ATTITUDE &amp; ORBIT CONTROL SYSTEM FOR GALILEO IOV*

Konrad, A.; Fischer, H.D.; Müller, Carsten; Oesterlin, Wilfried

doi:10.3182/20070625-5-fr-2916.00006

Cited by 5 publications

(3 citation statements)

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“…Galileo satellites are designed to operate in the yaw steering mode apart from the eclipsing phase (Konrad et al 2007;Montenbruck et al 2015a). In the yaw steering mode, the satellite is constantly rotated about the Earth-pointing antenna boresight axis in the way that the solar panel rotation axis is perpendicular to both Earth and Sun directions (see Fig.…”

Section: Galileo Vulnerability On the Yand B-biasmentioning

confidence: 99%

Toward the 1-cm Galileo orbits: challenges in modeling of perturbing forces

Bury

Sośnica

Zajdel

et al. 2020

J Geod

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Precise orbit determination demands knowledge of perturbing forces acting on the satellites of the Global Navigation Satellite Systems (GNSS). The metadata published by the European GNSS Agency for the Galileo satellites allow for the composition of the analytical box-wing model dedicated for coping with the direct solar radiation pressure (SRP), albedo, and infrared radiation (IR). Based on the box-wing model, we evaluated both the magnitude and the characteristic periods of accelerations caused by all the aforementioned forces. We assess which perturbations can be absorbed by the extended Empirical CODE Orbit Model (ECOM2) and what are the consequences of neglecting higher-order ECOM2 coefficients. In order to evaluate the impact of SRP, albedo, IR, and the navigation antenna thrust, we perform a series of precise Galileo orbit determination strategies for Galileo In-Orbit-Validation (IOV), Full Operational Capability (FOC), and two FOC satellites launched into eccentric orbits. The proposed box-wing model is capable of absorbing approximately 97% of the SRP in the Sun-satellite direction, whereas the rest can be mitigated by an additionally estimated small set of empirical parameters. The purely physical box-wing model does not fully handle satellite misorientation and re-radiation effects, such as Y -bias, solar panel rotation lag, that is the misalignment causing a constant acceleration perpendicular to the solar panel axis and the direction to the Sun. However, the box-wing model is especially crucial in terms of the absorption of the higher-order terms of SRP and stabilizes the orbit solutions during the eclipsing periods. Based on the SLR residual analysis, we found a systematic effect at the level up to 50 mm resulting from the omission of the high-order empirical orbit coefficients. We also found that the impact of the albedo, IR, and transmitter antenna thrust on the Galileo orbits reach the level of 5, 14, and 20 mm, respectively. Eventually, we obtain the overall accuracy of the Galileo-FOC orbits at the level of 22.5 mm, even for the eclipsing period for the solution which considers the box-wing model with the estimation of the constant empirical accelerations.

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Section: Galileo Vulnerability On the Yand B-biasmentioning

confidence: 99%

Toward the 1-cm Galileo orbits: challenges in modeling of perturbing forces

Bury

Sośnica

Zajdel

et al. 2020

J Geod

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“…Note, that this assumption is not correct during eclipse, which was shown, e.g., by Kouba (2009) for GPS andDilssner et al (2011) for GLONASS. Konrad et al (2007) presented an attitude law for Galileo IOV satellites during their midnight and noon turns. Even larger deviations from the assumed yaw-steering must be expected for the BeiDou and QZSS satellites, switching from yaw-steering to orbit normal attitude mode (i.e., the satellites solar panel axis is aligned normal to the orbital plane, the navigation antenna points to the Earth) at |β|-angles below 20…”

Section: Orbit Product Generationmentioning

confidence: 99%

CODE’s five-system orbit and clock solution—the challenges of multi-GNSS data analysis

Prange

Orliac

Dach

et al. 2016

J Geod

165

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This article describes the processing strategy and the validation results of CODE's MGEX (COM) orbit and satellite clock solution including the satellite systems GPS, GLONASS, Galileo, BeiDou, and QZSS. The validation with orbit misclosures and SLR residuals shows that the orbits of the new systems Galileo, BeiDou, and QZSS are affected by modelling deficiencies with impact on the orbit scale (e.g., antenna calibration, Earth albedo, transmitter antenna thrust). Another weakness is the attitude and solar radiation pressure (SRP) modelling of satellites moving in the orbit normal mode-which is not yet correctly considered in the COM solution. Due to these issues we consider the current state COM solution as preliminary. We, however, use the long time series of COM products for identifying the challenges and for the assessment of model improvements. The latter is demonstrated on the example of the solar radiation pressure (SRP) model, which has been replaced by a more generalized model. The SLR validation shows that the new SRP model significantly improves the orbit determination of Galileo and QZSS satellites at times when the satellite's attitude is maintained by yaw-steering. The impact of this orbit improvement is also visible in the estimated satellite clocks-demonstrating the potential use of the new

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“…IOV and FOC satellites will jointly be part of the operational system. As part of a MEO constellation, GIOVE-A (Johnston et al, 2008), GIOVE-B (Zentgraf et al, 2006), and the IOV satellites (Konrad et al, 2007) all use a yaw-steering attitude control strategy outside eclipse seasons. Although not publicly confirmed so far, it may be assumed that the same applies for the latest generation of FOC satellites.…”

Section: Galileomentioning

confidence: 98%

GNSS satellite geometry and attitude models

Montenbruck

Schmid

Mercier

et al. 2015

Advances in Space Research

194

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This article discusses the attitude modes employed by present Global (and Regional) Navigation Satellite Systems (GNSSs) and the models used to describe them along with definitions of the constellation-specific spacecraft body frames. A uniform convention for the labeling of the principal spacecraft axes is proposed by the International GNSS Service (IGS), which results in a common formulation of the nominal attitude of all GNSS satellites in yaw-steering mode irrespective of their specific orbit and constellation. The conventions defined within this document provide the basis for the specification of antenna phase center offsets and variations in a multi-GNSS version of the IGS absolute phase center model in the ANTEX (antenna exchange) format. To facilitate the joint analysis of GNSS observations and satellite laser ranging measurements, laser retroreflector array coordinates consistent with the IGS-specific spacecraft frame conventions are provided in addition to representative antenna offset values for all GNSS constellations.

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ATTITUDE & ORBIT CONTROL SYSTEM FOR GALILEO IOV*

Cited by 5 publications

References 0 publications

Toward the 1-cm Galileo orbits: challenges in modeling of perturbing forces

Toward the 1-cm Galileo orbits: challenges in modeling of perturbing forces

CODE’s five-system orbit and clock solution—the challenges of multi-GNSS data analysis

GNSS satellite geometry and attitude models

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