============================================================================= INTERNATIONAL LASER RANGING SERVICE NASA Goddard Joint Center for Earth Systems Technology (JCET) Analysis Strategy Summary ============================================================================= ANALYSIS CENTRE | Joint Center for Earth Systems Technology, | NASA Goddard & Univ. of Maryland, Baltimore County (JCET), | Baltimore, MD, USA ----------------------------------------------------------------------------- CONTACT PERSONS | Prof. Erricos C. Pavlis | (epavlis@umbc.edu; +1 410 455 5832) ----------------------------------------------------------------------------- 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) ----------------------------------------------------------------------------- PREPARATION DATE | effective for products delivered after November 1, 2007 ============================================================================= ----------------------------------------------------------------------------- | MEASUREMENT MODELS | |---------------------------------------------------------------------------| | Satellites used | LAGEOS-1, LAGEOS-2, ETALON-1, ETALON-2, | | | Starlette, Ajisai | |---------------------------------------------------------------------------| | 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 : 3 degrees | | | weighting : 1.0 m | | | range biases : est/d for all sites | | | time biases : est/d for all sites | | | 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 (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 | | | Starlette: 0.075 m | | | Ajisai: 1.016 m (0.976 m for 7840) | |---------------------------------------------------------------------------| | Other | Stanford ET corrections applied to 7840 ONLY | |---------------------------------------------------------------------------| ----------------------------------------------------------------------------- | ORBIT MODELS | |---------------------------------------------------------------------------| | Geopotential | GGM02C (static terms through degree and order 30) | | | (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 : applied | | | earth thermal radiation : applied | | |--------------------------------------------------------| | | Earth shadow model includes: penumbra | | | | | |--------------------------------------------------------| | | reemitted radiation: not applied | |---------------------------------------------------------------------------| | satellite | 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) | | | | | | STARLT: estimation of empirical (constant and | | | once-per-rev) along-track and (once-per-rev) | | | cross-track accelerations (1 set per weekly | | | solution) plus Cdrag/day | | | | | | AJISAI: estimation of empirical (constant and | | | once-per-rev) along-track and (once-per-rev) | | | cross-track accelerations (1 set per weekly | | | solution) plus Cdrag/day | | | | |---------------------------------------------------------------------------| | 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 | point-mass accelerations, Lense-Thirring effect, | | | coriolis force | |---------------------------------------------------------------------------| | Numerical | Cowell 11th order predictor-corrector | | integration |--------------------------------------------------------| | | integration step: L1: 150 s, L2: 60 s, E1 & E2: 300 s | | | STARLT: 30 s, AJISAI: 30 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 | | | for AJISAI: 1.03 | | | Empirical accelerations (unconstrained) | |---------------------------------------------------------------------------| | Stations | definition: SLR monument (eccentricities subtracted), | | | at mean epoch of each arc | | | a priori values: SLRF2005 (FIXED) | | | | |---------------------------------------------------------------------------| | 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 05 C04 (FIXED) | | | | |---------------------------------------------------------------------------| | Range biases | for all stations | | | a priori value: 0 m | | | a priori standard deviation: 100 m | |---------------------------------------------------------------------------| | Constraints | Stations and EOP are fixed | |---------------------------------------------------------------------------| ----------------------------------------------------------------------------- | REFERENCE FRAMES | |---------------------------------------------------------------------------| | Inertial | J2000.0 | |---------------------------------------------------------------------------| | Terrestrial | SLRF2005 (a priori station coordinates) | | | SLRF2005 (station velocities) | | | NUVEL-1A NNR (2nd source for station velocities) | | | tidal uplift: IERS 2003 Conventions | | | ocean loading: GOT00.2 | | | atmospheric pressure loading: not modeled/estimated | | | geocenter motion: not explicitly modeled/estimated | | | geocenter tidal frequencies: applied | | | pole tide: IERS 2003 Conventions | | | origin: C(1,0) = C(1,1) = S(1,1) = 0 | | | orientation: IERS 05 C04 | |---------------------------------------------------------------------------| | Interconnection | Precession: IERS 2003 corrections | | |--------------------------------------------------------| | | Nutation: IAU 2000A | | |--------------------------------------------------------| | | Celestial pole: IERS 2003 Conventions | | |--------------------------------------------------------| | | Relationship between UT1 and GMST: IERS 05 C04 | | |--------------------------------------------------------| | | Earth Orientation Parameters: IERS 05 C04 a priori | | |--------------------------------------------------------| | | Tidal variations in UT1 and PM: IERS 2003 Conventions | ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- | OTHER INFORMATION | |---------------------------------------------------------------------------| | QC/QA Process | The daily runs for short-term station bias monitoring | | | are done using the same standards as for our weekly | | | ILRS products, except that in this case, stations and | | | EOP are fixed to the a priori values and for all of | | | the stations in the arc we are estimating range and | | | time biases on a pass-by-pass mode. | | | Data editing is kept the same as in the standard runs | | | using a dynamic 3.5 x RMS of fit cut-off. | | | | |---------------------------------------------------------------------------|