Examine individual changes

'[[File:NASA's Space Communications Testbed.jpg|thumb|right|Technicians at NASA [[Glenn Research Center]] at work on the Space Communications and Navigation Testbed, formerly known as the Communications, Navigation, and Networking reConfigurable Testbed (CoNNeCT) project<ref>[http://spaceflightsystems.grc.nasa.gov/SOPO/SCO/SCaNTestbed/ SCaN Testbed homepage at NASA Glenn Research Center]</ref>]] The '''Space Communications and Navigation''' ('''SCaN''') program places the three prime [[NASA]] space communications networks, [[Space Network]] (SN), [[Near Earth Network]] (NEN) (previously known as the Ground Network or GN), and the [[Deep Space Network]] (DSN), under one [[Management]] and [[Systems Engineering]] 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.<ref name="ProgramPlan">{{cite book| title = Space Communications and Navigation (SCaN) Program Plan| edition = | last = NASA| first = | publisher = National Aeronautics and Space Administration| id = | pages =}}</ref> 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.<ref name="SEMP">{{cite book| title = SCaN Systems Engineering Management Plan (SEMP)| edition = | last = NASA| first = | date = January 30, 2009| publisher = NASA Space Communication and Navigation Program Office| id = SCaN-SEMP| pages =}}</ref> SCaN operates as a central organization within the ''Human Exploration and Operations Mission Directorate'' (HEOMD): {{quote|The Office’s responsibilities encompass the management of existing space networks including the Tracking and Data Relay Satellite system, the Deep Space Network, the Ground Network, the NASA Integrated Services Network; implementing any improvements and upgrades to those systems and networks; and developing any future NASA communications and navigation architectures.}} 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:<ref name="ConOps">{{cite book| title = Constellation Design Reference Missions And Operational Concepts (ConOps), Annex 1: Constellation Communications and Tracking Concept of Operations| edition = Baseline| last = NASA| first = | date = June 28, 2008| publisher = National Aeronautics and Space Administration| id = CxP 70007, ConOps| pages =}}</ref> * 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 [[Radio Frequency|RF]], with a selection of spectra, modulation, and encoding methods, enumerated below. ===Spectra=== The Space Network communicates with spacecraft using [[S-band]], [[Ku-band]],<ref name="SNUG1">{{cite book| title =Space Network User's Guide (SNUG), 2.3, Elements of the SN | edition = Rev 9| last = NASA| first = Exploration and Space Communications Projects Division |author2=Goddard Space Flight Center | year = August 2007 | publisher = National Aeronautics and Space Administration| id =450-SNUG}}</ref> 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]].<ref name="SNUG2">{{cite book| title =Space Network User's Guide (SNUG), 6.2 SSA Forward Services, and 6.2.3 Phase Modulation (PM) Signal Parameters| edition = Rev 9| last = NASA| first = Exploration and Space Communications Projects Division |author2=Goddard Space Flight Center | year = August 2007 | publisher = National Aeronautics and Space Administration| id =450-SNUG}}</ref> ===Encoding=== The Space Network (used for near-Earth communications) supports the following encoding schemes:<ref name="SNUG3">{{cite book| title =Space Network User's Guide (SNUGx)| edition = Rev 9| last = NASA| first = Exploration and Space Communications Projects Division |author2=Goddard Space Flight Center | year = August 2007 | publisher = National Aeronautics and Space Administration| id =450-SNUG}}</ref> * [[BPSK]] * [[QPSK]]/[[SQPSK]] * [[8PSK]] * Rate 1/2 [[Convolutional code|convolutional coding]] * [[Phase-shift keying|SQPN]] * [[Pseudorandom noise|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 code|error-correcting]] [[block code]] prior to the selected secondary encoding scheme. ==See also== * [[Indian Deep Space Network]] * [[Tracking and Data Relay Satellite]] * [[Eastern Range]] * [[NASCOM]] ==References== {{Reflist}} ==External links== * http://www.nasa.gov/directorates/heo/scan/index.html#.U15I0SfbyWY {{NASA centers}} {{NASA navbox|state=collapsed}} {{Use American English|date=January 2014}} [[Category:Deep Space Network]]'