Tracking and Data Relay Satellite System
Encyclopedia
The Tracking and Data Relay Satellite System (TDRSS) is a network of American communications satellite
Communications satellite
A communications satellite is an artificial satellite stationed in space for the purpose of telecommunications...

s (each called a Tracking and Data Relay Satellite or TDRS
TDRS
A Tracking and Data Relay Satellite is a type of communications satellite that forms part of the Tracking and Data Relay Satellite System used by NASA and other United States government agencies for communications to and from independent "User Platforms" such as satellites, balloons, aircraft,...

) and ground stations used by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 for space communications. The system was designed to replace an existing network of ground stations that had supported all of NASA's manned flight missions. The prime design goal was to increase the time spacecraft were in communication with the ground and improve the amount of data that could be transferred. Many Tracking and Data Relay Satellite
Tracking and Data Relay Satellite
A Tracking and Data Relay Satellite is a type of communications satellite that forms part of the Tracking and Data Relay Satellite System used by NASA and other United States government agencies for communications to and from independent "User Platforms" such as satellites, balloons, aircraft,...

s were launched in the 1980s and 1990s with the Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

 and made use of the Inertial Upper Stage
Inertial Upper Stage
The Inertial Upper Stage , originally known as the Interim Upper Stage, is a two-stage solid-fueled booster rocket developed by the U.S...

, a two-stage solid rocket booster developed for the shuttle. Other TDRS were launched by Atlas IIa and Atlas V
Atlas V
Atlas V is an active expendable launch system in the Atlas rocket family. Atlas V was formerly operated by Lockheed Martin, and is now operated by the Lockheed Martin-Boeing joint venture United Launch Alliance...

 rockets.

The most recent generation of satellites provides ground reception rates of 300 Mbit/s in the Ku- and Ka-bands and 800 Mbit/s in the S-band.

The term TDRSS is analogous to Space Network
Space Network
Space Network is a NASA program that combines space and ground elements to support spacecraft communications in Earth vicinity. The SN Project Office at Goddard Space Flight Center manages the SN, which consists of:...

.

Origins

To satisfy the requirement for long-duration, highly-available space-to-ground communications, NASA created the Spacecraft Tracking and Data Acquisition Network
Spacecraft Tracking and Data Acquisition Network
The Spacecraft Tracking and Data Network was established by NASA to satisfy the requirement for long-duration, highly-available space-to-ground communications...

 (STADAN). Consisting of parabolic dish antennas and telephone switching equipment deployed around the world, the STADAN provided space-to-ground communications for approximately 15 minutes of a 90-minute orbit period. This limited contact-period sufficed for unmanned spacecraft, but manned spacecraft require a much higher data collection time.

The follow-on network, called the Manned Space Flight Network
Manned Space Flight Network
The Manned Space Flight Network was a set of tracking stations built to support the American space efforts of Mercury, Gemini, Apollo and Skylab...

 (MSFN), interacted with manned craft in Earth orbit. Another network, the Deep Space Network
Deep Space Network
The Deep Space Network, or DSN, is a world-wide network of large antennas and communication facilities that supports interplanetary spacecraft missions. It also performs radio and radar astronomy observations for the exploration of the solar system and the universe, and supports selected...

 (DSN), interacted with manned craft higher than 10,000 miles from Earth, such as the Apollo missions, in addition to its primary mission of data collection from deep space probes.

With the creation of the Space Shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

 in the mid-1970s, a requirement for a higher performance space-based communication system arose. At the end of the Apollo program, NASA realized that MSFN and STADAN had evolved to have similar capabilities and decided to merge the two networks to create the Spacecraft Tracking and Data Network (STDN).

Even after consolidation, STDN had some drawbacks. Since the entire network consisted of ground stations spread around the globe, these sites were vulnerable to the political whims of the host country. In order to maintain a high-reliability rate coupled with higher data transfer speeds, NASA began a study to augment the system with a space-based communication nodes.

The space segment of the new system would rely upon satellites in geostationary orbit. These satellites, by virtue of their position, could transmit and receive data to lower orbiting satellites and still stay within sight of the ground station. The operational TDRSS constellation would use two satellites, designated TDE and TDW (for East and West), and one on-orbit spare.

After the study was completed, NASA realized that a minor system modification was needed to achieve 100% global coverage. A small area would not be within line-of-sight of any satellites – a so-called Zone of Exclusion (ZOE). With the ZOE, neither TDRS satellite could contact a spacecraft under a certain altitude (646 nautical miles). With the addition of another satellite to cover the ZOE and ground station nearby, 100% coverage could exist. The space-based network study created a system that became the plan for the present-day TDRSS network design.

As early as the 1960s, NASA's Application Technology Satellite (ATS) and Advanced Communications Technology Satellite (ACTS) programs prototyped many of the technologies used on TDRSS and other commercial communications satellites, including frequency division multiple-access (FDMA), three-axis spacecraft stabilization and high-performance communications technologies.

As of July 2009, TDRSS project manager is Jeff J. Gramling, NASA Goddard Space Flight Center. Boeing is responsible for the construction of TDRS K.

The network

TDRSS is similar to most other space systems, whereby it is composed of three segments: the ground, space and user segments. These three segments work in conjunction to accomplish the mission. An emergency or failure in any one segment could have catastrophic impact on the rest of the system. For this reason all segments have redundancy factored in.

Ground segment

The ground segment of TDRSS consists of two ground stations located at the White Sands Complex
White Sands Missile Range
White Sands Missile Range is a rocket range of almost in parts of five counties in southern New Mexico. The largest military installation in the United States, WSMR includes the and the WSMR Otera Mesa bombing range...

 (WSC), the Guam
Guam
Guam is an organized, unincorporated territory of the United States located in the western Pacific Ocean. It is one of five U.S. territories with an established civilian government. Guam is listed as one of 16 Non-Self-Governing Territories by the Special Committee on Decolonization of the United...

 Remote Ground Terminal (GRGT), and Network Control Center located at Goddard Space Flight Center
Goddard Space Flight Center
The Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately northeast of Washington, D.C. in Greenbelt, Maryland, USA. GSFC,...

 in Greenbelt, Maryland
Greenbelt, Maryland
Greenbelt is a city in Prince George's County, Maryland, United States. Contained within today's City of Greenbelt is the historic planned community now known locally as "Old Greenbelt" and designated as the Greenbelt Historic District...

. These three stations are the ‘heart’ of the network, providing command & control services.

WSC, located near Las Cruces
Las Cruces, New Mexico
Las Cruces, also known as "The City of the Crosses", is the county seat of Doña Ana County, New Mexico, United States. The population was 97,618 in 2010 according to the 2010 Census, making it the second largest city in the state....

 consists of:
  • White Sands Ground Terminal (WSGT)32.5007°N 106.6086°W
  • Second TDRSS Ground Terminal (STGT)32.5430°N 106.6120°W
  • Extended TDRS Ground Terminal (ETGT)


Additionally, the WSC remotely controls the GRGT on Guam
Guam
Guam is an organized, unincorporated territory of the United States located in the western Pacific Ocean. It is one of five U.S. territories with an established civilian government. Guam is listed as one of 16 Non-Self-Governing Territories by the Special Committee on Decolonization of the United...

.

The WSC has its own exit from U.S. Route 70
U.S. Route 70
U.S. Route 70 is an east–west United States highway that runs for 2,385 miles from eastern North Carolina to east-central Arizona. As can be derived from its number, it is a major east–west highway of the Southern and Southwestern United States...

 that is for facility staff only. NASA decided on the location of the ground terminals using very specific criteria. Foremost was the ground station’s view of the satellites; the location had to be close enough to the equator to view the skies, both east and west. Weather was another important factor – New Mexico has, on average, almost 350 days of sunshine per year, with a very low precipitation level.

WSGT went online in 1978, just in time for the space shuttle’s planned debut in early 1979. STGT became operational in 1994, completing the system after Flight-6’s on-orbit checkout earlier in the year. Additionally, after completion of the second terminal, NASA held a contest to name the two stations. Local middle school students chose Cacique (kah-see-keh), meaning “leader” for WSGT, and Danzante meaning “dancer” for STGT. These names seem to have been for publicity purposes only, for official NASA documentation use WSGT and STGT or WSC as designators.

WSGT and STGT are geographically separated and completely independent of one another, while retaining a backup fiber-optic link to transfer data between sites in case of emergency. Each ground station has 19-meter dishes, known as Space-Ground Link Terminals (SGLT), to communicate with the satellites. Three SGLTs are located at STGT, but only two are located at WSGT. The system architects moved remaining SGLT to Guam to provide full network support for the satellite covering the ZOE. Considered a remote part of the WSGT, the distance and location of the SGLT is transparent to network users.

The Guam Remote Ground Terminal (GRGT)13.6148°N 144.8565°E is an extension of the WSGT. The terminal contains SGLT 6, with the Communication Service Controller (CSC) located at WSGT’s TDRS Operations Control Center (TOCC). Before the GRGT was operational, an auxiliary system was located at Diego Garcia
Diego Garcia
Diego Garcia is a tropical, footprint-shaped coral atoll located south of the equator in the central Indian Ocean at 7 degrees, 26 minutes south latitude. It is part of the British Indian Ocean Territory [BIOT] and is positioned at 72°23' east longitude....

.

Incorporation into the STDN

The major parts of the Spaceflight Tracking and Data Network (STDN) are: the NASA Integrated Services Network
NASA Integrated Services Network
The NASA Integrated Services Network is a global system of communications transmission, switching, and terminal facilities that provides NASA with wide area network communications services...

 (NISN), network control center (NCC), mission operations center (MOC), spacecraft data processing facility (SDPF), and the multi mission flight dynamics lab (MMFD).

NISN provides the data transfer backbone for space missions. It is a cost-effect wide area network telecommunications service for transmission of data, video, and voice for all NASA enterprises, programs and centers. This part of the STDN consists of infrastructure and computers dedicated to monitor network traffic flow, such as fiber optic links, routers and switches. Data can flow through NISN two ways: using the Internet Protocol Operational Network (IPONET) or the High Data Rate System (HDRS). IPONET uses the TCP/IP protocol common to all computers connected to the Internet, and is a standard way to ship data. The High Data Rate System transports data rates from 2 Mbit/s to 48 Mbit/s, for specialized missions requiring a high rate of data transfer. HDRS does not require the infrastructure of routers, switches and gateways to send its data forward like IPONET.

The NCC provides service planning, control, assurance and accountability. Service planning takes user requests and disseminates the information to the appropriate SN elements. Service control and assurance supports functions of real-time usage, such as receipt, validation, display and dissemination of TDRSS performance data. Service accountability provides accounting reports on the use of the NCC and network resources. The NCC was originally located at Goddard Space-flight Center, in Greenbelt, Maryland until 2000, when it was relocated to the WSC.

The MOC is the focal point of spacecraft operations. It will schedule requests for support, monitor spacecraft performance and upload control information to the spacecraft (through TDRSS). MOC consists of principal investigators, mission planners and flight operators. Principal investigators initiate requests for SN support. Mission planners provide documentation for the spacecraft and its mission. And flight operators are the final link, sending commands to the spacecraft and performing the operations.

The MMFD lab provides flight project and tracking network support. Flight project support consists of orbital and attitude determination and control. Orbital parameters are traced through the actual orbit of the mission spacecraft and compared to its predicted orbit. Attitude determination computes sets of parameters that describe a spacecraft’s orientation relative to known objects (Sun, Moon, stars or Earth’s magnetic field). Tracking network support analyzes and evaluates the quality of the tracking data.

Space segment

The space segment of the TDRSS constellation is the most dynamic part of the system. Even with nine satellites on orbit, the system provides support with three primary satellites, while using the rest as on-orbit spares capable of immediate usage as primaries. The original TDRSS design had two primary satellites, designated TDE, for "east", and TDW, for "west" and one on-orbit spare. The surge in user requirements during the 1980s allowed NASA to expand the network with the addition of more satellites, with some being co-located in a particularly busy orbital slot. See Tracking and Data Relay Satellite
Tracking and Data Relay Satellite
A Tracking and Data Relay Satellite is a type of communications satellite that forms part of the Tracking and Data Relay Satellite System used by NASA and other United States government agencies for communications to and from independent "User Platforms" such as satellites, balloons, aircraft,...

 for more details on the satellites.

User segment

The user segment of TDRSS includes many of NASA's most prominent programs. Programs such as the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...

 and LANDSAT relay their observations to their respective mission control centers through TDRSS. Since manned space flight was one of the primary reasons for building TDRSS, the space shuttle and International Space Station voice communications are routed through the system.

Operations

The TDRSS system has been used to provide data relay services to many orbiting observatories, and also to Antarctic facilities such as McMurdo Station
McMurdo Station
McMurdo Station is a U.S. Antarctic research center located on the southern tip of Ross Island, which is in the New Zealand-claimed Ross Dependency on the shore of McMurdo Sound in Antarctica. It is operated by the United States through the United States Antarctic Program, a branch of the National...

 by way of the TDRSS South Pole Relay. The US-built sections of the International Space Station (ISS)
International Space Station
The International Space Station is a habitable, artificial satellite in low Earth orbit. The ISS follows the Salyut, Almaz, Cosmos, Skylab, and Mir space stations, as the 11th space station launched, not including the Genesis I and II prototypes...

 use TDRSS for data relay. TDRSS is also used to provide launch data relay for expendable boosters.

Military applications

As early as 1989, it was reported that an important function of TDRSS was to provide data relay for the Lacrosse
Lacrosse (satellite)
For the 2009 Lunar Impactor Mission designed to crash into the moon, see LCROSS.Lacrosse and Onyx are the code names for the United States' National Reconnaissance Office terrestrial radar imaging reconnaissance satellite. While not officially confirmed by the NRO or anybody in the U.S...

 radar imaging reconnaissance satellites operated by the National Reconnaissance Office
National Reconnaissance Office
The National Reconnaissance Office , located in Chantilly, Virginia, is one of the 16 U.S. intelligence agencies. It designs, builds, and operates the spy satellites of the United States government.-Mission:...

.

Almost twenty years later, on November 23, 2007, an on-line trade publication noted, "While NASA uses the (TDRSS) satellites to communicate with the space shuttle and international space station, most of their bandwidth is devoted to the Pentagon, which covers the lion's share of TDRSS operations costs and is driving many of the system's requirements, some of them classified."

In October 2008, the NRO declassified the existence of mission ground stations in the US called Aerospace Data Facility (ADF)- Colorado, ADF-East and ADF-Southwest near Denver, Colorado
Denver, Colorado
The City and County of Denver is the capital and the most populous city of the U.S. state of Colorado. Denver is a consolidated city-county, located in the South Platte River Valley on the western edge of the High Plains just east of the Front Range of the Rocky Mountains...

, Washington, D.C. and Las Cruces, New Mexico
Las Cruces, New Mexico
Las Cruces, also known as "The City of the Crosses", is the county seat of Doña Ana County, New Mexico, United States. The population was 97,618 in 2010 according to the 2010 Census, making it the second largest city in the state....

, respectively. ADF-Colorado and ADF-East are known to be located at Buckley AFB, CO and Fort Belvoir, Virginia; the exact location of ADF-Southwest is uncertain, but likely to be at the WSC.

Production

The first seven TDRS satellites were built by the TRW
TRW
TRW Inc. was an American corporation involved in a variety of businesses, mainly aerospace, automotive, and credit reporting. It was a pioneer in multiple fields including electronic components, integrated circuits, computers, software and systems engineering. TRW built many spacecraft,...

 corporation (now part of Northrop Grumman Aerospace Systems) in Redondo Beach, California
Redondo Beach, California
Redondo Beach is one of the three Beach Cities located in Los Angeles County, California, United States. The population was 66,748 at the 2010 census, up from 63,261 at the 2000 census. The city is located in the South Bay region of the greater Los Angeles area.Redondo Beach was originally part of...

, and all of the satellites since then by Hughes Space and Communications, Inc., in El Segundo, California
El Segundo, California
El Segundo is a city in Los Angeles County, California, United States. Located on the Santa Monica Bay, it was incorporated on January 18, 1917, and is one of the Beach Cities of Los Angeles County and part of the South Bay Cities Council of Governments...

, (now a part of the Boeing
Boeing
The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...

 corporation).

Cultural references

The TDRSS system is briefly mentioned in the James Bond
James Bond
James Bond, code name 007, is a fictional character created in 1953 by writer Ian Fleming, who featured him in twelve novels and two short story collections. There have been a six other authors who wrote authorised Bond novels or novelizations after Fleming's death in 1964: Kingsley Amis,...

 movie, Moonraker
Moonraker (film)
Moonraker is the eleventh spy film in the James Bond series, and the fourth to star Roger Moore as the fictional MI6 agent James Bond. The third and final film in the series to be directed by Lewis Gilbert, it co-stars Lois Chiles, Michael Lonsdale, Corinne Clery, and Richard Kiel...

. It is also brought up in the 1997 movie Event Horizon
Event Horizon (film)
Event Horizon is a 1997 science fantasy horror film. The screenplay was written by Philip Eisner and directed by Paul W. S. Anderson. The film stars Laurence Fishburne and Sam Neill...

.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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