============================================================================= INTERNATIONAL LASER RANGING SERVICE Natural Environment Research Council Space Geodesy Facility (NSGF) Analysis Strategy Summary ============================================================================= ANALYSIS CENTRE | NERC Space Geodesy Facility (NSGF), | Herstmonceux Castle, Hailsham, | East Sussex BN27 1RN, UK ----------------------------------------------------------------------------- CONTACT PERSONS | Dr Graham M Appleby (gapp@nerc.ac.uk +44 1323 833888 | ----------------------------------------------------------------------------- SOFTWARE USED | SATAN (ORBIT and RGODYN) ----------------------------------------------------------------------------- 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 | effective since October 30, 2003. Nov 2007 for daily EOP ============================================================================= ----------------------------------------------------------------------------- | 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, 847.0 & 694.3 nm| | | elevation angle cutoff : 8 degrees | | | weighting : 1.0 m & 1000 m as per AWG | | | range biases : est/d for non-core stations | | | time biases : not modeled/estimated | | | tropospheric biases : not modeled/estimated | |---------------------------------------------------------------------------| | Data editing | 3.0 sigma editing and minimum number of obs per stn/arc| |---------------------------------------------------------------------------| | Troposphere | Mendes-Pavlis zenith delay model | | |--------------------------------------------------------| | | M-P mapping function | |---------------------------------------------------------------------------| | Ionosphere | not modeled/estimated | |---------------------------------------------------------------------------| | Relativity | scale: LET (TT time scale) | | | effects: light time corrections | |---------------------------------------------------------------------------| | Satellite center | LAGEOS: 0.251 m (0.245 m for 7840) | | of mass | ETALON: 0.580 m or 0.610 m | |---------------------------------------------------------------------------| | 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 | IERS Conventions 2003 | | pressure | | | | direct radiation : applied | | | albedo radiation : applied | | | earth thermal radiation : not applied | | |--------------------------------------------------------| | | Earth shadow model includes: 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 (2 sets per weekly | | | solution) | | | ETALON: estimation of empirical (constant and | | | once-per-rev) along-track and (once-per-rev) | | | cross-track accelerations (1 set per weekly | | | solution) | | | | |---------------------------------------------------------------------------| | Tidal forces | solid earth tides: IERS 2003 Conventions model | | |--------------------------------------------------------| | | Ocean tides: Ray GOT00.2 | |---------------------------------------------------------------------------| | Atmospheric | not modeled/estimated | | gravitational | | | attraction | | |---------------------------------------------------------------------------| | Dynamic | applied, IERS Conventions 2003 | | polar motion | | |---------------------------------------------------------------------------| | Relativity | geodesic precession, Lense-Thirring effect | | | | |---------------------------------------------------------------------------| | Numerical | Gauss-Jackson 9th order predictor-corrector | | integration |--------------------------------------------------------| | | integration step: L1 & L2: 60 s, E1 & E2: 300 s | | |--------------------------------------------------------| | | 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: ITRF2005 pos and vel | | | a priori standard deviation: 100 m | |---------------------------------------------------------------------------| | 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: 10000 masec, 1000 sec | |---------------------------------------------------------------------------| | Range biases | for some (non-core) stations | | | a priori value: 0 m | | | a priori standard deviation: 100 m | |---------------------------------------------------------------------------| | Constraints | loose constraints (1 m, and equivalent for EOP) | |---------------------------------------------------------------------------| ----------------------------------------------------------------------------- | REFERENCE FRAMES | |---------------------------------------------------------------------------| | Inertial | J2000.0 | |---------------------------------------------------------------------------| | Terrestrial | ITRF2005 (a priori station coordinates) | | | ITRF2005 (station velocities) | | | NUVEL-1A (2nd source for station velocities) | | | tidal uplift: Love model (h2=0.609, l2=0.0852) | | | ocean loading: GOT00.2 | | | atmospheric pressure loading: not modeled/estimated | | | geocenter motion: not explicitly modeled/estimated | | | pole tide: IERS 2003 Conventions | | | origin: C(1,0) = C(1,1) = S(1,1) = 0 | | | orientation: loose constraints (1 m equivalent) | |---------------------------------------------------------------------------| | Interconnection | Precession: IAU 1976 with IERS 2003 corrections | | |--------------------------------------------------------| | | Nutation: IAU 1980 with IERS 2003 corrections | | |--------------------------------------------------------| | | Celestial pole offsets: none | | |--------------------------------------------------------| | | Relationship between UT1 and GMST: UT1-UTC estimated | | |--------------------------------------------------------| | | Earth Orientation Parameters: estimated | | | (IERS C04_05 + USNO rapid service for a-priori) | | |--------------------------------------------------------| ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- | OTHER INFORMATION | |---------------------------------------------------------------------------| | | | |---------------------------------------------------------------------------|