Space Communications and Navigation Program

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 Space Operations Mission Directorate. 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 to spacecraft) • Return data transfer (downlink from spacecraft to ground) • Dissimilar voice communications • Emergency communications • Post-landing communications • Radiometric measurement • Time correlation • Service monitoring • Ephemeris 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, Ku-band, and Ka-band with planned laser/optical communications. The Deep Space Network communicates with spacecraft using S-band, X-band, and Ka-band. Modulation SN uses phase-shift keying and phase modulation of the carrier signal. Encoding The Space Network (used for near-Earth communications) supports the following encoding schemes: • BPSK • QPSK/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 prior to the selected secondary encoding scheme. ==See also==