Subject: [IGSREPORT-3056] Wk 0873 COD Analysis Report
From: M. Rothacher
Date: Fri, 11 Oct 1996 5:47:05 PDT

******************************************************************************
IGS Electronic Report    Fri Oct 11  5:47:05 PDT 1996      Message Number 3056
******************************************************************************

Author: M. Rothacher
Subject: Wk 0873 COD Analysis Report

*******************************************************************************
CODE ANALYSIS REPORT GPS WEEK 0873 (DAYS 273-279, DATES 29-09-96 - 05-10-96)
*******************************************************************************
Submitted by: Astronomical Institute, University of Berne, Switzerland
              Products available through anonymous ftp using:
              ftp ubeclu.unibe.ch  -or-  ftp 130.92.6.11
              after login: cd aiub$ftp; cd code
 
FILES SENT TO CDDIS:
-----------------------------------------------------------------------------
COD08737.SUM           THIS TEXT FILE
COD08737.ERP           EARTH ROTATION PARAMETERS FOR GPS WEEK 0873
COD08737.SNX           MEAN GPS COORDINATE SOLUTION FOR GPS WEEK 0873
COD0873N.EPH           GPS EPHEMERIDES FOR GPS WEEK 0873, SP3 FORMAT (N=0..6)
-----------------------------------------------------------------------------
 
THREE DAY SOLUTION STATISTICS:
------------------------------------------------------
MIDDLE DAY  FILES  OBSERVATIONS   PARAMETERS  RMS (MM)
------------------------------------------------------
273         265    361515          8897        3.1
274         269    367478          9076        3.1
275         280    386776          9770        3.0
276         278    392511         10073        3.0
277         271    386826          9732        2.9
278         261    377028          9163        2.9
279         255    368214          8631        2.9
------------------------------------------------------
SINEX WEEKLY STATISTIC:
------------------------------------------------------
278         798   1122240         27127        3.0
------------------------------------------------------
 
 REFERENCE CLOCKS:
 ---------------------------------------------------------
 DAYS: 273-279  ALGO used as reference clock
 ---------------------------------------------------------
 
 ORBIT REPEATABILITY (CM) FOR PRN: (-- = NOT INCLUDED)
 ------------------------------------------------------------------------------
      1  2  3  4  5  6  7  9 10 14 15 16 17 18 19 21 22 23 24 25 26 27 28 29 30 31
 ------------------------------------------------------------------------------
 273  5  4  3  6  5  5  4  6  4139  4 12  5  4 36  5  2 14  4  5  9  6  4855 --  5
 274  4  3  3  5  4  4  3  6  5 96  3 11  6  3 34  4  4  9  4  5  8  4  4999 --  6
 275  5  4  3  5  3  4  2  7  7178  3 10  5 -- 30  5  3 11  3  5  6  5  4999 98  5
 276  5  5  4  5  5  5  4  9  6150  4 12  5 45 58  5  4 12  4  8  7  7  5974 65  6
 277  5  5  4  4  4  5  5  8  5105  4 18  4 53 87  5  3 10  3  9  6  7  5681 78  5
 278  4  5  4  5  5  4  5  9  4114  4 24  6 79 74  3  3  8  2  9  5  8  5577 48  6
 279  5  6  6  6  6  6  6  9  6117  4 72  7 80 51  6  4 14  4  7  9  8  6541 77  7
 ------------------------------------------------------------------------------
 ALL  5  5  4  5  5  5  4  8  5131  4 31  5 66 57  5  3 11  4  7  7  7  5896 75  6
 ------------------------------------------------------------------------------

  WEEKLY COORDINATE COMPARISON OF 1-DAY (G1) SOLUTIONS  
 -------------------------------------------------------------------------------
 TOTAL NUMBER OF STATIONS:    82
 -------------------------------------------------------------------------------
                       WEEKDAY  RESIDUAL RMS IN MM
 STATION        #DAYS  0123456     N     E     U
 -------------------------------------------------------------------------------
 ALBH 40129M003     7  PPPPPPP     2     5     7
 ALGO 40104M002     7  PPPPPPP     -     -     -   FIXED
 ANKR 20805M002     4   PPPP       3    10     5
 AREQ 42202M005B    7  PPPPPPP     4    14    11
 ASC1               7  PPPPPPP     6     8    10
 AUCK 50209M001     7  PPPPPPP     3    11    15
 BAHR 249010M02     6   PPPPPP     4     8    10
 BOGT 41901M001     4  PPPP        8    35    18
 BOR1 12205M002     7  PPPPPPP     3     3     6
 BRAZ 41606M001     7  PPPPPPP     4    12    15
 BRMU 42501S004     7  PPPPPPP     2     5    10
 BRUS 13101M004     7  PPPPPPP     1     3     6
 CAS1 66011M001     4  PPPP        8     5    10
 CHAT 50207M001     7  PPPPPPP     4    12    21
 CHUR               7  PPPPPPP     2     4     6
 COCO               3   PPP        2     6     7
 CRO1 43201M001     7  PPPPPPP     5     6    16
 DAV1 66010M001     6  PPPPP P    10    11     8
 DRAO 40105M002     7  PPPPPPP     1     2     9
 EISL 41703M003     7  PPPPPPP     4    12    20
 FAIR 40408M001B    7  PPPPPPP     -     -     -   FIXED
 FLIN               7  PPPPPPP     2     5     9
 FORT 41602M001     5  PPPPP       5     9     7
 GODE 40451M123     7  PPPPPPP     3     6    13
 GOLD 40405S031     7  PPPPPPP     -     -     -   FIXED
 GOPE 11502M002     7  PPPPPPP     3     3     7
 GRAS 10002M006B    3      PPP     3     3     7
 GRAZ 11001M002B    7  PPPPPPP     2     3     9
 GUAM 50501M002     7  PPPPPPP    12    46    58
 HART 30302M002     6  P PPPPP     -     -     -   FIXED
 HERS 13212M007     7  PPPPPPP     3     7    24
 HOB2 50116M004     3     PP P     4     5    12
 IRKT 12313M001     7  PPPPPPP     7     8    11
 JOZE 12204M001     7  PPPPPPP     3     4     6
 KERG 91201M002     7  PPPPPPP     2     7    10
 KIT3 12334M001     7  PPPPPPP     5     8     9
 KOKB 40424M004     7  PPPPPPP     -     -     -   FIXED
 KOSG 13504M003     7  PPPPPPP     -     -     -   FIXED
 KOUR 97301M210     6  PPPPP P     4    17    23
 KWJ1               7  PPPPPPP     5    14    20
 LAMA 12209M001     7  PPPPPPP     3     5     9
 LHAS 21613M001     6   PPPPPP     4    11    11
 LPGS 41510M001     7  PPPPPPP     7    13    13
 MAC1 50135M001     3  PPP         4    11     3
 MADR 13407S012B    4  PPPP        3     5    14
 MADR 13407S012C    1        P     -     -     -
 MALI 33201M001     7  PPPPPPP     3    12     9
 MASP 31303M002C    7  PPPPPPP     2     5    16
 MATE 12734M008B    7  PPPPPPP     3     4    12
 MCM4 66001M003     7  PPPPPPP     7    11    12
 MDO1 40442M012     7  PPPPPPP     3     5     5
 MDVO 12309M002     6  PP PPPP     7     6    15
 METS 10503S011     6  PPP PPP     2     3     5
 NLIB 40465M001     7  PPPPPPP     1     7     5
 NYAL 10317M001     3     P PP     3     3     8
 OHIG 66008M001     7  PPPPPPP    10    10    12
 ONSA 10402M004     6  PPPPPP      2     3     6
 PAMA 92201M003     6  PPPPP P     6    21    38
 PERT 50133M001     7  PPPPPPP     3     4     5
 PIE1 40456M001     7  PPPPPPP     2     6     7
 POTS 14106M003     7  PPPPPPP     2     2     6
 QUIN 40433M004     7  PPPPPPP     2     4     5
 RCM5 40499S018B    7  PPPPPPP     3     9     9
 REYK 10202M001     7  PPPPPPP     4     6     8
 SANT 41705M003B    7  PPPPPPP     5    13    10
 SHAO 21605M002     6  PPPPPP      6    10    10
 STJO 40101M001B    7  PPPPPPP     2     4    10
 TAEJ 23902M001     5  P  PPPP     3    16    11
 TAIW 23601M001     7  PPPPPPP     8    14    16
 THU1 43001M001     6   PPPPPP     2     4    12
 TIDB 50103M108B    7  PPPPPPP     5     7    16
 TROM 10302M003     5    PPPPP     -     -     -   FIXED
 TSKB 21730S005     7  PPPPPPP     5    14     7
 UPAD 12750M002     6   PPPPPP     2     2     8
 USUD 21729S007     7  PPPPPPP     4    15     7
 WES2 40440S020     7  PPPPPPP     1     4     8
 WHIT               7  PPPPPPP     3     2     7
 WTZR 14201M010     7  PPPPPPP     -     -     -   FIXED
 WUHN 21602M001     7  PPPPPPP     6    11    12
 YAR1 50107M004     7  PPPPPPP     -     -     -   FIXED
 YELL 40127M003B    7  PPPPPPP     -     -     -   FIXED
 ZIMM 14001M004     7  PPPPPPP     2     3     9
 -------------------------------------------------------------------------------
 # Coordinate Estimates:   450     4    10    13

Processing changes (last changes week 0860, see IGSREPORT.2807)
===============================================================

Starting with GPS week 0873 (day 273, 29-SEP-1996) we have made a 
couple of changes to our routine processing.
The changes are twofold: we have started to use a different orbit model 
which improves our orbit quality significantly and we have implemented 
some of the new IERS 1996 Conventions.

The radiation pressure (RPR) model is enhanced with 3 additional 
parameters of the Extended CODE Orbit Model. So instead of the "normal" 
2 parameters D0 and Y0, the direct solar radiation scale parameter and the so
called Y-bias, we added a term which is perpendicular to these two parameters,
called X0. For this "X" component we also estimate once per revolution
terms. So the forces in this "X" direction are modelled as follows:
  X = X0 + Xc cos(u) + Xs sin(u)    (u = argument of latitude)

Where X0 is the constant term and Xc and Xs are the cosine and sine amplitudes
of the once per revolution terms respectively. The D and Y directions are 
modelled with a constant term (D0 and Y0) only. The estimation of small
velocity changes every 12 hours in the Radial- and Along-track directions
(pseudo stochastic pulses) has not been changed.

The IERS 1996 Conventions which we have implemented are:

 - Use of the DE200 planetary ephemerides (should be DE403 but that will come)
 - Geopotential (using Elastic Earth):
   - Step 1 corrections 
   - Step 2 corrections using the 7 largest terms
   - Solid Earth Pole Tide
   - Ocean Tides upto N=M=4 and a "cut-off" value of 0.05 cm.
     We use the values from the OTIDES.CSRC file of the Univ. Texas.

We have studied the influence of these changes very carefully and found
that all our estimates improve except our LOD estimates. Our LOD bias
changes significantly and the noise of the estimates seems to increase
(which is also indicated by the increased formal error). The table below
summarizes these differences (based on days 217 to 272, 1996)

     ------------------------------------
               LOD BIAS  LOD RMS (us/day)
     ------------------------------------
     OLD MODEL    0.023    0.034
     NEW MODEL   -0.022    0.045
     ------------------------------------

Most significant is the improvement of our GPS satellite orbit estimates. 
We have checked the orbit quality by using long arc analysis, 
SLR observed-computed residuals and by studying the orbit discrepancies at 
the day boundaries.
In the long arc (7 days) analysis the new model is on average 10 mm better
then the old model. The results of the SLR analysis indicate an improvement
of the orbit quality from the 50-60 mm level to the 30-40 mm level. 
For the check at the day boundary we compare the orbital elements 
at the end of the (middle) day with the orbital elements at the start of 
the next (middle) day solution. Graphically this can be explained as 
follows:

 day:   1     2     3     4
      -----+-----+-----        first  3-day arc
            -----+-----+-----  second 3-day arc
                 ^
                 |__________ check point

The results of this check, which we believe to be a rather pessimistic 
estimate since it is taken at the day boundary, are summarized below
(based on days 217 to 279, 1996).

   --------------------------------------------------------------------
             #EPOCH  RAD    ALO    OUT    POS (all values in mm)
   --------------------------------------------------------------------
   non-eclipsing satellites:
   OLD MODEL  1128    36     82     89    126  
   NEW MODEL  1135    22     42     33     58  
   --------------------------------------------------------------------
   eclipsing satellites:
   OLD MODEL   301    96    144    127    215  
   NEW MODEL   364    22     42     35     59  
   --------------------------------------------------------------------
               
Shown are how many satellite epochs were used, and the rms of the radial, 
along, out of plane and 3D-position differences over all epochs.
Differences in the number of epochs between the OLD and NEW model are caused 
by the fact that if the 3D-position difference at the check point was larger 
then 400 mm the satellite was considered as an outlier.

REMARKS:  Day 273: PRN 30: Observed but not used.

          Day 274: PRN 14: Modeling problems: new state vector
                   set up at 00:00 UTC for all 3-day solutions. 
          Day 274: PRN 30: Observed but not used.

          Day 275: PRN 29: Modeling problems: new state vector
                   set up at 00:00 UTC for all 3-day solutions. 
          Day 275: PRN 18: Excluded due to manoeuvre.

          Day 276: PRNs 14 and 29: Modeling problems: new state vector
                   set up at 00:00 UTC for all 3-day solutions. 

          Day 278: PRN 19: Modeling problems: new state vector
                   set up at 00:00 UTC for all 3-day solutions. 

          Day 279: PRNs 16 and 18: Modeling problems: new state vector
                   set up at 00:00 UTC for all 3-day solutions. 

global: ALBH ALGO ANKR AREQ ASC1 AUCK BOR1 BOGT BRAZ BRMU BRUS CAS1 CHAT CRO1
global: DAV1 DRAO EISL FAIR FORT GODE GOLD GOPE GRAS GRAZ GUAM HART HERS HOB2
global: IISC IRKT JOZE KERG KIT3 KOKB KOSG KOUR KWJ1 LAMA LHAS LPGS MAC1 MADR
global: MALI MAS1 MATE MCM4 MDO1 MDVO METS NYAL NLIB OHIG ONSA PAMA PERT PIE1
global: POL2 POTS QUIN RCM5 REYK SANT SEY1 SHAO STJO TAIW TIDB TAEJ THU1 TROM
global: TSKB UPAD USUD WTZR YAR1 YELL WES2 ZIMM COCO CHUR FLIN WHIT BAHR WUHN

[Mailed From: MARKUS ROTHACHER <[email-masked]>]