ground stations onto magnetic tape, and air mailled to the control center at the Naval Research Laboratory. This reliance on military lines and stations undermined somewhat the purely scientific climate that the Navy and NASA sought to promote.
As NASA developed more advanced satellites in the early 1960s, the capability for telecommand grew, and Minitrack was no longer sufficient. Later, as NASA recruited personnel from military and industry, it began to accrue an in-house knowledge base for wide-band, real-time computer-based networks. Network technologies used in NORAD and the Semi-Automatic Ground Environment (SAGE) defense system contributed to the development of NASCOM.
NASCOM began taking shape in the early 1960s, and was formally established in 1964, under the administration of the recently formed Office of Tracking and Data Acquisition. NASCOM tied together NASA's three tracking and acquisition networks at the time: the Spacecraft Tracking and Data Acquisition Network (STADAN), the Manned Space Flight Network (MSFN), and the Deep Space Network (DSN).
Mercury
Manned missions, beginning with Project Mercury in 1958, demanded a real-time voice circuit in addition to data circuits, and improved reliability. Specifications for the Mercury Network were issued on May 21, 1959, establishing a baseline with a mission control center in Cape Canaveral (later Houston), data convergence at Goddard, and switching stations overseas to provide redundancy and trunking over expensive transoceanic cables. These decisions would shape NASCOM for years to follow.
The Mercury network was designed by the Tracking and Ground Instrumentation Unit (TAGIU) at Langley, with support from Goddard. It consisted of a voice network and a teletype network on separate channels, each with a backup channel. The teletype network, based on the Western Union Type 111 Torn-Tape Relay System, did not offer any speed improvement over the Minitrack network, though it allowed switching based on coded addresses. A data trunk was established between Goddard and Cape Canaveral, with four voice-bandwidth circuits each capable of carrying 1000 bits per second. Later, voice-band links were established from STADAN ground stations and Bermuda.
The Mercury Network was designed under significant time pressure, and integration of the new circuits with the existing Minitrack network was a low priority. Minitrack, Mercury, and JPL networks would eventually be integrated, albeit slowly; an integrated communications division was formed at Goddard in July 1963 to coordinate all NASA ground communications, in what became known as NASCOM. This consolidation was part of a wider effort to standardize communications among federal agencies (the National Communications System), in response to difficulties that arose during the Cuban Missile Crisis.
Gemini
The Gemini Program introduced digital encoding to what would become the NASCOM network, enabling convergence among NASA's disparate networks. Between 1964 and 1966, several other advances were made to the network, largely to support the demands of crewed missions. Torn-tape and electromechanical switching systems were replaced with solid state, automated systems, and the switching center at Goddard was redesigned to improve reliability and capacity, using IBM 7094 and UNIVAC 490 computers. Voice capability was expanded to all MSFN, DSN, and other sites, and multiplexing of teletype messages was introduced at overseas switching centers.