Author: AC Coordinator / AIUB/CODE Rapid IGS Orbit Combination - Week 1080 Day: 6 (Sep 23, 2000) Contacts: T.A. Springer (springer@aiub.unibe.ch) H. Bock (bock@aiub.unibe.ch), R. Dach (dach@aiub.unibe.ch) COMBINATION STRATEGY: For a complete description of the combination strategy along with all tables and statistics, please refer to the IGS Final Combination reports posted on CDDIS within 11 days after the end of the GPS week. REMARKS on IGS Rapid Orbit Combination: 1. Broadcast ("brd") orbits/clocks are included in the combination for statistics only. However broadcast clock corrections are used for clock alignment to GPS time and centre clock weight determination purposes. 2. The following IGR 2-day prediction and IGU Ultra rapid 1-day prediction orbits/clocks were excluded from the combination but kept for statistics: -> Centre: IGP IGU 3. Centre clock weights were determined using the following satellites: PRN list | Ref. Centre ----------+------------ All | GFZ (see note below) Note: A chosen reference centre is aligned to the broadcast GPS clocks using all satellites; all other centres are then aligned to that reference centre. The clock weights are computed from the absolute deviation of centre's aligned clock corrections with respect to the unweighted mean. 4. The following clock solutions were excluded from the combination because they were biasing the combined clock solutions. Centre | PRN list -------+--------------- JPL | 28 JPL | ALL 5. The following orbit solutions were excluded from the combination because they were biasing the weighted average. They were still used for statistics computation unless all centres were excluded for the problem satellites in which case they were simply eliminated from the combination and statistics. The following table lists the exclusions: Centre | PRN list -------+--------------- ESA | 23 6. Starting on 04-June-2000 (GPS Week 1065, day 0, MJD 51699) all IGS products, including the IGS combined orbits, are based on the IGS realization of the ITRF97 reference frame (IGS97). For more information see IGSMAILs #2899 and #2904. 7. In the navigation solution there is an additional solution labeled "igc". The orbit of this solution is the same as the orbit of the "igs" solution. The clocks, however, are based on a new clock combination scheme which uses the clock RINEX files as input if available, otherwise SP3 clocks are used. In the near future this "igc" clock solution will replace the "igs" solution but for now it is included for test purposes only. 8. Starting on 29-Nov-1998 (GPS Week 986, day 0; mjd=51146) all IGS clock products reflect the use of the following antenna phase center offsets (satellite fixed reference frame): Block II/IIA: 0.279 0.000 1.023 X, Y, Z in meters Block IIR : 0.000 0.000 0.000 X, Y, Z in meters _______________________________________________________________________________ Table 1: Daily transformation of each centre to the combined IGS orbit and clocks. WRMS - RMS weighted by the centres SP3 header accuracy codes. STA - Number of stations in the daily solutions. Units: meters, mas, ppb, nano-sec, nano-sec/day. Table 1.1080.6 GPS week: 1080 Day: 6 MJD: 51810.0 CENT STA| DX DY DZ RX RY RZ SCL RMS WRMS | TOFT TDRFT RMS --------|------------------------------------------------|--------------------- brd n/a|0.10 0.10 0.20 -0.72 -0.01 9.83 8.7 2.46 2.46 | 0.0 0.7 6.2 cod 113|0.00-0.01-0.01 -0.16 0.02 0.03 -0.2 0.04 0.03 | -4.3 0.8 0.2 esa 42 |0.00 0.00-0.01 -0.05 -0.06 0.16 0.4 0.13 0.08 | 394.9 0.8 0.4 gfz 32 |0.00 0.00 0.01 0.23 0.10 -0.26 -0.2 0.05 0.05 | 1.0 1.9 0.3 igp n/a|0.01 0.00-0.03 1.79 -0.09 -1.86 -0.7 0.51 0.31 | -0.3 1.5 20.3 igu n/a|0.00 0.00-0.02 1.04 0.25 0.64 0.0 0.31 0.35 | -2.5 0.2 8.8 jpl 21 |0.00 0.01 0.02 -0.12 0.01 0.13 0.4 0.06 0.06 | -1.6 3.9 1.2 sio 44 |-.02-0.01 0.00 0.29 -0.24 -0.08 -0.5 0.09 0.08 | 0.0 0.0 0.0 Table 2: Daily fit for each satellite and each centre resulting from weighted average combination. The last column gives the IGS resulting satellite accuracy measures found in the IGS SP3 header. Eclipsing satellites are flagged with and "E" beside the PRN number. "X" stands for excluded from combination but included in IGS orbit. "MEDI" stands for median of the centre's satellite RMS. Units: cm. Table 2.1080.6 GPS week: 1080 Day: 6 MJD: 51810.0 Weighted Average PRN | brd cod esa gfz igp igu jpl sio IGR | ------|--------------------------------------| 1 | 149 3 4 4 32 4 3 7 2 | 2 | 157 5 8 4 23 9 9 7 3 | 3 | 253 2 9 4 54 21 6 11 3 | 4E | 177 4 7 7 15 20 6 11 3 | 5 | 176 4 5 4 20 7 3 5 2 | 6 | 159 3 3 3 14 7 5 8 2 | 7 | 225 4 3 5 49 6 6 9 3 | 8E | 206 4 18 6 123 19 5 6 4 | 9E | 384 3 12 4 47 33 4 7 3 | 10 | 186 3 6 4 14 4 4 8 2 | 11E | 425 5 8 3 11 13 7 14 3 | 13 | 131 3 8 4 36 10 5 11 3 | X15E | 367 4 --- 4 --- 34 5 6 2 | 17E | 131 3 6 3 16 21 4 8 2 | 19 | 277 5 7 5 154 45 8 8 3 | 20 | 227 6 5 5 54 9 11 9 4 | 21 | 128 4 6 3 9 15 4 7 2 | 22 | 310 3 16 5 33 19 4 9 4 | 23 | 347 9 46 9 --- --- 13 11 11 | 24E | 244 7 12 11 27 72 5 10 4 | 25 | 226 2 5 4 25 22 5 8 2 | 26 | 191 4 11 6 20 12 5 9 3 | 27E | 320 3 7 3 62 49 6 8 3 | 28 | 372 3 9 4 9 17 4 10 3 | 29 | 241 9 12 7 75 100 6 10 4 | 30 | 144 3 8 6 11 10 6 8 3 | X31 | 216 6 7 5 61 18 6 --- 3 | ------|--------------------------------------| RMS | 246 4 13 5 51 31 6 9 | WRMS | 246 3 8 5 31 35 6 8 | MEDI | 225 4 8 4 27 18 5 8 | Table 3: Daily Precise Navigation Summary using the corresponding Centre orbit positions and satellite clock corrections at 15 min intervals. Each line gives the daily station RMS w.r.t. the estimated coordinates for the Latitude, Longitude and Height components. CLK - Satellite clocks used. EPO - Number of satellite clock epochs available for that day. Units: centimetres. Table 3.1080.6 GPS week: 1080 Day: 6 MJD: 51810.0 CENT| CLK EPO | BRUS | WILL | ----|----------|----------------|----------------| cod | cod 2564 | 3 3 6 | 4 3 9 | esa | esa 2448 | 2 2 6 | 4 5 12 | gfz | gfz 2546 | 3 3 5 | 2 2 4 | igc | igc 2541 | 1 1 3 | 2 2 4 | igr | igr 2592 | 2 2 4 | 3 2 6 | jpl | jpl 2568 | 3 3 4 | 2 2 4 | Table 4: Earth Orientation Parameters daily summary. Daily Centre ERP, ERP Rates and LOD differences with respect to IGR combined values. Xpole,Xrt: x pole and x pole rate (10**-5") Ypole,Yrt: y pole and y pole rate (10**-5"/day) LOD: Length Of Day (us) AC LOD BIAS: 21-day mean LOD bias with respect to Bulletin A (us) AC LOD BIAS RMS: RMS of AC LOD BIAS (us) FLAG: "u" (used), "x" (excluded), "-" (no submission) for Xpole, Ypole, Xrt, Yrt and LOD A star ("*") beside the AC name indicates that AC LOD values were derived from AC UT1-UTC values. Table 4.1080.6 GPS week: 1080 Day: 6 MJD: 51810.5 AC LOD AC LOD CENT FLAG | Xpole Ypole Xrt Yrt LOD | BIAS BIAS RMS ------------------------------------------------------------------------ cod uuuuu | 3 8 43 -13 -25 | -3 43 esa uuuuu | 10 -2 -41 24 31 | 49 53 gfz uuuuu | -8 -17 -7 -20 1 | 39 65 igu xxxxx | -27 -115 32 -66 50 | -39 60 jpl uuuuu | 14 -6 -7 22 53 | 45 54 sio uuuuu | -27 29 -56 15 -71 | 2 67