INTERNATIONAL LASER RANGING SERVICE GFZ German Research Centre for Geosciences Analysis Strategy Summary ============================================================================= ANALYSIS CENTRE | GFZ German Research Centre for Geosciences, | c/o DLR Oberpfaffenhofen | Wessling, Germany ----------------------------------------------------------------------------- CONTACT PERSONS | Dr. R. Koenig (rolf.koenig@gfz-potsdam.de; | tel +49-8153-281353) | M. Vei (vei@gfz-potsdam.de; | tel +49-8153-283371) ----------------------------------------------------------------------------- SOFTWARE USED | EPOSOC 06.71 ----------------------------------------------------------------------------- ILRS PRODUCTS | weekly solution for coordinates of global SLR stations | and daily Earth Orientation Parameters (x,y-pole, dLOD) | (SINEX format), orbits (SP3C format) | ----------------------------------------------------------------------------- PREPARATION DATE | 23 March 2016 ============================================================================= ----------------------------------------------------------------------------- | MEASUREMENT MODELS | |---------------------------------------------------------------------------| | Satellites used | LAGEOS-1, LAGEOS-2 | |---------------------------------------------------------------------------| | Basic measurement| Satellite Laser Ranging (SLR): round-trip travel time | | |--------------------------------------------------------| | | speed of light : 299792458 m/s | | | wavelength : station dependent | | | elevation angle cutoff : 10 degrees | | | weighting : 1.0 m to all data | | | range biases : estimated/applied for/to some | | | : stations according ILRS-AWG | | | : recommendations | | | time biases : not modeled/estimated | | | tropospheric biases : not modeled/estimated | |---------------------------------------------------------------------------| | Data editing | 3 sigma editing, minimum number of obs. and passes | |---------------------------------------------------------------------------| | Troposphere | Mendes-Pavlis zenith delay model | | |--------------------------------------------------------| | | Mendes-Pavlis mapping function | |---------------------------------------------------------------------------| | Ionosphere | not modeled/estimated | |---------------------------------------------------------------------------| | Relativity | light time corrections | |---------------------------------------------------------------------------| | Satellite center | Nominal values: LAGEOS: 0.251 m | of mass | As far as available using station dependent values from | | http://ilrs.dgfi.tum.de/fileadmin/data_handling/ | | com_lageos.txt |---------------------------------------------------------------------------| | Other | | |---------------------------------------------------------------------------| ----------------------------------------------------------------------------- | ORBIT MODELS | |---------------------------------------------------------------------------| | Geopotential | EGM96 (static terms through degree and order 20) | | | (C(2,0), C(2,1) and S(2,1) time dependent) | | |--------------------------------------------------------| | | Constants | | | AE = 6378.1363 km | | | GM = 398600.4415 km3/s2 | |---------------------------------------------------------------------------| | Third-body | planets: | | | Mercury, Venus, Earth Moon, Mars, Jupiter, Saturn, | | | Uranus, Neptune | | |--------------------------------------------------------| | | ephemeris: JPL DE403 | |---------------------------------------------------------------------------| | Solar radiation | direct radiation : applied | | pressure | albedo radiation : not 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 (polygonal and | | | once-per-rev) along-track and (once-per-rev) | | | cross-track accelerations (1 set per 4-days) | |---------------------------------------------------------------------------| | Tidal forces | solid earth tides: IERS Conventions 2003 | | |--------------------------------------------------------| | | Ocean tides: FES2004 | | |--------------------------------------------------------| | | Atmospheric tides: Bode&Biancale 2003 | |---------------------------------------------------------------------------| | Atmospheric | not modeled/estimated | | gravitational | | | attraction | | |---------------------------------------------------------------------------| | Dynamic | applied IERS Conventions 2003 | | polar motion | | |---------------------------------------------------------------------------| | Relativity | Schwarzschild correction + Lense-Thirring + DeSitter | |---------------------------------------------------------------------------| | Numerical | Cowell, Kulikov variant | | integration |--------------------------------------------------------| | | integration step: 120 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) | | | or intersection of axes | | | at mean epoch of each arc | | | a priori values: SLRF2008- latest release | | | a priori standard deviation: 1 m | |---------------------------------------------------------------------------| | Troposphere | not estimated | |---------------------------------------------------------------------------| | EOP | definition: x-pole, y-pole, dLOD | | | epoch: at noon of each day | | | frequency: daily | | | a priori values: IERS Bulletin A | | | a priori standard deviation: 30 mas, 2 ms | |---------------------------------------------------------------------------| | Range biases | for some stations (ILRS-AWG recommendations) | | | a priori value: 0 m | | | a priori standard deviation: 0 m | |---------------------------------------------------------------------------| | Constraints | loose constraints | |---------------------------------------------------------------------------| ----------------------------------------------------------------------------- | REFERENCE FRAMES | |---------------------------------------------------------------------------| | Inertial | J2000.0 | |---------------------------------------------------------------------------| | Terrestrial | SLRF2008 (a priori station coordinates) | | | SLRF2008 (station velocities) | | | tidal uplift: Love model (h2=0.609, l2=0.0852) | | | ocean loading: Scherneck, FES2004, CoM | | | atmospheric pressure loading: not modeled/estimated | | | geocenter motion: not explicitly modeled/estimated | | | pole tide: IERS Conventions 2003 | | | origin: C(1,0) = C(1,1) = S(1,1) = 0 | | | orientation: loose constraints | |---------------------------------------------------------------------------| | Interconnection | Precession: IAU 2000A (no corrections) | | |--------------------------------------------------------| | | Nutation: IAU 2000A (no corrections) | | |--------------------------------------------------------| | | Celestial pole offsets: none | | |--------------------------------------------------------| | | Relationship between UT1 and GMST: dLOD estimated | | |--------------------------------------------------------| | | Earth Orientation Parameters: estimated | ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- | 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.