|Space Flight Tracking
and Data Network
Division of Goddard Space Flight Center, Greenbelt, Md., is responsible
for operating, maintaining and controlling the space flight tracking
and data network, which consists of the space network and ground
network for providing tracking, data acquisition and associated
support. The network is operated through NASA contracts and interagency
and international agreements that provide staffing and logistic
support for space missions. The Networks Division also operates
the Network Control Center and NASA Ground Terminal. The division
is responsible for testing, calibration and configuring network
resources to ensure network support capability before each mission.
It coordinates, schedules and directs all network activity and provides
the necessary interface among GSFC elements and other agencies,
centers and networks.
The STDN, controlled
by the NCC at Goddard, is composed of the White Sands Ground Terminal
and NASA Ground Terminal in White Sands, N.M.; the NASA Communications
Network, Flight Dynamics Facility and Simulation Operations Center
at GSFC; and the ground network. These elements are linked by voice
and data communication services provided by Nascom. The prime operational
communications data are formatted into 4,800-bit blocks and transmitted
on the Nascom wide-band data and message switching system. Other
communications are transmitted by teletype and facsimile facilities.
and Data Relay Satellite system will consist of two Tracking and
Data Relay satellites in geosynchronous orbit (130 degrees apart
in longitude), an on-orbit spare, and a ground terminal facility
(located at White Sands). The TDRS can transmit and receive data
and track a user spacecraft in a low Earth orbit for a minimum of
85 percent of its orbit. TDRSS telecommunication services to and
from the user's control and data processing facilities operate in
a real-time, bent-pipe mode.
The White Sands
Ground Terminal contains the ground terminal communications relay
equipment for the command, telemetry, tracking and control equipment
of the TDRSS. The NASA Ground Terminal is colocated with WSGT. The
NGT is managed and operated by the Networks Division and, in combination
with Nascom, is NASA's physical and electrical interface with the
TDRSS. The NGT provides the interfaces with the common carrier,
monitors the quality of the service from the TDRSS, and remotes
data quality to the NCC.
tracking stations for various communications are located throughout
Ascension Island (ACN)-S-band and ultrahigh frequency air-to-ground.
Bermuda (BDA)-S-band, C-band and UHF air-to- ground.
Guam (GWM)-S-band and UHF air-to- ground.
Kauai, Hawaii (HAW)-S-band and UHF air-to- ground.
Merritt Island, Fla. (MIL)-S-band and UHF air-to- ground.
Santiago, Chile (AGO)- S-band.
Ponce de Leon, Fla. (PDL)- S-band.
Canberra, Australia (CAN)- S-band.
Dakar, Senegal-UHF air-to- ground.
Wallops, Va. (WFF)- C-band.
the STDN are several instrumented United States Air Force aircraft,
referred to as advanced range instrumentation aircraft, that are
situated upon request at various locations around the world where
ground stations cannot support space shuttle missions.
antennas at each STDN site accomplish a specific task, usually in
a specific frequency band. Functioning like giant electronic magnifying
glasses, the larger antennas absorb radiated electronic signals
transmitted by spacecraft in a radio form called telemetry.
Division at Goddard is responsible for providing an operational
telecommunication network for all NASA programs and projects. The
Nascom network is a worldwide complex of communications services,
including data, voice, teletype and television systems that are
a mixture of government-owned and leased equipment as well as leased
services. Nascom is responsible for the operations, maintenance
and testing required to provide optimum service to the users. The
major switching centers in Nascom are located at GSFC; the Jet Propulsion
Laboratory in Pasadena, Calif.; Cape Canaveral, Fla.; Canberra,
Australia; and Madrid, Spain.
network is composed of telephone, microwave, radio, submarine cables
and communication satellites. These various systems link the data
flow through 11 countries of the free world with 15 foreign and
domestic carriers and provide the required information between tracking
sites and Johnson Space Center (Houston, Texas) and Goddard control
centers. Special wide-band and video circuitry is used as needed.
GSFC has the largest wide-band system in existence.
the equipment of the worldwide STDN are numerous computers located
at the different stations that control tracking antennas, handle
commands and process data for transmission to the JSC and GSFC control
centers. Shuttle data from all the tracking stations are funneled
into the main switching computers at GSFC and rerouted to JSC without
delay by domestic communications satellites. Commands generated
at JSC are transmitted to the main switching computers at GSFC and
switched to the proper tracking station for transmission to the
If NASA's JSC
Mission Control Center should be impaired for an extended period
of time, an emergency control center would be established at NASA's
ground terminal at White Sands and manned by NASA JSC personnel.
A station conferencing
and monitoring arrangement allows various traffic managers to hold
conferences with as many as 220 different voice terminals throughout
the United States and abroad with talking and listening capability
at the touch of a few buttons. The system is redundant, which accounts
for its mission support reliability record of 99.6 percent. All
space shuttle voice traffic is routed through this arrangement at
satellites electronically connect the Earth stations and permit
transmission of 10 to 20 times more data. Ground terminals for domestic
communications satellites are situated at JSC; Kauai, Hawaii; Goldstone,
Calif.; Kennedy Space Center. Florida; NASA's Dryden Flight Research
Facility, California; GSFC, Greenbelt, Md.; and White Sands, N.M.
station at Ponce de Leon Inlet, Fla. (near New Smyrna Beach), provides
support during powered flight because of attenuation problems from
the solid rocket booster motor plume.
worldwide ground stations provide coverage for approximately 20
percent of a satellite's or spacecraft's orbit, limited to brief
periods when the satellite or spacecraft is within the line of sight
of a given tracking station.
A new era in
space communication began with the STS-6 mission in April 1983,
when the first Tracking and Data Relay Satellite was deployed. TDRS-A
was the first of three identical satellites planned for the system.
The TDRS system was developed after studies in the early 1970s showed
that a telecommunication satellite system could support the projected
scientific and application mission requirements better than ground
stations and also could halt the spiraling cost of upgrading and
operating a worldwide network of tracking and communication ground