Merajul Islam at 12:08, 10 January 2022

2022-01-10T12:08:04Z

New page

{{Short description|Signals broadcast by GPS satellites}}
{{Geodesy}}
[[File:GPS Satellite NASA art-iif.jpg|thumb|Artist's conception of GPS Block II-F satellite in Earth orbit]]
[[File:Magellan GPS Blazer12.jpg|thumb|Civilian GPS receiver ("[[GPS navigation device]]") in a marine application]]

'''GPS signals''' are broadcast by [[Global Positioning System]] satellites to enable [[satellite navigation]]. Receivers on or near the Earth's surface can determine location, time, and [[velocity]] using this information. The GPS [[satellite constellation]] is operated by the [[2nd Space Operations Squadron]] (2SOPS) of [[Space Delta 8]], [[United States Space Force]].

GPS signals include ranging signals, used to measure the distance to the satellite, and navigation messages. The navigation messages include ''[[ephemeris]]'' data, used to calculate the position of each satellite in orbit, and information about the time and status of the entire satellite constellation, called the ''[[#Almanac|almanac]]''.

There are four GPS signal specifications designed for civilian use. In order of date of introduction, these are: [[#Legacy GPS signals|L1 C/A]], [[#L2C|L2C]], [[#L5|L5]] and [[#L1C|L1C]].<ref name=":0">{{cite web|last=|first=|date=|title=New Civil Signals|url=https://www.gps.gov/systems/gps/modernization/civilsignals/|url-status=live|access-date=2021-01-18|website=}}</ref> L1 C/A is also called the ''legacy signal'' and is broadcast by all currently operational satellites. L2C, L5 and L1C are ''modernized signals,'' are only broadcast by newer satellites (or not yet at all), and {{As of|2021|January|lc=y}}, none are yet considered to be fully operational for civilian use. In addition, there are ''restricted signals'' with published frequencies and [[Chip (CDMA)|chip]] rates but encrypted coding intended to be used only by authorized parties. Some limited use of restricted signals can still be made by civilians without decryption; this is called ''codeless'' and ''semi-codeless'' access, and is officially supported.<ref>{{cite web|url=https://www.gps.gov/technical/codeless/|title=Codeless/Semi-Codeless GPS Access Commitments}}</ref><ref>[https://apps.dtic.mil/dtic/tr/fulltext/u2/a538975.pdf Civilian GPS Receivers Actually do Have Access to the L2 Frequency]</ref>

The interface to the User Segment ([[GPS receiver]]s) is described in the [https://www.gps.gov/technical/icwg/ Interface Control Documents (ICD)]. The format of civilian signals is described in the [[#Interface Specification|Interface Specification (IS)]] which is a subset of the ICD.

GPS signals - Revision history

Merajul Islam at 12:08, 10 January 2022