Parameterization Used for the HRD and RD POD of Sentinel-6 Michael Freilich (S6A)
| Model / data set / parameter | Choice for Sentinel-6A |
|---|---|
| Observation model | |
| Observation combination | Undifferenced ionosphere-free combination of GPS L1 P(Y) / L2-CL or L2 P(Y) and Galileo E1-C and E5-Q |
| Observation sampling | 30 s over 24-h arcs |
| Observation weighting | Constant (uncombined pseudorange σ = 1.0 m, uncombined carrier-phase σ = 1.0 cm) |
| GNSS orbits / clocks | CODE rapid products (Dach et al., 2023) (30-s clock sampling) |
| GNSS satellite biases | CODE rapid IAR OSB product (Dach et al., 2023; Schaer et al., 2021; Villiger et al., 2019) |
| GNSS PCO and PVs | IGS14 igs14.atx (Rebischung & Schmid, 2016) |
| GNSS attitude | Yaw-steering attitude (Montenbruck et al., 2015) |
| Earth orientation parameters | CODE rapid (Dach et al., 2023) |
| Reference frames | ITRF 2014 / GCRF 2014 |
| S6A ARP / CoM location | Values from Cullen (2023), x- and y-corrections estimated as random constant with σ0 = 2 cm |
| S6A PCO and PVs | sen08.atx (calibrated in-orbit) (CPOD Team, 2022) |
| S6A spacecraft attitude | Measured quaternions |
| Carrier-phase ambiguities | Estimated as pass-wise random constant (float) |
| Receiver ISB (Galileo) | Estimated as random walk with large process noise |
| Receiver clock offset | Estimated as integrated random walk |
| Dynamic model | |
| Geopotential | GOCO06s (Kvas et al., 2021) up to degree and order 100 (static and time-varying) |
| Solar system planets | Moon and sun (Fienga et al., 2019) |
| Solid Earth tides | IERS2010 (Petit & Luzum, 2010) |
| Pole tides | IERS2010 mean pole model (Petit & Luzum, 2010) |
| Ocean tides | FES2014b (Lyard et al., 2021) up to degree and order 80 |
| Relativity | IERS2010 (Petit & Luzum, 2010) |
| Radiation pressure | RD: Ray-tracing model (Zardaín et al., 2020) with geometry and surface properties from Cullen (2023) HRD: Cannonball model |
| Earth discretization | Method by Knocke et al. (1988) but with 6 rings and 103 segments with Earth albedo and emissivity coefficients from Hackel (2019) |
| Earth and moon shadow | Conical model (Montenbruck & Gill, 2000) |
| Atmospheric drag | Cannonball model with fixed drag coefficient |
| Atmospheric density | DTM2020 (Bruinsma & Boniface, 2021) |
| Integrator | Dormand Prince 6(5) (Prince & Dormand, 1981) |
| Radial acceleration | First-order Gauss–Markov with τ = 600 s and σ = 5 nm/s2 (RD) or σ = 10 nm/s2 (HRD) |
| Tangential and cross-track acceleration | Estimated one constant variable with σ0 = 5 nm/s2 (RD) or σ0 = 10 nm/s2 (HRD) and once-per-revolution sine and cosine amplitudes (first-order Gauss–Markov) with τ = 2 orbits and σ = 5 nm/s2 (RD) or σ = 20 nm/s2 (HRD) |
| SRP scale coefficient | Estimated as random constant (RD: σ0 = 0.1, HRD: σ0 = 0.2) |
Note: CODE: Center of Orbit Determination in Europe; IAR: integer ambiguity resolution; OSB: observable-specific bias; IGS: International GNSS Service; ITRF: International Terrestrial Reference Frame; GCRF: Geocentric Celestial Reference Frame; GOCO: Gravity Observation Combination; IERS: International Earth Rotation and Reference Systems Service; FES: finite element solution; ISB: inter-system bias