The Space Communications and Navigation (SCaN) program places the three prime

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

space communications networks,

Space Network Space Network (SN) 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 (GSFC) manages the SN, which consists of: * The geosynchr ...

(SN),

Near Earth Network The Near Earth Network (NEN, formerly GN or Ground Network) provides orbital communications support for near-Earth orbiting customer platforms via various ground stations, operated by NASA and other space agencies. It uses a number of different di ...

(NEN) (previously known as the Ground Network or GN), and the

Deep Space Network The NASA Deep Space Network (DSN) is a worldwide Telecommunications network, network of spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that supports NASA' ...

(DSN), under one

Management Management (or managing) is the administration of organizations, whether businesses, nonprofit organizations, or a Government agency, government bodies through business administration, Nonprofit studies, nonprofit management, or the political s ...

and

Systems Engineering Systems engineering is an interdisciplinary field of engineering and engineering management that focuses on how to design, integrate, and manage complex systems over their Enterprise life cycle, life cycles. At its core, systems engineering uti ...

umbrella. It was established in 2006. It was previously known as the Space Communications & Data Systems (SCDS) Program.

History

Before NASA's administrator Michael D. Griffin created SCaN to direct an integrated networks program, different organizations at NASA Headquarters have managed the Agency's space communications capabilities and functions under separate Programs using a variety of administrative approaches. The SCaN Office was established by direction of Griffin in a Memorandum entitled "Establishment of a Space Communications and Navigation Office," dated July 19, 2006. SCaN operates as a central organization within the ''Human Exploration and Operations Mission Directorate'' (HEOMD): The Ground Network (GN) has since been renamed the Near Earth Network.

Services

SCaN is viewed as a service provider supporting interfaces and performing a standard set of functions, including: * Forward data transfer (

uplink In a telecommunications network, a link is a communication channel that connects two or more devices for the purpose of data transmission. The link may be a dedicated physical link or a virtual circuit that uses one or more physical links or shar ...

to spacecraft) * Return data transfer (

downlink In a telecommunications network, a link is a communication channel that connects two or more devices for the purpose of data transmission. The link may be a dedicated physical link or a virtual circuit that uses one or more physical links or shar ...

from spacecraft to ground) * Dissimilar voice communications * Emergency communications * Post-landing communications *

Radiometric Radiometry is a set of techniques for measuring electromagnetic radiation, including visible light. Radiometric techniques in optics characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which ch ...

measurement * Time correlation * Service monitoring *

Ephemeris In astronomy and celestial navigation, an ephemeris (; ; , ) is a book with tables that gives the trajectory of naturally occurring astronomical objects and artificial satellites in the sky, i.e., the position (and possibly velocity) over tim ...

exchange * Operational coordination * Service scheduling.

Communications schemes

Communications with spaceborne platforms is performed by RF, with a selection of spectra, modulation, and encoding methods, enumerated below.

Spectra

The Space Network communicates with spacecraft using

S-band The S band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a part of the microwave band of the electromagnetic spectrum covering frequencies from 2 to 4 gigahertz (GHz). Thus it crosses the convention ...

Ku-band The Ku band () is the portion of the electromagnetic spectrum in the microwave range of frequencies from 12 to 18 gigahertz (GHz). The symbol is short for "K-under" (originally ), because it is the lower part of the original NATO K band ...

, and

Ka-band The Ka band (pronounced as either "kay-ay band" or "ka band") is a portion of the microwave part of the electromagnetic spectrum. The designation "Ka-band" is from Kurz-above, which stems from the German word ''kurz,'' meaning "short". There ...

with planned laser/optical communications. The Deep Space Network communicates with spacecraft using S-band,

X-band The X band is the designation for a band of frequency, frequencies in the microwave radio region of the electromagnetic spectrum. In some cases, such as in communication engineering, the frequency range of the X band is set at approximately 7.0� ...

, and

Modulation

SN uses

phase-shift keying Phase-shift keying (PSK) is a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency carrier wave. The modulation is accomplished by varying the sine and cosine inputs at a precise time. I ...

and

phase modulation Phase modulation (PM) is a signal modulation method for conditioning communication signals for transmission. It encodes a message signal as variations in the instantaneous phase of a carrier wave. Phase modulation is one of the two principal f ...

of the

carrier signal In telecommunications, a carrier wave, carrier signal, or just carrier, is a periodic waveform (usually sinusoidal) that conveys information through a process called ''modulation''. One or more of the wave's properties, such as amplitude or frequ ...

Encoding

The Space Network (used for near-Earth communications) supports the following encoding schemes: * BPSK *

QPSK Phase-shift keying (PSK) is a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency carrier wave. The modulation is accomplished by varying the sine and cosine inputs at a precise time. It is ...

/ SQPSK * 8PSK * Rate 1/2 convolutional coding * SQPN * PRN coding - used to reduce power spectral density for low bit rate signals, and for time transfer. The Reed–Solomon method is used as the initial error-correcting

block code In coding theory, block codes are a large and important family of Channel coding, error-correcting codes that encode data in blocks. There is a vast number of examples for block codes, many of which have a wide range of practical applications. Th ...

prior to the selected secondary encoding scheme.

References

External links

NASA.gov
{{Use American English, date=January 2014 Deep space networks NASA radio communications and spacecraft tracking facilities