IS-GPS-200H (797934), страница 12
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When feasible, the CS will endeavor to operate at least one satellite using anupper PRN number to serve as a source of almanac data for satellites using the upper range ofPRN numbers.6.4.2 PRN Number Consistency.For a given satellite, the same PRN number will be assigned to all operational signals (signalsmodulated by standard PRN code with data that indicates the signal health is OK).6.4.3 PRNs 33 and 37.PRN 33 should not be used by satellites because of its prior use in specialized groundapplications.
PRN 37 should not be used by satellites until after PRN 37 is no longer needed forSATZAP purposes.6.4.4 PRNs 33 through 63.The CS must ensure that satellites broadcasting PRNs 33 through 63 are synchronized to GPStime to avoid conflict with specialized ground applications.6.4.5 Health Code Setting of ‘11110’.For backward compatibility reasons, the SV signal component health code setting of ‘11110’ isanticipated for potential use only with satellites broadcasting PRNs 33 through 63.64IS-GPS-200H24 Sep 201310 APPENDIX I.
LETTERS OF EXCEPTION10.1 Scope.Approval of this document, as well as approval of any subsequent changes to the document, canbe contingent upon a "letter of exception". This appendix depicts such "letters of exception"when authorized by the GPS Directorate.10.2 Applicable Documents.The documents listed in Section 2.0 shall be applicable to this appendix.10.3 Letters of Exception.Any letter of exception which is in force for the revision of the IS is depicted in Figure 10.3-1 10.3-8.65IS-GPS-200H24 Sep 2013Figure 10.3-1. Letters of Exception.66IS-GPS-200H24 Sep 2013Figure 10.3-2.
Letters of Exception (continued)67IS-GPS-200H24 Sep 2013Figure 10.3-3. Letters of Exception (continued)68IS-GPS-200H24 Sep 2013Figure 10.3-4. Letters of Exception (continued).69IS-GPS-200H24 Sep 2013Figure 10.3-5. Letters of Exception (continued)70IS-GPS-200H24 Sep 2013Figure 10.3-6. Letters of Exception (continued).71IS-GPS-200H24 Sep 2013Figure 10.3-7. Letters of Exception (continued).72IS-GPS-200H24 Sep 2013Figure 10.3-8. Letters of Exception (continued).73IS-GPS-200H24 Sep 201320 APPENDIX II.
GPS NAVIGATION DATA STRUCTURE FORLNAV DATA, D(t), FOR PRN 1-3220.1 Scope.This appendix describes the specific legacy navigation (LNAV) data structure denoted by dataID number 2 for the lower set of PRN numbers (PRN 1-32). This data ID number, whentransmitted as part of the LNAV data, shall be represented by the two-bit binary notation as 01.Data ID number 1 is no longer in use. The LNAV data structure for the lower set of PRNnumbers is denoted as LNAV-L. The LNAV data structure for the upper set of PRN numbers(LNAV-U) is described in Appendix IV.20.2 Applicable Documents.20.2.1 Government Documents.In addition to the documents listed in paragraph 2.1, the following documents of the issuespecified contribute to the definition of the NAV data related interfaces and form a part of thisAppendix to the extent specified herein.SpecificationsFederalNoneMilitaryNoneOther Government ActivityNoneStandardsFederalNoneMilitaryNoneOther PublicationsGP-03-001 (GPS Interface Control Working Group Charter)20.2.2 Non-Government Documents.In addition to the documents listed in paragraph 2.2, the following documents of the issuespecified contribute to the definition of the NAV data related interfaces and form a part of thisAppendix to the extent specified herein.SpecificationsNoneOther Publications74IS-GPS-200H24 Sep 2013None20.3 Requirements.20.3.1 Data Characteristics.The data stream shall be transmitted by the SV on the L1 and L2 channels at a rate of 50 bps.
Inaddition, upon ground command, the data stream shall be transmitted by the Block IIR-M SV onthe L2 CM channel at a rate of 25 bps using FEC encoding resulting in 50 sps.20.3.2 Message Structure.As shown in Figure 20-1, the message structure shall utilize a basic format of a 1500 bit longframe made up of five subframes, each subframe being 300 bits long. Subframes 4 and 5 shallbe subcommutated 25 times each, so that a complete data message shall require the transmissionof 25 full frames. The 25 versions of subframes 4 and 5 shall be referred to herein as pages 1through 25 of each subframe.
Each subframe shall consist of ten words, each 30 bits long; theMSB of all words shall be transmitted first.Each subframe and/or page of a subframe shall contain a telemetry (TLM) word and a handoverword (HOW), both generated by the SV, and shall start with the TLM/HOW pair. The TLMword shall be transmitted first, immediately followed by the HOW. The HOW shall be followedby eight data words.
Each word in each frame shall contain parity (reference Section 20.3.5).Block II and IIA SVs are designed with sufficient memory capacity for storing at least 60 days ofuploaded NAV data. However, the memory retention of these SVs will determine the durationof data transmission. Block IIR SVs have the capability, with current memory margin, to store atleast 60 days of uploaded NAV data in the Block IIA mode and to store at least 60 days of CSdata needed to generate NAV data on-board in the Autonav mode. GPS III SVs have thecapability to support operation for at least 60 days without contact from the CS.
Alternatingones and zeros will be transmitted in words 3 through 10 in place of the normal NAV datawhenever the SV cannot locate the requisite valid control or data element in its on-boardcomputer memory. The following specifics apply to this default action: (a) the parity of theaffected words will be invalid, (b) the two trailing bits of word 10 will be zeros (to allow theparity of subsequent subframes to be valid -- reference paragraph 20.3.5), (c) if the problem isthe lack of a data element, only the directly related subframe(s) will be treated in this manner, (d)if a control element cannot be located, this default action will be applied to all subframes and allsubframes will indicate ID = 1 (Block II/IIA only) (i.e., an ID-code of 001) in the HOW(reference paragraph 20.3.3.2) (Block IIR/IIR-M, IIF, and GPS III SVs indicate the propersubframe ID for all subframes).
Certain failures of control elements which may occur in the SVmemory or during an upload will cause the SV to transmit in non-standard codes (NSC andNSY) which would preclude normal use by the US. Normal NAV data transmission will beresumed by the SV whenever a valid set of elements becomes available.75IS-GPS-200H24 Sep 2013Block II/IIA SVs are uploaded with a minimum of 60 days of NAV data. However, the EAROMretentivity for Block II SVs is designed and guaranteed for only 14 days. Therefore, Block II SVmemory is most likely to fail sometime during long-term extended operations after repeatedwrite operations.
In the case of memory failure, the SV will transmit alternating ones and zerosin word 3-10 as specified in the above paragraph. The EAROM retentivity for Block IIA SVs isdesigned and guaranteed for at least 60 days.The memory retentivity is guaranteed for at least 60 days for SVs subsequent to Block IIA.Although the data content of the SVs will be temporarily reduced during the upload process, thetransmission of valid NAV data will be continuous. The data capacity of specific operationalSVs may be reduced to accommodate partial memory failures.DIRECTION OF DATA FLOW FROM SV150 BITSWORD 1MSB FIRST3 SECONDSWORD 2WORD 3WORD 4WORD 571SUBFRAMENO.PAGENO.1N/A131TLM61HOWC P22 BITS73 77 8391121WNt22 BITSPP10BITS23 BITS***C/A OR P ON L2 - 2 BITSURA INDEX - 4 BITSSV HEALTH - 6 BITSP2 MSBs150 BITSIODC - 10 BITS TOTAL1N/A18124 BITS***P16BITS***WORD 8197T GDMSB FIRST3 SECONDSWORD 7151PL2 P DATA FLAG - 1 BITDIRECTION OF DATA FLOW FROM SVWORD 624 BITS***WORD 9211 219241P16 BITS271af2tocP8 BITSWORD 108BITSaf116 BITS8 LSBsPa f0tP22 BITSIODC - 10 BITS TOTAL*** RESERVEDP = 6 PARITY BITSt = 2 NONINFORMATION BEARING BITS USED FOR PARITY COMPUTATION (SEE PARAGRAPH 20.3.5)C = TLM BITS 23 AND 24.
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