The Near Earth Network Project, which is organized within the Exploration and Space Communications Projects Division, is located at the Goddard Space Flight Center, with members at both the Greenbelt campus and the Wallops Flight Facility campus. The Near Earth Network Project manages and operates NASA's Near Earth Network (NEN) and the Satellite Laser Ranging (SLR) Network.
The Near Earth Network is comprised of tracking stations distributed throughout the world in locations including Svalbard, Norway; Kiruna, Sweden; Weilheim, Germany; Fairbanks, Alaska; Santiago, Chile; McMurdo, Antarctica; Wallops Island, Virginia; South Point, Hawaii; Dongara, Australia; Hartebeesthoek, South Africa; White Sands, New Mexico; and Merritt Island, Florida. The NEN provides Telemetry, Tracking, and Commanding (TT&C) services to an extensive and diverse customer base, which includes approximately 35 missions - from the high-rate Earth Observing System (EOS) missions such as Aqua, Aura, ICESAT, and QUIKSCAT, to Small Explorer (SMEX) missions including GALEX, SWAS, SWIFT, TIMED and TRACE. It also provides TT&C services for an average of 140 passes per day. The polar stations, Kongsberg Satellite SA (KSAT) Svalbard Ground Station (SGS) in Norway and the SSC/USN Alaska Ground Station in Fairbanks, Alaska, provide almost half of the 140 passes per day collectively.
The services provided by the Near Earth Network are primarily for flight missions over short link distances. These missions require daily and sometimes hourly periodic contacts in their orbital and suborbital locations, including Low Earth Orbit (LEO), Geosynchronous Earth Orbit (GEO), lunar, and highly elliptical orbits.
Each of the 140 TT&C supports per day is scheduled from the Data Services Management Center, located at the White Sands Complex in White Sands, New Mexico.
The NEN utilizes test equipment, which can be deployed to the spacecraft prior to launch to test its compatibility with the NEN stations after launch.
The Satellite Laser Ranging Network uses lasers to measure distances from ground stations to satellite borne retro-reflectors to the millimeter level. During satellite laser ranging, a short pulse of coherent light generated by a laser is transmitted in a narrow beam to illuminate corner cube retroreflectors on the satellite. The return signal, typically a few photons, is collected by a telescope and the time-of-flight is measured. Using information about the satellite's orbit, the time-of-flight, and the speed of light, the precise location of the satellite and ranging station can be determined. Similar data acquired by another station, many kilometers distant from the first, or on a different continent, can be used to determine the distance between stations to precisions of centimeters or better. Repetitive measurements over months and years yield the change in distance, or the motion of the Earth's crust. Observations of the Earth's variable shape, gravity, and rotation provide input for the reference systems that are required in order to assign coordinates to points and objects, and to describe the motion of the Earth in space.
NASA-affiliated stations provide 3,000 ranging contacts per month, supporting approximately 30 satellites. These stations are:
MOBLAS-7 Greenbelt, Maryland (GGAO)
NGSLR Greenbelt, Maryland (GGAO)
MLRS Fort Davis, Texas
MOBLAS-4 Monument Peak, California
MOBLAS-5 Yarragadee, Australia
MOBLAS-6 Hartebeesthoek, South Africa
MOBLAS-8 Tahiti, French Polynesia
TLRS-4 Haleakala, Maui, Hawaii
TLRS-3 Arequipa, Peru
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ENDING YEAR IN SPACE: NASA GODDARD NETWORK MAINTAINS COMMUNICATIONS FROM SPACE TO GROUND