Improved GPS-Based Single-Frequency Orbit Determination for the CYGNSS Spacecraft Using GipsyX

Conrad, Alex; Axelrad, Penina; Haines, Bruce; Zuffada, Cinzia; O’Brien, Andrew

doi:10.33012/navi.565

Cited by 5 publications

(1 citation statement)

References 36 publications

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“…Although the impact of multipath errors is not as significant for space-borne receivers compared to ground-based receivers, they can still introduce errors ranging from 30 to 60 cm and from 6 to 9 mm for ionosphere-free pseudorange and carrier phase observations, respectively (Hauschild & Montenbruck, 2021). To address these errors, a common approach is to let the estimated PCV maps absorb these multipath effects (Conrad et al, 2023). This strategy is particularly effective for satellites without moving parts.…”

Section: Multipath Errorsmentioning

confidence: 99%

Precise Relative Navigation in Medium Earth Orbits with Global Navigation Satellite Systems and Intersatellite Links for Black Hole Imaging

Salas,

Fernández,

van den IJssel

2024

Preprint

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The Event Horizon Telescope (EHT) is a ground-based array of Very Long Baseline Interferometry (VLBI) telescopes designed to image the event horizon of black holes. To overcome its limitations, this work explores a mission concept involving a two-satellite constellation of VLBI telescopes deployed in circular and polar Medium Earth Orbit (MEO) at more than 8000 km altitude.  The attainment of high-resolution black hole images requires extremely precise baseline determination at the few millimetre level. To address this challenge, each satellite within the constellation is equipped with two Global Navigation Satellite System (GNSS) receivers and an optical Intersatellite Link (ISL) for relative navigation. This work assesses the feasibility of achieving highly accurate relative positioning within the constellation, particularly considering the large intersatellite distances involved. The methodology employed in this simulation study encompasses several steps. Initially, the satellite orbits are estimated independently for each satellite using GNSS observations. Following this, the orbit of one of the satellites is held fixed as a reference, while the orbit of the other satellite is re-estimated by incorporating the ISL observations. To enhance the accuracy of the orbit estimation, integer GNSS ambiguity resolution is implemented in the precise orbit determination process. The simulated data incorporates an extensive set of realistic error sources, including thermal noise, instrumental delays, clock biases, errors in the GNSS ephemerides and clocks, uncertainties in the geopotential and solar radiation pressure models, and white noise in the ISL observations.The results highlight the importance of integer ambiguity resolution in meeting the stringent relative navigation requirements of the mission. The analysis also reveals that the ISL observations primarily improve the baseline estimation along the direction of the link itself. However, in the direction of the black hole, the impact of ISL observations is minimal, indicating that the ISL does not significantly contribute to meeting the specific relative navigation requirements. Furthermore, the study identifies that large intersatellite distances lead to degraded relative orbit accuracy due to fewer shared errors between the two satellites. The work will show the accuracy obtained with the simulations, the assumptions considered, and the next steps needed.

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Section: Multipath Errorsmentioning

confidence: 99%

Precise Relative Navigation in Medium Earth Orbits with Global Navigation Satellite Systems and Intersatellite Links for Black Hole Imaging

Salas,

Fernández,

van den IJssel

2024

Preprint

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Ionospheric tomography for SWARM satellite orbit determination using single-frequency GNSS data

Prol,

Pignalberi,

Smirnov

et al. 2024

GPS Solut

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Ionospheric tomography offers three-dimensional (3D) description of the electron density distribution, enabling the direct incorporation of electron density data into the slant total electron content (STEC) computation. As a result, STEC derived from tomography helps mitigate the ionospheric delay experienced in the line of sight between global navigation satellite systems (GNSS) and satellites positioned in low Earth orbits (LEO). Tomography can therefore be effectively employed to correct single-frequency GNSS observations and allow enhanced positioning of spaceborne platforms. We demonstrate the accuracy and performance of a global-scale ionospheric tomography method for determining satellite orbits, utilizing single-frequency GNSS measurements combined with a precise point positioning (PPP) algorithm. We compare the tomographic outcomes against orbit determination derived from the GRoup and PHase ionospheric correction (GRAPHIC) observable and based on an ionospheric climatological model. Near the peak of solar cycle 24, the overall accuracy achieved with tomography was around 3.8 m. notably, compared to the background climatological model, tomography demonstrated improvements ranging from 15 to 20%. The GRAPHIC method outperformed tomography, achieving an accuracy of 0.7 m, whereas we obtained around 7 m accuracy when no ionospheric model is employed. Although the developed ionospheric tomography has yet to match the precision of GRAPHIC, our results bring us relatively closer to this objective.

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Inter-satellite tracking methods and applications: A comprehensive survey

Jain,

Speretta,

Dirkx

et al. 2024

Advances in Space Research

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Improved GPS-Based Single-Frequency Orbit Determination for the CYGNSS Spacecraft Using GipsyX

Cited by 5 publications

References 36 publications

Precise Relative Navigation in Medium Earth Orbits with Global Navigation Satellite Systems and Intersatellite Links for Black Hole Imaging

Precise Relative Navigation in Medium Earth Orbits with Global Navigation Satellite Systems and Intersatellite Links for Black Hole Imaging

Ionospheric tomography for SWARM satellite orbit determination using single-frequency GNSS data

Inter-satellite tracking methods and applications: A comprehensive survey

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