============================================================================= INTERNATIONAL LASER RANGING SERVICE Agenzia Spaziale Italiana (ASI) Analysis Strategy Summary ============================================================================= ANALYSIS CENTRE | Centro di Geodesia Spaziale, | Agenzia Spaziale Italiane (ASI), | Matera, Italy ----------------------------------------------------------------------------- CONTACT PERSONS | dr. V. Luceri (cinzia.luceri@telespazio.com; | tel +39-0835-377231) | dr. G. Bianco (giuseppe.bianco@asi.it; | tel +39-0835-377209) ----------------------------------------------------------------------------- SOFTWARE USED | GEODYN-II, SOLVE ----------------------------------------------------------------------------- ILRS PRODUCTS | weekly solution for coordinates of global SLR stations | and daily Earth Orientation Parameters (x,y-pole, LOD) | (SINEX format) | Daily 7-day solutions primarily for rapid EOP | (SINEX format) ----------------------------------------------------------------------------- PREPARATION DATE | June 2003 for weekly products, Nov 2007 for daily ============================================================================= ----------------------------------------------------------------------------- | MEASUREMENT MODELS | |---------------------------------------------------------------------------| | Satellites used | LAGEOS-1, LAGEOS-2, ETALON-1, ETALON-2 | |---------------------------------------------------------------------------| | Basic measurement| Satellite Laser Ranging (SLR): round-trip travel time | | |--------------------------------------------------------| | | speed of light : 299792458 m/s | | | wavelength : 532.0, 423.0 and 694.3 nm | | | elevation angle cutoff : 20 degrees | | | weighting : 1.0 m to all data | | | range biases : estimated for some stations | | | time biases : not modeled/estimated | | | tropospheric biases : not modeled/estimated | |---------------------------------------------------------------------------| | Data editing | 3.5 sigma editing | |---------------------------------------------------------------------------| | Troposphere | Mendes-Pavlis zenith delay model | | |--------------------------------------------------------| | | Mendes-Pavlis mapping function | |---------------------------------------------------------------------------| | Ionosphere | not modeled/estimated | |---------------------------------------------------------------------------| | Relativity | scale: LET | | | effects: light time corrections | |---------------------------------------------------------------------------| | Satellite center | LAGEOS: 0.251 m , 0.245 for 7840 | | of mass | ETALON: 0.580 m or 0.610 m | |---------------------------------------------------------------------------| | Other | | |---------------------------------------------------------------------------| ----------------------------------------------------------------------------- | ORBIT MODELS | |---------------------------------------------------------------------------| | Geopotential | EGM96 (static terms through degree and order 70) | | | (C(2,0), C(2,1) and S(2,1) time dependent) | | |--------------------------------------------------------| | | Constants | | | AE = 6378.1363 km | | | 1/F = 298.2564 | | | GM = 398600.4415 km3/s2 | |---------------------------------------------------------------------------| | Third-body | planets: | | | Mercury, Venus, Earth Moon, Mars, Jupiter, Saturn, | | | Uranus, Neptune | | |--------------------------------------------------------| | | ephemeris: JPL DE403 | |---------------------------------------------------------------------------| | Solar radiation | IERS Conventions 2003 | | pressure | | | | direct radiation : applied | | | albedo radiation : not applied | | | earth thermal radiation : not applied | | |--------------------------------------------------------| | | Earth shadow model includes: umbra, penumbra | | |--------------------------------------------------------| | | reemitted radiation: not applied | |---------------------------------------------------------------------------| | satellite | not modeled | | thermal thrust | LAGEOS: estimation of empirical (constant and | | | once-per-rev) along-track and (once-per-rev) | | | cross-track accelerations (1 set per weekly | | | solution) | | | ETALON: estimation of empirical (constant and | | | once-per-rev) along-track accelerations | | | (1 set per weekly solution) | |---------------------------------------------------------------------------| | Tidal forces | solid earth tides: Wahr model | | |--------------------------------------------------------| | | Ocean tides: Ray GOT99.2b | |---------------------------------------------------------------------------| | Atmospheric | not modeled/estimated | | gravitational | | | attraction | | |---------------------------------------------------------------------------| | Dynamic | applied | | polar motion | | |---------------------------------------------------------------------------| | Relativity | point-mass accelerations, Lense-Thirring effects, | | | coriolis force | |---------------------------------------------------------------------------| | Numerical | Cowell 11th order predictor-corrector | | 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: CR kept fixed at 1.13 | | | Empirical accelerations (unconstrained) | |---------------------------------------------------------------------------| | Stations | definition: SLR monument (eccentricities subtracted), | | | at mean epoch of each arc | | | a priori values: SLRF2005 | | | a priori standard deviation: 1 meter | |---------------------------------------------------------------------------| | 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_05 | | | a priori standard deviation: 35 mas, 3 ms | |---------------------------------------------------------------------------| | Range biases | for some (non-core) stations | | | a priori value: 0 m | | | a priori standard deviation: 100 m | |---------------------------------------------------------------------------| | Constraints | loose constraints | |---------------------------------------------------------------------------| ----------------------------------------------------------------------------- | REFERENCE FRAMES | |---------------------------------------------------------------------------| | Inertial | J2000.0 | |---------------------------------------------------------------------------| | Terrestrial | SLRF2005 (a priori station coordinates) | | | SLRF2005 (station velocities) | | | tidal uplift: Love model (h2=0.609, l2=0.0852) | | | ocean loading: Scherneck model, based on GOT99.2 | | | atmospheric pressure loading: not modeled/estimated | | | geocenter motion: not explicitly modeled/estimated | | | geocenter tidal frequencies: applied | | | pole tide: IERS Conventions (1996) | | | origin: C(1,0) = C(1,1) = S(1,1) = 0 | | | orientation: loose constraints | |---------------------------------------------------------------------------| | Interconnection | Precession: IAU 2000 | | |--------------------------------------------------------| | | Nutation: IAU 2000 | | |--------------------------------------------------------| | | Celestial pole offsets: modeled using IERS C04 values | | |--------------------------------------------------------| | | Relationship between UT1 and GMST: UT1-UTC estimated | | |--------------------------------------------------------| | | Earth Orientation Parameters: estimated | | | (IERS C04_05 + USNO rapid service as a priori) | | |--------------------------------------------------------| | | Tidal variations in UT1 and xp: sub-daily not modeled | ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- | OTHER INFORMATION | |---------------------------------------------------------------------------| | | | |---------------------------------------------------------------------------| References : Pearlman, M.R., Degnan, J.J., and Bosworth, J.M.: "The International Laser Ranging Service", Advances in Space Research, Vol. 30, No. 2, pp. 135-143, July 2002. Rowlands, D.D., J.A. Marshall, J.J. McCarthy, S.C.Rowton, D. Moore, D.E.Pavlis, S.B. Luthcke, and L.S. Tsaoussi, 1993, GEODYN II System Description, Hughes STX Contractor Report, Greenbelt, Maryland.