IGS Analysis Center Workshop - IGS - NASA

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problem satellites, DRAO, one of the most reliable station in the whole IGS network developedhardware problems, resulting in data loss on January 28,29 as well as shorter observation periodsfor January 24 and 27. For these reasons the DRAO data for Jan 24,28 and 29 was not used in theEMR orbit computation. All the available data sets (including the January 24 and 27 data atDRAO) were used in this baseline test. It should also be noted that two stations ALGO and YELLwere held fixed in all the orbit computations along with additional 10 globally distributed stations.So the YELL-ALGO baseline results cannot be considered representative of achievablerepeatability.* Baseline results are summarized in Table 4.1. As one can see the combined orbits compare quitewell with the best individual orbits. It was not expected that the EMR orbits would perform betterthan the combined orbits, since the baseline software used is different and independent from theEMR orbit generation. This maybe due to the fact that the EMR orbits favor N.A. and Canada inparticular by including data from six Canadian stations. The situation maybe completely differentin other parts of the globe. The North baseline component is the most stable, the formal errorsranged from 1.5mm to 2mm, and thus is well suited to check orientation (EOP) errors at or belowthe 0.5mas (2.5ppb) level. From Table 4.1 it is apparent that the orientation for the combined orbitsand EMR is at the 4-5mm level which corresponds to about 0.3mas at 3000km. The lengthrepeatability is at the 3- 4ppb level for both combined and the best orbits. The formal length sigmasvaried between 1 ppb for YELL-ALGO and about 2ppb for the remaining two baselines. Asmentioned before, YELL-ALGO repeatability is not representative of achievable precision, butDRAO-ALGO and STJO-ALGO sigmas are meaningful. Removing the two most problematicdays (January 17 and 27) results in significant scale improvements for the longest baseline(DRAO-ALGO), down to about 2ppb. Also listed in Table 4.1 are the height sigmas and they arealso lower for the combined and regional orbits. Finally, the combined orbits of the fiist type (IGS)appears to be slightly better here, at least as viewed from North America. This may be due toproblems on Jan. 22 mentioned in Section 3 and also due to the fact that IGS orbits employs the L1norm which is supposed to be less affected by marginal and outlier orbits..51
Table 4.1 N.A. Baseline Repeatability Sigmas (Jan 17-30, 1993)North(mm)East(mm)up(mm)Length(Ppb)#STJO-ALGO(1931km)IGSCOMCODEMRGFZ5.06.35,33.97.29.69.911.67.612.611.212.912$89.813.14,74.65.83.76.21414141414YELL-ALGO (2913km)IGSCOMCODEMRGFZ6.78.18.16$610.410,79.810.58.411.321,425.623.213.323.72.52.63.01.93.11414141414DRAO-ALGO (3075km)IGSCOMCODEMRGFZ5.04.37.54.16.712.916.714.313.821.314.818,013.216.224.13.64.55.04.65.712121212124.2 European baselinesThesecondpartof thetest concentrates ontheorbitsabove Europeandinvolves thesitesMADR,KOSG, TROM and WETT. Stations MADR, TROM and WETT were held fixed in all orbitreprocessing, The same orbits as for the North American baseline test were used. The Bemesesoftware version 3.4 was used and therefore the COD orbits might be favored due to using the samesoftware which was used in creating the orbits. The same strategy as outlined above was used, i.e.the only differences between the solutions for a given day were the orbits used. On January 18,1993 the TROM data was missing and could not be used in the KOSG-TROM baseline processing.Results of all the baseline processing are summarized in Table 4.2. Again the combined orbitscompare quite well with the best orbits. However the COD orbit performs better than the combinedorbits. This might be caused by the fact that COD orbits favor Europe.Tables 4.1 and 4.2 show that viewed on a regional scale clear differences between the orbits of theindividual Processing Centers exist. The combined orbits are performing well in both regions.Surprisingly the GFZ orbits which looked very good in the orbit combinations of Section 2 and 3did not perform as well as one would’expect.52
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●INTERNATIONAL ASSOCIATION OF GEO
Page 3 and 4: TABLE OF CONTENTS.FINAL AGENDA . .
Page 5 and 6: 13:30 NGS14:00 S1014:30 EMR15:00 CO
Page 7 and 8: LIST OF PARTICIPANTS:Prof. Gerhard
Page 10 and 11: Table 1. Current IGS Analysis Cente
Page 12 and 13: The first field identifies the reco
Page 14 and 15: Summary InformationThe third produc
Page 16 and 17: From Figure 1 we find that there ar
Page 18: to define a reference clock in thei
Page 22 and 23: SESSION 2(IGS orbit products)
Page 24 and 25: 1. introductionThe main objectives
Page 26 and 27: ecause of the above averaging. This
Page 28 and 29: RMS per center (m)o 0 0 0 0 0 oA0Iv
Page 30: Scale (ppb)I I I I I 11+-b~ul0Amo&I
Page 33 and 34: and NGS. Note that the day to day v
Page 35 and 36: Rotation around X-axis (mas)1&0 0o
Page 37 and 38: discussed in Section 3 are here see
Page 39 and 40: -----------------------------------
Page 41 and 42: Residuals in Meters1 1 1 1 1 1 1=%m
Page 43 and 44: Residuals inMeters11111cnficJJw-o A
Page 45 and 46: I I I—Residuals in Meters..—.
Page 47 and 48: 1111ResidualsMeters,—{44
Page 49 and 50: Residuals in MetersI I I II I I IIc
Page 51 and 52: Rms in MetersI 1 ! I 1 10 n0 a0n.ff
Page 53: IGS- and the COM-sets, but that the
Page 57 and 58: ..Figure 5.1:Clock solutions for FA
Page 59 and 60: specifically the preanalysis can be
Page 61 and 62: discussion, a question as to whethe
Page 63 and 64: SUMMARY OF SESSION 3This Session be
Page 65 and 66: IGS POSITION PAPER, IGS ANALYSIS CE
Page 67 and 68: and Earth orientation parameters (E
Page 69 and 70: LbPIERS and IGSCentral Bureausand D
Page 71 and 72: @ IGS will develop instructions, an
Page 73: 2.2 Analysis Center System DesignFi
Page 76 and 77: applied to the solution in order to
Page 78 and 79: ..standard deviations. This is conv
Page 80 and 81: known, the two solutions will be ad
Page 82 and 83: errors, and can therefore be used a
Page 84 and 85: International Terrestrial Reference
Page 86 and 87: Thus, there is the potential of fee
Page 88 and 89: 90” 100” 110” 120” 130” 1
Page 91 and 92: adiation parameters for each satell
Page 93 and 94: Bock, Y., R.I. Abbot, C.C. Counselm
Page 95 and 96: SUMMARY OF SESSION 4This session st
Page 97 and 98: INTERNATIONAL EARTH ROTATION SERVIC
Page 99 and 100: x- differences with IERS0.001”I I
Page 101 and 102: SUMMARY OF SESSION 5In the last ses
Page 103 and 104: 1) I(X3 PROCESSING/REPORTS/FORMATSS
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IGS should foster and encourage reg
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..INTERNATIONAL GPS SERVICE FORGEOD
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ortL.s.4
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. Ruth Neilan16S Central BureauJet
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ON1T.>● Jim ZumbergeJet Propulsio
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PROPOSED ORGANIZATION OF THE INTERN
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