IS-GPS-200F (811524), страница 4
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162Table 30-III.Clock Correction and Accuracy Parameters .................................................................................... 164Table 30-IV.Group Delay Differential Parameters **** ..................................................................................... 169Table 30-V.Midi Almanac Parameters ...............................................................................................................
174Table 30-VI.Reduced Almanac Parameters ***** .............................................................................................. 175Table 30-VII.Earth Orientation Parameters ...................................................................................................... 177Table 30-VIII.Application of EOP Parameters .................................................................................................. 178Table 30-IX.UTC Parameters .............................................................................................................................. 179Table 30-X.Differential Correction Parameters .................................................................................................. 183Table 30-XI.GPS/GNSS Time Offset Parameters ...............................................................................................
187Table 30-XII.Table 40-V.Message Broadcast Intervals ....................................................................................................... 188Data IDs and SV IDs in Subframes 4 and 5 .................................................................................... 206ixIS-GPS-200F21 Sep 20111.
INTRODUCTION1.1 Scope. This Interface Specification (IS) defines the requirements related to the interface between the SpaceSegment (SS) of the Global Positioning System (GPS) and the navigation User Segment (US) of the GPS for radiofrequency (RF) link 1 (L1) and link 2 (L2).1.2 IS Approval and Changes. The Interface Control Contractor (ICC) designated by the government is responsiblefor the basic preparation, approval coordination, distribution, retention, and Interface Control Working Group(ICWG) coordination of the IS in accordance with GP-03-001.
The Navstar GPS Directorate (SMC/GP) is thenecessary authority to make this IS effective.SMC/GP administers approvals under the auspices of theConfiguration Control Board (CCB), which is governed by the appropriate GPS Directorate Operating Instruction(OI). Military organizations and contractors are represented at the CCB by their respective segment member.
Allcivil organizations and public interest are represented by the Department of Transportation representative of theSMC/GP.A proposal to change the approved version of this IS can be submitted by any ICWG participating organization tothe GPS Directorate and/or the ICC. The ICC is responsible for the preparation of the change paper and changecoordination, in accordance with GP-03-001. The ICC prepares the change paper as a Proposed Interface RevisionNotice (PIRN) and is responsible for coordination of PIRNs with the ICWG.
The ICWG coordinated PIRN must besubmitted to the GPS Directorate CCB for review and approval.The ICWG review period for all Proposed Interface Revisions Notices (PIRNs) is 45 days after receipt by individualaddressees. A written request to extend the review period may be submitted to the ICC for consideration.2. APPLICABLE DOCUMENTS2.1 Government Documents. The following documents of the issue specified contribute to the definition of theinterfaces between the GPS Space Segment and the GPS navigation User Segment, and form a part of this IS to theextent specified herein.1IS-GPS-200F21 Sep 2011SpecificationsFederalNoneMilitaryNoneOther Government ActivityNoneStandardsFederalNoneMilitaryNoneOther PublicationsGP-03-001 (GPS Interface Control Working Group Charter)International Earth Rotation and Reference Systems Service(IERS) Technical Note 362.2 Non-Government Documents.
The following documents of the issue specified contribute to the definition of theinterfaces between the GPS Space Segment and the GPS Navigation User Segment and form a part of this IS to theextent specified herein.SpecificationsNoneOther PublicationsNone2IS-GPS-200F21 Sep 20113. REQUIREMENTS3.1 Interface Definition. The interface between the GPS Space Segment (SS) and the GPS navigation User Segment(US) includes two RF links, L1 and L2. Utilizing these links, the space vehicles (SVs) of the SS shall providecontinuous earth coverage signals that provide to the US the ranging codes and the system data needed toaccomplish the GPS navigation (NAV) mission.
These signals shall be available to a suitably equipped user withRF visibility to an SV.3.2 Interface Identification. The carriers of L1 and L2 are typically modulated by one or more bit trains, each ofwhich normally is a composite generated by the modulo-2 addition of a pseudo-random noise (PRN) ranging codeand the downlink system data (referred to as NAV data).3.2.1 Ranging Codes. Three PRN ranging codes are transmitted: the precision (P) code which is the principalnavigation ranging code; the Y-code, used in place of the P-code whenever the anti-spoofing (A-S) mode ofoperation is activated; and the coarse/acquisition (C/A) code which is used for acquisition of the P (or Y) code(denoted as P(Y)) and as a civil ranging signal.
Code-division-multiple-access techniques allow differentiatingbetween the SVs even though they may transmit at the same frequencies. The SVs will transmit intentionally"incorrect" versions of the C/A and the P(Y) codes where needed to protect the users from receiving and utilizinganomalous navigation signals. These two "incorrect" codes are termed non-standard C/A (NSC) and non-standard Y(NSY) codes.For Block IIR-M, IIF, and subsequent blocks of SVs, two additional PRN ranging codes are transmitted. They arethe L2 civil-moderate (L2 CM) code and the L2 civil-long (L2 CL) code. The SVs will transmit intentionally"incorrect" versions of the L2 CM and L2 CL codes where needed to protect the users from receiving and utilizinganomalous navigation signals.
These "incorrect" codes are termed non-standard L2 CM (NSCM) and non-standardL2 CL (NSCL) codes. The SVs shall also be capable of initiating and terminating the broadcast of NSCM and/orNSCL code(s) independently of each other, in response to CS command.Users shall only use non-dummy satellites as defined via current broadcast almanac.
See Section 20.3.3.5.1.2.2and/or Section 30.3.3.4 and/or Section 40.3.3.5.1.2.2 for the definition of information about the almanac.3IS-GPS-200F21 Sep 20113.2.1.1 P-Code. The PRN P-code for SV ID number i, for i = 1 to 37, is a ranging code, Pi(t), of 7 days in length at achipping rate of 10.23 Mbps. The 7 day sequence is the modulo-2 sum of two sub-sequences referred to as X1 andX2i; their lengths are 15,345,000 chips and 15,345,037 chips, respectively. The X2i sequence is an X2 sequenceselectively delayed by 1 to 37 chips thereby allowing the basic code generation technique to produce a set of 37mutually exclusive P-code sequences of 7 days in length.Assignment of these code phase segments by SV IDnumber is given in Table 3-Ia. (NOTE: previous versions of this document reserved PRNs 33 through 37 for otheruses.
Due to increased system capability, PRNs 33 through 37 are being redesignated to allow for use by SVs.)An initial almanac collected from P(Y)-code in the upper PRNs must be obtained from PRNs 35 or 36.3.2.1.1.1 Expanded P-Code (GPS III). An expanded set of 26 P-code PRN sequences are generated by circularlyshifting 26 of the original 37 sequences (over one week) by an amount corresponding to 1 day. These expandedsequences are therefore time shifted (i.e.
offset) versions of 26 of the original sequences. Assignment of theseexpanded code phase segments by SV ID number is given in Table 3-Ib. Additional PRN P-code sequences withassigned PRN numbers are provided in Section 6.3.7, Table 6-I.3.2.1.2 Y-Code. The PRN Y-code is used in place of the P-code when the A-S mode of operation is activated.3.2.1.3 C/A-Code.
The PRN C/A-Code for SV ID number i is a Gold code, Gi(t), of 1 millisecond in length at achipping rate of 1023 Kbps. The Gi(t) sequence is a linear pattern generated by the modulo-2 addition of two subsequences, G1 and G2i, each of which is a 1023 chip long linear pattern. The epochs of the Gold code aresynchronized with the X1 epochs of the P-code. As shown in Table 3-Ia, the G2i sequence is a G2 sequenceselectively delayed by pre-assigned number of chips, thereby generating a set of different C/A-codes. Assignmentof these by GPS PRN signal number are given in Table 3-Ia and Table 3-Ib.An initial almanac collected from C/A Code in the upper PRNs must be obtained from PRNs 35, 36, or 38 through63.CS will prevent the simultaneous transmission of PRNs 34 and 37 of C/A code.4IS-GPS-200F21 Sep 20113.2.1.3.1 Expanded C/A Code (GPS III).
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