Subject: [IGSMAIL-0656] GFZ ACquestionnaire
From: G.Gendt, G. Dick
Date: Thu, 30 Jun 1994 23:00:48 PDT

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IGS Electronic Mail      Thu Jun 30 23:00:48 PDT 1994      Message Number 0656
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Author: G.Gendt, G. Dick
Subject: GFZ ACquestionnaire

Subject: GFZ AC Questionnaire

Dear Colleagues,

The following AC questionnaire was submitted to IGS CB.

Best regards
                    Gerd Gendt

------------------------------------------------------------------------------
GeoForschungsZentrum Potsdam

                INTERNATIONAL GPS SERVICE FOR GEODYNAMICS
                     Analysis Centre Questionnaire

 ==============================================================================
| ANALYSIS CENTRE   | GFZ,  GeoForschungsZentrum Potsdam                       |
|                   |       Dept. 1                                            |
|                   |       D-14473 Potsdam                                    |
|                   |                                                          |
|------------------------------------------------------------------------------|
| CONTACT PERSON(S) | Christoph Reigber                                        |
|                   |               ([email-masked]),ph.(0331) 2881100 |
|                   | Gerd Gendt    ([email-masked]),   ph.(0331) 2881114 |
|                   | Galina Dick   ([email-masked]),   ph.(0331) 2881185 |
|------------------------------------------------------------------------------|
| SOFTWARE USED     | EPOS.P.V2 developed at GFZ                               |
| -----------------------------------------------------------------------------|
| IGS PRODUCTS      | GFZwwww0-6.sp3 GPS ephemeris/clock files in 7 daily files|
| GENERATED FOR     |              at 15 min intervals in sp3 format,          |
| GPS WEEK 'wwww'   |              including accuracy codes, which are assigned|
|                   |              25 cm nominally, and adjusted upward when   |
|                   |              indicated by orbit corrections              |
|                   | GFZwwww7.erp   ERP (pole, LOD) solutions                 |
|                   | GFZwwww7.sum   Processing summary.                       |
|------------------------------------------------------------------------------|
| PREPARATION DATE  |  June 29, 1994                                           |
 ==============================================================================

 --------------------------------------------------------------------------- 
|                     MEASUREMENT MODELS                                    |
|---------------------------------------------------------------------------|
| Preprocessing    |  no preprocessing performed                            | 
|---------------------------------------------------------------------------| 
| Basic Observable | carrier phases ( pseudo-ranges normally used for       |
|                  |                  ambiguity-fixing only)                |
|                  |--------------------------------------------------------|
|                  | elevation angle cutoff : 20 degrees                    |
|                  | sampling rate          :  6 minutes                    |
|                  | no weighting                                           |
|---------------------------------------------------------------------------| 
| Modelled         | undifferenced, corrected for ionosphere (L3, P3),      |
| observable       | CA pseudoranges not corrected for CA-P1 biases         |
|---------------------------------------------------------------------------| 
| RHC phase        | not applied                                            |
| rotation corr.   |                                                        |
|---------------------------------------------------------------------------|
| Ground antenna   | not applied                                            |
| phase centre cal.|                                                        |
|---------------------------------------------------------------------------|
| Troposphere      | Zenith delay: adjusted in 4 hour- intervals            |
|                  |--------------------------------------------------------| 
|                  | Mapping function: Saastamoinen                         |
|---------------------------------------------------------------------------| 
| Ionosphere       | not modelled (ionospheric effects accounted for by     |
|                  | dual frequency observations, see above)                |
|---------------------------------------------------------------------------| 
| Plate motions    | ITRF 92 station velocities fixed  (see IGSMAIL#421)    |
|---------------------------------------------------------------------------| 
| Tidal            | Solid earth tidal displacement: Wahr model             | 
| displacements    |--------------------------------------------------------| 
|                  | Pole tide:   applied                                   |
|                  |--------------------------------------------------------| 
|                  | Ocean loading: Scherneck (1991) model                  |
|---------------------------------------------------------------------------|
| Atmospheric load.| not applied                                            |
|---------------------------------------------------------------------------| 
| Satellite center | Block I      x,y & z : (0.2100 m , 0 , 0.8540 m)       |
| of mass          |--------------------------------------------------------|
| correction       | Block II/IIA x,y & z : (0.2794 m , 0 , 1.0229 m)       |
|---------------------------------------------------------------------------| 
| Satellite phase  | not applied                                            |
| centre calibrat. |                                                        |
|---------------------------------------------------------------------------| 
| Satellite clock  | relativistic corrections applied                       |
| corrections      |                                                        |
 ---------------------------------------------------------------------------

 --------------------------------------------------------------------------- 
|                           ORBIT MODELS                                    |
|---------------------------------------------------------------------------| 
| Geopotential     | JGM2 degree and order 8                                |
|                  |             (C21, S21 modelled acc. to polar motion )  |
|                  |--------------------------------------------------------| 
|                  | GM=398600.4418 km**3/sec**2                            |
|                  |--------------------------------------------------------| 
|                  | AE = 6378.137 km                                       |
|---------------------------------------------------------------------------| 
| Third-body       | Sun, Moon , Venus, Jupiter (regarded as point masses)  |
|                  |--------------------------------------------------------| 
|                  | ephemeris: JPL DE200                                   |
|                  |--------------------------------------------------------| 
|                  | Earth-Moon mass ratio = 81.300587                      |
|                  |--------------------------------------------------------| 
|                  | Sun-Earth  mass ratio = 332946.045                     |
|---------------------------------------------------------------------------| 
| Solar radiation  | direct radiation: T10 and T20 models for               |
| pressure         |                   Block I and II satellites, resp.     |
|                  |                                                        |
|                  | masses:                                                |
|                  | 972.90 kg for PRN 1 4 5 6 7 9 22-32                    |
|                  | 878.15 kg for PRN 2                                    |
|                  | 521.81 kg for PRN 3                                    |
|                  | 440.89 kg for PRN 8                                    |
|                  | 522.16 kg for PRN 11                                   |
|                  | 519.82 kg for PRN 12                                   |
|                  | 520.42 kg for PRN 13                                   |
|                  | 887.36 kg for PRN 14                                   |
|                  | 885.90 kg for PRN 15                                   |
|                  | 883.23 kg for PRN 16 17 18 19                          |
|                  | 887.36 kg for PRN 20                                   |
|                  | 883.90 kg for PRN 21                                   |
|                  |--------------------------------------------------------| 
|                  | direct-scale and y-radiation biases: taken into account|
|                  |--------------------------------------------------------| 
|                  | Earth shadow model includes: penumbra                  |
|                  |--------------------------------------------------------| 
|                  | new GPS satellite attitude model: NOT APPLIED          |
|---------------------------------------------------------------------------| 
| Tidal forces     | solid earth tides: frequency dependent Love's          |
|                  | numbers by Wahr-model ( nominal k2= 0.300 )            |
|                  |--------------------------------------------------------| 
|                  | Ocean tides: Schwiderski-model                         |
|---------------------------------------------------------------------------| 
| Relativity       | not applied                                            |
|---------------------------------------------------------------------------| 
| Numerical        | single step integrator from Everhart                   | 
| integration      | with direct integration of second-order equations      |
| of orbit         |--------------------------------------------------------|
|                  | integration step: variable, automatically controlled   |
|                  |--------------------------------------------------------| 
|                  | arc length: 32 hours                                   |
|---------------------------------------------------------------------------| 
| Numerical        | multistep step integrator Stoermar-Cowell              | 
| integration      | with direct integration of second-order equations      |
| of var. equations|--------------------------------------------------------|
|                  | integration step: fixed                                |
|                  |--------------------------------------------------------| 
|                  | start procedure: Cowell-Kulikov                        |
 --------------------------------------------------------------------------- 

 --------------------------------------------------------------------------- 
|                    ESTIMATED PARAMETERS (APRIORI VALUES & SIGMAS)         |
|---------------------------------------------------------------------------| 
| Adjustment       | Helmert blocking method                                |
|---------------------------------------------------------------------------| 
| Station          | 13 stations constrained to the ITRF92 positions (using |
| coordinates      | ITF92 sigmas) as given in IGSMAIL#430, the remaining   |
|                  | stations estimated. The ITRF92 velocities are used     |
|                  | for daily coordinates updates.                         |
|---------------------------------------------------------------------------| 
| Satellite clock  | solved for at each epoch  (white noise process)        |
|                  |                                                        |
|---------------------------------------------------------------------------| 
| Receiver clock   | solved for at each epoch  (white noise process)        |
|                  | One clock fixed and used as a time reference,          |
|                  | usually ALGO.                                          |
|---------------------------------------------------------------------------| 
| Orbital          | initial position and velocity, solar radiation pressure|
| parameters       | scale  and y-bias                                      | 
|                  | constant through the orbital arc.                      |
|---------------------------------------------------------------------------| 
| Troposphere      | estimated in steps of 4 hours                          |
|---------------------------------------------------------------------------| 
| Ionospheric      | not estimated                                          |
| correction       |                                                        |
|---------------------------------------------------------------------------| 
| Ambiguity        | real value                                             |
|                  | apriori values from pseudorange observation            |
|                  | constrained to about 50 meter                          |
|---------------------------------------------------------------------------| 
| ERP              | x & y pole and LOD.                                    |
 --------------------------------------------------------------------------- 

 --------------------------------------------------------------------------- 
|                       REFERENCE FRAMES                                    |
|---------------------------------------------------------------------------| 
| Inertial         | Geocentric; mean equator and equinox of 2000 Jan 1.5   |
|                  | (J2000.0)                                              |
|---------------------------------------------------------------------------| 
| Terrestrial      | ITRF92 reference frame realized through the set of 13  |
|                  | station coordinates and velocities as given in IGSMAIL#|
|                  | 430 as well as the antenna offsets for the above       |
|                  | stations given in /igscb/station/tie/localtie.tab      |
|                  | available from IGS CB (sideshow.jpl.nasa.gov)          |
|---------------------------------------------------------------------------| 
| Interconnection  | Precession: IAU 1976 Precession Theory                 | 
|                  |--------------------------------------------------------|
|                  | Nutation  : IAU 1980 Nutation Theory                   |
|                  |--------------------------------------------------------| 
|                  | Tidal variations in UT1: applied for periods <= 32 days|
 --------------------------------------------------------------------------- 

References:

Scherneck,  H.-G.,  1991. A parametrized solid earth tide model and ocean
  tide   loading  effects  for  global  geodetic  baseline  measurements,
  Geophys. J. Int., 106, 677-694.

-- 

********************************************************************************
* Gerd Gendt                                                                   *
* GeoForschungsZentrum                                                         *
* Aufgabenbereich 1                                Tel.: (0331) 288 1114       *
* Telegrafenberg A17                               Fax.: (0331) 288 1111       *
* D-14473 Potsdam                                e-Mail: [email-masked]   *
* GERMANY                                                                      *
********************************************************************************

[Mailed From: [email-masked] (Gerd Gendt)]