IS-GPS-200H (797934), страница 10
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The rate of accuracydegradation is slow over the short-term extended operations interval, such that at the end of thisinterval (approximately 14 days after upload) the US will be able to achieve a positioningaccuracy of 425 meters SEP. The rate of accuracy degradation increases in the long-termextended interval, such that by the 180th day after the last upload, the positioning errors will havegrown to 10 kilometers SEP. During these intervals the URA will continue to provide the properestimate of the user range errors.During short-term and long-term extended operations (approximately day 2 through day 62 afteran upload), the almanac data, UTC parameters and ionospheric data will not be maintainedcurrent and will degrade in accuracy from the time of last upload.6.3.3Block IIA Mode (Block IIR/IIR-M) and Extended Navigation Mode (Block II-F).6.3.3.1 Block IIA Mode (Block IIR/IIR-M).The Block IIR/IIR-M SVs, when operating in the Block IIA mode, will perform similarly to theBlock IIA SVs and have the capability of storing at least 60 days of navigation data, with currentmemory margins, to provide positioning service without contact from the CS for that period(through short-term and long-term extended operations).
(Contractual requirements for theseSVs specify transmission of correct data for only 14 days to support short-term extendedoperations while in IIA mode.) Under normal conditions, the CS will provide daily uploads toeach SV, which will allow the SV to maintain normal operations as defined in paragraph 6.2.3.1and described within this IS.If the CS is unable to upload the SVs (the CS is unavailable or the SV is unable to accept andprocess the upload), each SV will individually transition to short-term extended operations andeventually to long-term extended operations (based on time from each SV’s last upload) asdefined in paragraph 6.2.3.2 and 6.2.3.3, and as further described throughout this IS. As timefrom upload continues through these three operational intervals, the user range error (URE) ofthe SV will increase, causing a positioning service accuracy degradation.53IS-GPS-200H24 Sep 20136.3.3.2 Extended Navigation Mode (Block II-F).The Block II-F SVs shall be capable of being uploaded by the CS with a minimum of 60 days ofdata to support a 60 day positioning service.
Under normal conditions, the CS will provide dailyuploads to each SV, which will allow the SV to maintain normal operations as defined inparagraph 6.2.3.1 and described within this IS.If the CS is unable to upload the SVs (the CS is unavailable or the SV is unable to accept andprocess the upload), each SV shall individually transition to short-term extended operations andeventually to long-term extended operations (based on time from each SV’s last upload) asdefined in paragraph 6.2.3.2 and 6.2.3.3, and as further described throughout this IS.
As timefrom upload continues through these three operational intervals, the user range error (URE) ofthe SV will increase, causing a positioning service accuracy degradation.6.3.4 Extended Navigation Mode (GPS III).The GPS III SVs shall be capable of being uploaded by the CS with a minimum of 60 days ofdata to support a 60 day positioning service. Under normal conditions, the CS will provide dailyuploads to each SV, which will allow the SV to maintain normal operations as defined inparagraph 6.2.3.1 and described within this IS.If the CS is unable to upload the SVs (the CS is unavailable or the SV is unable to accept andprocess the upload), each SV shall individually transition to short-term extended operations andeventually to long-term extended operations (based on time from each SV’s last upload) asdefined in paragraph 6.2.3.2 and 6.2.3.3, and as further described throughout this IS.
As timefrom upload continues through these three operational intervals, the user range error (URE) ofthe SV will increase, causing a positioning service accuracy degradation.6.3.5 Autonomous Navigation Mode.The Block IIR/IIR-M, Block IIF, and directional crosslink-capable GPS III SV in conjunctionwith a sufficient number of other Block IIR/IIR-M, Block IIF or directional crosslink-capableGPS III SVs, operates in an Autonav mode when commanded by the CS. Each Block IIR/IIRM/IIF/directional crosslink-capable GPS III SV in the constellation determines its ownephemeris and clock correction parameters via SV-to-SV ranging, communication of data, andon-board data processing which updates data uploaded by the CS.In the Autonav mode the Block IIR/IIR-M/IIF/directional crosslink-capable GPS III SV willmaintain normal operations as defined in paragraph 6.2.3.1 and as further described within thisIS, and will have a URE of no larger than 6 meters, one sigma for Block IIR/IIR-M.
URE of 6meters, one sigma, is expected to support 16 meter SEP accuracy under a nominal positiondilution of precision. If the CS is unable to upload the SVs, the Block IIR/IIR-M/IIF/directionalcrosslink-capable GPS III SVs will maintain normal operations for period of at least 60 daysafter the last upload.54IS-GPS-200H24 Sep 2013In the Autonav mode, the almanac data, UTC parameters and ionospheric data are still calculatedand maintained current by the CS and uploaded to the SV as required. If the CS is unable toupload the SVs, the almanac data, UTC parameters and ionospheric data will not be maintainedcurrent and will degrade in accuracy from the time of the last upload.6.3.6 Additional PRN Code Sequences.The additional PRN sequences provided in this section are for information only.
The additionalPRN sequences identified in this section are not applicable to GPS SVs. In addition, the currentvalid ranges for GPS PRN signal number for C/A- and P-code are 1-37 and 38-63 as specified inTable 3-Ia and Table 3-Ib. The PRN sequences provided in this section are for other L1/L2signal applications, such as Satellite Based Augmentation System (SBAS) satellite signals. PRNsequences numbered 211-1023 are reserved for internal system use and are therefore notprovided in this section.6.3.6.1 Additional C/A-code PRN sequences.The PRN C/A-code is described in Section 3.2.1.3 and 62 unique C/A-code sequences areassigned by SV ID number in Tables 3-Ia and 3-Ib.
An additional set of 147 C/A-code PRNsequences are selected and assigned with PRN numbers in this section as shown in Table 6-I.Among the 147 additional sequences; PRN numbers 120 through 158 are reserved for SBAS;PRN numbers 64 through 119 and PRN numbers 159 through 210 are reserved for other GlobalNavigation Satellite System (GNSS) applications.Any assignment of a C/A-code PRN number and its code sequence for any additional SV and/orother L1/L2 signal applications, such as SBAS satellite signals, will be selected from thesequences of Table 6-I and will be approved, controlled, and managed by the GPS Directorate.It should be noted that, in Table 6-I, the C/A-code sequences are identified by “G2 Delay” and“Initial G2 Setting” which are not the same as the method used in Table 3-Ia.
The two-tap coderimplementation method referenced and used in Table 3-Ia is not used in Table 6-I due to itslimitation in generating C/A-code sequences. The “G2 Delay” specified in Table 6-I may beaccomplished by using the “Initial G2 Setting” as the initialization vector for the G2 shift registerof Figure 3-9. For higher order PRNs (>37) the two-tap output mask is not used and the outputof the G2 register becomes tap -10 (10th tap) which is labeled as the "output" in Figure 3-9.6.3.6.2 Additional P-Code PRN sequences.The PRN P-code set of 63 mutually exclusive sequences are described in Section 3.2.1.1, andassignment of these code segments by SV ID number is given in Tables 3-Ia and 3-Ib. Anadditional set of 147 P-code PRN sequences are described in this section.
Among the 147additional sequences PRN numbers 120 through 210 are reserved for other future GNSSapplications. The P-code PRN numbers and their code sequences defined in Table 6-I are not forgeneral use and will be approved, controlled, and managed by the GPS Directorate.55IS-GPS-200H24 Sep 20136.3.6.2.1 Additional P-code Generation.The generation of 37 mutually exclusive P-code PRN sequences are described in Section 3.3.2.2.An additional set of 147 P-code PRN sequences are generated by circularly shifting each of theoriginal 37 sequences (over one week) by an amount corresponding to 1, 2, 3, 4, or 5 days. Theadditional sequences are therefore time shifted (i.e.
offset) versions of the original 37 sequences.These offset P-code PRN sequences, Pi(t), are described as follows:Pi(t) = Pi-37x(t + xT),where i is an integer from 64 to 210, x is an integer portion of (i-1)/37, and T is defined to equal24 hours.As an example, P-code sequence for PRN 91 would be the same sequence as PRN 17 shifted 48hours into a week (i.e. 1st chip of PRN 91 at beginning of week is the same chip for PRN 17 at 48hours after beginning of week). The complete list of the additional P-code PRN assignments isshown in Table 6-I. Any assignment of a P-code PRN number and its code sequence for anyadditional SV and/or other L1/L2 signal applications will be selected from the sequences ofTable 6-I.As an example, P-code sequence for PRN 38 would be the same sequence as PRN 1 shifted 24hours into a week (i.e.
1st chip of PRN 38 at beginning of week is the same chip for PRN 1 at 24hours after beginning of week). The complete list of the additional P-code PRN assignments isshown in Table 6-I. Any assignment of a P-code PRN number and its code sequence for anyadditional SV and/or other L1/L2 signal applications will be selected from the sequences ofTable 6-I.56IS-GPS-200H24 Sep 2013Table 6-IAdditional C/A-/P-Code Phase Assignments (sheet 1 of 5)C/APRNSignalNo.6465666768697071727374757677787980818283848586878889909192939495*G2 Delay(Chips)72969578080178873234320327389407525405221761260326955653699422188438959539879677586153792814446PInitial G2Setting(Octal)*First 10 Chips(Octal)**X2 Delay(Chips)P-code RelativeAdvance(Hours) **First 12 Chips(Octal)02541602116011141342002515231046040414451054007202620077052114001010144103650270026306130277156216741113124506060136025615501234152301750617066304351752025407311373033207231705151517001256037707670336141215071514116415000215010306640532117116411521022705432728293031323334353637123456789101112131415161718192021P27(t+24)P28(t+24)P29(t+24)P30(t+24)P31(t+24)P32(t+24)P33(t+24)P34(t+24)P35(t+24)P36(t+24)P37(t+24)P1(t+48)P2(t+48)P3(t+48)P4(t+48)P5(t+48)P6(t+48)P7(t+48)P8(t+48)P9(t+48)P10(t+48)P11(t+48)P12(t+48)P13(t-48)P14(t+48)P15(t+48)P16(t+48)P17(t+48)P18(t+48)P19(t+48)P20(t+48)P21(t+48)51120667211152664711416622515306476121525247573625753054360435205472441720253230573645752054320437205572445740052220333237773555In the octal notation for the first 10 chips of the C/A-code or the initial settings as shown in this table, thefirst digit (1/0) represents a "1" or “0”, respectively, for the first chip and the last three digits are theconventional octal representation of the remaining 9 chips.
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