============================================================================= INTERNATIONAL LASER RANGING SERVICE GRGS Analysis Strategy Summary ============================================================================= ANALYSIS CENTRE | Observatoire de la Côte d'Azur | 4 Avenue Nicolas Copernic | 06460 Grasse ----------------------------------------------------------------------------- CONTACT PERSONS | Florent Deleflie (florent.deleflie@obs-azur.fr) | Philippe Berio (philippe.berio@obs-azur.fr) ----------------------------------------------------------------------------- SOFTWARE USED | GINS+MATLO ----------------------------------------------------------------------------- ILRS PRODUCTS | weekly solution for coordinates of global SLR stations and | daily Earth Orientation Parameters (x,y-pole, LOD) | (SINEX format) ----------------------------------------------------------------------------- PREPARATION DATE | effective since October, 2007 ============================================================================= ----------------------------------------------------------------------------- | MEASUREMENT MODELS | |---------------------------------------------------------------------------| | Satellites used | LAGEOS-1, LAGEOS-2 |---------------------------------------------------------------------------| | Basic measurement| Satellite Laser Ranging (SLR): | |--------------------------------------------------------| | | speed of light : 299792458 m/s | | wavelength : 532.0, 423.0, 847.0 & 694.3 nm | | elevation angle cutoff : 8 degrees | | weighting : 1m | | range biases : est/week for non-core stations | | time biases : not modeled/estimated | | tropospheric biases : not modeled/estimated |---------------------------------------------------------------------------| | Data editing | 3.5 sigma editing |---------------------------------------------------------------------------| | Troposphere | Mendes-Pavlis | |--------------------------------------------------------| | | Mendes-Pavlis mapping function |---------------------------------------------------------------------------| | Ionosphere | not modeled/estimated |---------------------------------------------------------------------------| | Relativity | scale: LET | | effects: light time corrections |---------------------------------------------------------------------------| | Satellite center | 0.251 m | of mass | |---------------------------------------------------------------------------| | Other | | |---------------------------------------------------------------------------| ----------------------------------------------------------------------------- | ORBIT MODELS | |---------------------------------------------------------------------------| | Geopotential | GRIM5 (static terms through degree and order 40) | | (C(2,0), C(2,1) and S(2,1) time dependent) | |--------------------------------------------------------| | | Constants | | | AE = 6378.1363 km | | 1/F = 298.2564 | | GM = 98600.4415 km3/s2 |---------------------------------------------------------------------------| | Third-body | planets: 8 | | | | | | |--------------------------------------------------------| | | ephemeris: JPL DE405 |---------------------------------------------------------------------------| | Solar radiation | | pressure | | | | direct radiation : applied | | albedo radiation : applied | | earth thermal radiation : not applied | |--------------------------------------------------------| | | Earth shadow model includes: penumbra,lunar eclipses | |--------------------------------------------------------| | | reemitted radiation: not applied |---------------------------------------------------------------------------| | satellite | not modeled | thermal thrust | LAGEOS: estimation of empirical (constant and | | one-per-rev) radial/along/across track | | accelerations (1 set per week) | | | | ETALON: | | | | |---------------------------------------------------------------------------| | Tidal forces | solid earth tides: Wahr model | |--------------------------------------------------------| | | Ocean tides: FES2004 |---------------------------------------------------------------------------| | Atmospheric | not modeled/estimated | gravitational | | | attraction | | |---------------------------------------------------------------------------| | Dynamic | applied | polar motion | | |---------------------------------------------------------------------------| | Relativity | point-mass accelerations, Lense-Thirring effects, | | coriolis force |---------------------------------------------------------------------------| | Numerical | Cowell | integration |--------------------------------------------------------| | | integration step: 90 sec | |--------------------------------------------------------| | | arc length (orbits): 7 days ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- | ESTIMATED PARAMETERS (APRIORI VALUES & SIGMAS) | |---------------------------------------------------------------------------| | Adjustment | weighted least-squares adjustment |---------------------------------------------------------------------------| | Orbital | Initial position and velocity: | | parameters | estimated for each satellite (unconstrained) | | Solar radiaton pressure: (unconstrained) | | Empirical acceleration |---------------------------------------------------------------------------| | Stations | definition: SLR monument (eccentricities subtracted), | | at mean epoch of each arc) | | a priori values: SLRF2005 | | a priori standard deviation: 1m |---------------------------------------------------------------------------| | Troposphere | not estimated |---------------------------------------------------------------------------| | EOP | definition: x-pole, y-pole, UT1-UTC and LOD | | epoch: at noon of each day | | frequency: daily | | a priori values: IERS C04 | | a priori standard deviation: 35 mas, 3 ms |---------------------------------------------------------------------------| | Range biases | for some (non-core) stations | | a priori value: 0 m | | a priori standard deviation: 1m |---------------------------------------------------------------------------| | Constraints | loose constraints |---------------------------------------------------------------------------| ----------------------------------------------------------------------------- | REFERENCE FRAMES | |---------------------------------------------------------------------------| | Inertial | J2000 |---------------------------------------------------------------------------| | Terrestrial | ITRF2005 | | | | tidal uplift: applied | | ocean loading: applied | | atmospheric pressure loading: not applied | | geocenter motion: not moeled/estimated | | geocenter tidal frequencies: included in ocean load model | | pole tide: IERS Conventions 2003 | | origin: realized by adjusted stations'coordinates | | orientation: ITRF2005 a priori (constrained at 1 m) |---------------------------------------------------------------------------| | Interconnection | Precession: IAU 1976 + corrections IERS2003 | |--------------------------------------------------------| | | Nutation: IAU 2000 | |--------------------------------------------------------| | | Celestial pole offsets: modeled using IERS C04 values | |--------------------------------------------------------| | | Relationship between UT1 and GMST: UT1-UTC estimated | |--------------------------------------------------------| | | Earth Orientation Parameters: IERS C04 | | | |--------------------------------------------------------| | | Tidal variations in UT1 and xp: IERS 2003 ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- | OTHER INFORMATION | |---------------------------------------------------------------------------| | | | |---------------------------------------------------------------------------| References :