Abstract
In this study, submillimeter level accuracy K-band microwave ranging (MWR) equipment is demonstrated, aiming to verify the detection of the Earth’s gravity field (EGF) and digital elevation models (DEM), through spacecraft formation flying (SFF) in low Earth orbit (LEO). In particular, this paper introduces in detail an integrated BeiDou III B1C/B2a dual frequency receiver we designed and developed, including signal processing scheme, gain allocation, and frequency planning. The receiver matched the 0.1 ns precise synchronize time-frequency benchmark for the MWR system, verified by a static and dynamic test, compared with a time interval counter synchronization solution. Moreover, MWR equipment ranging accuracy is explored in-depth by using different ranging techniques. The test results show that MWR achieved 40 m and 1.6 m/s accuracy for ranging and range rate during tests, using synchronous dual one-way ranging (DOWR) microwave phase accumulation frame, and 6 m/s range rate accuracy obtained through a one-way ranging experiment. The ranging error sources of the whole MWR system in-orbit are analyzed, while the relative orbit dynamic models, for formation scenes, and adaptive Kalman filter algorithms, for SFF relative navigation designs, are introduced. The performance of SFF relative navigation using MWR are tested in a hardware in loop (HIL) simulation system within a high precision six degree of freedom (6-DOF) moving platform. The final estimation error from adaptive relative navigation system using MWR are about 0.42 mm (range/RMS) and 0.87 m/s (range rate/RMS), which demonstrated the promising accuracy for future applications of EGF and DEM formation missions in space.
Highlights
Introduction iationsSpacecraft formation flying has attracted much attention since it can perform space missions with more reliability, adaptability, and low life-cycle cost, compared with traditional monolithic spacecraft [1,2]
Several spacecraft formation flying (SFF) missions have been successfully deployed in low Earth orbit, such as GRACE and GRACE Follow-on mission for precise Earth gravity field measurement [3,4,5,6], EO-1/LandSat 7 for Earth observation [7], and PRISMA for millimeter level SFF technology in-orbit demonstration [8]
The results clearly demonstrated the effectiveness of adaptive filter that incorporating process noise uncertainty, and submillimeter level ranging accuracy for formation flight in low Earth orbit (LEO) by using microwave ranging (MWR) technology
Summary
Introduction iationsSpacecraft formation flying has attracted much attention since it can perform space missions with more reliability, adaptability, and low life-cycle cost, compared with traditional monolithic spacecraft [1,2]. Several SFF missions have been successfully deployed in low Earth orbit, such as GRACE and GRACE Follow-on mission for precise Earth gravity field measurement [3,4,5,6], EO-1/LandSat 7 for Earth observation [7], and PRISMA for millimeter level SFF technology in-orbit demonstration [8]. Among the many LEO SFF space applications, the most frequently used ones are the Earth’s gravity field detection through follow-on formation [9], and digital elevation models mapping by using pendulum formation configurations. EGF is one basic physical field, that reflects the influences on the distribution and movement of the Earth’s materials. The EGF and its time variation reflect the density distribution and material movement state.
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