[IGSREPORT-456] EMR Analysis Report (week 710)

[Jan]

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IGS Electronic Report     26-AUG-1993 08:58:05       Message Number 456
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From: Jan Kouba 
Subj: EMR Analysis Report (week 710)
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					          (Aug 15 - Aug 21,93)

      Our analysis utilizes the JPL GIPSY/OASIS II (UNIX) software system 
and data from all (up to 7) Canadian stations augmented by up to 12, globally 
distributed, core stations (see Table 1 for the list of stations).  

      This effort is a part of a joint pilot project  called 
"Active Control System" and involves the Geodetic Survey Division  (GSD),
SMRSS; the Geophysics Division and Pacific Geoscience Centre of the
Geological Survey of Canada, all three institutions are part of the  
Department of Energy, Mines & Resources (EMR).

      Table 1 : Station Summary (also indicated are day no. for which a 
particular station is not included in the daily solution, either due to
being down or data being late). 
                               
   STATION            IGS code       MISSING DAY NO. 1993
Albert Head, CAN       ALBH            
Algonquin, CAN         ALGO*             
Fairbanks              FAIR*                              
Goldstone              GOLD*             
Hartebeesthoek         HART*             233
Holberg,CAN            HOLB               
Kokee Park             KOKB              
Madrid                 MADR*             
McMurdo                MCMU*             233 
Pamatai                PAMA              227 to 233 
Penticton, CAN         DRAO             
Santiago               SANT*             232 
St. Johns, CAN         STJO             
Canbera                TIDB*             
Tromsoe                TROM*             
Wettzell               WETT*            
Yarragadee             YAR1*                    
Yellowknife, CAN       YELL*            
* indicates constrained stations, remaining are solved for (50m apriori sig.)

SOLUTION CHARACTERISTICS

Reference frame and orientation:
      Nominally ITRF91, at epoch 1992.5 is realized by constraining up to 12 
of the above stations at the IGS coordinates (see IGS message #90). 
Orientation is realized through the above coordinates and, once a week, 
the fixed DUT1 values from the current NEOS/IERS (Bull. A).

Constants and models: 
- no change, see the IGS mess. #101 for details.

Estimation strategies:
- no change, see the IGS mess. #101 for details - , except for the estimation
  of DUT1, stochastic orbit modeling, new weighting of L3,P3,
  see IGS mess. #130.

      ALGO was used as time reference.                           
      Aposteriori variance factors typically are between 0.5 and 1.0 (noise 
about 3mm and 200mm for phase and smoothed pseudorange observations, resp.). 


PRODUCTS GENERATED:
The following products are generated and uploaded into CDDIS @ NASA/GSFC
   EMR07100-6.EPH       GPS ephem. files for days 0-6, week # 710 in sp3 format 
   EMR07107.ERP        	pole x,y and DUT1 solutions for week # 710
   EMR07107.SUM		name of this text summary file 


REMARKS on EMR's products:
1. ALGO hydrogen maser used as a time reference. In the sp3 EPH file sat.
   epochs with no reference (e.g. ALGO not observing a satellite) have a value 
   of 99999. microseconds. 
   ALGO clock error & drift were about -250 ns (49214) & -25 ns/day w.r.t.
   GPS time.  
2. Starting with the week #709 we are including orbit sigma estimates in 
   the sp3 header format (lines 8 to 12), conforming to the sp3 convention 
   (see NOAA Technical Report NOS 133 NGS 46),  i.e. the binary exponent 
   of sigma in mm. For the orbits passing our quality analysis we are 
   assigning 9, which, in the sp3 convention, translates into 2**9=512mm 
   sigmas. For  errors larger than 2.5 we are assigning sigmas of 
   abs(error)/4 , again expressed by the binary exponent. In this way we 
   feel that problematic satellites indentification is easier and that 
   a range of errors formerly reported in our summary files can be recovered 
   as well.
3. AS was on for PRN 18 on Aug 20 (day232), all observations for PRN 18 
   were downweighted, no DUT1 estimation on this day.
4. PRN31 data  was removed from the orbit processing on Aug 20 (day232) due to 
   maintainance/orbit repositioning, the PRN31 orbit in the eph file for this
   day is  predicted and asigned accuracy code of 11.